Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties
Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties
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合成聚丁二烯折射率增量的测定以及接枝密度和液晶性能的微观结构控制
DOI：
10.1039/d0py00050g
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发表时间：
2020-04-14
影响因子：
4.6
通讯作者：
Li, Yang
中科院分区：
文献类型：
--
作者：
Huang, Shuai;Han, Li;Li, Yang
具有微观结构控制的聚丁二烯（PB），即，通过改变极性添加剂和它们在BuLi上的摩尔比，使用活性阴离子聚合（living anionic polymerization，CHR）容易地合成了范围从8%至94%（摩尔分数）的1，2-烯烃。本文中，使用配备有差示折射率（RI）和小角度激光散射（LALLS）检测器的凝胶渗透色谱法测定PB的折射率增量（dn/dc）和重均分子量（Mw（GPC-RI/LALLS），并且如预期的，dn/dc的值对1具有显著的依赖性，2-烯烃的微观结构，这是相关的玻璃化转变温度（Tg）的PB。这些PB主链随后用作合成PB基液晶聚合物（LCP）（PB-M1和PB-M2）的前体，其中在偶氮苯部分（Azo-M1和Azo-M2）沿沿着PB纵向连接之后，接枝密度的微观结构控制为15%、30%和50%（摩尔）。更重要的是，不变的接枝密度对于PB-M1和PB-M2两者，观察到随着1，2-烯烃级分的增加，（≥50%的1，2-烯烃），这解释了相变方面的1，2-烯烃微观结构控制（介晶形成）无论Azo-M1或Azo-M2是否用作侧连接，而使用不同加工温度的DSC曲线和具有随温度的畴间距偏移的X射线分析表明，与PB-M1相比，PB-M2的介晶相变化更大，ΔT值更宽。
Polybutadienes (PBs) with microstructural control, i.e., 1,2-olefins ranging from 8% to 94% (mole fractions), were readily synthesized using living anionic polymerization (LAP) by varying the polar additives and their mole ratios over BuLi. Herein, the determination of refractive index increment (dn/dc) and weight-average molecular weight (Mw) of PBs using gel permeation chromatography equipped with differential refractive index (RI) and low angle laser light scattering (LALLS) detectors (GPC-RI/LALLS) is shown, and as expected, the values of dn/dc have a significant dependence on 1,2-olefins of microstructures which is relevant to the glass transition temperature (Tg) of PBs. These PB backbones were subsequently used as precursors for the synthesis of PB-based liquid crystal polymers (LCPs) (PB-M1 and PB-M2) with a microstructural control of grafting densities of 15%, 30% and 50% (moles) after the longitudinal attachment of azobenzene moieties (Azo-M1 and Azo-M2) along PBs. More importantly, the unchanged grafting density (almost 50%) with increasing 1,2-olefin fractions was observed for both PB-M1 and PB-M2 (≥50% 1,2-olefins), which explained the 1,2-olefin microstructural control in terms of phase transitions (mesogenic formation) regardless of whether Azo-M1 or Azo-M2 was used as a side attachment, while DSC curves using different processing temperatures and X-ray analysis with a domain spacing shift over temperature demonstrate a much more variable mesogenic phase and wider ΔT values of PB-M2 compared to PB-M1.