Polymerization-induced self-assembly (PISA) has become an important one pot method for the preparation of well-defined block copolymer nanoparticles. In PISA, morphology is typically controlled by changing molecular architecture and polymer concentration. However, several computational and experimental studies have suggested that changes in polymerization rate can lead to morphological differences. Here, we demonstrate that catalyst selection can be used to control morphology independent of polymer structure and concentration in ring-opening polymerization-induced crystallization-driven self-assembly (ROPI-CDSA). Slower rates of polymerization give rise to slower rates of self-assembly, resulting in denser lamellae and more 3D structures when compared to faster rates of polymerization. Our explanation for this is that the fast samples transiently exist in a nonequilibrium state as self-assembly starts at a higher solvophobic block length when compared to the slow polymerization. We expect that subsequent examples of rate variation in PISA will allow for greater control over morphological outcome.

Conjugated polymers offer a number of unique and useful properties for use as battery electrodes, and recent work has reported that conjugated polymers can exhibit excellent rate performance due to electron transport along the polymer backbone. However, the rate performance depends on both ion and electron conduction, and strategies for increasing the intrinsic ionic conductivities of conjugated polymer electrodes are lacking. Here, we investigate a series of conjugated polynapthalene dicarboximide (PNDI) polymers containing oligo(ethylene glycol) (EG) side chains that enhance ion transport. We produced PNDI polymers with varying contents of alkylated and glycolated side chains and investigated the impact on rate performance, specific capacity, cycling stability, and electrochemical properties through a series of charge–discharge, electrochemical impedance spectroscopy, and cyclic voltammetry measurements. We find that the incorporation of glycolated side chains results in electrode materials with exceptional rate performance (up to 500C, 14.4 s per cycle) in thick (up to 20 μm), high-polymer-content (up to 80 wt %) electrodes. Incorporation of EG side chains enhances both ionic and electronic conductivities, and we found that PNDI polymers with at least 90% of NDI units containing EG side chains functioned as carbon-free polymer electrodes. This work demonstrates that polymers with mixed ionic and electronic conduction are excellent candidates for battery electrodes with good cycling stability and capable of ultra-fast rate performance.

Figure 1. Workflow of Kendrick mass-analysis. Left: Traditional mass spectrometric characterization of polymers (i.e., MALDI-MS) provides a one-dimensional spectrum. Identification and assignment of all species in an ensemble of polymers with a distribution of molecular weights, chain-end types, and number of end groups per chain is challenging. Right: Application of a second-dimension resolves species with identical nonconstitutional repeating units (CRU; e.g., chain-ends, adducting ions, comonomers). The diameter of each circle in the Kendrick plot is proportional to the intensity of the corresponding MALDI peak. aOligomers were generated by frontal ring-opening metathesis oligomerization (FROMO). Conditions. (A/B) FROMO of 5-ethylidene-2-norbornene (A) and DCPD (B) catalyzed by G2 with styrene as the CTA. (C) FROMO of DCPD catalyzed by G2 with 3-bromostyrene as the CTA. Trace 3-chlorostyrene impurities existed in the CTA, as reflected in this detectable species. (D) FROMO of norbornene catalyzed by G2 with styrene as the CTA. Trace DCPD impurities in the monomer source resulted in detectable quantities of this co-oligomer. (E) FROMO of DCPD catalyzed by G2 and terminated with either 3-bromostyrene or ethyl vinyl ether. This species is likely the first oligomer generated and contains a precatalyst derived end-group. Figure reprinted and adapted ref (9). Copyright 2022 American Chemical Society. Figure 2. Fractional masses of stable nuclides derived from different Kendrick mass scales (≈ 350, m/z reported by the National Institute of Standards and Technology (11)). Kendrick masses were determined using eq 2, and the corresponding reference isotope is provided next to each curve. Fractional masses were calculated with eq 3. Inset: Common, low-mass nuclides most relevant for polymer chemistry (i.e., 1H through 37Cl). Dr. Diego Alzate-Sanchez, Dr. Julian Cooper, Dr. Oleg Davydovich, Dr. Jacob Lessard, Dr. Katherine Stawiasz, Henry Wang, and Christina Yu are thanked for insightful discussions. B.A.S. and J.S.M. acknowledge the Department of Energy (Office of Basic Energy Sciences, Energy Frontier Research Center) under Award number DE-SC0023457, titled Regenerative Energy-Efficient Manufacturing of Thermoset Polymeric Materials (REMAT). This article references 29 other publications. N denotes the set of natural numbers. N0 is the set of natural numbers including 0. This article has not yet been cited by other publications. Figure 1. Workflow of Kendrick mass-analysis. Left: Traditional mass spectrometric characterization of polymers (i.e., MALDI-MS) provides a one-dimensional spectrum. Identification and assignment of all species in an ensemble of polymers with a distribution of molecular weights, chain-end types, and number of end groups per chain is challenging. Right: Application of a second-dimension resolves species with identical nonconstitutional repeating units (CRU; e.g., chain-ends, adducting ions, comonomers). The diameter of each circle in the Kendrick plot is proportional to the intensity of the corresponding MALDI peak. aOligomers were generated by frontal ring-opening metathesis oligomerization (FROMO). Conditions. (A/B) FROMO of 5-ethylidene-2-norbornene (A) and DCPD (B) catalyzed by G2 with styrene as the CTA. (C) FROMO of DCPD catalyzed by G2 with 3-bromostyrene as the CTA. Trace 3-chlorostyrene impurities existed in the CTA, as reflected in this detectable species. (D) FROMO of norbornene catalyzed by G2 with styrene as the CTA. Trace DCPD impurities in the monomer source resulted in detectable quantities of this co-oligomer. (E) FROMO of DCPD catalyzed by G2 and terminated with either 3-bromostyrene or ethyl vinyl ether. This species is likely the first oligomer generated and contains a precatalyst derived end-group. Figure reprinted and adapted ref (9). Copyright 2022 American Chemical Society. Figure 2. Fractional masses of stable nuclides derived from different Kendrick mass scales (≈ 350, m/z reported by the National Institute of Standards and Technology (11)). Kendrick masses were determined using eq 2, and the corresponding reference isotope is provided next to each curve. Fractional masses were calculated with eq 3. Inset: Common, low-mass nuclides most relevant for polymer chemistry (i.e., 1H through 37Cl). This article references 29 other publications. N denotes the set of natural numbers. N0 is the set of natural numbers including 0.

