The ultrasonic degradation of polyvinyl alcohol (PVA) in aqueous solution and the copolymerization of PVA with acrylonitrile (AN) were studied. It was confirmed that the rate of degradation of PVA followed the kinetic equation suggested by N. K. Baramboim. Both water-soluble and water-insoluble copoly-mers could be obtained by changing the irradiation time or the amount of AN added to the aqueous solution of PVA. The structure of the copolymer was identified by IR

MS

PGC and X-ray diffraction. The copolymer prepared was mainly a blocked one. By irradiating 2% PVA/AN (1/1.6

by mass) at 20±1℃ and 21.5 kHz with 490W for a period of 28 min.

the yield of the water-soluble copolymer was 25.49%

with a AN content of 13.98%. When the irradiating period was extended to 100 min.

with the mass ratio between PVA and AN at 1/4

the yield of the water-insoluble copolymer amounted to 296.01%

with a AN content 75.56%.