Study On Solution Properties Of ZnO QDs-embedded MEO₂ MA_m -HEMA_n -MEO₂ MA_m Triblock Copolymers

Two ABA triblock thermoresponsive copolymers (A= 2-(2-Methoxyethoxy)ethyl methacrylate, MEO₂MA; B=2-Hydroxyethyl methacrylate, HEMA) MEO₂MA₂₀₀-HEMA₅₀-MEO₂MA₂₀₀ and MEO₂MA₂₀₀-HEMA₃₀-MEO₂MA₂₀₀ were prepared using atom transfer radical polymerization (ATRP). The formation of copolymers was characterized. The differences in the thermo-sensitiveness and gelation capacity of copolymer solutions were studied. ZnO quantum dots were embedded into copolymer solutions to form ZnO QDs/ MEO₂MA_m-HEMA_n-MEO₂MA_m complex which displayed strong photoluminescence. The thesis include the following sections:ABA triblock copolymers were synthesized by ATRP via sequential monomer addition using an initiator with double functional groups. The copolymers were characterized by FT-IR, ¹H NMR spectroscopy and Viscotek TDA_max GPC/SEC. The molecular weights were well controlled and the polydispersity was quite low. The absorbency of copolymer solutions at varied temperatures were recorded to determine the lower critical solution temperature (LCST) of copolymer solutions. LCSTs were found to decrease a few degrees as the concentration and hydrophobic HEMA moiety increased. The critical gelation concentration and five regions of copolymer solutions were determined by the phase diagrams. MEO₂MA₂₀₀-HEMA₅₀-MEO₂MA₂₀₀ was shown to have a lower critical gelation concentration than MEO₂MA₂₀₀-HEMA₃₀-MEO₂MA₂₀₀. The rheological properties of copolymer solutions were recorded to study the gelation capacity of copolymer solutions. It revealed that the moduli of MEO₂MA₂₀₀-HEMA₅₀-MEO₂MA₂₀₀ were higher than those of MEO₂MA₂₀₀-HEMA₃₀-MEO₂MA₂₀₀ above the gelation temperature.To investigate the micellization behaviors of the polymers, the steady fluorescence spectroscopy using pyrene as the probe was recorded. The results indicated that the critical micelle concentration of MEO₂MA₂₀₀-HEMA₅₀-MEO₂MA₂₀₀ solution was lower than that of MEO₂MA₂₀₀-HEMA₃₀-MEO₂MA₂₀₀. The microenvironment of the micelles in MEO₂MA₂₀₀-HEMA₅₀-MEO₂MA₂₀₀ solution was less polar than that of MEO₂MA₂₀₀-HEMA₃₀-MEO₂MA₂₀₀.Embedding quantum dots into thermoresponsive polymers did not vary the LCSTs and gelation capacity in spite of slight influence on G'and G''moduli. The compolex exhibited strong yellow emission from ZnO QDs under UV light.