Synthesis by RAFT of Amphiphilic Block and Comblike Cationic Copolymers and Their Use in Emulsion Polymerization for the Electrosteric Stabilization of Latexes

Abstract

A series of diblock and comblike copolymers based on styrene and 4-vinylbenzyl chloride were synthesized by reversible addition fragmentation transfer (RAFT) using benzyl dithiobenzoate as a control agent. After quaternization of the well-defined hydrophobic precursors with triethylamine, the micellar aggregates, formed by the cationic amphiphilic diblock copolymer when dissolved in water, were investigated by static and dynamic light scattering. The spherical shape of the micelles was established in salted water. Then, the poly(styrene)-b-poly(vinylbenzyltriethylammonium chloride) cationic diblock copolymers were used as a stabilizer for the emulsion polymerization of styrene and appeared to display very good stabilization properties. The ratio between the initial number of micelles and the final number of latex particles was particularly high, as a characteristic of the high mobility of the copolymer chains. Finally, we underlined the strong influence of salt on the nucleation step of the emulsion polymerization. The influence of the architecture of the copolymers on the stabilization of latexes has also been established by using random copolymers quaternized with N,N-dimethyldodecylamine, which led to cationic comblike copolymers. They were used for the first time as stabilizers for the emulsion polymerization of styrene. These amphiphilic copolymers proved to be good stabilizers in very low proportions (0.5-1 wt% styrene), which makes them valuable due to their simple synthesis.

Recent Research Progress in the Synthesis and Properties of Amphiphilic Block Co-polymers and Their Applications in Emulsion Polymerization

“…RAFT operates on the principle of a rapid and reversible transfer of the growing radical to thiocarbonylthio compounds [34], as illustrated in Scheme 6. The thiocarbonylthio group(s) is retained in the polymer which can be reactivated for use as precursors to produce block polymers, star polymers or polymers with more complex architectures [35].…”

“…SEC analyses showed that the molecular weight increased linearly with conversion, and experimental molecular weights were close to the theoretical values, but the polydispersities (M w /M n = 1.8-1.9) were higher. Save et al [34] first synthesized poly(styrene)-b-poly(4-vinylbenzyl chloride) block co-polymer with S-(benzyldithio) benzoate (BDB) (CTA3) as CTA in bulk. After quaternization of PS-b-PVBC, poly(styrene)-b-poly(vinylbenzyltriethylammonium chloride) PS-b-P(VBTEAC) co-polymer was obtained (Scheme 8).…”

“…In fact, the efficiency of a stabilizer is related to the stabilized surface area per macromolecular chain, and consequently for the same amount of stabilizer, the larger the final latex particle number, the better the efficiency [34].…”

“…In analogy to classic low-molecular-weight surfactants, the hydrophilic blocks can be classified as three categories by the sign of the electrical charge of the hydrophilic blocks: the non-ionic blocks, such as PEO [52], the anionic blocks, such as PAA [18], PMAA [53], poly(styrene sulfonate) [25,54] and poly(2-acrylamido-2-methylpropanesulfonic acid) [8], and the cationic blocks, such as poly(3-acrylamidopropyltrimethylammonium chloride) [8] and poly(vinylbenzyltriethylammonium chloride) [34].…”

“…The polyelectrolyte blocks, including the anionic blocks and the cationic blocks, provide electrosteric stabilization for latex, imparting good stability to the latex particles during polymerization and future storage [34]. Compared to their main analogues with carboxylate ionic groups, the stabilizing ability of block co-polymers with sulfonate ionic groups is insensitive to changes of both pH and temperature [25,56].…”