Organoboron chemistry has been widely explored and developed in synthetic chemistry for over half a century and provides various elegant synthetic protocols in polymer synthesis. Compared with most trivalent bare organoboron compounds, N-coordinated organoboron shows better performances, such as air and moisture stability. This review summarizes the application of various N-coordinated boranes and boronic acid/esters in polymer synthesis and materials science. We introduce the significance of N-coordinated boranes and boronate esters for controllable polymer synthesis and systematically summarize the structures and properties of polymers containing N-coordinated boronate esters. Furthermore, we highlight the effect of N→B dative bonds on improving the performance of self-healing materials. We hope that, through this review, more researchers will realize the advantages of N-coordinated organoboron and promote the development of this direction in polymer synthesis and materials science.

We are happy to present this first collection of Perspectives on the “Grand Challenges in Polymer Science”. These six Perspectives from world-leading experts in various subfields of polymer science and engineering present their views on the important problems that researchers in the polymer community could tackle to find sustainable long-term solutions. Some of these technical questions are new as the field evolves, some are yet to be answered due to limitations in existing─synthetic, characterization, computation/theory─methods, while others have been answered partially or continue to be debated by researchers with opposing scientific observations. The Perspectives in this virtual special issue highlight the past, present, and future for each of these complex problems in polymer science. As we started writing this Editorial on ACS Polymers Au’s “Grand Challenges in Polymer Science”, it dawned on us that this issue comes exactly five years after Tim Lodge, then Editor-in-Chief of Macromolecules, penned his Editorial “Celebrating 50 years of Macromolecules”. (1) In his retrospective and forward-looking Editorial, he presented his thoughts on the “top ten technological and intellectual achievements” in polymer science over the past five decades as well as the “top ten current challenges” in polymer science that remained to be solved. Table 1 below lists these top ten current challenges from his Editorial. List taken from Table 3 of the Macromolecules Editorial by Tim Lodge in 2017, DOI: 10.1021/acs.macromol.7b02507. Unsurprisingly, many of the problems presented in the Perspectives in this ACS Polymers Auvirtual special issue fall under one or more of these ‘top ten challenges’ (Table 1). Additionally, these Perspectives capture recent advances in the past five years since that Editorial by Lodge, and present the current critical needs for new experimental and computational approaches to find answers to the many unsolved complex questions in polymer science. In this Editorial, we briefly summarize the topic(s) covered in each of these six Perspectives, along with quotes from the lead author and/or statements from their Perspective. We also share our personal views on why we think these are important problems and highlight with bold-italicized phrases the Grand Challenges in Polymer Science that we think each Perspective connects to. We start with the Perspective by Glenn Fredrickson and co-workers [DOI: 10.1021/acspolymersau.2c00026] titled “Ionic Compatibilization of Polymers” (Figure 1). Fredrickson says, “The compatibilization of immiscible polymers has been a central theme since the genesis of polymer science and technology. Underappreciated, however, is the use of ionic bonds or ionic correlations. Vast categories of dissimilar polymers can be homogenized using this strategy, modifying not only mechanical, optical, and electronic properties, but processability.” We believe that with the growing number of new processing techniques involved in high-throughput manufacturing of multicomponent polymer materials, where incompatible polymer chemistries are blended/layered, compatibilization of those interfaces between immiscible polymer chemistries will continue to be an important problem to address. This Perspective presents some solutions to improve compatibilization within multicomponent blends of ion-containing polymers and ways to use that knowledge to engineer new and improved polymer-based electronics. Figure 1. Table of Contents Image from “Ionic Compatibilization of Polymers” [DOI: 10.1021/acspolymersau.2c00026]. Fredrickson et al. also discuss how ionic compatibilization can be useful in plastic waste upcycling, which we believe is a significant grand challenge in polymer science. Polyolefin waste, which is composed primarily of isotactic polypropylene (iPP) and various grades of polyethylenes (PE), constitutes a large fraction of the plastics manufactured globally. Isolating the individual iPP and PE components in the waste stream is a challenge. When molten, mixtures of iPP and PE phase separate into macroscopic iPP and PE-rich domains; in solid-state, the interfaces between these dissimilar domains exhibit poor entanglement leading to brittle materials. Fredrickson et al. present alternative approaches involving the ionic compatibilization of these interfaces and discuss the cost implications of such procedures. They conclude with this statement: “Evidently, the level of ionic modification required for strong interfaces and materials, the chemistries used to install such (ionic) functionality, and the optimal selection of acid, base, or salt units are subjects that will all require significant fundamental research”. motivating future research in this direction. The Perspective by Rachel Segalman and co-workers [DOI: 10.1021/acspolymersau.2c00024] titled “Decoupling Ion Transport and Matrix Dynamics to Make High Performance Solid Polymer Electrolytes” (Figure 2) tackles the subject of ion transport through solid polymer electrolytes (SPEs). Nanostructured SPEs provide a promising alternative route to homogeneous liquid electrolytes because SPEs can achieve high ionic conductivity and selectivity. Design of effective SPEs requires a fundamental understanding of ion motion in polymer materials, which depends on a complex “interplay of intrachain transport, interchain hopping, and co-diffusion of segments and ions.” As a result, understanding ion transport is very much coupled with understanding polymer dynamics and segmental relaxation time (i.e., glassy dynamics in polymers). However, “balancing the low glass transition temperature as well as other requirements of an electrolyte presents a major challenge, particularly since mechanical robustness is generally a major justification for choosing a polymer over a liquid electrolyte.” This Perspective by Segalman and co-workers presents alternative strategies one could use to decouple the polymer matrix dynamics and ion transport. We think identifying approaches to independently control multiple coupled phenomena (e.g., ion transport and glass transition) for creation of new and improved polymeric materials for batteries and (ion-selective) membranes are substantial grand challenges for the polymer community to address. Figure 2. Table of Contents image from “Decoupling Ion Transport and Matrix Dynamics to Make High Performance Solid Polymer Electrolytes” [DOI: 10.1021/acspolymersau.2c00024]. The Perspective written by Tim Lodge [DOI: 10.1021/acspolymersau.2c00033] is titled “Dynamics and Equilibration Mechanisms in Block Copolymer Particles” (Figure 3). Lodge writes, “Self-assembly of block copolymers into interesting and useful nanostructures, in both solution and bulk, is a vibrant research area. Nanoparticles prepared by block copolymer self-assembly exhibit structures that are often not at equilibrium. A quantitative understanding of the mechanisms by which equilibrium is approached is still lacking, and presents a rich challenge for theory, simulation, and experiment.” This Perspective on the classic block copolymer self-assembly problem highlights newer unsolved/partially solved issues related to understanding and tailoring non-equilibrium effects of processing to achieve desired nanostructures in polymers. We think this Perspective also nicely highlights the power of structural characterization techniques like time-resolved small-angle neutron scattering, liquid-phase TEM, and the combination of simulations and experiments to better understand time evolution of macromolecular assembled structures near and far from equilibrium. Figure 3. Table of Contents Image from “Dynamics and Equilibration Mechanisms in Block Copolymer Particles” [DOI: 10.1021/acspolymersau.2c00033]. Understanding nonequilibrium effects in polymers is not only an experimental challenge but also a quest in molecular simulations. We quote Friederike Schmid: “The (next) big challenge in polymer science is to gain a comprehensive and predictive understanding of the behavior of polymeric systems over all relevant scales and up to very late times, close to and far from equilibrium.