Water Uptake, Thin-Film Characterization, and Gravimetric pH-Sensing of Poly(vinylphosphonate)-Based Hydrogels

IF 8.3 2区 材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY
Anton S. Maier, Matjaž Finšgar, Beatrice De Chiara, Rupert Kargl, Bernhard Wolfrum, Karin Stana Kleinschek, Bernhard Rieger
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Abstract

Herein, novel, superabsorbent, and pH-responsive hydrogels obtained by the photochemical cross-linking of hydrophilic poly(vinylphosphonates) are introduced. First, statistical copolymers of diethyl vinylphosphonate (DEVP) and diallyl vinylphosphonate (DAlVP) are synthesized via rare earth metal-mediated group-transfer polymerization (REM-GTP) yielding similar molecular weights (Mn,NMR = 127–142 kg/mol) and narrow polydispersities (Đ < 1.12). Subsequently, polymer analogous transformations of P(DEVP-stat-DAlVP) introduced vinylphosphonic acid (VPA) units into the polymers. In this context, the partial dealkylation of the polymers revealed a preference for DAlVP hydrolysis, which was observed via 1H NMR spectroscopy and explained mechanistically. Furthermore, the P(DEVP-stat-DAlVP-stat-VPA) polymers were cross-linked under photochemical reaction conditions (λ = 365 nm) via thiol–ene click chemistry, yielding superabsorbent hydrogels with water uptakes up to 150 ± 27 g (H2O)/g (hydrogel). Regarding water absorption, evident structure–property relationships between cross-linking density, polarity, and swelling behavior were found. Finally, the pH-responsiveness of thin films of these hydrogels was investigated. In this regard, films with a thickness of 39.4 ± 2.33 nm determined via profilometry were spin-coated on sensors of a quartz crystal microbalance with dissipation monitoring (QCM-D) and thoroughly characterized by atomic force microscopy (AFM). QCM-D measurements exposing the hydrogel films to different aqueous media revealed different swelling states of the hydrogels depending on the pH values (1, 6, 10, and 13) of the surrounding environment, as reflected by corresponding frequency and dissipation values. The hydrogels exhibited fully reversible swelling and deswelling upon switching between pH 1 and 13 (three cycles), sustaining the harsh conditions without erosion from the gold surface and thus acting as a gravimetric sensor discriminating between the two pH values. The high stability of the films on the gold surfaces of QCM-D sensors was explained by anchoring of the P(DEVP-stat-DAlVP-stat-VPA) networks through the dithiol cross-linker as confirmed by detailed X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies.

Abstract Image

聚膦酸乙烯基水凝胶的吸水、薄膜表征和重量ph传感
本文介绍了一种新型的、高吸水性的、ph响应性的水凝胶,这种水凝胶是由亲水性聚苯乙烯膦酸酯光化学交联而成的。首先,通过稀土金属基团转移聚合(REM-GTP)合成了二乙基乙烯基膦酸酯(DEVP)和二烯丙基乙烯基膦酸酯(DAlVP)的统计共聚物,得到了相似的分子量(Mn,NMR = 127-142 kg/mol)和窄多分散度(Đ <;1.12)。随后,P(DEVP-stat-DAlVP)的聚合物类似转化将乙烯基膦酸(VPA)单元引入聚合物中。在这种情况下,聚合物的部分脱烷基反应显示了对DAlVP水解的偏好,这是通过1H NMR光谱观察到的,并从机理上解释了。此外,P(DEVP-stat-DAlVP-stat-VPA)聚合物在光化学反应条件下(λ = 365 nm)通过巯基点击化学交联,得到吸水性高达150±27 g (H2O)/g(水凝胶)的高吸水性水凝胶。在吸水率方面,交联密度、极性和膨胀行为之间存在明显的结构-性能关系。最后,研究了这些水凝胶薄膜的ph响应性。为此,我们在石英晶体微天平的传感器上进行了自旋镀膜,并用原子力显微镜(AFM)对薄膜进行了彻底的表征,薄膜厚度为39.4±2.33 nm。将水凝胶膜暴露在不同水介质中的QCM-D测量显示,水凝胶的膨胀状态随周围环境的pH值(1、6、10和13)不同而不同,这反映在相应的频率和耗散值上。在pH值1和13之间切换(三个循环)时,水凝胶表现出完全可逆的膨胀和溶胀,维持了恶劣的条件而不会受到金表面的侵蚀,因此可以作为区分两种pH值的重力传感器。通过详细的x射线光电子能谱(XPS)和飞行时间二次离子质谱(ToF-SIMS)研究证实,通过二硫醇交联剂锚定P(DEVP-stat-DAlVP-stat-VPA)网络可以解释薄膜在QCM-D传感器金表面上的高稳定性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
ACS Applied Materials & Interfaces
ACS Applied Materials & Interfaces 工程技术-材料科学:综合
CiteScore
16.00
自引率
6.30%
发文量
4978
审稿时长
1.8 months
期刊介绍: ACS Applied Materials & Interfaces is a leading interdisciplinary journal that brings together chemists, engineers, physicists, and biologists to explore the development and utilization of newly-discovered materials and interfacial processes for specific applications. Our journal has experienced remarkable growth since its establishment in 2009, both in terms of the number of articles published and the impact of the research showcased. We are proud to foster a truly global community, with the majority of published articles originating from outside the United States, reflecting the rapid growth of applied research worldwide.
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