Photodegradation of some ethylene-norbornene random copolymers

We investigated the photodegradation of specific ethylene-norbornene random copolymers (ENRC) - a group of substances which has been attracting much attention in recent years. ENRCs having various contents of norbornene were studied. After irradiation, each sample was separated into chloroform-insoluble and soluble portions. The chloroform-insoluble portion was weighed and analyzed by FTIR. The chloroform-soluble portion was analyzed by size elimination chromatography (SEC), FTIR and 1H NMR. The yield of the chloroform-insoluble portion increased with increased irradiation time. Formyl, formate, acyl, hydroxy groups and a carbon-carbon double bond were formed by photo-irradiation. Apparently, hydrogen atoms bound to the tertiary and secondary carbon atom in the parent ENRCs are abstracted. From these results, it is suggested that auto-oxidation results from photo-irradiation of the ENRCs. In ENRCs with similar stereoregularity, the degree of photodegradation increases with increasing norbornene content.