Radiation-induced main-chain scission and dehydrofluorination of poly(vinylidene fluoride) in solution

Poly(vinylidene fluoride) (PVdF), dissolved in N, N'-dimethylformamide, N, N'-dimethylacetamide, 1-methyl-2-pyrrolidinone, and dimethyl sulfoxide, has been irradiated with Co-60 γ-rays. Although PVdF is crosslinked in the solid state, this crosslinking was not observed in the solution. The number-average molecular weight of PVdF decreased with increasing dose. The G value for main-chain scission G(S), was independent of the kind of solvent (Table 1), polymer concentration (Table 2), and the initial molecular weight distribution; it was 0.3+-0.05. This value was smaller than the G(S) for solid PVdF. The molecular weight distribution varied from initial broad distribution to final random one as the dose increased (Figs.1 and 2). The results were interpreted in terms of energy and charge transfers from PVdF to solvent. The PVdF irradiated in the solvents except dimethyl sulfoxide acquires color. Its UV spectra are different from those of PVdF irradiated in the solid state (Fig.3). This coloration is caused by dehydrofluorination catalyzed by amines formed by radiolysis of these solvents. (auth.)