″ We think this computational challenge can be partly addressed through bridging of scales–molecular to continuum. Schmid’s Perspective titled “Understanding and Modeling Polymers: The Challenge of Multiple Scales” [DOI: 10.1021/acspolymersau.2c00049] (Figure 4) describes popular models that are used to study polymers at different length scales and the strategies (e.g., static and dynamic coarse-graining methods and multiresolution approaches) to bridge across different scales. Figure 4. Table of Contents Image from “Understanding and Modeling Polymers: The Challenge of Multiple Scales” [DOI: 10.1021/acspolymersau.2c00049]. Highlighting the power of molecular simulations, Lodge said in his 2017 Editorial that “hardware and current algorithms have elevated simulations to the level of an essential family of techniques, both for fundamental understanding and for prediction.” [DOI: 10.1021/acs.macromol.7b02507]. We agree with that sentiment completely. We also believe that, in the past 5–10 years, researchers in the polymer community have begun to see the tremendous value not only of physics-based (e.g., molecular simulations) methods but also of data-driven computational methods (e.g., machine learning) for predicting new polymer chemical designs, elucidating new polymer physics, in objective interpretation of characterization data, and establishing design-nanostructure–property relationships. Debra Audus and Tyler Martin’s Perspective points toward key questions and methodological needs within the growing subfield of data-driven polymer science [DOI: 10.1021/acspolymersau.2c00053] (Figure 5). Quoting Audus and Martin, “Polymer research driven by machine learning has made tremendous progress in the past five years, but barriers remain. The movement toward Open Science offers many opportunities to advance the field and address key challenges in polymer machine learning, such as data scarcity, and data quality. A culture shift where we become more collaborative and more open in data and code, while building capabilities in autonomous science, use of domain knowledge, and uncertainty quantification could enable unprecedented progress.” Figure 5. Table of Contents Image from “Emerging Trends in Machine Learning: A Polymer Perspective” [DOI: 10.1021/acspolymersau.2c00053]. Based on the two Perspectives from Schmid, and Audus and Martin, and personal views (including biases of yours truly, Jayaraman), we feel that the combination of physics-based and data-driven computational methods (e.g., linking theory and machine learning or molecular simulations and machine learning) as well as the combination of computations and experiments for automation in polymer science (e.g., machine learning-driven synthesis of new polymers, machine learning enabled fast and automated characterization) are meaningful grand challenges for the polymer community. With the growing influence of artificial intelligence (AI) in chemical and materials-focused industries, it is vital to find ways to integrate physics, chemistry, and machine learning in our pursuit for finding answers to complex new questions as the polymer field continues to evolve. How could there be a virtual special issue on the grand challenges in polymer science without a Perspective focused on polymerization? All subfields of polymer science (polymer physics, polymer theory, simulations, machine learning, polymer processing, polymer engineering) rely on robust and controllable polymerization methods. The Perspective from Nikos Hadjichristidis‬‬‬‬‬ [DOI: 10.1021/acspolymersau.2c00058] (Figure 6) titled “Quo Vadis Carbanionic Polymerization?” presents “significant achievements, current status, where it is going (Quo Vadis) and what the future holds for” living anionic polymerization of vinyl monomers. We quote Hadjichristidis: “Carbanionic polymerization is, without any doubt, the best method to design and produce well-defined polymers with different macromolecular architectures. It paved the way for other controlled/living polymerizations and industries when precise structures were needed. On the other hand, controlled/living polymerizations paved the way for simplicity. The next big challenge is to find a way to simplify carbanionic polymerization so that it is accessible to more laboratories and industrial products.” Along with the advances in anionic polymerization, great strides have also been made over the past decades in refining other polymerization strategies, such as radical and carbocation-based processes as well as catalytic polymerizations, toward the preparation of precisely defined polymers. The quest for scalable and sustainable polymer synthesis methods that enable precise control over monomer sequence, molecular weight, and architecture, however, continues to be a grand challenge. Figure 6. Table of Contents Image from “Quo Vadis Carbanionic Polymerization?” [DOI: 10.1021/acspolymersau.2c00058]. Table 2 lists all of the grand challenges we have identified from the Perspectives in this virtual special issue. We note that the problems highlighted in these six Perspectives only constitute a partial list of the grand challenges we face as polymer researchers. There are additional topics that are “Grand Challenges in Polymer Science”, including (but not limited to) new and improved polymers for personalized medicine and sustainable, cheap, and environment-friendly new commodity plastics. We hope to have leading experts in these subfields share their perspectives on these important topics in the near future. We also hope to have Perspectives and Editorials published in ACS Polymers Au on how we as a community can do better in (a) tackling mental health-related challenges that many researchers at all career stages face and (b) improving diversity, equity, inclusion, and respect (DEIR) in our workplaces. Many consider these to be important social issues but, unfortunately, treat them as issues separate from education and research. In contrast, we believe that these are closely coupled, because the health and welfare of our current and next generation of researchers are closely linked to them realizing their scientific potential and fostering their creativity to develop innovative sustainable solutions for the many Grand Challenges in Polymer Science. The 2022 Nobel Laureate Carolyn Bertozzi, Editor-in-Chief of ACS Central Science, has shared in her speeches, after receiving the 2022 Nobel Prize, how diversity, equity, inclusion, and respect toward different cultures and backgrounds in her lab fostered true creativity and innovation. So, we wrap up this Editorial with an inspirational quote from her: “Diversity powers creativity and advances science.” (2) We thank you, the readers, for reading this Editorial, and we hope you are as inspired as we were reading the Perspectives in this first Grand Challenges in Polymer Sciencevirtual special issue. We thank the authors for their hard work and thoughtfulness as they prepared these Perspectives. Finally, as always, we are grateful to the reviewers for their time and effort in constructively critiquing these Perspectives during peer review. This article references 2 other publications. This article has not yet been cited by other publications. Figure 1. Table of Contents Image from “Ionic Compatibilization of Polymers” [DOI: 10.1021/acspolymersau.2c00026]. Figure 2. Table of Contents image from “Decoupling Ion Transport and Matrix Dynamics to Make High Performance Solid Polymer Electrolytes” [DOI: 10.1021/acspolymersau.2c00024]. Figure 3. Table of Contents Image from “Dynamics and Equilibration Mechanisms in Block Copolymer Particles” [DOI: 10.1021/acspolymersau.2c00033]. Figure 4. Table of Contents Image from “Understanding and Modeling Polymers: The Challenge of Multiple Scales” [DOI: 10.1021/acspolymersau.2c00049]. Figure 5. Table of Contents Image from “Emerging Trends in Machine Learning: A Polymer Perspective” [DOI: 10.1021/acspolymersau.2c00053]. Figure 6. Table of Contents Image from “Quo Vadis Carbanionic Polymerization?” [DOI: 10.1021/acspolymersau.2c00058]. This article references 2 other publications.

