Equilibrium free-radical polymerization of methyl methacrylate under nanoconfinement

The effect of nanoconfinement on the equilibrium free radical polymerization of methyl methacrylate (MMA) is investigated using differential scanning calorimetry. The ceiling temperature is shifted to lower temperatures in 13 nm diameter pores, with pore surface chemistry showing no significant effect. The results indicate that the change in the entropy of propagation decreases in nanopores due to confinement effects (i.e. ΔS_p,conf is a more negative value than ΔS_p,bulk). The change in the entropy of propagation is independent of temperature for the bulk equilibrium polymerization, whereas the change in the entropy of propagation in nanopores becomes less negative and more bulk-like with increasing polymerization temperature presumably due to the lower molecular weight chains produced at high temperature. The data suggest that our system is one of weak confinement with chain entropy scaling with molecular weight to the 1.1 power (i.e. ∼ N^1.1).