(441i) Polymerization Thermodynamics Under Nanoconfinement

The behavior of materials confined at the nanoscale has been of considerable interest over the past several decades. Here, our focus is the influence of nanoconfinement on the thermodynamics of free radical n-alkyl methacrylate polymerizations. Using differential scanning calorimetry to follow the reaction, we observe that the ceiling temperature decreases when the methacrylate reactions are performed in nanopores and that the total entropy loss on going from monomer to polymer increases upon nanoconfinement (i.e., the entropy of propagation, ΔS_p, becomes a larger negative value). These confinement effects are observed to become weaker as temperature increases and as the n-alkyl group increases in size, from methyl to ethyl to butyl. The entropy loss on confining a chain is expected to scale with nanoconfinement size and with chain length, and the scaling relationships will be tested and compared to the literature. The results will also be discussed in the context of other nanoscale confinement effects, such as the T_g depression.