Polymeric mixed ionic-electronic conductors (MIECs) are of broad interest in the field of energy storage and conversion, optoelectronics, and bioelectronics. A class of polymeric MIECs are conjugated polyelectrolytes (CPEs), which possess a π-conjugated backbone imparting electronic transport characteristics along with side chains composed of a pendant ionic group to allow for ionic transport. Here, our study focuses on the humidity-dependent structure–transport properties of poly[3-(potassium-n-alkanoate) thiophene-2,5-diyl] (P3KnT) CPEs with varied side-chain lengths of n = 4–7. UV–vis spectroscopy along with electronic paramagnetic resonance (EPR) spectroscopy reveals that the infiltration of water leads to a hydrated, self-doped state that allows for electronic transport. The resulting humidity-dependent ionic conductivity (σi) of the thin films shows a monotonic increase with relative humidity (RH) while electronic conductivity (σe) follows a non-monotonic profile. The values of σe continue to rise with increasing RH reaching a local maximum after which σe begins to decrease. P3KnTs with higher n values demonstrate greater resiliency to increasing RH before suffering a decrease in σe. This drop in σe is attributed to two factors. First, disruption of the locally ordered π-stacked domains observed through in situ humidity-dependent grazing incidence wide-angle X-ray scattering (GIWAXS) experiments can account for some of the decrease in σe. A second and more dominant factor is attributed to the swelling of the amorphous domains where electronic transport pathways connecting ordered domains are impeded. P3K7T is most resilient to swelling (based on ellipsometry and water uptake measurements) where sufficient hydration allows for high σi (1.0 × 10–1 S/cm at 95% RH) while not substantially disrupting σe (1.7 × 10–2 S/cm at 85% RH and 8.0 × 10–3 S/cm at 95% RH). Overall, our study highlights the complexity of balancing electronic and ionic transport in hydrated CPEs.

Conventional cryopreservation solutions rely on the addition of organic solvents such as DMSO or glycerol, but these do not give full recovery for all cell types, and innovative cryoprotectants may address damage pathways which these solvents do not protect against. Macromolecular cryoprotectants are emerging, but there is a need to understand their structure–property relationships and mechanisms of action. Here we synthesized and investigated the cryoprotective behavior of sulfoxide (i.e., “DMSO-like”) side-chain polymers, which have been reported to be cryoprotective using poly(ethylene glycol)-based polymers. We also wanted to determine if the polarized sulfoxide bond (S+O– character) introduces cryoprotective effects, as this has been seen for mixed-charge cryoprotective polyampholytes, whose mechanism of action is not yet understood. Poly(2-(methylsulfinyl)ethyl methacrylate) was synthesized by RAFT polymerization of 2-(methylthio)ethyl methacrylate and subsequent oxidation to sulfoxide. A corresponding N-oxide polymer was also prepared and characterized: (poly(2-(dimethylamineoxide)ethyl methacrylate). Ice recrystallization inhibition assays and differential scanning calorimetry analysis show that the sulfoxide side chains do not modulate the frozen components during cryopreservation. In cytotoxicity assays, it was found that long-term (24 h) exposure of the polymers was not tolerated by cells, but shorter (30 min) incubation times, which are relevant for cryopreservation, were tolerated. It was also observed that overoxidation to the sulfone significantly increased the cytotoxicity, and hence, these materials require a precision oxidation step to be deployed. In suspension cell cryopreservation investigations, the polysulfoxides did not increase cell recovery 24 h post-thaw. These results show that unlike hydrophilic backboned polysulfides, which can aid cryopreservation, the installation of the sulfoxide group onto a polymer does not necessarily bring cryoprotective properties, highlighting the challenges of developing and discovering macromolecular cryoprotectants.

Herein, N-heterocyclic olefins (NHOs) are utilized as catalysts for the ring-opening polymerization (ROP) of functional aliphatic carbonates. This emerging class of catalysts provides high reactivity and rapid conversion. Aiming for the polymerization of monomers with high side chain functionality, six-membered carbonates derived from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) served as model compounds. Tuning the reactivity of NHO from predominant side chain transesterification at room temperature toward ring-opening at lowered temperatures (−40 °C) enables controlled ROP. These refined conditions give narrowly distributed polymers of the hydrophobic carbonate 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MTC-OBn) (Đ < 1.30) at (pseudo)first-order kinetic polymerization progression. End group definition of these polymers demonstrated by mass spectrometry underlines the absence of side reactions. For the active ester monomer 5-methyl-5-pentafluorophenyloxycarbonyl-1,3-dioxane-2-one (MTC-PFP) with elevated side chain reactivity, a cocatalysis system consisting of NHO and the Lewis acid magnesium iodide is required to retune the reactivity from side chains toward controlled ROP. Excellent definition of the products (Đ < 1.30) and mass spectrometry data demonstrate the feasibility of this cocatalyst approach, since MTC-PFP has thus far only been polymerized successfully using acidic catalysts with moderate control. The broad feasibility of our findings was further demonstrated by the synthesis of block copolymers for bioapplications and their successful nanoparticular assembly. High tolerability of NHO in vitro with concentrations ranging up to 400 μM (equivalent to 0.056 mg/mL) further emphasize the suitability as a catalyst for the synthesis of bioapplicable materials. The polycarbonate block copolymer mPEG44-b-poly(MTC-OBn) enables physical entrapment of hydrophobic dyes in sub-20 nm micelles, whereas the active ester block copolymer mPEG44-b-poly(MTC-PFP) is postfunctionalizable by covalent dye attachment. Both block copolymers thereby serve as platforms for physical or covalent modification of nanocarriers for drug delivery.

With DNA-based nanomaterials being designed for applications in cellular environments, the need arises to accurately understand their surface interactions toward biological targets. As for any material exposed to protein-rich cell culture conditions, a protein corona will establish around DNA nanoparticles, potentially altering the a-priori designed particle function. Here, we first set out to identify the protein corona around DNA origami nanomaterials, taking into account the application of stabilizing block co-polymer coatings (oligolysine-1kPEG or oligolysine-5kPEG) widely used to ensure particle integrity. By implementing a label-free methodology, the distinct polymer coating conditions show unique protein profiles, predominantly defined by differences in the molecular weight and isoelectric point of the adsorbed proteins. Interestingly, none of the applied coatings reduced the diversity of the proteins detected within the specific coronae. We then biased the protein corona through pre-incubation with selected proteins and show significant changes in the cell uptake. Our study contributes to a deeper understanding of the complex interplay between DNA nanomaterials, proteins, and cells at the bio-interface.

