Synthesis of Organic-Inorganic Polymer Hybrids Derived from Polyamides with Triphenylimidazole Skeletons as Side Chains and Alkoxysilanes

Organic-inorganic polymer hybrids were synthesized using a copolymer of DL-3-[ α -4-(4,5-diphenyl-1 H -imidazole-2-yl)-phenylacryloylamine]- ε -caprolactam and ε -caprolactam (PDC) and three alkoxysilanes: phenyltrimethoxysilane (PhTMOS), tolyltrimethoxysilane (TolTMOS), and tetramethoxysilane (TMOS). Despite the π−π interactions between the aromatic rings in the PDC side chains and those in the inorganic matrix, opaque composites were obtained when PhTMOS or TolTMOS was used as alkoxysilanes. On the other hand, when TMOS was used, the resulting polymer hybrids were transparent. FT-IR spectra of various polymer hybrids prepared by varying the PDC/TMOS ratio revealed that the peak corresponding to the C = O stretching vibration of the amide group in PDC shifted to lower wavenumbers as the proportion of inorganic oxide increased. This suggests that hydrogen bonds are formed between the amide groups in the organic polymer and the hydroxyl groups in the inorganic oxide, resulting in a transparent polymer hybrid. Furthermore, TMOS and PDC were coexisted in formic acid, stirred at room temperature for 1 hour while irradiating with UV light, then left at 40°C for 2 weeks, and then dried under reduced pressure at 60°C for 2 days to obtain an organic-inorganic polymer hybrid. In the hybrid prepared with UV irradiation, UV irradiation partially promoted the crosslinking reaction via dimerization of the cinnamoyl group, improving the thermal stability of the hybrid material.