Thermo-Sensitivity Of Water Soluble Polymers Tuned By Local Synergism Of Hydrogen Bonding

Thermo-sensitive water soluble polymers were extensively applied in biomedical, intelligent materials and other fields. Recent studies demonstrated that their thermal response behaviors may be effectively regulated by varing hydrogen bonding. However, in-depth understanding the thermal responsive mechanism of thermo-sensitive polymers is still challenging. In this thesis, we synthesized a series of PNMEP70, P(NMEP65-ran-FPHPMA5), PNMEP32-b-P(NMEP34-ran-FPHPMA5), PNMEP57-b-P(NMEP7-ran-FPHPMA6) and PNMEP63-b-PFPHPMA7via visible light activating RAFT polymerization at25℃, in which N-(2-meth acrylatoethyl) pyrrolidone (NMEP) units acted as basic water-soluble units, and small amount of3-(4-formylphenyl)-2-hydroxylbutylmethacrylate (FPHPMA) units were incorporated into polymer chains as hydrogen bonding effectors. The thermal response behaviors were investigated by laser light scattering (LLS) and temperature-variable1H NMR. The results demonstrated that introducing small amount of FPHPMA effectors in polymer chains led to the significant decrease of the cloud points. More importantly, varying the distribution from P(NMEP65-ran-FPHPMA5) to PNMEP32-b-P(NMEP34-ran-FPHPMA5) led to ca.8℃lower cloud point. However, varying from PNMEP32-b-P(NMEP34-ran-FPHPMA5) to PNMEP57-b-P(NMEP7-ran-FPHPMA6) gave rise to ca.12℃higher cloud point. The thermal hysteresis on cooling and solvent isotope effect demonstrated that their thermo-responsive behaviors strongly depended on the distribution of FPHPMA effectors. These results confirmed the strong effect of thermo-responsive behaviors on local synergism of hydrogen bonding. PNMEP32-b-P(NMEP34-ran-FPHPMA5) and P(NMEP65-ran-FPHPMA5) were separately converted to the oxime-functionalized PNMEP32-b-P(NMEP34-ran-HHMPPMA5) and P(NMEP65-ran-HHMPPMA5) via further reacting their aldehyde groups with hydroxylamine, where HHMPPMA is2-hydroxy-3-(4-((hydroxyimino) methyl)phenoxy)propylmethacrylate. The cloud points clearly lowered down on converting aldehyde groups to oxime groups, the thermal hysteresis were also enhanced. In addition, the decrease of cloud point and the thermal hysteresis of PNMEP32-b-P(NMEP34-ran-HHMPPMA5) were more remarkable than P(NMEP65-ran-HHMPPMA5). These results further demonstrated the strong dependence of thermo-responsive behaviors on local synergism of hydrogen bonding. This thesis provides a new avenue toward novel water-soluble thermo-sensitive polymers.