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Connecting the Stimuli-Responsive Rheology of Biopolymer Hydrogels to Underlying Hydrogen-Bonding Interactions. | LitMetric

AI Article Synopsis

  • Many biopolymer hydrogels, like hyaluronan, are sensitive to environmental changes in pH and temperature, affecting their physical properties.
  • This study examines how pH changes influence molecular interactions in hyaluronan, finding that lower pH increases hydrogen bonding between chains.
  • The research reveals that these hydrogen bonds lead to slower stress relaxation in hydrogels at acidic pH, which could help in designing responsive materials for medical uses.

Article Abstract

Many biopolymer hydrogels are environmentally responsive because they are held together by physical associations that depend on pH and temperature. Here, we investigate how the pH and temperature responses of the rheology of hyaluronan hydrogels are connected to the underlying molecular interactions. Hyaluronan is an essential structural biopolymer in the human body with many applications in biomedicine. Using two-dimensional infrared spectroscopy, we show that hyaluronan chains become connected by hydrogen bonds when the pH is changed from 7.0 to 2.5 and that the bond density at pH 2.5 is independent of temperature. Temperature-dependent rheology measurements show that because of this hydrogen bonding the stress relaxation at pH 2.5 is strongly slowed down in comparison to pH 7.0, consistent with the sticky reptation model of associative polymers. From the flow activation energy, we conclude that each polymer is cross-linked by multiple (5-15) hydrogen bonds to others, causing slow macroscopic stress relaxation, despite the short time scale of breaking and reformation of each individual hydrogen bond. Our findings can aid the design of stimuli-responsive hydrogels with tailored viscoelastic properties for biomedical applications.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7735748PMC
http://dx.doi.org/10.1021/acs.macromol.0c01742DOI Listing

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