152241-49-1Relevant academic research and scientific papers
Liquid crystalline rod-coil block copolymers by stable free radical polymerization: Synthesis, morphology, and rheology
Gopalan, Padma,Zhang, Yuanming,Li, Xuefa,Wiesner, Ulrich,Ober, Christopher K.
, p. 3357 - 3364 (2003)
We have synthesized and characterized rod-coil diblock, triblock, and starblock copolymers of controlled molecular weight by stable free radical polymerization, where the rod part consists of "mesogen jacketed liquid crystalline segments" (MJLCP). The MJLCP segmented examined in our studies is poly{2,5-(4-butylbenzol)oxystyrene} (PBBOS) while the coil part is poly(styrene). SAXS studies of the block copolymers at room temperature predominantly show only a first-order maximum in their SAXS spectra. Above the Tg of the two blocks (～150°C) no phase-separated morphology could be detected in temperature-dependent SAXS measurements of the block copolymers. Slow cooling regenerates the morphology, indicating very slow ordering kinetics. The effects of variation in molecular architecture and increasing topological constraint in going from homopolymer to star block copolymer on melt rheology (i.e., viscosity, relaxation times, and activation energies) are reported. In the master curves of all the block copolymers and homopolymers studied, nonterminal behavior was observed at low shear frequencies along with the absence of an entanglement plateau. In the PBBOS homopolymer an increase in molecular weight resulted in a decrease in the modulus of the nematic phase that was associated with a greater extent of shear orientation. On varying the molecular architecture from homopolymer to diblock to starblock copolymer, a decrease in the complex viscosity was observed that is attributable to the presence of polystyrene as the second block and the effect of topological constraints on molecular relaxation. The activation energies also follow the same trend as complex viscosity and relaxation times.
Restudy of the Old Poly-2,5-di(benzoyloxy)styrene as a New Liquid Crystal Polymer
Zhou, Qi-Feng,Wan, Xinhua,Zhu, Xin-Long,Zhang, Fei,Feng, Xinde
, p. 107 - 118 (2007/10/02)
The 40 year old polymer, poly-2,5-di(benzoyloxy)styrene, has been restudied from the view point of the "mesogen-jacketed liquid crystal polymer".This old polymer was synthesized in 1952 as a precursor of an electron exchange polymer and is now found to be thermotropically liquid crystalline, from which the characteristic banded texture of rigid and semi-rigid liquid crystal polymers may be obtained.The monomer of this polymer, 2,5-di(benzoyloxy)styrene, was then also not realized as liquid crystalline, is now found to be liquid crystalline forming too.This finding offers probably the first example of liquid crystal rigid rod-like molecules with lateral but without terminal substitutions.The synthesis and primary characterization of a series of the closely related polymers poly-2,5-bisstyrenes are also reported. - Keywords: mesogen jacketed liquid crystal polymers, rigid side chain liquid crystal polymers, liquid crystal monomers, liquid crystal polymers, 2,5-bisstyrene, 2,5-bisstyrene, 2,5-bisstyrene, 2,5-di(benzoyloxy)styrene, poly-2,5-di(benzoyloxy)styrene
