Supramolecular organogel formation behaviors of beads-on-string shaped poly(azomethine)s dependent on POSS structures in the main chains
Supramolecular organogel formation behaviors of beads-on-string shaped poly(azomethine)s dependent on POSS structures in the main chains
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DOI：
10.1039/d1py00346a
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发表时间：
2021-05-03
影响因子：
4.6
通讯作者：
Naka, Kensuke
中科院分区：
文献类型：
--
作者：
Ishida, Ayano;Fujii, Shunichi;Naka, Kensuke
在主链中引入笼型倍半硅氧烷的串珠状聚合物，特别是双层苯基取代的倍半硅氧烷（DDSQ），在过去几十年中受到了极大的关注。双官能化异丁基取代的笼型八倍半硅氧烷（T-8）也已经产生这种类型的聚合物结构。然而，包含苯基取代的DDSQ和异丁基取代的T-8单元的主链型聚合物之间的直接比较很少报道。本论文以3，13-二氢八苯基六环十硅氧烷（dihydro-DDSQ）为原料，与N-烯丙基氨基甲酸叔丁酯进行硅氢加成反应，再用三氟乙酸脱保护，合成了双（3-氨丙基）-DDSQ（6）。对-双（3-氨丙基）六异丁基取代的T-8笼（1）和6分别与苯甲醛（2a）、苯甲醛（2b）和4，4 ′-羟基二苯甲醛（2c）聚合，得到相应的T-8-聚甲亚胺（3a-c）和DDSQ-聚甲亚胺（7a-c）。虽然当7的聚合溶液在减压下浓缩时观察到沉淀，但是3经历有机凝胶形成。分别作为3和7中POSS单元的模型化合物的七异丁基-氢化物-POSS（8）和二氢-DDSQ（9）的溶解度测试结果表明，3中异丁基取代的T-8部分的较宽溶解度谱可以为有机凝胶形成提供合适的平衡，并且7中苯基取代的DDSQ部分的较窄溶解度谱可阻止用于合适平衡凝胶形成的特定溶剂区域的存在。对于含有各种连接体结构的3a-c的聚合溶液，零剪切相对粘度（eta（0，r））的浓度（c）依赖性由具有单一值的特征指数的方程很好地描述，使用不同的凝胶化阈值浓度值。
Beads-on-string-shaped polymers incorporating cage silsesquioxanes in the main chain, especially double-decker-shaped phenyl-substituted silsesquioxanes (DDSQ), have received significant attention in the past few decades. Difunctionalized isobutyl-substituted cage octasilsesquioxanes (T-8) have also been generating this type of polymer architecture. However, direct comparisons between main-chain-type polymers comprising phenyl-substituted DDSQ and isobutyl-substituted T-8 units have seldom been reported. In this study, we prepared bis(3-aminopropyl)-DDSQ (6) via the hydrosilylation of 3,13-dihy-drooctaphenylhexacyclodecasiloxane (dihydro-DDSQ) with t-butyl N-allylcarbamate and deprotection with trifluoroacetic acid. Both para-bis(3-aminopropyl)hexaisobutyl-substituted T-8 cage (1), which was developed by us, and 6 were polymerized with terephthalaldehyde (2a), isophthalaldehyde (2b), and 4,4'-oxydibenzaldehyde (2c) to produce the corresponding T-8-poly(azomethine)s (3a-c) and DDSQ-poly(azomethine)s (7a-c), respectively. Although precipitates were observed when the polymerization solution of 7 was concentrated under reduced pressure, 3 underwent organogel formation. Solubility test results for heptaisobutyl-hydride-POSS (8) and dihydro-DDSQ (9) as model compounds for the POSS units in 3 and 7, respectively, suggested that the wider solubility spectrum of the isobutyl-substituted T-8 moieties in 3 may provide a suitable balance for organogel formation, and the narrower spectrum of solubility for the phenyl-substituted DDSQ moieties in 7 may prevent the existence of a specific solvent region for suitable balanced gel formation. The concentration (c) dependences of zero shear relative viscosity (eta(0,r)) for the polymerization solutions of 3a-c, containing various linker structures were well described by an equation with a single value of the characteristic exponent using different values of gelation threshold concentration.