Delayed Swelling and Dissolution of Hydrophobically Associated Hydrogel Coatings by Dilute Aqueous Surfactants
Non-covalently crosslinked hydrogels can exhibit toughness and mechanical adaptability typically associated with biological tissues, which make them promising for a variety of applications. However, molecules in the environment can interact to significantly alter the properties of these hydrogels, which could adversely impact their performance. Here, we illustrate how two common ionic surfactants, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), influence the swelling and rheological properties of hydrogel films crosslinked by hydrophobic associations based on a random copolymer of poly(N,N-dimethylacryalmide-co-2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (DMA-FOSA) using quartz crystal microbalance with dissipation (QCM-D). The effect of the surfactants on the swelling and stability of the hydrogels is contrasted with aqueous 2-propanol (IPA), which can dissolve the copolymer readily. The addition of IPA, SDS and CTAB at low concentrations increases the swelling of the hydrogel film, decreases the elastic modulus and increases the rheological phase angle (more fluid-like). A transition from swelling to (partial) dissolution occurs at higher concentrations, even for originally <200 nm thick copolymer films, with a threshold of approximately 7 wt% IPA, 0.1 CMC for SDS, and 0.5 CMC for CTAB to promote partial dissolution. With IPA, initial swelling is always observed after the solvent is added, whereas the initial swelling can be significantly delayed with long incubation times to dissolution, on the order of hours, at low concentrations of surfactant. These results illustrate that simple ionic surfactants can dissolve these hydrophobically crosslinked hydrogels, but identification of the maximum concentration of surfactant that will not dissolve the hydrogels may be challenged by the long incubation times that increase as the concentration decreases. The long times to dissolve these thin films suggest that stability of bulk physically crosslinked hydrogels in complex aqueous environments may be challenging to accurately assess if surfactant diffusion is limiting factor.
|Work Title||Delayed Swelling and Dissolution of Hydrophobically Associated Hydrogel Coatings by Dilute Aqueous Surfactants|
|License||In Copyright (Rights Reserved)|
|Publication Date||January 1, 2021|
|Publisher Identifier (DOI)||
|Deposited||July 19, 2022|
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