Polysulfamides are the −SO2– analogues of polyureas and form an intriguing family of polymers containing hydrogen-bond donor and acceptor groups. However, unlike polyureas, their physical properties are mostly unknown because of the scarcity of synthetic methods to access such polymers. Herein, we report an expedient synthesis of AB monomers for the synthesis of polysulfamides via Sulfur(VI) Fluoride Exchange (SuFEx) click polymerization. Upon optimization of the step-growth process, a variety of polysulfamides were isolated and characterized. The versatility of the SuFEx polymerization allowed structural modulation of the main chain through the incorporation of aliphatic or aromatic amines. While all synthesized polymers presented high thermal stability via thermogravimetric analysis, the glass-transition temperature and crystallinity were shown to be highly tied to the structure of the backbone between repeating sulfamide units through differential scanning calorimetry and powder X-ray diffraction. Careful analysis via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and X-ray crystallography also revealed the formation of macrocyclic oligomers during the polymerization of one AB monomer. Finally, two protocols were developed to efficiently degrade all synthesized polysulfamides through either chemical recycling for polymers derived from aromatic amines or oxidative upcycling for those based on aliphatic amines.

It is our pleasure to write this Editorial for the ACS Polymers Au 2022 Rising Stars in Polymers virtual special issue. This virtual special issue is a collection of peer-reviewed Articles, Perspectives, and Reviews presenting impactful research in polymer science and engineering, from laboratories led by 12 outstanding independent early career researchers from around the world. We hope you enjoy learning about these principal investigators and their laboratories’ current research interests. ACS Polymers Au’s 2022 Rising Stars in Polymers. Dr. Shrayesh N. Patel is currently an Assistant Professor in the Pritzker School of Molecular Engineering at the University of Chicago. He holds a joint appointment in the Chemical Sciences and Engineering Division at Argonne National Lab, and is also a member of the Joint Center for Energy Storage Research (JCESR) – a DOE Energy Innovation Hub. Dr. Patel completed his undergraduate degree at the Georgia Institute of Technology in Chemical and Biomolecular Engineering in 2007, then received his Ph.D. in Chemical Engineering from the University of California, Berkeley in 2013 under the supervision of Dr. Nitash P. Balsara. Before joining the University of Chicago, he was a postdoctoral research associate in the Materials Research Laboratory at the University of California, Santa Barbara under the supervision of Dr. Michael Chabinyc and Dr. Edward Kramer. Dr. Patel’s research interests focus on enabling polymers for sustainable energy systems through fundamental understanding of charge and mass transport, relevant to energy storage and conversion devices such as lithium-ion and beyond lithium-ion batteries, redox flow batteries, and thermoelectrics. Overall, his research expertise lies at the interface of polymer science and engineering, electrochemistry, and organic electronics. You can learn about his group’s research by visiting: http://pme.uchicago.edu/group/patel-group. His Article for this issue is titled “Structure–Transport Properties Governing the Interplay in Humidity-Dependent Mixed Ionic and Electronic Conduction of Conjugated Polyelectrolytes”. Article DOI:10.1021/acspolymersau.2c00005. Dr. Miao Hong is currently Full Professor of Chemistry in the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences. She obtained her B.S. in Chemistry at Northeastern Normal University in 2007 and received a Ph.D. degree in Polymer Chemistry and Physics in 2013 under the supervision of Dr. Yuesheng Li from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. After a four-year postdoctoral stint at Colorado State University with Dr. Eugene Y.-X. Chen, Dr. Hong joined the Shanghai Institute of Organic in the Chemistry Chinese Academy of Sciences in 2017. Her group’s research is centered on polymer science, catalytic chemistry, green and sustainable chemistry. One of her main interests is the development of new catalysts and novel methodologies for the synthesis of sustainable polymers with controlled structures from renewable feedstocks. You can learn about Dr. Miao Hong and her research by visiting: http://miaohong.sioc.ac.cn. Her Article for this issue is titled “Zinc-Mediated Allylation-Lactonization One-Pot Reaction to Methylene Butyrolactones: Renewable Monomers for Sustainable Acrylic Polymers with Closed-Loop Recyclability”. Article DOI: 10.1021/acspolymersau.2c00001. Dr. Helen Tran is currently an Assistant Professor at the University of Toronto in the Department of Chemistry (cross-appointed in the Department of Chemical Engineering). She received her B.S. in Chemistry with a minor in Chemical Engineering from UC Berkeley in 2009, conducting undergraduate research with Dr. Tsu-Jae King Liu (Electrical Engineering, Berkeley). In 2009–2011, she was a postbaccalaureate fellow in Dr. Ronald Zuckermann’s research group at the Molecular Foundry at Berkeley National Laboratories, exploring the self-assembly of biomimetic polymers into 2D nanosheets. She completed her Ph.D. at Columbia University in 2016 under the supervision of Dr. Luis Campos, broadly investigating hierarchical ordering and periodic patterning in block copolymer systems. She was an Intelligence Community postdoctoral fellow at Stanford University under the mentorship of Dr. Zhenan Bao in the Chemical Engineering Department 2016–2020, where she worked on stretchable and biodegradable electronics. Dr. Tran is interested in building next-generation electronics that will autonomously respond to local stimuli for applications in environmental monitoring, advanced consumer products, and health diagnostics for personalized therapy. Dr. Tran’s team leverages a rich palette of polymer chemistry to design new materials encoded with information for self-assembly, degradability, and electronic transport. You can learn about Dr. Helen Tran and her research group by visiting: http://helen-t.com/. Her Perspective for this issue is titled “A Field Guide to Optimizing Peptoid Synthesis”. Article DOI: 10.1021/acspolymersau.2c00036. Dr. Lutz Nuhn is currently leading the Chair of Macromolecular Chemistry at the Julius-Maximilians-University in Würzburg, Germany. He studied biomedical chemistry at the Johannes Gutenberg-University in Mainz (Germany) and received his diploma degree in 2010. In 2008–2009, he worked in the laboratories of Dr. Robert Langer (MIT, USA). For his doctoral degree he studied in the group of Dr. Rudolf Zentel, and during summer 2013 also in the group of Dr. Kazunori Kataoka (University of Tokyo, Japan). In 2014, he was awarded a Ph.D. with distinction from the Johannes Gutenberg-University, Mainz. For his postdoctoral research, he worked with Dr. Bruno De Geest and Dr. Richard Hoogenboom at Ghent University. In summer 2017, Dr. Nuhn joined the group of Dr. Tanja Weil at the Max Planck Institute for Polymer Research in Mainz. In April 2022 he was appointed as full Professor at the Julius-Maximilians-University in Würzburg. His research focuses on the synthesis and application of multiresponsive and degradable polymeric nanocarrier systems, especially for immunotherapeutic purposes. You can learn about his group and research at: http://www.chemie.uni-wuerzburg.de/mmc/. His Article for this issue is titled “Nontoxic N-Heterocyclic Olefin Catalyst Systems for Well-Defined Polymerization of Biocompatible Aliphatic Polycarbonates”. Article DOI: 10.1021/acspolymersau.2c00017. Dr. Jian Qin is currently an Assistant Professor in the Department of Chemical Engineering at Stanford University. He received his B.S. (2002) and M.S. (2004) degrees in Materials Science from Tsinghua University, and his Ph.D. (2009) in Materials Science from University of Minnesota under the supervision of Dr. David Morse and Dr. Frank Bates. He worked as postdoctoral fellow with Dr. Scott Milner at Penn State University (2009–2012), and with Dr. Juan de Pablo at the University of Chicago (2012–2015). His research focuses on theoretical modeling of ionic and electronically active polymers, the rheology of entangled polymers, and associative polymers. More information about his group and research can be found at: http://web.stanford.edu/~jianq/. His Article for this issue is titled “Distribution Cutoff for Clusters near the Gel Point”. Article DOI: 10.1021/acspolymersau.2c00020. Dr. Joseph (Joe) P. Patterson is currently an Assistant Professor in the Department of Chemistry at the University of California, Irvine. He received his master’s degree in Chemistry from the University of York, UK in 2009. In 2013, he completed his Ph.D. in Chemistry under the guidance of Dr. Rachel O’Reilly at the University of