Hu Neng, Chen Chen, Metwalli Ezzeldin, Bießmann Lorenz, Herold Christian, Fu Jun, Cubitt Robert, Zhong Qi, Müller-Buschbaum Peter
Key Laboratory of Advanced Textile Materials & Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, 310018 Hangzhou, China.
Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, James-Franck-Str. 1, 85748 Garching, Germany.
Langmuir. 2021 Jun 8;37(22):6819-6829. doi: 10.1021/acs.langmuir.1c00931. Epub 2021 May 27.
The hydration and thermal response kinetics of the cross-linked thermoresponsive copolymer poly((diethylene glycol monomethyl ether methacrylate)--poly(ethylene glycol) methyl ether methacrylate), abbreviated as P(MEOMA--OEGMA), thin film on a hydrophobic polyacrylonitrile (PAN) substrate coating, which resembles a synthetic fabric, is probed by neutron reflectivity (NR). The PAN and monomer (MEOMA and OEGMA) solutions are sequentially spin-coated onto a silicon (Si) substrate. Afterward, plasma treatment is applied to realize the cross-linking of PAN and monomers. The as-prepared cross-linked P(MEOMA--OEGMA) film on the hydrophobic PAN substrate coating presents a two-layer structure: a substrate-near layer, which is a mixture of PAN and P(MEOMA--OEGMA), and a main layer, which is composed of pure hydrophilic P(MEOMA--OEGMA). During hydration in DO vapor atmosphere, the hydrophobic PAN component prevents the formation of DO enrichment in the substrate-near layer. However, an additional vapor-near layer is observed on top of the main layer, which is enriched with DO. The hydration process is constrained by the cross-linking points in the film, inducing the relaxation time to be longer than that in a spin-coated P(MEOMA--OEGMA) film. Because the as-prepared cross-linked film presents a transition temperature (TT) at 38 °C, the hydrated film switches to the collapsed state when the temperature is increased from 23 to 50 °C. The response to a thermal stimulus is also slower due to the existence of the internal cross-linking points as compared to the spin-coated film. Interestingly, no reswelling is observed at the end of the thermal stimulus, which can be also attributed to the presence of internal cross-linking points.
通过中子反射率（NR）研究了交联热响应共聚物聚（二乙二醇单甲醚甲基丙烯酸酯 - 聚乙二醇甲醚甲基丙烯酸酯），简称为P（MEOMA - OEGMA），在类似合成织物的疏水性聚丙烯腈（PAN）基底涂层上的薄膜的水合和热响应动力学。将PAN和单体（MEOMA和OEGMA）溶液依次旋涂到硅（Si）基底上。之后，进行等离子体处理以实现PAN和单体的交联。在疏水性PAN基底涂层上制备的交联P（MEOMA - OEGMA）薄膜呈现两层结构：靠近基底的层，它是PAN和P（MEOMA - OEGMA）的混合物；以及主要层，它由纯亲水性P（MEOMA - OEGMA）组成。在DO蒸汽气氛中进行水合时，疏水性PAN组分可防止在靠近基底的层中形成DO富集。然而，在主要层的顶部观察到一个额外的靠近蒸汽的层，其富含DO。水合过程受到薄膜中交联点的限制，导致弛豫时间比旋涂的P（MEOMA - OEGMA）薄膜中的弛豫时间更长。由于制备的交联薄膜在38°C时呈现转变温度（TT），当温度从23°C升高到50°C时，水合薄膜会转变为塌陷状态。与旋涂薄膜相比，由于内部交联点的存在，对热刺激的响应也较慢。有趣的是，在热刺激结束时未观察到再溶胀，这也可归因于内部交联点的存在。
