Molecular-weight dependence of simulated glass transition temperature for isolated poly(ethylene oxide) chain

ABSTRACT

Molecular dynamics simulations have been performed with chemically realistic coarse-grained potentials to assess the effects of molecular weight on the glass transition temperatures (T_g) of single-chain particle of poly(ethylene oxide) in a vacuum. It is found that all the long isolated chains form impact globule like configurations, and higher molecular weight and lower temperature lead to more perfect sphericity. With increasing molecular weight, the simulated T_g of the isolated chain tends to increase whereas the T_g of the bulk undergoes a slight change. The confinement effects are associated with localisation of chain ends at the surface and specific surface areas. More importantly, the T_g shift can be quantified by the solubility parameter that includes the contribution of conformational change. As compared to the conventional definition that only sums intermolecular interactions, such solubility parameter is a better metric in simulations to explain the confinement effects since it does not depend upon the degree of equilibration as the T_g. These results can be quite valuable to clarifying glass transition behaviour of polymers films.

KEYWORDS:

• Glass transition temperatures
• isolated polymer chains
• confinement effects
• multiscale simulations

Acknowledgements

This work is financially supported by the double first-class discipline construction programme of Hunan province, and the Innovative Research Team in Higher Educational Institute of Hunan Province, and the Talent Support Plan of Hunan University of Humanities Science & Technology (HUHST). The author is indebted to the Molecular Simulation Center of Hunan Province (situated at Hunan University), which provides the commercial software (Materials Studio-4.0) to build the initial structural models and to perform the empirical calculations. The MD simulations were carried out at Supercomputing Center of Lv Liang Cloud Computing Center in China.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work is financially supported by the double first-class discipline construction programme of Hunan province, and the Innovative Research Team in Higher Educational Institute of Hunan Province, and the Talent Support Plan of Hunan University of Humanities Science & Technology (HUHST).