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首页> 外文期刊>Gels >Cryostructuring of Polymeric Systems. 49. Unexpected “Kosmotropic-Like” Impact of Organic Chaotropes on Freeze–Thaw-Induced Gelation of PVA in DMSO
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Cryostructuring of Polymeric Systems. 49. Unexpected “Kosmotropic-Like” Impact of Organic Chaotropes on Freeze–Thaw-Induced Gelation of PVA in DMSO

机译：聚合物系统的低温结构化。 49.有机离液剂对DMSO中PVA的冻融诱导的PVA胶凝的意想不到的“类似同调”的影响

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Urea (URE) and guanidine hydrochloride (GHC) possessing strong chaotropic properties in aqueous media were added to DMSO solutions of poly(vinyl alcohol) (PVA) to be gelled via freeze–thaw processing. Unexpectedly, it turned out that in the case of the PVA cryotropic gel formation in DMSO medium, the URE and GHC additives caused the opposite effects to those observed in water, i.e., the formation of the PVA cryogels (PVACGs) was strengthened rather than inhibited. Our studies of this phenomenon showed that such “kosmotropic-like” effects were more pronounced for the PVACGs that were formed in DMSO in the presence of URE additives, with the effects being concentration-dependent. The additives also caused significant changes in the macroporous morphology of the cryogels; the commonly observed trend was a decrease in the structural regularity of the additive-containing samples compared to the additive-free gel sample. The viscosity measurements revealed consistent changes in the intrinsic viscosity, Huggins constant, and the excess activation heat of the viscosity caused by the additives. The results obtained evidently point to the urea-induced decrease in the solvation ability of DMSO with respect to PVA. As a result, this effect can be the key factor that is responsible for strengthening the structure formation upon the freeze–thaw gelation of this polymer in DMSO additionally containing additives such as urea, which is capable of competing with PVA for the solvent.
机译：在水性介质中具有强离液性的尿素（URE）和盐酸胍（GHC）被添加到聚乙烯醇（PVA）的DMSO溶液中，通过冻融处理使其胶凝。出乎意料的是，事实证明，在DMSO介质中形成PVA低温凝胶的情况下，URE和GHC添加剂与在水中观察到的相反，即增强而不是抑制了PVA低温凝胶（PVACG）的形成。 。我们对这种现象的研究表明，在存在URE添加剂的情况下，在DMSO中形成的PVACG的这种“类似趋同性”的效应更为明显。添加剂还引起了冷冻凝胶大孔形态的显着变化。通常观察到的趋势是与不含添加剂的凝胶样品相比，含添加剂的样品的结构规则性降低。粘度测量结果表明特性粘度，Huggins常数以及由添加剂引起的粘度过量活化热的变化一致。显然获得的结果表明尿素引起的DMSO相对于PVA的溶剂化能力的降低。结果，这种作用可能是导致这种聚合物在DMSO中冻融凝胶后加强结构形成的关键因素，该DMSO还含有尿素等添加剂，能够与PVA竞争溶剂。

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