Manipulating the Phase Transition Behavior of Dual Temperature-Responsive Block Copolymers by Adjusting Composition and Sequence

Temperature-responsive polymers have garnered significant attention due to their ability to respond to external stimuli. In this work, dual temperature-responsive block copolymers are synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT) polymerization utilizing zwitterionic monomer methacryloyl ethyl sulfobetaine (SBMA) and N-isopropyl acrylamide (NIPAAm) as monomers. The thermal responsive behaviors can be easily modulated by incorporating additional hydrophobic monomer benzyl acrylate (BN) or hydrophilic monomer acrylic acid (AA), adjusting concentration or pH, or varying the degree of polymerization of the block chain segments. The cloud points of the copolymers are determined by UV-Vis spectrophotometry, and these copolymers exhibit both controlled upper and lower critical solubility temperatures (LCST and UCST) in aqueous solution. This study analyzes and summarizes the influencing factors of dual temperature responsive block copolymers by exploring the effects of various conditions on the phase transition temperature of temperature-sensitive polymers to explore the relationship between their properties and environment and structure to make them more selective in terms of temperature application range and regulation laws. It is very interesting that the introduction of poly-acrylic acid (PAA) segments in the middle of di-block copolymer PSBMA(55)-b-PNIPAAm(80) to form PSBMA(55)-b-PAA(x)-b-PNIPAAm(80) results in a reversal of temperature-responsive behaviors from 'U' (LCST < UCST) to 'n' (LCST > UCST) type, while the copolymer PSBMA(55)-b-P(NIPAAm(80)-co-AA(x)) not. This work provides a clue for tuning the phase transition behavior of polymers for manufacture of extreme smart materials.

Automated summary

In this study, dual temperature-responsive block copolymers are synthesized and the influencing factors of temperature-responsive behaviors are analyzed. The introduction of poly-acrylic acid segments is found to change the type of temperature-responsive behavior. This research is important for tuning the phase transition behavior of polymers in the manufacture of extreme smart materials.