Hydrogen‐Bonded Complexes of Star Polymers
Hydrogen‐Bonded Complexes of Star Polymers
复制标题
星形聚合物的氢键配合物
DOI：
10.1002/marc.202100097
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发表时间：
2021
影响因子：
4.6
通讯作者：
Sukhishvili, Svetlana A.
中科院分区：
文献类型：
--
作者：
Aliakseyeu, Aliaksei;Dormidontova, Elena E.;Sukhishvili, Svetlana A.
实验研究了分子结构、星星与线性聚环氧乙烷（PEO）对线性聚甲基丙烯酸（PMAA）形成氢键复合物的影响，并从理论上进行了合理化。等温滴定量热法表明，在pH 2.5时，PMMA与6-臂星星PEO（sPEO）的互聚物复合物（IPC）比与线性PEO（lPEO）形成的IPC多含约50%的多酸。虽然IPC形成的焓在这两种情况下都是正的，但对于表现出比lPEO/多酸复合物低的解离常数的sPEO/PMAA复合物，IPC形成的焓的幅度大约50%。这些结果是合理化的基础上形成betweensPEO和多酸，防止星星分子渗透到PMAA线圈的氢键的局部密度较高。因此，傅里叶变换红外结果表明，在含PEO的复合物中，自缔合的>COOH单元比分子间键合的>COOH单元大约多两倍。IPC中PMAA链的过量和PEO/PMAA复合物中自缔合羧基的百分比都随着多酸分子量的增加而增加。其他的发现，包括正熵，在强酸性pH值的组成滞后，并逐步平衡的IPC在pH值增加是一致的电荷和释放的水分子的形成ofsPEO/PMAA和lPEO/PMAA复合物的关键作用。
The effect of molecular architecture, star versus linear, poly(ethylene oxide) (PEO) on the formation of hydrogen‐bonded complexes with linear poly(methacrylic acid) (PMAA) is investigated experimentally and rationalized theoretically. Isothermal titration calorimetry reveals that at pH 2.5 interpolymer complexes (IPCs) of PMMA with a 6‐arm star PEO (sPEO) contains ≈50% more polyacid than IPCs formed with linear PEO (lPEO). While the enthalpy of IPC formation is positive in both cases, its magnitude is ≈50% larger forsPEO/PMAA complexes that exhibit a lower dissociation constant thanlPEO/polyacid complexes. These results are rationalized based on a higher localized density of hydrogen bonds formed betweensPEO and the polyacid which prevents penetration of star molecules into PMAA coils. Accordingly, Fourier transform infrared results indicate approximately twofold excess of self‐associated >COOH units over intermolecularly bonded >COOH units insPEO‐containing complexes. The excess of PMAA chains in IPCs and the percentage of self‐associated carboxylic groups insPEO/PMAA complexes both increase with polyacid molecular weight. Other findings, including a positive entropy, hysteresis in composition at strongly acidic pH, and progressive equilibration of IPCs at increased pH are consistent with the critical role of charge and release of water molecules in the formation ofsPEO/PMAA andlPEO/PMAA complexes.