Synthesis And Properties Of Star Polymers With Layered Structure

Star polymers, a kind of polymers with special morphological structures, have attracted great interests throughout the world due to its good performance in the responsiveness and versatility. A variety of star polymers with different structures, such as multi-arm, miktoarm, block, graft, and so on, have been prepared and studied. Due to their special topological structures, star polymers with a layered structure have exhibited good application prospects in the field of drug delivery/controlled release, medical imaging, multi-layer nano-membranes, molecular capturing and metal scavengers, etc. Based on the work of precursors, this dissertation mainly describes several interesting research in synthesis of star polymers with a layered structure and studied their performance thereby. In addition, we also do some research about enzymatic polymerization of phenol in water. The main results could be summarized as follows:1. We have synthesized macrocyclic polystyrene-(PS-) terminated star polymers via a core-crosslinking approach, and similar work has also not been reported. A tadpole-shaped macrocyclic PS-linear-PS copolymer was synthesized at first via both click reaction and ATRP polymerization method. The "living"ATRP chain-ends of the tadpole-shaped copolymers were linked together via ATRP polymerization with divinylbenzene to form a core-crosslinked star polymer. The number of arms attached to the macrocyclic star polymers was measured by using NMR, and absolute molecular weights by using gel permeation chromatography (GPC) with multiangle laser light scattering detector. The shorter tadpole-shaped precursors caused core-crosslinked star polymers with higher molecular weights and more arm numbers. These macrocyclic star polymers had a highly crosslinked core and many radiating arms. The macrocycle-terminated core-cross-linked star polymers showed two glass transition temperatures, one arising from the linear branches and another from the macrocycles.2. In this work, novel star-hyperbranched block copolymers containing four polystyrene arms and hyperbranched polyglycidol at the end of each arm (sPS-b-HPG)4 have been synthesized. The star polystyrenes were prepared through atom transfer radical polymerization of styrene starting from a four-arm initiator. The hydroxyl terminated PS star polymers served as precursors for the cationic ring opening polymerization of glycidol using BF3·OEt2 as the catalyst. The chemical structures of these block copolymers were characterized by using 1H and 13C NMR. DSC analysis indicated that the star-hyperbranched block copolymers exhibited two distinct glass transition temperatures corresponding to the linear PS and the HPG segments, respectively. The addition of LiClO4 increased the Tg of HPG segments at low concentrations, however, decreased the Tg at high concentrations. The Tg of PS segments was not affected by the addition of salts at all. Furthermore, the interaction of (sPS-b-HPG)4 with Li ions was studied by using viscosity analysis based on the Jones-Dole equation, and HPG was used as the control trial. The ionic conductivity of (sPS-b-HPG)4/LiClO4 electrolyte was measured to be higher than that of HPG/LiClO4 electrolyte at the same ratio of HPG/Li.3. Carbon nanotubes (CNTs) acted as a structural regulator for enzymatic polymerization of phenol in water. About 90% of total polymeric units in the obtained polymers are the highly thermally stable oxyphenylene units. The polymer-yields are dependent on the quantities of CNTs used. On the basis of MWNT-templated enzymatic polymerization of phenol, we grafted polyphenol chains to the surface of MWNT starting from the covalently anchored hydroquinone. This approach supplies a novel way for producing high performance polymers and for functionalization of the surface of CNT.