Solvent effects on surface-grafted and solution-born poly[N-(2-hydroxypropyl)methacrylamide] during surface-initiated RAFT polymerization

The difference in the molar mass between surface-grafted and solution-born polymers grown during surface-initiated (SI) polymerization has caused controversy for years. To understand it, we study the solvent effects on the polymer formed on the surface and in the solution by investigating their macromolecular parameters. We utilized reversible addition fragmentation chain-transfer (RAFT) polymerization to grow surface-grafted and solution-born poly[N-(2-hydroxypropyl)methacrylamide] (p(HPMA)) under different solvent conditions. Changing the solvent proticity and/or polarity influences the solution propagation rate, leading to mass transfer limitations and a concomitant discrepancy in the molar masses of the polymer formed in solution and grafted from the surface. Moreover, the solvent effects were found to directly determine the grafting density of surface-grafted p(HPMA). These results highlight how decisive the solvent effects on the SI-RAFT polymerization of HPMA are and that they may be key to regulate the physical and macromolecular parameters of the obtained surface-grafted p(HPMA) brushes.