Abstract

A series of polyesters containing a photosensitive benzylidene chromophore in the main chain were synthesized from 2,6-bis(4-hydroxybenzylidene)cyclohexanone with various aliphatic and aromatic diacid chlorides by interfacial polycondensation technique. The intrinsic viscosity of the synthesized homo and copolymers determined by Ubbelohde viscometer and found to be 0.13–0.18 dL/g. The molecular structure of the monomer and polymers was confirmed by Fourier Transform infrared, ¹H NMR and ¹³C NMR spectroscopic techniques. These polymers were studied for their thermal stability and photochemical properties. Thermal properties were evaluated by thermogravimetric analysis and differential scanning calorimetry. It was found that the polymers were stable up to 238°C and start degrading thereafter. Increase in acid methylene spacer length decreases the thermal stability. The self-extinguishing property of the synthesized polymers was studied by calculating the limiting oxygen index value using Van Krevelen equation. The influence of the length of methylene spacer on phase transition was investigated and it was found that isotropic temperature decreases on increasing the acid methylene spacer length. Hot-stage optical polarizing microscopic study showed that synthesized polymers exhibit grainy texture in the temperature range of 115–127°C. The photolysis of liquid crystalline polyesters revealed that α,β-unsaturated ketone moiety in the main chain dimerizes through 2π+2π cycloaddition reaction to form a cyclobutane derivative that leads to crosslinking.

中文翻译：

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2,6-双（4-羟基亚苄基）环己酮主链上含α，β-不饱和酮基的液晶聚酯的合成与表征

摘要

通过2,6-双（4-羟基亚苄基）环己酮与各种脂族和芳族二酰氯的界面缩聚反应，合成了一系列主链上含有光敏亚苄基发色团的聚酯。用乌氏粘度计测定的合成均聚物和共聚物的特性粘度为0.13-0.18 dL / g。单体和聚合物的分子结构通过傅立叶变换红外光谱，¹ H NMR和¹³确证。13 C NMR光谱技术。研究了这些聚合物的热稳定性和光化学性质。通过热重分析和差示扫描量热法评估热性能。发现该聚合物在238℃下是稳定的，此后开始降解。酸性亚甲基间隔基长度的增加降低了热稳定性。通过使用Van Krevelen方程计算极限氧指数值，研究了合成聚合物的自熄性能。研究了亚甲基间隔基的长度对相变的影响，发现随着酸性亚甲基间隔基长度的增加，各向同性温度降低。热台光学偏振显微镜研究表明，合成聚合物在115–127°C的温度范围内显示出颗粒状质地。