Side-Chain Liquid-Crystalline Polyoxetanes with a Spacer-Separated Azobenzene Moiety. II. Preparation and Characterization of Polyoxetanes Derived from 4-(4-Alkoxyphenylazo)phenyl 4-[7-(3-Methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates
A series of polyoxetanes were prepared by the cationic ring-opening polymerization of 4-(4-alkoxyphenylazo)phenyl 4-[7-(3-methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates using 0.08 molar amount of THF·BF3 in dichloromethane at 20 to 30 °C. Although the product polymers indicated GPC-average molecular weights of around 9000 to 23000, in most cases, they did not have an unimodal molecular weight dispersity. The liquid-crystalline mesophases of the polymers were examined by differential scanning calorimetry and polarized optical microscopy; these textures were observed due to nematic and/or smectic mesophases over a wide temperature range from about 250 °C to room temperature. The benzoate moiety, the longer p-substituted alkoxy tails, and the oxetane main chain play important roles in maintaining highly ordered, stable mesophases.
在 20 至 30 °C 的二氯甲烷中,使用 0.08 摩尔量的 THF-BF3,通过阳离子开环聚合 4-(4-烷氧基苯基偶氮)苯基 4-[7-(3-甲基-3-氧杂环丁基)-1,6-二氧杂庚基]苯甲酸酯,制备了一系列聚氧杂环丁烷。尽管产品聚合物的 GPC 平均分子量约为 9000 到 23000,但在大多数情况下,它们并不具有单峰分子量分散性。聚合物的液晶介相通过差示扫描量热法和偏振光学显微镜进行了检测;在从约 250 °C 到室温的较宽温度范围内,均可观察到由于向列型和/或胶粘型介相而产生的纹理。苯甲酸酯分子、较长的对取代烷氧基尾端和氧杂环丁烷主链在维持高度有序、稳定的介相方面发挥了重要作用。
Azobenzene-decorated cellulose nanocrystals as photo-switchable chiral solutes in nematic liquid crystals
作者:Barış Sezgin、Torsten Hegmann
DOI:10.1039/d2tc04444g
日期:——
validate that cellulosenanocrystals (CNCs), surface-functionalized with pro-mesogenic azobenzene pendants, can act as photoswitchable chiral solutes in a nematic liquid crystal (N-LC). Upon UV illumination, the helical pitch and thus the helical twisting power (βw) can be altered based on the trans–cis photoisomerization of the azobenzene pendants. This approach shows that CNCs—biorenewable chiral additives
Burmistrov, V. A.; Kuz'mina, S. A.; Koifman, O. I., Russian Journal of Organic Chemistry, 1995, vol. 31, # 3, p. 351 - 353
作者:Burmistrov, V. A.、Kuz'mina, S. A.、Koifman, O. I.
DOI:——
日期:——
Molecular flexibility operated mesomorphism by end groups in azoester series
作者:B. B. Jain、U. H. Jadeja、R. B. Patel
DOI:10.1080/15421406.2016.1263098
日期:2017.7.24
A novel azoester homologous series, RO-C6H4-COO-C6H4-N = N-C6H4-OC7H15 (n) (para) has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on mesomorphic properties with reference to tthe flexible terminal chain. The novel azoester series consists of thirteen (C-1-C-18) members. Mesomorphism commences from C-5 homologue. C-1-C-4 homologues are nonmesomorphic, C-5 homologue is only nematogenic and C-6-C-18 homologues are smectogenic and nematogenic. All mesogenic homologues are enantiotropically mesomorphic. Transition temperatures and textures were determined by polarizing optical microscopy (POM) and a heating stage. Cr-M/I transition curve follows a zigzag path of rising and falling values and behaves in a normal manner. The Sm-N and N-I transition curves of a phase diagram behave in the normal established manner except for a small deviation for the higher homologues (C-14 and C-16). An odd-even effect is exhibited by Sm-N and N-I transition curves. Analytical spectral and thermal data support the molecular structures. Smectic and nematic thermal stabilities are 93.62 degrees C and 114.3 degrees C, respectively. Smectic and nematic mesophas elengths range from 12.0 degrees C to 18.0 degrees C and 11.0 degrees C to 31.0 degrees C. The series is predominantly nematogenic and partly smectogenic and of middle order melting type. Group efficiency order derived for smectic and nematic. Smectic and nematic: -OCH3 > -OC4H9 > -OC7H15 (n).