Search

Water-soluble polymers obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization were used for the production of surfactant-free poly(vinylidene chloride) (PVDC)-based latexes in a one-pot/two-step process that was exclusively conducted in water. In the first step, the hydrophilic macromolecular RAFT (macroRAFT) agent ( i.e. poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA) or poly(sodium 4-styrenesulfonate) (PSSNa)) was synthesized in water using a trithiocarbonate RAFT agent, 4-cyano-4-thiothiopropylsulfanyl pentanoic acid (CTPPA). The macroRAFT agent was then directly utilized as reactive stabilizer for the aqueous emulsion copolymerization of vinylidene chloride (VDC) and methyl acrylate (MA) inspired by a polymerization-induced self-assembly (PISA) process. The developed recipes employed a very low amount of macroRAFT agent compared to the hydrophobic monomers (typically less than 2 wt%) and amphiphilic block copolymers of PAA- b -P(VDC- co -MA), PMAA- b -P(VDC- co -MA) or PSSNa- b -P(VDC- co -MA) were thus produced in situ , providing stabilization to the P(VDC- co -MA) particles. Stable, surfactant-free latexes were successfully obtained in each case with solids content up to 40 wt%. Surface tension measurements performed on the final dispersions showed that the amount of residual macroRAFT agent in water was negligible demonstrating that this strategy indeed gave rise to particles stabilized by covalently-anchored hydrophilic polymers. The PSSNa macroRAFT agents proved to be particularly interesting candidates achieving stable latexes of less than 100 nm leading to the formation of transparent films which did not whiten after being immersed in water. [ABSTRACT FROM AUTHOR]

Abstract: The reversible addition-fragmentation chain transfer (RAFT) copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) was studied in the presence of poly(ethylene oxide)-based macromolecular RAFT (macroRAFT) agents of the trithiocarbonate type (PEO-TTC) in solution and in aqueous emulsion. Firstly the formation of PEO-b-P(VDC-co-MeA) diblock copolymers was performed in toluene solution at 30 °C and a good control over the polymerization with high chain-end functionality was shown. A first aqueous emulsion copolymerization of VDC with MeA was performed using one of the amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers as macromolecular stabilizer. Then, in a series of experiments the PEO-TTC macroRAFT agents were directly tested as both chain transfer agents and stabilizing agents in similar conditions (aqueous batch emulsion copolymerization of VDC with MeA at 70 °C). The influence of the nature and concentration of the initiating system and the presence or not of a buffer were studied. We demonstrated that in simple conditions, nanometric latex particles composed of amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers formed by polymerization-induced self-assembly (PISA). It can thus be concluded that PEO-TTC macroRAFT agents are valuable non-ionic macromolecular stabilizers in the emulsion copolymerization of VDC and MeA and allow the formation of core–shell diblock copolymer particles in the absence of free surfactant. However, when rather high molar masses of the hydrophobic PVDC-based block were targeted, the determined molar masses deviated from the theoretical values. [Copyright &y& Elsevier]

The controlled/living free-radical copolymerization ofvinylidenechloride (VDC) with methyl acrylate (MeA) or acrylic acid (AA) wasstudied by the reversible addition–fragmentation chain transfer(RAFT) technique using a trithiocarbonate RAFT agent. The reactionswere performed in 1,4-dioxane solution at 30 °C and led to goodcontrol 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 sameconditions, starting either from a hydrophobic P(VDC-co-MeA) macromolecular RAFT (macro-RAFT) agent or from a hydrophilicPAA one. The advantage of the first synthesis pathway relies on thevery good transfer efficiency to trithiocarbonate-ended P(VDC-co-MeA) and on the rapid consumption of the latter evenwhen low percentages (10 mol %) of MeA comonomer are incorporatedin the macro-RAFT agent. In contrast, for the second approach a rapidconsumption of the macro-RAFT agent is only reached with 30 mol %of MeA in the comonomer feed, whereas with 10 mol % of MeA the transferconstant was determined to be only close to 1. Finally, we demonstratedthat PAA-b-P(VDC-co-AA) diblockcopolymers might also be obtained with controlled features in a one-potprocess. [ABSTRACT FROM AUTHOR]