Structural insights on the metal cross-linking of polymers from the first principles: Calcium – Polymethacrylic acid case study. (12th February 2021)

• Record Type: Journal Article
• Authors: Syzgantseva, Maria A.; Syzgantseva, Olga A.
• Is Part Of: Polymer. Volume 215(2021)
• Publication Date: 2021-02-12
• Subjects: Cross-linked polymeric networks -- Metal-polymer contacts -- Hydrogels -- Polycarboxylate -- Interfaces -- Gelation; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.123368
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Metal – polymer interactions are widely exploited for the formation of composite polymer materials, such as hydrogels. Despite the interest towards these systems, still few information is available about the atomistic structure of contacts formed at the interface between the polymer chains, as well as interactions responsible for their formation. In this work the interface formed through the interaction between a widely used polymer system – polymethacrylic acid (PMAA) and Ca 2+ cation, as a frequently applied metal cross-linker, is investigated by an ab initio modeling. The local environment of Ca binding sites, including coordination patterns of carboxylic groups, the maximum number of chains cross-linked by one Ca cation, as well as the impact of the PMAA protonation state on the polymer cross-linking are studied. The dynamics of Ca cross-linking process in polymer-rich environment is analyzed. These findings shed the light on the mechanism of Ca – PMAA hydrogel formation and provide the atomistic scale insights on the structure of metal cross-links in the polymer environment, necessary for the optimization of experimental conditions required to obtain polymer composites with enhanced stability and targeted functional characteristics. Graphical abstract: Image 1 Highlights: Crosslinking of polymethacrylic acid (PMAA) by Ca 2+ environment is investigated from the first principles. The local structure of Ca contacts at the PMAA interfaces is studied. Typical Ca coordination patterns, Ca–O distances and a total number of polymer chains that can bind to Ca cation in a polymer-rich environment are reported. The timescale of Ca binding dynamics is revealed. Spontaneous replacement of water in the coordination sphere of Ca by carboxylate groups during the crosslinking process is demonstrated.