Preparation Of New Thermoresponsive Polymers Through Modification Of Water-Soluble Macromolecules

In this dissertation, water-soluble macromolecules with a large number ofhydroxyl or amino groups were endowed thermoresponsive property in water throughchemical modification. The details were as follows:1. Hyperbranched polyglycerol (HPG) macromolecules were modified bydifferent saturated fatty acids with different chain length through esterificationreaction. When the saturated fatty acids with chain length of equal or more than10were used, the obtained polymers in water were not thermoresponsive. When thechain lengths of saturated fatty acids used were equal or less than8,thermorespoonsive HPGs could be obtained. The cloud point temperature (CP) ofsuch thermoresponsive HPGs could be adjusted in a broad range of0-100℃throughchanging the type and the degree of substitution of saturated fatty acids andconcentration of polymer.2. Five kinds of N-isobutyl amino-acid derivatives were each used to modifyHPGs through esterification reaction, resulting in a series of novel thermoresponsiveHPGs. The CP values of such thermoresponsive HPGs could be adjusted in a broadrange of0-100℃through changing the type and the degree of substitution ofamino-acid derivatives and concentration of polymer.3. Three amino-acid derivatives were each conjugated with some of the hydroxylgroups of poly (vinyl alcohol)(PVA) through a one-step esterification reaction,resulting in a series of thermoresponsive PVAs. The influence of the type and thedegree of substitution of amino-acid derivatives and concentration of polymer on CPwas studied. The CP values were adjustable in a broad range of0-100℃. Suchthermoresponsive PVA derivatives were good dispersing agents for colloidal goldnanoparticles (AuNPs) in water when enough polymers were used. The composites ofsuch PVA derivatives and AuNPs were also thermoresponsive. Moreover, AuNPsstabilized by such thermoresponsive PVA derivatives showed better stability thanthose stabilized by neat PVAs.4. Three amino-acid derivatives were each conjugated with some of the hydroxylgroups of β-cyclodextrin (β-CD) through a one-step esterification reaction, resultingin a series of thermoresponsive CDs with adjustable CP. The influence of the type and the degree of substitution of amino-acid derivatives and concentration of polymer onCP was studied.5. On the basis of the above experiments, N-isobutyl valine (Val-IBAm, VI) wasused as the universal molecular unit to endow thermoresponsive properties to otherfour water-soluble macromolecules with plenty of hydroxyl or amine groups,including poly(hydroxyethyl acrylate)(PHEA), hydroxyethylcellulose (HEC),hyperbranched polyethylenimine (HPEI) and polyallylamine (PAAm). It was foundthat Val-IBAm could also effectively render these typical water-solublemacromolecules thermoresponsive, and the CP could also be modulated by varyingthe degree of substitution.