Application of periodically modulated driving force to the transition kinetics in vinylidene fluoride/trifluoroethylene copolymers

The method of "modulated driving force" has been applied to the kinetics of ferroelectric-paraelectric transition in copolymers of vinylidene fluoride (VDF) with trifluoroethylene (TrFE). The method examines the response of t ransition kinetics to a periodically modulated driving force, e.g., superco oling or superheating. The response to the modulation in temperature appear s in the apparent heat capacity obtained by a temperature-modulated differe ntial scanning calorimeter. By examining the frequency dispersion and its d ependence on underlying linear heating (or cooling) rate, the mean time req uired for the completion of transition in each crystallite and the dependen ce of transition rate on superheating (or supercooling) are obtainable. In VDF/TrFE copolymers, it is known that the transition behavior undergoes a d rastic change from reversible transition with low VDF content to nucleation -controlled transition with higher content. Several types of compositions ( VDF/TrFE=47/53, 52/48, 59/41, 65/35, 69/31 and 73/27 by mol %) have been ex amined experimentally with this method in terms of the crossover of transit ion behaviors. (C) 2001 American Institute of Physics.