Slowing down of the crystallization kinetics in ultrathin polymer films:: A size or an interface effect?

The cold crystallization kinetics in ultrathin polymer films were analyzed by using spectroscopic techniques. The Dielectric spectroscopy (DS) used to monitor in real time the crystallization of ultrathin polymer films of PHB resulted that the thickness of the sample does not influence the change occurring in the amorphous phase due to crystallization. The DS technique also offered the possibility of accessing a broadband frequencies of the changes induced by geometrical constraint and confinement to the segmental mobility. The access of the dynamic glass transition temperature on the nanometer scale by this technique resulted in the possibility to discriminate the difference between the influence of temperature and the reduction of mobility of the polymer layers at its interface with the substrate on the changes in the crystallization kinetics.