Dual Thermoresponsive Boc-Lysine-Based Acryl Polymer: RAFT Kinetics and Anti-Protein-Fouling of Its Zwitterionic Form

There are significant developments on the responsive polymers that are programmed for various stimuli such as temperature, pH, light, and so forth. Such focus and progress remain mainly centered around conventional polymers compared to amino acid-based polymers offering a diverse range of applications in biomedical area. Thus, this study focuses on designing of a Boc-lysine-based monomer and its reversible addition-fragmentation chain transfer (RAFT) polymerization to poly(Boc-L-lysinylacrylamide)s [P(Boc-lysMs] of controllable molecular weights (M(n)s) and low dispersities (Ds <= 1.23). This RAFT polymerization follows a first order rate kinetics up to very high monomer conversions (ca. 91.4%) with a good control over M-n and excellent agreement with the theoretical value. P(Boc-lysA) exhibits an interesting reversible upper critical solution temperature (UCST)-type phase behavior in mixed solvents comprising water and different polar organics (e.g., N,N-dimethylformamide, dimethyl sulfoxide, and methanol). The UCST-type cloud point (T-cU) increases linearly with increase of molecular weight of P(Boc-lysA) and percentage of water content in the mixed solvent. The addition of large organic cations in the aqueous solution of P(Boc-lysA) at pH 8.5 induces a lower critical solution temperature (LCST)-type phase transition with a tunable cloud point (T-cL) with respect to polymer concentration and its M-n as well as nature of added ion and its concentration. Furthermore, the Boc-deprotection of P(Boc-lysA) produces zwitterionic PlysA, which shows excellent anti-protein-fouling property compared to those of conventional antifouling polymers when tested with bovine serum albumin and monitored by dynamic light scattering.

Automated summary

This study focuses on the design of a Boc-lysine-based monomer and its reversible addition-fragmentation chain transfer (RAFT) polymerization to synthesize polymers with controllable molecular weights and low dispersities. These polymers show interesting upper critical solution temperature (UCST) and cloud point behavior in mixed solvents, as well as a tunable lower critical solution temperature (LCST) and cloud point under different conditions.