The controlled/living free-radical copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) or acrylic acid (AA) was studied by the reversible addition−fragmentation chain transfer (RAFT) technique using a trithiocarbonate RAFT agent. The reactions were performed in 1,4-dioxane solution at 30 °C and led to good control and high chain-end functionality. P(VDC-co-MeA)-b-PAA, PAA-b-P(VDC-co-MeA), and PAA-b-P(VDC-co-AA) amphiphilic block copolymers were then prepared in the same conditions, starting either from a hydrophobic P(VDCco-MeA) macromolecular RAFT (macro-RAFT) agent or from a hydrophilic PAA one. The advantage of the first synthesis pathway relies on the very good transfer efficiency to trithiocarbonate-ended P(VDC-co-MeA) and on the rapid consumption of the latter even when low percentages (10 mol %) of MeA comonomer are incorporated in the macro-RAFT agent. In contrast, for the second approach a rapid consumption of the macro-RAFT agent is only reached with 30 mol % of MeA in the comonomer feed, whereas with 10 mol % of MeA the transfer constant was determined to be only close to 1. Finally, we demonstrated that PAA-b-P(VDC-co-AA) diblock copolymers might also be obtained with controlled features in a one-pot process.
Poly(chloroprene) is a synthetic crystallizable polymer used in several applications, including rubber gloves. The film formation of poly(chloroprene) latex offers opportunities to define structures at length scales between the molecular and macroscopic, thereby adjusting the elastomer's mechanical properties. However, the connections between processing and the resultant film properties are not fully understood. Here, we investigate the competition between the coalescence of latex particles to build cohesive strength and their crystallization to raise the elastic modulus. We demonstrate that when coalescence precedes crystallization, the elastomer has greater extensibility and a higher tensile strength compared to when crystallization occurs during coalescence. The mechanical properties of poly(chloroprene) were tuned by blending two colloids with differing gel contents and crystallizabilities. Heating above poly(chloroprene)'s melting temperature allows increased particle interdiffusion and builds cohesion, prior to recrystallization. We provide evidence from in situ wide-angle X-ray scattering for the strain-induced crystallization of as-cast films from particle blends.
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