Preparation Of Latex With High Stability Against Electrolyte And Film With Controlled Microstrcutures Based On Vinylic Groups Functionalized RAFT Agent In Combination With Click Chemistry

Two kinds of amphiphilic macroRAFT agents with pendent alkenyl groups andcyclohexenyl groups were synthesized. They were used to mediate (mini)emulsionpolymerization, which produced latexes with stable microphase separation structure andwith surface-riched vinyl groups. The interfacial distribution profile of the vinyl groups wasdemonstrated through interfacially confined thiol-ene click chemistry (TEC). The colloidalstability against relative high electrolytic concentration and latex film with improvedmechanical properties are achieved through TEC. The main research works are outlined asfollows:The macroRAFT agent with pendent alkenyl groups can be used as a reactive surfactantto stabilize styrene miniemulsion and ab initio emulsion polymerization. The propagation ofalkenyl groups occurred exclusively during the early stage of miniemulsion polymerization,leading to coupling reaction between polymer chains and the positive deviation of molecularweights from the theoretical values. The conversion of monomer can reach at100%at the endof the reaction. In contrast, during ab initio emulsion polymerization, propagation of thealkenyl group was observed not only at the beginning but also at the end of polymerization.Furthermore, a phenomenon of “limiting monomer conversion” was observed. It wasdemonstrated the plasticization effect brought by co-stabilizer hexadecane in theminiemulsion polymerization bearing the primary responsibilities for the difference betweenthese two systems.The macroRAFT agent with pendent cyclohexenyl units can be also used as a reactivesurfactant in styrene miniemulsion polymerization. The cyclohexenyl units remain unreactedand the molecular weights follow with the theoretical values throughout the polymerization.The final conversion of styrene can get100%. The resulting polymers retained quantitative pendent cyclohexenyl functionalities with a density of1.79units per square nanometer at theparticle surface. The particle surface can be post-modified with nonionic hydrophilic chainsvia TEC reaction. In the case when the grafting density was1.03chains per square nanometer,the grafted PDMAAm chains increased particles’ critical coagulation concentration of sodiumchloride by one order of magnitude, compared with those particles without covalent-bondedPDMAAm.The PBA-b-PSt “shell-core” latex can be prepared by RAFT batch-semicontinuoustwo-stage miniemulsion polymerization mediated by the macroRAFT with pendentcyclohexenyl groups. The diameter of the particles decreased with the increase of the sodiumdodecyl sulfate concentration. Films with stable microphase separation structure can beprepared from these latexes experiencing TEC reactions. The efficiency of the TEC reactions,as well as the mechanical properties, of the films improved significantly with the decrease ofthe particle size.