کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5188850 | 1381170 | 2008 | 4 صفحه PDF | دانلود رایگان |
It is well known that the intrinsic melting mechanism is independent of crystal size according to Lindemann's melting criterion. In order to probe whether the glass transition mechanism is also size-independent, segment dynamics of free-standing polystyrene (PS) films is determined by considering the temperature- and thickness-dependent number of styrene segments Nα(T,D) in the cooperative rearranging region (CRR). Under the help of Adams-Gibbs glass transition theory and molecular dynamics simulation, Nα(T,D) function is established and it decreases as D decreases or T increases. However, Nα[Tg(D),D] at the glass transition temperature Tg(D) is size-independent, which is consistent with the simulation results obtained by Donth's method. Meanwhile, its relative temperature function Nα{[T â Tg(D)]/Tg(D)} is also size-independent. Therefore, Nα[Tg(D),D] function as a criterion for glass transition, which describes the physical nature of the glass transition, is similar to the vibrational amplitude in Lindemann's melting criterion.
Journal: Polymer - Volume 49, Issue 16, 28 July 2008, Pages 3578-3581