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Polymers 2018, 10(6), 630; https://doi.org/10.3390/polym10060630

Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials

1
Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), Jeonbuk 55324, Korea
2
Department of Chemistry Education, Chemistry Building, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Korea
These authors contributed equally to this paper.
*
Authors to whom correspondence should be addressed.
Received: 3 May 2018 / Revised: 5 June 2018 / Accepted: 5 June 2018 / Published: 7 June 2018
(This article belongs to the Special Issue Thermal Properties and Applications of Polymers)
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Abstract

To meet the demand for next-generation flexible optoelectronic devices, it is crucial to accurately establish the chemical structure-property relationships of new optical polymer films from a theoretical point of view, prior to production. In the current study, computer-aided simulations of newly designed poly(ester imide)s (PEsIs) with various side groups (–H, –CH3, and –CF3) and substituted positions were employed to study substituent-derived steric effects on their optical and thermal properties. From calculations of the dihedral angle distribution of the model compounds, it was found that the torsion angle of the C–N imide bonds was effectively constrained by the judicious introduction of di-, tetra-, and hexa-substituted aromatic diamines with –CF3 groups. A high degree of fluorination of the PEsI repeating units resulted in weaker intra- and intermolecular conjugations. Their behavior was consistent with the molecular orbital energies obtained using density functional theory (DFT). In addition, various potential energy components of the PEsIs were investigated, and their role in glass-transition behavior was studied. The van der Waals energy (EvdW) played a crucial role in the segmental chain motion, which had an abrupt change near glass-transition temperature (Tg). The more effective steric effect caused by –CF3 substituents at the 3-position of the 4-aminophenyl group significantly improved the chain rigidity, and showed high thermal stability (Tg > 731 K) when compared with the –CH3 substituent at the same position, by highly distorting (89.7°) the conformation of the main chain. View Full-Text
Keywords: poly(ester imide); substituent effect; glass-transition temperature; molecular dynamics simulation; optical property poly(ester imide); substituent effect; glass-transition temperature; molecular dynamics simulation; optical property
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Nam, K.-H.; Choi, H.K.; Yeo, H.; You, N.-H.; Ku, B.-C.; Yu, J. Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials. Polymers 2018, 10, 630.

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