This study provides a new method to prepare CO2-philic amphiphilic surfactants by copolymerizing a less activated monomer (VAc) with an activated monomer (DMAEMA). Initially, the difunctional RAFT agent S-(1-methyl-4-hydroxyethyl acetate) O-ethyl dithiocarbonate, containing the xanthate group and 2-bromopropionyl group in its structure, was synthesized. By successive living radical polymerization, a series of new cationic surfactants poly(vinyl acetate)-block-poly(dimethylaminoethyl methacrylate) (PVAc-b-PDMAEMA) was obtained. PVAc-b-PDMAEMA cationic surfactants can emulsify CO2–H2O systems effectively to obtain high internal phase emulsion that remains stable up to 12 h. Further study indicates that the emulsifying ability of the surfactant is affected by the pH of solution, pressure, etc. After the high internal phase CO2-in-water (40% w/v, acrylamide solution) emulsion was polymerized, polyacrylamide-based highly porous emulsion-templated materials were obtained with tunable size and interconnected pores. These porous materials were then used as scaffolds to guide cellular growth.
Controlled synthesis of A 2m B 2n -type (m ≈ n ≈ 8) starlike copolymers comprising an oligomeric poly(styrene- co -maleimide) core and two types of V-shaped arms individually generated by ATRP and ROP was described. Multistep syntheses involving RAFT copolymerization , end group removal, ATRP of vinyl monomers such as styrene (St), methoxyethyl methacrylate (MEMA) and tert -butyl acrylate ( t BA), and ROP of ε -caprolactone (CL) were used to construct the target miktoarm stars with controlled molecular weight and relatively low polydispersity (PDI = 1.07–1.22). The resultant star copolymers had high bromide functionality and uniform chain length of ATRP-generated arms, evident from chain extension polymerization and cleavage of arms. Meanwhile, a pH-responsive (PAA) 2m (PCL) 2n star was also obtained by selective hydrolysis. The synthetic strategy via combination of RAFT copolymerization and “core first” approach is versatile in constructing various A 2m B 2n stars, and this study further paves way for facile synthesis and properties of new types of miktoarm stars.
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