A facile, robust, scalable and eco-friendly route as part of a relatively simple system to prepare polymer capsules has always been desired but remains challenging. Herein, a multifunctional, active, amphiphilic macromolecule, 1,1-diphenylethylene (DPE)-capped hydrolyzed poly(glycidyl methacrylate) (D-PGMA), was found to act as both the surfactant and the initiator in an interfacial emulsion polymerization process for polymer capsules. This simplified the emulsion system to only three components: water, monomer and D-PGMA. The interfacial distribution of amphiphilic D-PGMA and the controlled/living radical polymerization owing to the semi-quinoid structure were synergistically responsible for the formation of polymer capsules. Besides, by employing this method, microcapsules encapsulating phase change materials (PCMs) whose encapsulation ratio could be up to 92% were readily fabricated and possessed large heat storage capability and good thermal stability. We believe that this facile, robust, scalable and eco-friendly method will inspire new strategies for preparing polymeric capsules and will find promising application in the field of energy storage.