Optimization and comparison of polysiloxane acrylic hybrid latex synthesis methods

Two methods were used to prepare polysiloxane-functionalized acrylic latexes via emulsion polymerization. Ethyl acrylate and 2-ethylhexyl acrylate were used in both methods as acrylic phase. In the first method, an acrylic core was prepared with addition of a coupling agent, 3-(trimethoxysilyl) propyl methacrylate, after which cyclic siloxane monomer (octamethylcyclotetrasiloxane) was reacted with the coupling agent. In the second method, a silane-terminated polysiloxane (H-PDMS) was reacted with ethylene glycol dimethacrylate, and then copolymerized with ethyl acrylate and 2-ethylhexyl acrylate in a batch emulsion polymerization. Particle size distribution and particle morphology were evaluated by using dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. Core-shell morphology was observed in TEM for the first preparation method as proposed. After film formation, surface tension, morphology and dynamic mechanical properties were investigated. Stratification of polysiloxane was examined by Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray (EDX). Energy dispersive X-ray data indicated that only the second preparation method had higher silicon content at film-air interface than film-substrate interface. In both methods, storage modulus and surface energy of latex films decreased after grafting polysiloxane.