Preparation Of Graft Copolymers With Polyisoprene Backbone And Investigations Of Their Properties

In this thesis we combined living/control polymerization such as anionic polymerization, RAFT polymerization, with thiol-ene click chemistry to modify the polyisoprene by introducing the polar structures. The thermoplastic elastomers and amphiphilic graft copolymers are prepared with clear and adjustable structure, controllable molecular weight and narrow molecular weight distribution via "graft onto" method. And the graft copolymers obtained contain active double bonds in the backbone.Polyisoprene (PI) in which the structure of double bonds can be adjustable were synthesized by anionic polymerization using n-BuLi as initiator in n-hexane, THF was used as polar modifier. The dithiobenzoate-terminated polystyrene (PS) synthesized by RAFT polymerization was reduced by hexylamine to obtain the thiol end group modified-polystyrene (PS-SH). PI coupled with thiol end group functionalized PS via thiol-ene "click" reaction and a novel graft copolymer polyisoprene-graft-polystyrene (PI-g-PEG) was prepared. The SEC has confirmed that the graft copolymer was successfully prepared, but the product was hard to purify, still existing a little PS homopolymer.A novel graft copolymer consisting of polyisoprene (PI) backbone and hydrophilic side chain with carbamic acid ester functional group was prepared via thiol-ene "click" reaction and alcohol-isocyanate reactions. Hydrophobic PI was functionalized with hydroxyl group by the thiol-ene reaction of mercaptoethanol with the double bond of PI backbone to provide the modified polymer PI-OH. Isocyanate end group capped poly(ethylene glycol)(mPEG-NCO) was grafted onto the PI backbone through alcohol-isocyanate reaction between the pendant hydroxyl groups and isocyanate group of mPEG-NCO. The properties of amphiphilic graft copolymers can be adjusted by varying the molar ratio of mercapto group and double bonds, and the chain length of PEG used. The structures of the graft copolymers were characterized and confirmed by means of size-exclusion chromatography (SEC), 1H-NMR, FT-IR spectroscopy and contact angle measuring instrument. The micellization behaviors of graft copolymers were investigated by transmission electron microscopy (TEM), and dynamic light scattering (DLS). And the thermodynamic behavior was studied by TGA and DSC characterization. Due to their amphiphilic characteristics, they can self-assemble spontaneously into micelles in water. The particle size of micells became smaller and smaller with the increase of graft chain length, and the hydrophilicity significantly increased, even more it can directly soluble in water. As the side chain introduced into the backbone, the thermal decomposition temperature of PI decreased, Tg of the modified polymer PI-OH increased, and introducing more flexible PEG chains it reduced.