New insights into contribution of aromatic ring versus aliphatic ring to thermal transition temperatures of heat resistant polyamides: A comparison study of PA 10T and t-PA 10C. (13th February 2023)

• Record Type: Journal Article
• Authors: Qiu, Zonglin; Chen, Chen; Huang, Zhengqiang; Fu, Peng; Zhang, Xiaomeng; Zhao, Wei; Qiao, Xiaoguang; Pang, Xinchang; Liu, Minying; Chen, Shuang; Cui, Zhe
• Is Part Of: Polymer. Volume 267(2023)
• Publication Date: 2023-02-13
• Subjects: Heat resistant polyamide -- Thermal transition temperature -- Interchain interaction; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2023.125701
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: In order to understand the differences in the contribution of aromatic ( p -phenylene) ring versus aliphatic ( trans -1, 4-cyclohexylene) ring to the thermal transition temperature of heat-resistant polyamides, a comparison study is both experimentally and computationally implemented on a typical aromatic-heat-resistant polyamide PA 10T containing p -phenylene moieties and a typical alicyclic-heat-resistant polyamide t-PA 10C containing trans -1, 4-cyclohexylene moieties. DSC, WAXD, solid state-NMR, computational simulations, and in-situ FTIR were utilized in sequence to reveal the differences in thermal performance, crystal structure, chain conformation, cohesive energy, interchain interaction, and melting process of PA 10T and t-PA 10C. t-PA 10C displays 30 °C-higher T m and 50 °C-higher T g than PA 10T. As indicated by the hydrogen bonding dissociation process, the enthalpy change dominates the difference in T m as the gap in the entropy change between PA 10T and t-PA 10C is negligible. Computational simulation indicates that the energy-favorable hydrogen bonding conformation and dense trans -1, 4-cyclohexylene-associated chain packing endow the formation of stronger interchain interactions in t-PA 10C which results in larger cohesive energy and greater cohesive energy density. The higher melting enthalpy change in the melting process derived from in-situ FT-IR experiment also verifies the simulated energy results. Henceforth, the question that WHY can the building block change, from rigid planar aromatic unit (PA 10T) to conformation-switchable nonplanar aliphatic unit (t-PA 10C), in the two polyamides induce so large improvement in T g and T m is systematically answered. Graphical abstract: Image 1 Highlights: Why t-PA 10C has higher T g and T m than PA 10T is answered experimentally and computationally. Compared with PA 10T, t-PA 10C possesses larger E HB, E cohesive and CED . The difference in Δ S during the melting of PA 10T and t-PA 10C is negligible.