| Among many stimuli-responsive polymer materials, temperature-sensitive polymers have become a hot topic in the current smart polymer materials research because of their response to environmental temperature changes and their broad development prospects in drug control-release, sensors and biomedical application. In this thesis, temperature-sensitive polymer with quaternary ammonium-borate anion inner-salt structure was designed and synthesized. The main contents were as follows:A betaine-type styrene monomer with the quaternary ammonium-borate anion inner-salt pair was synthesized through the quaternization reaction and the always charged quaternary ammonium was bridged to the borate anion through an eight-membered diethanolamine borate ester ring, which can improve the stability of borate ester. We discussed the effects of initiator, temperature, solvent, concentration and time on the free radical polymerization of VMAB, and finally determined the optimal polymerization conditions as follows:AIBN as initiator, DMF/H2O (v/v,1/3) as solvent, keeping the concentration of VMAB at 0.35 g/mL and the system was polymerized at 70? for 24 h.The chemical structures of the betaine-type styrene monomer of VMAB and the corresponding polybetaine of PVMAB were characterized by FT-IR,1H-NMR, "B-NMR, SEC, TG and so on. Additonally, a series of tests were carried out to study the phase transition behavior of polymer PVMAB solution by ultraviolet visible spectrophotometer (UV-vis) and dynamic light scattering (DLS), and the effects of polymer concentration, solution pH, molecular weight of polymer, adding of organic solvents on the thermal-sensitive property of the polymer solution were discussed, respectively. The thermal-sensitive experiment showed that PVMAB in water afforded gradually well-defined sigmoidal S-shaped transmittance-temperature (T-t) curves along with the increasing polymer concentration. The bottom of these S-shaped curves shifted down greatly from 91.0%to 38.4% along with the increasing polymer concentration; whereas, the top decreased relatively slightly from 97.9% to 78.9%. However, the phase transition temperatures at the bottom of the S-shaped curves were always below 10? due to the very weak zwitterionic association of the ammonium-borate inner-salt pairs. The polymer solution afforded very small changes of the solution transmittance at different pH values, indicating that the pH condition has little impact to the thermal-sensitivity of PVMAB aqueous solution. For different degree of polymerization (DP), the transmittance of PVMAB aqueous solution showed S-shaped during heating and cooling procedure. When the degree of polymerization increased from 33 to 60 and 85, the transmittance of PVMAB aqueous solution decreased. The UCST phase transition could also be tuned by changing the ethanol content in the ethanol/water mixture. PVMAB in ethanol/water blend showed the similar trend of thermal-sensitivity with PVMAB aqueous solution. PVMAB ethanol/water blend (Pc=2.0 mg/mL) transmittance decreased slightly and linearly from 94.4% to 92.0% at XEtOH 0.00-0.60 intervals, and decreased sharply to 36.5% and 8.1% at XEtOH 0.70 and 0.72, respectively. It was clear that critical ethanol content (CEC) was lowered with the increasing polymer concentration in ethanol/water mixture.Besides, the cell cytotoxicity test was carried out to test whether the polymer PVMAB has a good biocompatibility. It was found that the cell viability of HCT-116 after the incubation treatment with PVMAB aqueous solution decreased from 112.09±2.33 to 95.31±4.13 in the assessed polymer concentration range of 0.05-1.00 mg/mL, which indicated the good biocompatibility of PVMAB. |
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