Warwick, UK. He worked as a postdoctoral researcher at the University of California, San Diego under the guidance of Dr. Nathan Gianneschi. He also worked in the Laboratory of Materials and Interface Chemistry at the Eindhoven University of Technology, under the guidance of Dr. Nico Sommerdijk. His research includes the development of new materials through a deep understanding of their structural dynamics. He is particularly interested in the development and application of advanced electron microscopy methods. You can learn about Dr. Patterson and his research group at http://www.thepattersonlab.com. His Article for this issue is titled “Gaining Structural Control by Modification of Polymerization Rate in Ring-Opening Polymerization-Induced Crystallization-Driven Self-Assembly”. Article DOI: 10.1021/acspolymersau.2c00027. Dr. Xiangcheng Pan is currently an Associate Professor and principal investigator in the State Key Laboratory of Molecular Engineering of Polymers and the Department of Macromolecular Science at Fudan University. He received a B.S. degree (Magna Cum Laude) from Eastern Washington University in 2009. He obtained his Ph.D. in organic chemistry from the University of Pittsburgh under the guidance of Dr. Dennis P. Curran in 2014. He then spent three years doing postdoctoral research with the group of Dr. Krzysztof Matyjaszewski at Carnegie Mellon University. In 2017, he returned to China and joined Fudan University. His research group at Fudan University has been focused on developing novel radical polymerization methods and heteroatom-involved controlled/precise polymer synthesis. More information about Dr. Pan and his research can be found at http://www.panxlab.com. His Review for this issue is titled “N-Coordinated Organoboron in Polymer Synthesis and Material Science”. Article DOI: 10.1021/acspolymersau.2c00046. Dr. Louis M. Pitet is currently an Assistant Professor at Hasselt University, working in the Institute for Materials Research (IMO), located in Hasselt, Belgium. He obtained his bachelor’s degree in chemistry from the Colorado School of Mines working with Dr. Daniel Knauss. He went on to obtain a Ph.D. in 2011 in the Chemistry department at the University of Minnesota under the supervision of Dr. Marc Hillmyer. Dr. Pitet moved to The Netherlands for a postdoctoral fellowship in the Institute for Complex Molecular Systems at the Eindhoven University of Technology, working with Dr. Bert Meijer. Since 2018, he has been leading his research group in Hasselt focusing on understanding processing–structure–property relationships in complex functional polymer constructs. His group is interested in the fundamental relationships that are critical for global challenges in polymer science, including reutilizing plastic waste streams, creating smart scaffolds for tissue engineering, and improving processing–manufacturing efficiency with advanced reactors. You can learn about his group and research at www.uhasselt.be/en/onderzoeksgroepen-en/imo-imomec-afp/people/prof-dr-louis-pitet. His Article for this issue is titled “Utility of Chemical Upcycling in Transforming Postconsumer PET to PBT-Based Thermoplastic Copolyesters Containing a Renewable Fatty-Acid-Derived Soft Block”. Article DOI: 10.1021/acspolymersau.2c00019. Dr. Davide Michieletto is currently a Royal Society University Research Fellow & Reader at the University of Edinburgh. He received a Physics degree from the University of Padova (Italy) in 2009 (BSc) and a MSc in Theoretical Physics again from the University of Padova in 2011. He then moved to the University of Warwick (UK) where he first received a MSc degree in Complexity Science (2012), and then he did a Ph.D. in Physics and Complexity Science under the supervision of Dr. Matthew Turner (2012–2015). He subsequently worked as a postdoctoral researcher with Dr. Davide Marenduzzo and Dr. Nick Gilbert on computational models of genome organization and on super-resolution microscopy of chromatin structure (2016–2019). In 2019, Dr. Michieletto worked with Dr. Dorothy Buck at the University of Bath on DNA topology. Dr. Michieletto’s research is inspired by how sophisticated proteins exert exquisite topological and mechanical control over the organization and function of the DNA in our cells, and his work aims to discover novel topological soft materials and complex fluids with exotic viscoelastic properties. You can learn more about his research from his group Web site: http://www2.ph.ed.ac.uk/http://web.stanford.edu/~jianq/dmichiel/index.html. His Article for this issue is titled “Geometric Predictors of Knotted and Linked Arcs. Article DOI: 10.1021/acspolymersau.2c00021. Dr. Maxwell Robb is currently an Assistant Professor of Chemistry in the Division of Chemistry and Chemical Engineering at Caltech. He obtained his B.S. in Chemistry (2009) from the Colorado School of Mines where he began research in synthetic polymer chemistry under the guidance of Dr. Daniel M. Knauss. Max carried out his doctoral studies in the laboratories of Dr. Craig J. Hawker at the University of California, Santa Barbara, earning his Ph.D. in Chemistry in 2014. Dr. Robb conducted postdoctoral research with Dr. Jeffrey S. Moore at the University of Illinois, Urbana–Champaign as a Beckman Institute Postdoctoral Fellow from 2014–2017. In September 2017, he joined the faculty at Caltech. Research in Dr. Robb’s group seeks to advance fundamental understanding of mechanical force transduction at the molecular level and develop strategies to create force-responsive molecules and functional polymeric materials. You can learn more about Dr. Maxwell Robb and his group webpage at http://robbgroup.caltech.edu. His Article for this issue is titled “Competitive Activation Experiments Reveal Significantly Different Mechanochemical Reactivity of Furan–Maleimide and Anthracene–Maleimide Mechanophores”. Article DOI: 10.1021/acspolymersau.2c00047. Dr. Fiona L. Hatton is currently a Lecturer in Polymer Chemistry in the Department of Materials at Loughborough University. Dr. Hatton obtained a first class MChem degree in Medicinal Chemistry with Pharmacology from the University of Liverpool in 2010. She stayed at the University of Liverpool for her Ph.D. (2010–2014) which focused on the preparation of highly branched dendritic polymers, hyperbranched polydendrons, and using ATRP for biomedical applications, with Dr. Steve Rannard. In 2014, she joined the Division of Coating Technology, KTH Royal Institute of Technology, Stockholm as a postdoctoral researcher with Dr. Anna Carlmark and Dr. Eva Malmström. In 2016, Dr Hatton joined the group of Dr. Steve Armes at the University of Sheffield as a postdoctoral research associate, before taking up a permanent position at Loughborough University. Her research interests are in sustainable polymer science, for example reducing single use plastic by focusing on reuse systems, facilitated by the fluorescent labeling of packaging. Within this theme she also researches renewable monomer synthesis and their polymerization using aqueous radical polymerization techniques and also has interests in block copolymer self-assembly. You can learn about Dr. Hatton and her research group from http://hattonpolymergroup.com/. Her Review for this issue is titled “Enabling the Polymer Circular Economy: Innovations in Photoluminescent Labeling of Plastic Waste for Enhanced Sorting”. Article DOI: 10.1021/acspolymersau.2c00040. Dr. Danielle J. Mai is currently an Assistant Professor of Chemical Engineering at Stanford University. She earned her B.SE in Chemical Engineering from the University of Michigan in 2011 and her Ph.D. in Chemical Engineering from the University of Illinois at Urbana–Champaign in 2016, under the guidance of Dr. Charles M. Schroeder. After that, she became the Arnold O. Beckman Postdoctoral Fellow in Dr. Bradley D. Olsen’s group at MIT from 2016 to 2019. Dr. Mai’s lab integrates precise biopolymer engineering with multiscale experimental characterization to advance biomaterials development and to enhance fundamental understanding of soft matter physics. Her current research interests include engineering calcium-responsive polypeptides as muscle-mimetic materials, investigating graft biopolymers to elucidate bio- lubrication mechanisms, and developing polymer nanocomposites to 3D-print biocompatible hydrogels. You can learn about Dr. Danielle Mai and her research group from http://mailab.stanford.edu. Her Article for this issue is titled “Gelation dynamics during photo-cross-linking of polymer nanocomposite hydrogels”. Article DOI: 10.1021/acspolymersau.2c00051. We extend our sincere thanks and congratulations to these Rising Stars. We are grateful to the referees for their input in reviewing these manuscripts and to you, our readers, for your support. We hope you enjoy reading the contributions from these outstanding investigators and members of their teams as much as we have. This article has not yet been cited by other publications. ACS Polymers Au’s 2022 Rising Stars in Polymers.

