Abstract
Atomistic molecular dynamics simulations are performed to study the initial crystallization process of poly(trimethylene terephthalate) (PTT). The structure development of ordering structures (nuclei precursors) in the isothermal and stress-induced crystallization process has been observed in our simulations. The formation of nucleus precursors is found to be driven mainly by the torsional and van der Waals forces. The thermal properties, such as the glass transition temperature (Tg) and the melting temperature (Tm), determined from our simulation are in good agreement with experimental values. In isothermal processes, it is found that, between these two temperatures, the amount of precursors quickly arises during thermal relaxation period soon after the system is quenched and starts to fluctuate afterwards. The variation of precursor fraction with temperature exhibits a maximum between Tg and Tm, resembling temperature dependence of crystallization rate for most polymers. In addition, the backbone torsion distribution for segments within the precursor preferentially reorganizes to the trans-gauche-gauche-trans (t-g-g-t) conformation, the same as that in the crystalline state. On the other hand, during stress-induced crystallization, the amount of stress-induced precursor increases in all regions of temperature. The torsional distribution of the polymer backbone for segments rapidly rearrange to the t-t-t-t conformation in bulk phase. Within oriented precursors, the response of the torsional angle induced by stress is faster than that only induced by thermal stimulation, especially trans in
Published Version
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