It is well-known that polymerisation-induced self-assembly (PISA) offers a versatile and efficient synthetic route for the production of highly anisotropic methacrylic diblock copolymer worms directly in aqueous solution. Such worms form thermoresponsive free-standing hydrogels that can (i) act as a 3D matrix for the culture of normal mammalian cells and (ii) induce stasis in human stem cell colonies. Herein we critically examine the aqueous gelation behavior of such copolymer worms in terms of recent advances in percolation theory for rigid rods, which explicitly account for the effect of rod length polydispersity. More specifically, we use small-angle X-ray scattering (SAXS) to determine the weight-average worm length Lw and the mean worm cross-sectional radius R: this enables a direct comparison to be made between the theoretical critical worm volume fraction required for gelation and the experimental worm volume fraction indicated by rheological measurements and tube inversion experiments. Bearing in mind that the copolymer worms are relatively flexible rather than rod-like, reasonably good agreement between these two parameters is observed. These findings are expected to have implications for the aqueous gelation behaviour exhibited by various other anisotropic particles, such as cellulose nanocrystals, small molecule (e.g. dipeptide) gelators and semicrystalline block copolymer rods.

Can percolation theory account for the aqueous gelation behavior of diblock copolymer worms?

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.