Tuning the Persistence Length of Semiflexible Methylcellulose Chains by Grafting

Low molecular weight thiol-terminated poly(ethylene glycol) has been grafted onto a high molecular weight methylcellulose by a facile thiol-ene click reaction; graft densities varied from 0.7% to 33% (grafts per anhydroglucose unit). Static and dynamic light scattering reveals that the overall radius of the chain increases systematically with graft density, in a manner in excellent agreement with excluded volume theory. As the underlying contour length remains unchanged, it is apparent that grafting leads to an increase in the persistence length, by as much as a factor of four. These results represent the first experimental verification of the excluded volume theory at low grafting densities, and demonstrate a promising synthetic platform for systematically increasing the persistence length of a model water-soluble semiflexible polymer.