Anomalous Loss of Stiffness with Increasing Reinforcement in a Photo‐Activated Nanocomposite. Issue 14 (29th May 2021)

• Record Type: Journal Article
• Authors: Zhu, Hongyuan; Lu, Tian Jian; Xu, Feng; Genin, Guy M.; Lin, Min
• Is Part Of: Macromolecular rapid communications. Volume 42:Issue 14(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-29
• Subjects: gelation kinetics -- micromechanics -- nanocomposite hydrogels -- photo‐activated nanocomposites; Macromolecules -- Periodicals; Polymers -- Periodicals; Chemistry -- Periodicals; 547.705
• DOI: 10.1002/marc.202100147
• Languages: English
• ISSNs: 1022-1336

Abstract

Abstract: Hydrogels are commonly doped with stiff nanoscale fillers to endow them with the strength and stiffness needed for engineering applications. Although structure–property relations for many polymer matrix nanocomposites are well established, modeling the new generation of hydrogel nanocomposites requires the study of processing–structure–property relationships because subtle differences in chemical kinetics during their synthesis can cause nearly identical hydrogels to have dramatically different mechanical properties. The authors therefore assembled a framework to relate synthesis conditions (including hydrogel and nanofiller mechanical properties and light absorbance) to gelation kinetics and mechanical properties. They validated the model against experiments on a graphene oxide (GO) doped oligo (ethylene glycol) diacrylate (OEGDA), a system in which, in apparent violation of laws from continuum mechanics, doping can reduce rather than increase the stiffness of the resulting hydrogel nanocomposites. Both model and experiment showed a key role light absorbance‐dominated gelation kinetics in determining nanocomposite mechanical properties in conjunction with nanofiller reinforcement, with the nanofiller's attenuation of chemical kinetics sometimes outweighing stiffening effects to explain the observed, anomalous loss of stiffness. By bridging the chemical kinetics and mechanics of nanocomposite hydrogels, the authors' modeling framework shows promise for broad applicability to design of hydrogel nanocomposites. Abstract : Modeling the new generation of hydrogel nanocomposites requires study of processing–structure–property relationships. A framework to relate synthesis conditions to gelation kinetics and mechanical properties is established and is validated against a graphene oxide‐oligo(ethylene glycol)diacrylate hydrogel system. The model reveals how doping can reduce the hydrogel stiffness. The chemical–mechanical modeling framework provides a powerful tool for designing hydrogel nanocomposites.