Thermoresponsive Microgels with High Loading of Zwitterions Exhibiting Superior Performance: A Macromonomer Approach

In this investigation, the synthesis of temperature-responsive microgels containing high content of zwitterionic poly(phosphorylcholine) (PMPC) is reported. High loadings of polyzwitterionic chains are achieved by using PMPC-based "macromonomers," which are synthesized via a three-step reaction process. The first step involves synthesis of PMPC homopolymers via reversible addition fragmentation transfer (RAFT) polymerization, followed by end-group removal to generate reactive thiol groups, and last of all, introduction of polymerizable double bonds at the chain ends to provide PMPC-based macromonomers. Macromonomers of three different molar masses (3000, 5000, and 10 000 g mol(-1)) are used in three different molar ratios (1, 3, and 5 mol%) to synthesize microgels using N-vinylcaprolactam (NVCL) as the main co-monomer in precipitation polymerization. It is observed that the extent of total incorporation of the zwitterionic moiety is a function of both the macromonomer molar mass as well as its molar fraction in the feed which has a direct effect on their solution properties such as hydrodynamic radii and volume phase transition temperature (VPTT). Interestingly, these microgels show unprecedented extent of protein-repelling behavior owing to higher loading of zwitterionic moieties, what makes them interesting for the fabrication of protective coatings with anti-fouling properties.