(544a) The Glass Transition and Polymerization in Nanoconfined Systems

The behavior of materials confined at the nanoscale has been of considerable interest over the past several decades. Our recent work using chip calorimetry has examined the changes in the glass transition temperature (T_g) of ultrathin film and nanorod geometries as a function of confinement size, as well investigation of the nature of the "confined" rigid amorphous fraction in semi-crystalline polymers. In addition, we have studied the effects of nanoconfinement on polymerization kinetics, thermodynamics, and the resulting properties of the polymers synthesized. We find that changes in reaction rates for step growth, radical, and ring-opening polymerizations under confinement can be explained by a competition between changes in local packing, diffusivity, and surface effects. The result is generally, but not always, an acceleration of the rate of the nanoconfined polymerization. In addition, nanoconfinement influences the chain length, PDI, and tacticity of the synthesized polymer, making confinement a potential tool for controlling synthetic outcomes. In the case of equilibrium polymerizations, nanoconfinement influences the monomer/polymer equilibrium shifting it back towards monomer, and this effect can be exploited to determine the entropy loss on confining a chain and to test scaling theories in the literature concerning confinement entropy.