Molecular-weight and cooling-rate dependence of polymer thermodynamics in molecular dynamics simulation

Molecular dynamics (MD) simulations are conducted to systematically benchmark the effects of molecular weight, chain number, and cooling rate on the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of poly(ethylene oxide) (PEO). Hyperbolic regression as an objective ident...

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Bibliographic Details
Published in:Polymer journal 2021-03, Vol.53 (3), p.455-462
Main Authors: Wang, Yao-Chun, Zhang, Jun-Fu, Chiu, Min-Hsueh, Li, Jia-Han, Jui, Chia-Yung, Yang, Te-Hsun, Lee, Wen-Jay
Format: Article
Language:English
Subjects:
119/118
639/638/455/958
639/638/563/981
Biomaterials
Bioorganic Chemistry
Chemistry
Chemistry and Materials Science
Chemistry/Food Science
Cooling
Cooling rate
Ethylene oxide
Glass transition temperature
High temperature
Molecular chains
Molecular dynamics
Molecular weight
Monomers
Original Article
Polyethylene oxide
Polymer Sciences
Polymers
Rapid quenching (metallurgy)
Simulation
Size effects
Surfaces and Interfaces
Thermal expansion
Thermodynamics
Thin Films
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Summary:Molecular dynamics (MD) simulations are conducted to systematically benchmark the effects of molecular weight, chain number, and cooling rate on the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of poly(ethylene oxide) (PEO). Hyperbolic regression as an objective identified method is used to extract Tg and CTE. The results show that for a cooling rate higher than 5 × 10 13  K/min, Tg and CTE are both strongly affected by rapid quenching. For a cooling rate lower than 5 × 10 13  K/min, Tg and CTE in the high-temperature domain still slightly depend on the cooling rate. Eventually, to eliminate the finite size effect of the model, a threshold molecular weight of 11,240 g/mol should be satisfied in the system. In addition, the chain number must be more than 10, at least for an oligomer system (50 monomers). This study comprehensively reveal the critical parameters of poly(ethylene oxide) (PEO) in the MD simulation that causes the numerical effect on polymer simulation and the variation of thermodynamics property. The threshold value of total molecular weight of 11,240 g/mol must be satisfied, which leads the polymer that exhibits its steady state bulk properties. For the oligomer system (Mw 
ISSN:0032-3896
1349-0540
DOI:10.1038/s41428-020-00443-1