Photochemical cross-linking of poly(ethylene terephthalate-co-2,6-anthracenedicarboxylate)

Poly(ethylene terephthalate) copolymers containing 2,6-anthracenedicarboxyl ate structural units are chain extended and cross-linked by irradiation at 350 nm. The cross-linked materials were characterized by NMR, UV-vis, DSC, and dilute solution viscometry. The cross-linking is attributed to face-to- face dimerization of the anthracene units and radical reactions. Model anth racene photodimers are cleaved in solid films of PET by irradiation at 254 nm, but polymeric anthracene photodimerization reactions are irreversible u nder these conditions. The combination of irreversible anthracene photodime rization and irreversible radical reactions renders the cross-links permane nt.