Molecular packing and phase transitions of side-chain liquid crystalline   polymethacrylates based on p-methoxyazobenzene

doi:10.1016/j.polymer.2008.04.054

CORC > 北京大学 > 化学与分子工程学院

	Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on p-methoxyazobenzene
	Zhu, Xing-Qi ; Liu, Jia-Hao ; Liu, Yi-Xin ; Chen, Er-Qiang
刊名	polymer
	2008
关键词	side-chain liquid crystalline polymer azobenzene phase structure LINEARLY-POLARIZED-LIGHT LANGMUIR-BLODGETT-FILMS 633 NM LIGHT BLOCK-COPOLYMERS MAIN-CHAIN AZOBENZENE MOIETIES NONPOLARIZED LIGHT THERMAL-PROPERTIES SPACER LENGTH POLYMER-FILMS
DOI	10.1016/j.polymer.2008.04.054
英文摘要	The phase structures and transition behaviors of a series of side-chain liquid crystalline (LC) polymethacrylates based on p-methoxyazobenzene (PMnAzs, n = 6, 8,10,12) were studied using differential scanning calorimetry, one- and two-dimensional (11) and 2D) wide-angle X-ray diffraction, and Fourier transform infrared spectroscopic experiments. The LC phase transition of PMnAz follows the sequence of smectic A (SmA) <-> nematic (N) <-> isotropic (1). For PM10Az and PM12Az, the transition of SmA-to-N is not complete upon heating. In the low-temperature SmA phase, the polymers adopt a fully interdigitated side-chain packing with the smectic layer period almost identical to the side-chain length. For all the four samples, the first-order diffraction of the SmA structure only renders when the temperature approaches the transition of SmA - N, with the intensity much lower than that of the second-order diffraction. The absence of the first-order diffraction at low temperatures is ascribed to the possible matching of the electron densities between the center portion of the side-chain sublayer and the main-chain sublayer of the SmA structure. Since only the mesogens from the same main-chain sublayer can stack parallel together, the distribution of the azobenzene domains may cause some sort of density undulation within the smectic layer. Among the samples, PM6Az presents the strongest undulation with some additional orders. We also examined the annealing effect on the H-aggregation of PMnAzs. It is found that isothermal annealing at a temperature slightly higher than the T-g of PM8Az and PM10Az can significantly enhance the UV absorption at 326 nm, indicating a further development of H-aggregation. However, for PM6Az and PM12Az, the UV-vis spectrum of the annealed sample is nearly identical to that without annealing. (c) 2008 Elsevier Ltd. All rights reserved.; Polymer Science; SCI(E); 21; ARTICLE; 13-14; 3103-3110; 49
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/248874]
专题	化学与分子工程学院
推荐引用方式 GB/T 7714	Zhu, Xing-Qi,Liu, Jia-Hao,Liu, Yi-Xin,et al. Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on p-methoxyazobenzene[J]. polymer,2008.
APA	Zhu, Xing-Qi,Liu, Jia-Hao,Liu, Yi-Xin,&Chen, Er-Qiang.(2008).Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on p-methoxyazobenzene.polymer.
MLA	Zhu, Xing-Qi,et al."Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on p-methoxyazobenzene".polymer (2008).