INFLUENCE OF SUBSTITUENTS ON POSITRON-ANNIHILATION IN STYRENE COPOLYMERS

Results of angular correlation of annihilation radiation (ACAR) and po sitron annihilation lifetime (PAL) measurements are presented for five styrene copolymers: poly(co-styrene-phenylmaleimide) and its three de rivatives with chlorine as well as for one with the OH group substitut ed at the benzene ring. It occurs that the chlorine substituted at thr ee different positions at the benzene ring poly (co-styrene-o (or -m, -p>chlorophenylmaleimide) inhibits the formation of the positronium to different extent. The greatest effect is observed in case of the chlo rine atom substituted at the benzene ring at the ortho-position toward s the nitrogen atom The two long lifetimes (tau(3) and tau(4)) observe d in the lifetime spectra are connected with the bimodal distributions of the free volume radius in the samples.