Nam, Ki-Ho Choi, Hoi Kil Yeo, Hyeonuk You, Nam-Ho Ku, Bon-Cheol Yu, Jaesang 2024-01-19T22:33:05Z 2024-01-19T22:33:05Z 2021-09-03 2018-06 2073-4360 https://pubs.kist.re.kr/handle/201004/121302 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 (E-vdW) played a crucial role in the segmental chain motion, which had an abrupt change near glass-transition temperature (T-g). 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 (T-g > 731 K) when compared with the -CH3 substituent at the same position, by highly distorting (89.7 degrees) the conformation of the main chain. English MDPI GLASS-TRANSITION TEMPERATURE MECHANICAL-PROPERTIES HIGHLY TRANSPARENT OPTICAL-PROPERTIES DYNAMICS DIANHYDRIDE SIMULATIONS FILMS OXIDE Molecular Design and Property Prediction of Sterically Confined Polyimides for Thermally Stable and Transparent Materials Article 10.3390/polym10060630 1 POLYMERS, v.10, no.6 POLYMERS 10 6 scie scopus 000436560200067 2-s2.0-85048453860 Polymer Science Polymer Science Article GLASS-TRANSITION TEMPERATURE MECHANICAL-PROPERTIES HIGHLY TRANSPARENT OPTICAL-PROPERTIES DYNAMICS DIANHYDRIDE SIMULATIONS FILMS OXIDE poly(ester imide) substituent effect glass-transition temperature molecular dynamics simulation optical property