Getting control of hydrogel networks with cross-linkable monomers

• Published in: Journal of materials chemistry. B, Materials for biology and medicine Vol. 9; no. 46; pp. 9497 - 954
• Main Authors: Cohn, Pamela G, Qavi, Sahar, Cubuk, Jasmine, Jani, Mihir, Megdad, Mohamed Lamine, Shah, Dhvani, Cattafi, Cara, Baul, Panchatapa, Rajaraman, Shanthi, Foudazi, Reza
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.12.2021
• Subjects: Acrylamide; Biocompatible Materials; Composition; Compressive strength; Crosslinking; Ductility; Gels; Hydrogels; Hydrogels - chemistry; Materials Testing; Mechanical Phenomena; Mechanical properties; Molecular Structure; Monomers; Networks; NMR; Nuclear magnetic resonance; Polymerization; Rheology; Stoichiometry; Stress transfer
• ISSN: 2050-750X; 2050-7518
• DOI: 10.1039/d1tb00482d

The structure of a hydrogel network determines its ability to dissipate stress upon deformation, as well as its ability to swell in water. By designing systems with cross-linkable thiol groups in the monomers, radical thiol-ene chemistry was used to form controlled networks for acrylamide monomers. The use of radical thiol-ene chemistry effectively suppressed homo-polymerization of the bis(acrylamide) monomer and resulted in networks of alternating thiol and acrylamide monomers. Additionally, if the stoichiometry between the monomers is controlled, the network should approach that of ideality. In the case of bis(acrylamide) monomers, the incorporation of hydrogen-bond donors into the network creates a single network hydrogel with the benefits of high strength and ductility from the simultaneous incorporation of chemical and physical cross-links. Additionally, this strategy suppresses the formation of homo-polymerization in the acrylamide monomer to achieve an alternating network, which is supported with NMR characterization of base-digested fragments. For three different monomer compositions, the resulting gels had high compressive strength (up to 40 MPa) and tunable mechanical properties. The high mechanical strength of the 1 : 1, thiol : ene gel composition is due to the uniform distribution of cross-links, which creates defect-free networks for efficient stress transfer. The present one-pot synthetic strategy toward controlled gel networks affords monomer versatility and synthetic ease, as well as the potential for mechanically robust materials. The work describes the synthesis of hydrogels with a one-pot strategy for co-polymerization and cross-linking with thiol-ene chemistry between monomers.