Polymeric nanosphere formed from temperature-responsive polymer composed of (N,N-dimethylamino)ethyl methacrylate and ethyl acrylamide

A nanosphere was formed from a temperature-responsive random copolymer of (N,N-dimethylamino)ethyl methacrylate (DMAEMA) and ethyl acrylamide (EAAm) without a crosslinker. When the copolymerization was performed in a water/ethanol solvent mixture (90/10 v/v %) above the lower critical-solution temperature of poly(DMAEMA-co-EAAm), the nanosphere was formed with the propagation of copolymerization. Atomic force microscopy analysis and dynamic light scattering both showed the formation of nanosphere and the size was decreased as the EAAm content increased in the copolymer. To illuminate this nanosphere formation phenomena, molecular dynamic simulations were performed with model polymer solutions. According to the analysis of the simulation trajectory, the ethyl groups of ethanol bind to the hydrophobic sites of poly(DMAEMA) or poly(DMAEMA-co-EAAm), and water molecules can bind preferentially to C double bond O groups that are abundant on the surface of the core, which is composed of oligomer and ethanol. This may enable the polymerization to proceed within the core, which is transformed into nanosphere.