Implementing miniemulsion photopolymerization for synthesis of waterborne biobased poly(thioethers) coatings

Abstract

Herein, miniemulsion photopolymerization is implemented as a useful tool for synthesis of waterborne poly(thioether) dispersions from biobased monomers isosorbide-based dithiol (3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(3-mercaptopropanoate) and diallyl (3R,3aR,6S,6aR)-3,6-bis(allyloxy)hexahydrofuro[3,2-b]furan and their combination with the petroleum-based dienes diallyl terephthalate, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5]undecane, and 1,4-bis(allyloxy)benzene. The synthetic process is optimized to achieve 30 % solids content latexes with weight average molecular weight ranging from 8.2 kg/mol to 136 kg/mol. The resulting poly(thioether) latexes yield consistent continuous polymer films after water evaporation at atmospheric conditions. Poly(thioether) films based on both biobased thiol and ene are soft and sticky, and thus, present insufficient mechanical properties for coating application. On the other hand, when biobased thiol was combined with petroleum based enes with aromatic and cyclic moieties within the structure, the obtained films are rigid and film forming. Only the film based on diallyl terephthalate diene present excellent balance of stiffness and flexibility, therefore with potential for coating application. Moreover, this film shows relatively good water sensitivity, with water uptake below 20 % after 11 days of water immersion and high gloss (above 80 gloss unit) measured at 60° angle of incidence. The properties are within the range of requirements for decorative coatings applications.