Synthesis And Characterization Of Star Mesogen-Jacketed Liquid Crystal Polymerand Related Block Copolymer

The literature reporting star-shape polymers were briefly reviewed in the first part of this dissertation. Two-armed, three-armed and four-armed mesogen-jacketed liquid crystal star-shape polymers, with rigid chain of PMPCS as their arms have been designed and synthesized. The relation of molecular weight or molecular shaped to liquid crystalline of multi arms mesogen-jacketed polymers was researched. Four-arm star-shape rod-coil block mesogen-jacketed liquid crystal was also achieved by atom transfer radical polymerization (ATRP) and its phase behavior was discussed.1. The di- or tri- or tetra-functional initiators carried bromine at the periphery were prepared from esterification between di- or tri- and tetra-functional group alcohol or phenol and 2-bromo-2-methylpropionyl bromide. The monomers (PMPCS) were initiated to polymerize in chlorbenzene solution (w/w 20%). Two-armed, three-armed and four-armed star-shaped mesogen-jacketed liquid crystal polymers with rigid chain PMPCS as their arms were synthesized successfully by ATRP. *H NMR confirmed these multi-arm PMPCS of structure. The liquid-crystalline behavior of these multi-arm PMPCS with arms ranging from two to four-armed was studied by using differential scanning calorimetry (DSC^ polarized optical microscope (POM) and wide-angle X-ray diffraction (WAXD). It was found that a liquid crystalline phase could be formed only by a certain values of number molecular weights, that is only these multi-arm PMPCS with a M^QPC beyond 1.87 x 104 (Pa), 1.84 x 104 (Pb), 2.69 xio4 (Pc), ), 2.73 xlO4 (Pd), 3.68xl04g/mol (Pe) of these multi-armed polymers of the Myopes respectively. (Pa, Pb, Pc, Pd and Pe representing the ATRP of MPCS initiated by di-(Ia, Ib), tri-(Ic, Id) and tetrafunctional (Ie) initiators containing 2-bromopropionlyoxy species, respectively). The liquid crystalline of these multi-armed star-shapedmesogen-jacketed polymer related to molecular weight but not to molecular shaped.2. A type of four-armed star-shape rod-coil block mesogen-jacketed liquid crystal copolymer S-(PMMA-6-PMPCS)4 was designed and synthesized by ATRP. 1H NMR confirmed the four-armed rod-coil block PMPCS of structure. The liquid crystalline of this block copolymer was characterized by differential scanning calorimetry (DSC), polarized optical microscope (POM) and wide-angle X-ray diffraction (WAXD). The results showed that only those copolymers with molecular weight of rigid block segments beyond a certain length could form liquid crystalline phase above the glass transition temperature of the rigid block.