Document 3Qr7rpvgpn6ZdLJEVy6Z04zK0

1963, (s)p. cited te R- Banin*, iadSwwty. Houston, JOURNAL OP POLYMER SCIENCE: Pc&m*rCb*mi*toyBditis VOL. 14. 1617-1SJS (MW) ESR Study on Photodecomposition Mechanism of Oxidized Poly(vinyl Alcohol) TOSHIO YASUNAGA, HITOSHI KUBOTA, and YOSHITAKA OGIWARA, Department of Chemistry, Faculty of Engineering, Gunma University, Kiryu, Gunma 376, Japan Synopsis Photolysis bthorior of nidited poiy(vinyl alcohol) (PVA) in which carbonyl group* wers introducd by oxidation with (odium hypochlorite and periodic acid waa investigated by usmg ESR (pectrouatry. Increaaed formation of PVA radical* waa obeerved in the aample with low degree of oxidation, which showed an emphasized formation of triplet component radical. On the other hand, the formation of radicals tended to be depressed in the highly oxidised sample, and a singlet component was dominant in the ESR spectrum. By examining infrared and ultra violet spectra of the oxidised sample, the sample was found to contain taro structures, a saturated ketone group and an a^f-unsaturated group; the latter structure was intensified with increasing degree of oxidation. Based on ESR studies of the photoirradiated acetone and mesityl oxide, the models of saturated and o4-un*aturated ketone structure* in the oxidised PVA, respectively, a photodecomposition mechanism of oxidised PVA eras proposed. INTRODUCTION It is generally known that aliphatic carbonyl compounds are easily photolyzed by ultraviolet light Some studies1-3 on photolysis of polymeric materi als activated by carbonyl groups present in the main chains have been re ported. We analyzed ESR spectra of photoirradiated poly(vinyl alcohol) (PVA) to find the formation of three kinds of radical, showing singlet, quar tet and triplet spectra, depending on irradiation conditions.4 These were as signed to alkoxy and methyl radicals which originated from the acetyl group remaining in the sample, and to carbon radicals generated by abstraction of hydrogen from the a-carbon to the hydroxyl group, respectively. Oxidation of PVA with various oxidizing agents,3-8 such as hydrogen per oxide, potassium permanganate, potassium dichromate, sodium hypochlorite (NaCIO), and periodic acid (HIO4), are known to lead to the introduction of carbonyl groups into the main chain. In the present paper, photoinduced radicals in NaCIO- and HlOs-oxidized PVA samples were investigate^ by using BSR spectrometry. The relationship between the oxidized states and the formation of radicals is discussed. Finally, photodecomposition mecha nisms of the oxidized PVA are discussed on the basis of analysis of the ESR spectra of photoirradiated acetone and mesityl oxide as the models of the oxidized PVA. 1617 C1976 by John Wilty A Sons, Inc. ( i' 7T n vrr 1 n wrp.rwfun in' mil m * 11, ,-i ? ' ;f ' 1 .1 * r' ' T.V' *' ` ' ' ucc 042073