Fabrication and morphological evolution of inverse core/shell structural latex particles of poly(vinyl acetate)/polystyrene by maleic anhydride grafting

In order to overcome the large differences in reactivity ratio and hydrophilicity between vinyl acetate (VAc) monomer and styrene (St) monomer and synthesize a stable poly(vinyl acetate)/polystyrene (PVAc/PS) inverse core/shell (ICS) structural emulsion, this paper presented a novel method to prepare PVAc/PS ICS structural latex particles. Maleic anhydride (MA) grafting, for the first time, was introduced to fabricate the ICS latex particles, where VAc monomer was used as the core monomer and St monomer as the shell monomer. By adjusting the core/shell (CS) ratio and MA content, the morphology of the particles could be controlled to have a regular evolution from strawberry-like to semi-wrapped and final ball-like. In addition, upon MA content exceeding 1 % (percentage of the total monomer), the secondary nucleation almost disappeared gradually. The resulting ICS particles had an average diameter approximately 330 nm and a controllable distribution. Further results of characterization such as phase separation structure, existence of thin transition layer, and special morphological feature of latex particle also demonstrated that this ICS structure had been fabricated successfully. The mechanism of formation was displayed as well.