Precise Isotactic or Atactic Pendant Alcohols on a Polyethylene Backbone at Every Fifth Carbon: Synthesis, Crystallization, and Thermal Properties
Precise Isotactic or Atactic Pendant Alcohols on a Polyethylene Backbone at Every Fifth Carbon: Synthesis, Crystallization, and Thermal Properties
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DOI：
10.1021/acs.macromol.2c01090
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发表时间：
2022-07
期刊：
影响因子：
5.5
通讯作者：
G. Guillory;Stephanie F. Marxsen;R. Alamo;Justin G. Kennemur
中科院分区：
文献类型：
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作者：
G. Guillory;Stephanie F. Marxsen;R. Alamo;Justin G. Kennemur
通过(S)或(R)-3-（叔丁基二甲基硅氧基）环戊烯的高度区域规则开环复分解聚合，然后进行烯烃加氢和醇脱保护，合成了一种高摩尔质量（> - 100kg mol-1）、中等分散性（~ 1.6）和在线性聚乙烯主链上每5个碳上都有等规醇的半结晶精度聚合物。将这些材料的热学和半结晶性质与具有无规醇悬垂和不同程度的头尾（HT）区域规则的类似物进行比较。对于HT为77% ~ 99%的无规聚合物，玻璃化转变温度（Tg）的变化受影响最小（47±2℃），但结晶熔化温度（Tm）从96 ~ 137℃显著升高。当存在高度等规醇悬垂基团（90%对映纯单体，HT = 96%）时，温度略微升高至~ 53℃，但温度急剧降低至190℃。虽然无规材料和等规材料的广角x射线衍射图相似，并推断出等效的晶体单位胞填料，但等规样品的结晶度为~ 40%，是高HT = 99%的无规样品（20%）的两倍。所有样品的热稳定性均为bb0 ~ 360℃。这些研究提供了关于等规和精密微观结构如何影响乙烯基单体等规聚合物的二碳支周期性以外的聚合物系统的材料性能的未探索的见解。基于战术比较讨论了合成、结构表征、热性能以及分子间氢键和其他晶体结构数据。
A semi-crystalline precision polymer with a high molar mass (>100 kg mol–1), a moderate dispersity (∼1.6), and an isotactic alcohol pendant on each and every fifth carbon of a linear polyethylene backbone is synthesized through highly regioregular ring-opening metathesis polymerization of (S) or (R)-3-(tert-butyldimethylsiloxy)cyclopentene followed by olefin hydrogenation and alcohol deprotection. The thermal and semi-crystalline properties of these materials are compared to analogues with atactic alcohol pendants and varying degrees of head-to-tail (HT) regioregularity. For atactic polymers with HT from 77 to 99%, the change in glass transition temperature (Tg) is minimally affected (47 ± 2 °C), but the crystalline melting temperature (Tm) increases substantially from 96 to 137 °C. When highly isotactic alcohol pendant groups are present (90% enantiopure monomer and HT = 96%), theTgincreases slightly to ∼53 °C, but theTmincreases dramatically to 190 °C. Although the wide-angle X-ray diffraction patterns of atactic and isotactic materials are similar and infer equivalent crystal unit cell packing, the isotactic sample develops ∼40% crystallinity, which is double that observed for an atactic sample (20%) with high HT = 99%. The thermal stability of all samples was >360 °C. Such investigations present unexplored insights on how isotactic and precision microstructure affect material properties of polymeric systems outside the two-carbon branch periodicity of isotactic polymers from vinyl monomers. Synthesis, structural characterizations, thermal properties in addition to intermolecular hydrogen bonding, and other crystalline structural data are discussed comparatively based on tacticity.