Amphiphilic-zwitterionic block polymers

Amphiphilic block copolymers have broad research interest and demonstrated applications due to their self-assembly over a range of different conditions. Polyzwitterions have attracted attention due to their higher hydrophilicity, charge sensitivity and anti-fouling properties making them a popular material in the field of stimuli responsive soft materials, e.g., self-healing hydrogels, water transport membranes, etc. An array of novel amphiphilic-zwitterionic block copolymers was designed where the hydrophilic segment is a polyzwitterion along with a low Tg hydrophobic block. As a first step, a parent block copolymer precursor of poly (dimethyl amino ethyl methacrylate)-b-poly (n-butyl acrylate-ran-allyl methacrylate) with different copolymer volume fractions was synthesized using RAFT polymerization. The advantage of using this technique is the ability to synthesize polymers with predetermined molecular weight, well-defined chemical composition, and a narrow dispersity. Variation of the content of the zwitterionic sulfobetaine was investigated through post-polymerization modification of the poly (dimethyl amino ethyl methacrylate) block using nucleophilic ring-opening reactions with varying amounts of 1,3-propane sultone. NMR spectroscopy and GPC data were analyzed to calculate the degree of polymerization and molecular weight in parent neutral block copolymers and its modified amphiphilic-zwitterionic counterpart. Thermal analysis of these zwitterionic systems was investigated by using TGA and DSC showing high thermal stability and also to determine the Tg. This study creates a platform to synthesize novel amphiphilic zwitterionic block polymer systems with well-defined molecular weight, copolymer composition and tunable zwitterionic moiety using a two-step strategy. Combining higher hydrophilicity of zwitterionic polymers with self-assembly of amphiphilic block copolymers, these materials will open an opportunity for future fundamental structure-property studies. Amphiphilic zwitterionic (AZ) block copolymers are readily prepared using post-polymerization modification, which offers exciting prospects for structure property relationship studies.