Polymerization Method of Ethylhexyl methacrylate

Ethylhexyl methacrylate is an unsaturated carboxylic ester compound. At room temperature and under normal pressure, it appears as a colorless transparent liquid. It possesses the general physicochemical properties and polymerization characteristics typical of ester compounds. It is insoluble in water but miscible with most organic solvents. Ethylhexyl methacrylate can be prepared through the esterification condensation reaction between methacrylic acid and isooctanol. This compound is primarily used as a comonomer in organic glass (PMMA) production, where it enhances the plasticity of the organic glass. It is also widely applied in various industries, including coating resins, adhesives, lubricants, textile auxiliaries, papermaking, and fiber manufacturing.

Figure1: Picture of Ethylhexyl methacrylate

Polymerization Method

Ethylhexyl methacrylate (EHMA) was successfully polymerized via emulsion atom transfer radical polymerization (ATRP) using ethyl 2-bromoisobutyrate (EBiB) as the initiator and a catalyst system composed of copper bromide (CuBr) together with 4,4'-dinonyl-2,2'-bipyridyl (dNbpy). The effects of several key parameters—namely the type and concentration of surfactant, the reaction temperature, the molar ratio of monomer to initiator, and the addition of CuBr₂—were systematically investigated with respect to the livingness of the polymerization system, the control over polymer molecular weight, and the stability of the resulting latex. Among the various conditions tested, it was found that Ethylhexyl methacrylate (EHMA) polymerizations employing Tween 80 or Brij 98 as surfactants at 30 °C provided the most favorable latex stability. Under these optimized conditions, the polymer samples derived from Ethylhexyl methacrylate exhibited narrow molecular weight distributions (with Mw/Mn values in the range of 1.1–1.2), as well as linear relationships between the number-average molecular weight and monomer conversion. [1]

Preparation of adhesives

The researchers present the experimental results obtained from the emulsion atom transfer radical polymerization (ATRP) of Ethylhexyl methacrylate (EHMA). Recently, Ethylhexyl methacrylate has been the focus of several investigations due to its versatile polymerization behavior and promising material properties. Among the various potential applications, the researchers are particularly interested in the use of Ethylhexyl methacrylate as a precursor for adhesives, as the resulting poly(EHMA) exhibits a low glass transition temperature (Tg) of –10 °C. Furthermore, Ethylhexyl methacrylate is more polar compared to hydrocarbon-based elastomers, which endows it with good oil resistance and strong adhesion to a variety of substrates; additionally, it can readily undergo copolymerization with other methacrylate monomers. The primary objectives of this work are to investigate the control of molecular weight and latex stability of poly(EHMA) during the emulsion ATRP process, and to systematically examine the effects of various reaction parameters on the overall polymerization behavior. In general, one notable advantage of achieving a product with controlled molecular weight and narrow polydispersity is the resulting low content of volatile organic compounds (VOC). This advantage is particularly important for low-molecular-weight products, because if such a product were synthesized via conventional free-radical polymerization. [1]

Thermal behaviour of copolymers

Five copolymer samples containing different mole fractions of methyl methacrylate (MMA) and Ethylhexyl methacrylate (EHMA) were prepared via bulk polymerization at 70 °C using 0.2% benzoyl peroxide as the initiator. Ethylhexyl methacrylate, when copolymerized with MMA, significantly influences the resulting copolymer composition, which was determined by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Additionally, Ethylhexyl methacrylate plays a key role in determining the molecular weight of the copolymers, as measured by both gel permeation chromatography and viscosity measurements. Thermogravimetric experiments were conducted to evaluate the activation energy for the degradation of the copolymers, and it was observed that Ethylhexyl methacrylate-rich copolymers exhibited two to four distinct weight-loss reaction stages. Importantly, an increase in the content of 2-ethylhexyl methacrylate within the copolymer structure led to a noticeable decrease in thermal stability. [2]

Reference

[1] Eslami H, Zhu S. Emulsion atom transfer radical polymerization of 2-ethylhexyl methacrylate[J]. Polymer, 2005, 46(15): 5484-5493.

[2] Varma I K, Patnaik M, Choudhary V. Thermal behaviour of copolymers of methyl methacrylate and 2-ethylhexyl methacrylate[J]. Journal of thermal analysis, 1990, 36: 617-628.