STRUCTURAL CHARACTERIZATION OF THE CROSS-POLYMERIZATION OF A DIACETYLENE-FUNCTIONALIZED POLYAMIDE

The molecular structural changes caused by the radiation-induced cross -polymerization of diacetylene units across host chains of a diacetyle ne-functionalized polyamide have been studied by solid-state C-13 NMR and wide-angle X-ray diffraction. By measuring C-13 NMR spin-lattice r elaxation times of poly(hexamethylene-10,12-docosadiyne-1,22-diamide) before and after diacetylene cross-polymerization, it was found that c ross-linking occurred primarily within the crystallites, as evidenced by the complete retention of amorphous-phase segmental mobility and co nstant rigid-component mass fractions. Cross-linking was also found to be accompanied by an increase in the local segmental mobility within the crystallites which was shown to result from a trans to gauche conf ormational transition of the methylene carbons pendant to the newly fo rmed polydiacetylene chains. Wide-angle X-ray diffraction revealed tha t the diacetylene-functionalized polyamide crystallizes in a manner si milar to that of conventional polyamides. Upon cross-polymerization, t he formation of gauche conformers expanded the interplanar spacing bet ween the hydrogen-bonded sheets while the spacing between the hydrogen -bonded chains remained constant, at least adjacent to the amide group s. Thus, the full hydrogen-bonding strength is retained since any latt ice strains imposed by polymerization of the diacetylene units to poly diacetylene chains are accommodated by the conformational changes of t he methylene segments connecting the amide groups to the polydiacetyle ne cross-links.