| 초록 |
Polyisobutene has an unusually low glass transition temperature (~200 K) despite the severe steric hindrance due to the pendant methyl groups. The origin of such a low glass transition temperature has been intensively studied, but it is not well understood. It has been long suggested that the glass transition can occur in a polymer single chain with very high conformational activation energies. Such polymers are expected to have unique characteristics. This is the ‘single chain glass’ concept proposed by de Gennes. In this study, the existence of the glass transition of a polyisobutene single chain was investigated. Molecular dynamics simulations of melt chains and Brownian dynamics simulations of various phantom chains were performed at various temperatures. The relaxation dynamics of the chain backbone was studied by means of calculating the torsional autocorrelation functions of the skeletal bonds. Similar 1,5 phantom–chain Brownian dynamics simulations were done for single chains of linear polyethylene for comparison. |
