Stimuli-Responsive Methionine-Based Zwitterionic Methacryloyl Sulfonium Sulfonate Monomer and Corresponding Antifouling Polymer with Tunable Thermosensitivity
This report describes design and synthesis of a zwitterionic [Boc-L-methionine-(2-methacryloylethyl)]sulfoniopropanesulfonate (METMASPS) monomer derived from methionine followed by its subsequent RAFT polymerization in water to produce zwitterionic polymer (PMETMASPS). The aqueous METMASPS monomer solution exhibits transparent to turbid and turbid to transparent transitions near to its isoelectric point (5.75) upon switching the pH from anything below 4.8 to 4.8-6.8 and 4.8-6.8 to above 6.8. Furthermore, in the pH range of 4.8-6.8, this turbid suspension transforms into transparent solution showing a clear upper critical solution temperature (UCST)-type phase transition. However, the zwitterionic polymer is soluble in water at any pHs ranging from 1 to 12, but its transparent aqueous solution turns into turbid exhibiting a soluble-insoluble phase transition upon addition of different kosmotropic anions such as SO42-, Ct3-, H2PO4ˉ and Ac @#x0304; of Hofmeister series. This colloidal turbid suspension containing anion becomes transparent showing a distinct UCST-type phase transition upon heating. The cloud point (Tcp) is tunable with respect to molecular weight of the polymer, concentration of ion as well as with solution pH. Finally, the antifouling property of the as-synthesized zwitterionic PMETMASPS is studied against resistance towards a model protein, bovine serum albumin (BSA) through the monitoring of anti-aggregating behaviour via DLS and is compared with that of poly(ethylene glycol) (PEG).