| This dissertation highlights the development of star polymer, miktoarm star copolymer and dendritic polymer with unique structures. The research status of liquid crystalline polymers (LCP) is reviewed as well. By combining the nonlinear polymer with liquid crystalline polymer, several nonlinear liquid crystalline polymers with special structure have been designed and successfully synthesized.Novel miktoarm star copolymer of AB2, such as PS(PMPCS)2 and PS(PMMAZO)2, were successfully prepared by by atom transfer radical polymerization (ATRP). The liquid-crystalline behavior of PS(PMPCS)2 and PS(PMMAZO)2 were studied using differential scanning calorimetry (DSC), polarized optical microscope (POM) and wide angle X-ray diffraction (WAXD). Compared to the related liquid crystalline homopolymer and block copolymer, we find out that thermal stability of the mesophases of PS(PMMAZO)2 increased, while the smectic order of PS(PMMAZO)2 was limited. However, the liquid crystailline behavior of PS(PMPCS)2 is similar to the related liquid crystalline homopolymer. Only when the Mn beyond a certain value, it presents the liquid crystalline, which is related to the length of the arm not the distribute of molecular weight or the shape of the molecular.(PEO)n star polymer and (PEO)n(PS)n miktoarm star copolymer were prepared by ATRP. Their structures were characterized by FT-IR and 1H NMR. The GPC trace of (PEO)n(PS)n miktoarm star copolymer indicate the high efficency of coupling agent, high molecular weight of the so-prepared star polymer with low molecular weight distribution. Several factors play important roles during the star polymer formation. The apt condition is as follows: O-xylene as the solvent; divinylbenzene(DVB) as the coupling reagent; CuBr/bpy as the catalyst. And the temperature is 110°C, PEO-Br (0.072M) as the macroinitiator. The feed ratio of DVB to PEO macroinitiator is 12: 1. The results showed that efficiency of coupling agent was higher than 99 %, with narrow molecular weight distribution less than 1.2.The crystalline behaviors of (PEO)n star polymer, (PEO)n(PS)n miktoarm star copolymer and their related linear polymers were studied using DSC and POM . A... |
PDF Full Text Request