Polymerization and Crystallization Kinetics of Nanoconfined PLLA

摘要

The influence of nanoconfinement on the reaction kinetics of L-Lactide ring-opening polymerization and the subsequent thermal behavior of Poly(l-lactic acid) (PLLA) are investigated by differential scanning calorimetry (DSC). Both hydrophobic and hydrophilic controlled pore glass (CPG) with pore diameters of 50 nm are used as the confined matrix for the polymer synthesis. Compared with bulk PLLA polymerization, the extent of reaction is reduced under nanoconfinement for the same reaction temperature at the same reaction time. Post-polymerization thermal treatment is performed to remove any residual monomer in order to facilitate the study of the thermal properties and crystallization behavior of pure PLLA under both nanoconfined and bulk conditions. It was found that under nanoconfinement, Tg and the melting temperature of PLLA are shifted to lower temperatures, as expected. Similarly, the onset of the cold crystallization occurs at lower temperatures for nanoconfined PLLA, but the peak position is unchanged. The reaction and crystallization kinetics, as well as reasons for differences between bulk and nanoconfined PLLA, will be discussed.