Thermodynamics and Entropy Loss in Nanoconfined Chain Polymerization

The effect of nanoconfinement on the thermodynamics of methyl‐, butyl‐, and benzyl‐methacrylate free‐radical chain polymerizations is investigated using differential scanning calorimetry. Controlled pore glass (CPG) and ordered mesoporous carbon are used as confinement media with pore sizes from 3 to 13 nm. Relative to bulk polymerization, nanoconfinement shifts the monomer/polymer equilibrium toward monomer, resulting in a rounding of the transition at high temperatures. In addition, a new floor temperature emerges in both nanoconfined butyl‐ and benzyl‐methacrylate chain polymerizations in the vicinity of 40°C–80°C, with the floor temperature dependent on pore size and chain length synthesized. The difference in the change in the entropy on propagation between bulk and nanoconfined polymerizations is found to be as high as 48 J/K/mol monomer and to superpose when plotted versus R g / D . The experimental confinement entropy data are 1–2 orders of magnitude higher than the values obtained from self‐avoiding walk (SAW) simulations in cylindrical confinement. Furthermore, the experimental confinement entropy is super‐extensive in chain length suggesting that an important difference between experiments and simulations lies in the collective effect of multiple chains growing in the same confinement space.