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Free keywords:
double hydrophilic thermo-sensitive macro-RAFT agents; RAFT emulsion polymerization; triblock copolymer particles; laponite composite latex particles
Abstract:
The properties of amphiphilic triblock copolymer particles, which consist of a hydrophobic polystyrene (PS) core and a thermo-sensitive double hydrophilic block copolymer shell made of polyacrylic acid (PAA) and poly-N-isopropylacrylamide (PNIPAM) sequences, differ significantly depending on the sequence of the hydrophilic blocks from the core to the shell—either PS-PNIPAM-PAA or PS-PAA-PNIPAM. These triblock copolymer particles were prepared via reversible addition-fragmentation chain transfer polymerization (RAFT) following the PISA approach, using the corresponding double hydrophilic block copolymer macro-RAFT agents. The macro-RAFT agents (MRA) were synthesized through sequential polymerization of the corresponding monomers, using 4-cyano-4-(propylsulfonyl thiocarbonyl) sulfonyl pentanoic acid as the RAFT agent. These two different MRAs result in remarkable differences in the course of styrene emulsion polymerization (EP). Furthermore, the two types of polystyrene latexes behave differently in two key aspects: firstly, in terms of particle size and latex stability, which depend on both temperature and ionic strength, and secondly, in their capacity to disperse laponite disks within the particle shell when present during styrene emulsion polymerization.
