基于“甲壳”效应、不同尾链长度的离子液晶高分子的相行为和相结构

考察了一系列基于"甲壳"效应的离子液晶高分子poly(2,5-bis{6-(4-butoxy-4?-imidazolium phenyl)k-alkyl]oxy carbonyl}styrene bis(fluoroborate)salts)Pk-6-BF4(k=4,8,12,16)的相行为和相结构.热重分析结果表明,该系列聚合物的热分解温度都在320?C以上,说明其均具有优异的热稳定性能.示差扫描量热仪结果表明,P4-6-BF4和P8-6-BF4仅表现出一个玻璃化转变,随着尾链的增长,P12-6-BF4和P16-6-BF4具有一个结晶熔融峰.偏光显微镜、一维广角X衍射、二维广角X衍射结果表明,该系列聚合物均形成稳定的近晶A相结构,并且随着烷烃尾链的增长,层间距增加、近晶结构内部分子堆积形式有所改变.

Phase Behavior and Phase Structure of Polymerized Ionic Liquid Crystals with Different Alkyl Tail Length Based on "Jacketing" Effect

We synthesized a series of ILCPs contained imidazolium based on "Jacketing" effect via radical polymerization,poly(2,5-bis6-(4-butoxy-4'-imidazolium phenyl) k-alkyl] oxy carbonyl] styrene bis (fluoroborate) salts) (denoted as Pk.6-BF4,k represents the number of carbon in the alkyl tails,k =4,8,12,16).Especially,we mainly focused on their phase behaviors and the supra-molecular structures.Firstly,thermogravimetric analysis (TGA) showed that the decomposition temperature of ILCPs exceeded 320 ℃,revealing the excellent thermal stability of the samples.Differential scanning calorimetry (DSC) results showed that the samples with relatively short alkyl tail (Pk-6-BF4,k =4,8) had only glass transition temperature (Tg),while the samples with relatively long alkyl tail (Pk-6-BF4,k =12,16) also exhibited a melting peak,indicating that increasing the tail length resulted in the crystallization of the alkyl.Polarized light microscopy (PLM) results showed that the liquid crystalline (LC) texture always existed prior to the decomposition,indicating that this kind of ILCPs showed a broad LC temperature.One-(1D) and two-dimensional (2D) wide-angle X-ray diffraction (WAXD) results indicated that Pk.6-BF4 (k =4,8,12,16) formed SmA phase,wherein the side-chain mesogens were perpendicular to the main-chain.Combining the experimental data and the calculated result,we could conclude that the side-chain molecular packing adopted an interpenetrating mode.Furthermore,reconstructed relative electron density map by fast Fourier transform algorithm (FFT) was used to confirm the above results.The FFT result revealed that the increase of alkyl tail length would increase not only the d-spacing of the layer but also affect the interaction between the ions and the side chains,resulting in different molecular packing within SmA phase.It is evident that molecular packing of the ordered structure of ILCPs can be changed by tuning the length of the alkyl tail,which is beneficial to pave a way for the applications of ILCPs.