Elastic strain-hardening and shear-thickening exhibited by thermoreversible physical hydrogels based on poly(alkylene oxide)-grafted hyaluronic acid or carboxymethylcellulose

• Published in: Physical chemistry chemical physics : PCCP Vol. 22; no. 26; pp. 14579 - 1459
• Main Authors: Andersson Trojer, Markus, Andersson, Mats, Bergenholtz, Johan, Gatenholm, Paul
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2020
• Subjects: Activation energy; Aggregation numbers; Aqueous solutions; Bio Materials; Biomaterial; Carboxy methylcellulose; Carboxymethylcellulose Sodium - chemistry; Cold Temperature; Continuous transitions; Evolution; Fysikalisk kemi; Graft copolymers; Grafting (chemical); Hot Temperature; Hyaluronic acid; Hyaluronic Acid - chemistry; Hydrogels; Hydrogels - chemistry; Low temperature; Material properties; Materialkemi; Materials Chemistry; Newtonian fluids; Newtonian liquids; Olefins; Phase Transition; Physical Chemistry; Poly(alkylene oxide); Polymer Chemistry; Polymer Technologies; Polymerkemi; Polymers - chemistry; Polymerteknologi; Reaction conditions; Relaxation time; Rheology; Rheology Thermosensitive hydrogels Lower critical solution temperature Transient network theory Strain hardening; Rheometry; Shear thickening (liquids); Shear viscosity; Strain hardening; Temperature regimes; Thickening; Viscoelastic solids; Viscoelastic Substances - chemistry; Viscoelasticity; Viscosity; Zero shear viscosity
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d0cp02124e

The formation of strongly elastic physical gels based on poly(alkylene oxide)-grafted hyaluronan or carboxymethylcellulose, exhibiting both shear-thickening and strain-hardening have been studied using rheometry and explained using a slightly different interpretation of the transient network theory. The graft copolymers were prepared by a quantitative coupling reaction. Their aqueous solutions displayed a thermoreversible continuous transition from Newtonian fluid to viscoelastic solid which could be controlled by the reaction conditions. The evolution of all material properties of the gel could be categorized into two distinct temperature regimes with a fast evolution at low temperatures followed by a slow evolution at high temperatures. The activation energy of the zero shear viscosity and the relaxation time of the graft inside the interconnecting microdomains were almost identical to each other in both temperature regimes. This suggests that the number of microdomains remained approximately constant whereas the aggregation number inside the microdomains increased according to the binodal curve of the thermosensitive graft. An alternative interpretation of the transient network theory is necessary to explain the evolution of the viscoelastic parameters during the temperature-dependent formation into a solid gel structure.