Small dop of comonomer, giant shift of dynamics: α-methyl-regulated viscoelasticity of poly(methacrylamide) hydrogels

• Published in: Giant (Oxford, England) England), 2024-12, Vol.20, p.100342, Article 100342
• Main Authors: Guan, Xin, Zhou, Zhiheng, Fan, Xinzhen, Xu, Wenchao, Jin, Yijie, Zhao, Chuanzhuang
• Format: Article
• Language: English
• Subjects: Dynamics; Hydrogel; Hydrogen bond; α-methyl
• ISSN: 2666-5425; 2666-5425
• DOI: 10.1016/j.giant.2024.100342

•Incorporating a small amount (≤6 mol%) of α-methyl-absent monomer, acrylamide into polymethacrylamide hydrogels significantly alters their viscoelasticity,•The α-methyl-absent monomer acts as a hydrophilic defect, enhancing water molecule dynamics and accelerating polymer chain dissociation.•Modulating the α-methyl-regulated dynamic properties enables the development of copolymer hydrogels with rapid self-healing capabilities and tunable adhesion. α-Methyl groups play significant roles in the regulation of water molecules within both small molecular systems and bio-macromolecular systems. Systematically studying the influence of α-methyl on the dynamics of water molecules within hydrogel systems is therefore worthwhile. In this study, we prepared a series of hydrogen-bonded (H-bonded) hydrogels with varying densities of α-methyl groups by copolymerizing methacrylamide (MAm) with its α-methyl-absent analogue, acrylamide (Am). Introducing a small amount of Am (≤6 mol%) into the polymer chain resulted in significant shifts in the viscoelasticity of the hydrogels. The hydrogels exhibit a “time-temperature-α-methyl equivalence”, meaning that introduction of α-methyl-absent monomer has effects similar to elevating temperature and prolonging observation time on the dynamic properties. Based on low-field nuclear magnetic resonance spectroscopy and Raman scattering, a “hydrophilic defects-assisted H-bonds dissociation” mechanism is proposed, depicting that the α-methyl-absent monomer can disturb the rearrangement of water molecules surrounding the polymer chain and accelerate chain dissociation. These findings enabled the copolymer hydrogels with functions such as fast self-healing and tunable interface adhesion. [Display omitted]