Highly deformable hydrogels constructed by pH-triggered polyacid nanoparticle disassembly in aqueous dispersions. Issue 18 (19th April 2018)

• Record Type: Journal Article
• Authors: Wang, Wenkai; Lu, Dongdong; Zhu, Mingning; Saunders, Jennifer M.; Milani, Amir H.; Armes, Steven P.; Saunders, Brian R.
• Is Part Of: Soft matter. Volume 14:Issue 18(2018)
• Page Start: 3510
• Page End: 3520
• Publication Date: 2018-04-19
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c8sm00325d
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : We study remarkably deformable and resilient pH-responsive hydrogels constructed using crosslinker-free polymer nanoparticles as the only gel building blocks in the absence of added small molecule monomers. Abstract : Most hydrogels are prepared using small-molecule monomers but unfortunately this approach may not be feasible for certain biomaterial applications. Consequently, alternative gel construction strategies have been established, which include using covalent inter-linking of preformed gel particles, or microgels (MGs). For example, covalently interlinking pH-responsive MGs can produce hydrogels comprising doubly crosslinked microgels (DX MGs). We hypothesised that the deformability of such DX MGs was limited by the presence of intra-MG crosslinking. Thus, in this study we designed new nanoparticle (NP)-based gels based on pH-swellable NPs that are not internally crosslinked. Two polyacid NPs were synthesised containing methacrylic acid (MAA) and either ethyl acrylate (EA) or methyl methacrylate (MMA). The PMAA–EA and PMAA–MMA NPs were subsequently vinyl-functionalised using glycidyl methacrylate (GMA) prior to gel formation via free-radical crosslinking. The NPs mostly disassembled on raising the solution pH but some self-crosslinking was nevertheless evident. The gels constructed from the EA- and MMA-based NPs had greater breaking strains than a control DX MG. The effect of varying the solution pH during curing on the morphology and mechanical properties of gels prepared using PMAA–MMA–GMA NPs was studied and both remarkable deformability and excellent recovery were observed. The gels were strongly pH-responsive and had tensile breaking strains of up to 420% with a compressive strain-at-break of more than 93%. An optimised formulation produced the most deformable and stretchable gel yet constructed using NPs or MGs as the only building block.