The polymerization of styrene in latex particles by means of pulsed high-energy electrons has been studied. Using a sequence of electron beam pulses, periodic initiation is accomplished, similar to that used in pulsed laser polymerization. The larger penetration depth of electron beams offers advantages as compared to laser light in heterogeneous systems since samples do not need to be optically transparent. Therefore pulsed electron beam irradiations are more suitable to study polymerizations homogeneously irradiated in emulsion. From the molar mass distribution of the formed polymer, the monomer concentration in the particles can be determined. Polystyrene particles swollen with styrene were used. A typical dose per pulse was 1.5 Gy. The monomer concentration in 46 nm diameter particles was found to be 6 mol dm-3. Cationic and anionic polymerization of styrene was suppressed by the presence of water.

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The radical spectra of mixtures of thymidine 5'-monophosphate (TMP) or uridine 5'-monophosphate (UMP) with adenine 5'-monophosphate (AMP) after hydrated electron attack, measured from 5 to 3000 microsecond after pulse radiolysis, can only be described in terms of the radical spectra of the nucleotides if an electron transfer is taken into account from the purine radical anion to the pyrimidine, resulting in the formation of a pyrimidine radical anion. From analysis of the spectra of the dinucleoside phosphates ApU, dApT and dCpdA after eaq- attack it follows that the electron-donating species is the purine radical anion (A-.) rather than the protonated purine radical. The electron transfer competes with the fast protonation of the purine radical anion: A-. + py----A + py.- and A-. + H2O in equilibrium AH. respectively. The electron transfer is found to have a diffusion-controlled reaction rate constant of approximately 1.2 X 10(10) for TMP and 3.5 X 10(9) dm3 mol-1 s-1 for UMP.

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