Inspired by how certain proteins “sense” knots and entanglements in DNA molecules, here, we ask if local geometric features that may be used as a readout of the underlying topology of generic polymers exist. We perform molecular simulations of knotted and linked semiflexible polymers and study four geometric measures to predict topological entanglements: local curvature, local density, local 1D writhe, and nonlocal 3D writhe. We discover that local curvature is a poor predictor of entanglements. In contrast, segments with maximum local density or writhe correlate as much as 90% of the time with the shortest knotted and linked arcs. We find that this accuracy is preserved across different knot types and also under significant spherical confinement, which is known to delocalize essential crossings in knotted polymers. We further discover that nonlocal 3D writhe is the best geometric readout of the knot location. Finally, we discuss how these geometric features may be used to computationally analyze entanglements in generic polymer melts and gels.

Polymer materials are multiscale systems by definition. Already the description of a single macromolecule involves a multitude of scales, and cooperative processes in polymer assemblies are governed by their interplay. Polymers have been among the first materials for which systematic multiscale techniques were developed, yet they continue to present extraordinary challenges for modellers. In this Perspective, we review popular models that are used to describe polymers on different scales and discuss scale-bridging strategies such as static and dynamic coarse-graining methods and multiresolution approaches. We close with a list of hard problems which still need to be solved in order to gain a comprehensive quantitative understanding of polymer systems.

The assembly of ligand-functionalized (macro)monomers with suitable metal ions affords metallosupramolecular polymers (MSPs). On account of the reversible and dynamic nature of the metal–ligand complexes, these materials can be temporarily (dis-)assembled upon exposure to a suitable stimulus, and this effect can be exploited to heal damaged samples, to facilitate processing and recycling, or to enable reversible adhesion. We here report on the plasticization of a semicrystalline, stimuli-responsive MSP network that was assembled by combining a low-molecular-weight building block carrying three 2,6-bis(1′-methylbenzimidazolyl) pyridine (Mebip) ligands and zinc bis(trifluoromethylsulfonyl)imide (Zn(NTf2)2). The pristine material exhibits high melting (Tm = 230 °C) and glass transition (Tg ≈ 157 °C) temperatures and offers robust mechanical properties between these temperatures. We show that this regime can be substantially extended through plasticization. To achieve this, the MSP network was blended with diisodecyl phthalate. The weight fraction of this plasticizer was systematically varied, and the thermal and mechanical properties of the resulting materials were investigated. We show that the Tg can be lowered by more than 60 °C and the toughness above the Tg is considerably increased.

