Łukaszewska Izabela, Bukowczan Artur, Raftopoulos Konstantinos N, Pielichowski Krzysztof
Department of Chemistry and Technology of Polymers, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland.
Polymers (Basel). 2023 Dec 23;16(1):57. doi: 10.3390/polym16010057.
Non-isocyanate polyurethane (NIPU) networks physically modified with octa(3-hydroxy-3-methylbutyldimethylsiloxy)POSS (8OHPOSS, 0-10 wt%) were conditioned in environments of different relative humidities (up to 97%) to study water-polymer interactions. The equilibrium sorption isotherms are of Brunauer type III in a water activity range of 0-0.97 and are discussed in terms of the Guggenheim (GAB) sorption model. The study shows that the introduction of 8OHPOSS, even in a large amount (10 wt%), does not hinder the water affinity of the NIPU network despite the hydrophobic nature of POSS; this is attributable to the homogenous dispersion of POSS in the polymer matrix. The shift in the urethane-derived carbonyl bands toward lower wavenumbers with a simultaneous shift in the urethane N-H bending bands toward higher wavenumbers exposes the breakage of polymer-polymer hydrogen bonds upon water uptake due to the formation of stronger water-polymer hydrogen bonds. Upon water absorption, a notable decrease in the glass transition temperature (Tg) is observed for all studied materials. The progressive reduction in Tg with water uptake is driven by plasticization and slaving mechanisms. POSS moieties are thought to impact slaving indirectly by slightly affecting water uptake at very high hydration levels.
用八（3-羟基-3-甲基丁基二甲基硅氧基）倍半硅氧烷（8OHPOSS，0-10重量%）进行物理改性的非异氰酸酯聚氨酯（NIPU）网络在不同相对湿度（高达97%）的环境中进行处理，以研究水-聚合物相互作用。在水活度范围为0-0.97时，平衡吸附等温线属于布鲁诺尔III型，并根据古根海姆（GAB）吸附模型进行讨论。研究表明，尽管POSS具有疏水性，但即使大量引入8OHPOSS（10重量%）也不会阻碍NIPU网络的亲水性；这归因于POSS在聚合物基体中的均匀分散。聚氨酯衍生的羰基带向低波数移动，同时聚氨酯N-H弯曲带向高波数移动，这表明由于形成了更强的水-聚合物氢键，吸水时聚合物-聚合物氢键断裂。对于所有研究的材料，吸水后玻璃化转变温度（Tg）都有显著降低。随着吸水，Tg的逐渐降低是由增塑和从属机制驱动的。据认为，POSS部分通过在非常高的水合水平下略微影响吸水来间接影响从属作用。
