Unveiling the Trans-Cis Isomerization Mechanism in Alicyclic PA10C: the Vital Role of Water Cluster and Hydrogen Bonds

Stereoisomerism exerts critical influence on the physicochemical properties and biofunctionality. Precise regulation of stereoisomeric composition enables programmable manipulation of polymeric aggregation states and macroscopic properties. Herein, the trans – cis isomerization mechanism inherent to alicyclic PA10C was comprehensively deciphered through an integrated experimental and computational methodology. Primarily, regulated polymerization was conducted under varied thermal regimes within a reactor environment to strategically manipulate the stereoisomeric ratio. Experimental results demonstrated that isomerization transpires at temperatures as low as 170°C, with trans -PA10C as the predominant configuration. Subsequently, the energy barrier of trans- to -cis isomerization of PA10C was calculated using Density Functional Theory (DFT) to be 72.9 kcal/mol. This suggests that configurational inversion necessitates thermal activation exceeding 300°C, exhibiting a substantial discrepancy with experimental observations at 170°C. Theoretical simulations further corroborated that H 2 O markedly reduced the activation energy to 29.2 kcal/mol, as water cluster facilitate rapid proton transfer through dynamic hydrogen bond during polymerization. Furthermore, trans -PA10C macromolecules adopt a centrosymmetric structure, which facilitates dense packing into crystalline regions with an energy barrier of 7.6 kcal/mol. Therefore, trans -to- cis isomerization requires overcoming the hydrogen bond energy, thereby resulting in the thermodynamic predominance of the trans -configuration. Ultimately, stereoisomerism dynamics of cis/trans -PA10C was carried out, and their characteristic critical isomerization temperature were determined to be 204°C and 300°C, respectively.