Chemically crosslinked elastomers are a class of polymeric materials with properties that render them useful as adhesives, sealants, and in other engineering applications. Poly(γ-methyl-ε-caprolactone) (PγMCL) is a hydrolytically degradable and compostable aliphatic polyester that can be biosourced and exhibits competitive mechanical properties to traditional elastomers when chemically crosslinked. A typical limitation of chemically crosslinked elastomers is that they cannot be reprocessed; however, the incorporation of dynamic covalent bonds can allow for bonds to reversibly break and reform under an external stimulus, usually heat. In this work, we study the dynamic behavior and mechanical properties of PγMCL elastomers synthesized from aliphatic dianhydride crosslinkers. The crosslinked elastomers in this work were synthesized using the commercially available crosslinkers, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride and three-arm hydroxy-telechelic PγMCL star polymers. Stress relaxation experiments on the crosslinked networks showed an Arrhenius dependence of viscosity with temperature with an activation energy of 118 ± 8 kJ/mol, which agrees well with the activation energy of transesterification exchange chemistry obtained from small molecule model studies. Dynamic mechanical thermal analysis and rheological experiments confirmed the dynamic nature of the networks and provided insight into the mechanism of exchange (i.e., associative or dissociative). Tensile testing showed that these materials can exhibit high strains at break and low Young’s moduli, characteristic of soft and strong elastomers. By controlling the exchange chemistry and understanding the effect of macromolecular structure on mechanical properties, we prepared the high-performance elastomers that can be potentially reprocessed at moderately elevated temperatures.

Polyproline is a material of great interest in biomedicine due to its helical scaffold of structural importance in collagen and mucins and its ability to gel and to change conformations in response to temperature. Appending of function-modulating chemical groups to such a material is desirable to diversify potential applications. Here, we describe the synthesis of high-molecular-weight homo, block, and statistical polymers of azide-functionalized proline. The azide groups served as moieties for highly efficient click-grafting, as stabilizers of the polyproline PPII helix, and as modulators of thermoresponsiveness. Saccharides and ethylene glycol were utilized to explore small-molecule grafting, and glutamate polymers were utilized to form polyelectrolyte bottlebrush architectures. Secondary structure effects of both the azide and click modifications, as well as lower critical solution temperature behavior, were characterized. The polyazidoprolines and click products were well tolerated by live human cells and are expected to find use in diverse biomedical applications.

A major objective of research in nanofluidics is to achieve better selectivity in manipulating the fluxes of nano-objects and in particular of biopolymers. Numerical simulations allow one to better understand the physical mechanisms at play in such situations. We performed hybrid mesoscale simulations to investigate the properties of polymers under flows in slit pores at the nanoscale. We use multiparticle collision dynamics, an algorithm that includes hydrodynamics and thermal fluctuations, to investigate the properties of fully flexible and stiff polymers under several types of flow, showing that Poiseuille flows and electroosmotic flows can lead to quantitatively and qualitatively different behaviors of the chain. In particular, a counterintuitive phenomenon occurs in the presence of an electroosmotic flow: When the monomers are attracted by the solid surfaces through van der Waals forces, shear-induced forces lead to a stronger repulsion of the polymers from these surfaces. Such focusing of the chain in the middle of the channel increases its flowing velocity, a phenomenon that may be exploited to separate different types of polymers.

It is widely accepted that moving from a linear to circular economy for plastics will be beneficial to reduce plastic pollution in our environment and to prevent loss of material value. However, challenges within the sorting of plastic waste often lead to contaminated waste streams that can devalue recyclates and hinder reprocessing. Therefore, the improvement of the sorting of plastic waste can lead to dramatic improvements in recyclate quality and enable circularity for plastics. Here, we discuss current sorting methods for plastic waste and review labeling techniques to enable enhanced sorting of plastic recyclates. Photoluminescent-based labeling is discussed in detail, including UV–vis organic and inorganic photoluminescent markers, infrared up-conversion, and X-ray fluorescent markers. Methods of incorporating labels within packaging, such as extrusion, surface coatings, and incorporation within external labels are also discussed. Additionally, we highlight some practical models for implementing some of the sorting techniques and provide an outlook for this growing field of research.

Embedding nanomaterials into polymer hydrogels enables the design of functional materials with tailored chemical, mechanical, and optical properties. Nanocapsules that protect interior cargo and disperse readily through a polymeric matrix have drawn particular interest for their ability to integrate chemically incompatible systems and to further expand the parameter space for polymer nanocomposite hydrogels. The properties of polymer nanocomposite hydrogels depend on the material composition and processing route, which were explored systematically in this work. The gelation kinetics of network-forming polymer solutions with and without silica-coated nanocapsules bearing polyethylene glycol (PEG) surface ligands were investigated using in situ dynamic rheology measurements. Network-forming polymers comprised either 4-arm or 8-arm star PEG with terminal anthracene groups, which dimerize upon irradiation with ultraviolet (UV) light. The PEG-anthracene solutions exhibited rapid gel formation upon UV exposure (365 nm); gel formation was observed as a crossover from liquid-like to solid-like behavior during in situ small-amplitude oscillatory shear rheology. This crossover time was non-monotonic with polymer concentration. Far below the overlap concentration (c/c* ≪ 1), spatially separated PEG-anthracene molecules were subject to forming intramolecular loops over intermolecular cross-links, thereby slowing the gelation process. Near the polymer overlap concentration (c/c* ∼ 1), rapid gelation was attributed to the ideal proximity of anthracene end groups from neighboring polymer molecules. Above the overlap concentration (c/c* > 1), increased solution viscosities hindered molecular diffusion, thereby reducing the frequency of dimerization reactions. Adding nanocapsules to PEG-anthracene solutions resulted in faster gelation than nanocapsule-free PEG-anthracene solutions with equivalent effective polymer concentrations. The final elastic modulus of nanocomposite hydrogels increased with nanocapsule volume fraction, signifying synergistic mechanical reinforcement by nanocapsules despite not being cross-linked into the polymer network. Overall, these findings quantify the impact of nanocapsule addition on the gelation kinetics and mechanical properties of polymer nanocomposite hydrogels, which are promising materials for applications in optoelectronics, biotechnology, and additive manufacturing.

BigSMILES, a line notation for encapsulating the molecular structure of stochastic molecules such as polymers, was recently proposed as a compact and readable solution for writing macromolecules. While BigSMILES strings serve as useful identifiers for reconstructing the molecular connectivity for polymers, in general, BigSMILES allows the same polymer to be codified into multiple equally valid representations. Having a canonicalization scheme that eliminates the multiplicity would be very useful in reducing time-intensive tasks like structural comparison and molecular search into simple string-matching tasks. Motivated by this, in this work, two strategies for deriving canonical representations for linear polymers are proposed. In the first approach, a canonicalization scheme is proposed to standardize the expression of BigSMILES stochastic objects, thereby standardizing the expression of overall BigSMILES strings. In the second approach, an analogy between formal language theory and the molecular ensemble of polymer molecules is drawn. Linear polymers can be converted into regular languages, and the minimal deterministic finite automaton uniquely associated with each prescribed language is used as the basis for constructing the unique text identifier associated with each distinct polymer. Overall, this work presents algorithms to convert linear polymers into unique structure-based text identifiers. The derived identifiers can be readily applied in chemical information systems for polymers and other polymer informatics applications.