The formation of diphenyl nitroxide in diphenylamine inhibited, z,cl'-azo-bis-isob~~tyronitrile initiated, autoxidations at 65' has been s t~~d i e d by electron spin resonance. Diphenylamine is oxidized to a diphenylamino radical which is then conlerted to the nitroxide by an oxygen atom transfer from a pcroxy radical. The initial rates of conversion of diphenylamine to diphenyl nitroxide and the maxiinurn nitrovide concentrations attained are generally greater for oxidations with tertiary peroxy radicals than for oxidations with primary or secondary peroxy radicals. The lobver efficiency of nitroxide formation by primary and secondary peroxy radicals is attributed to a cage disproportionation between alkoxy radical and nitroxide which leads to the foriiiation of a carbonyl compound and diphenyl hydroxylamine. This reaction cannot occur \\it11 tcrtiary radicals. The rate of formation of diphenyl nitroxide is greater for tertiary peroxy radicals which give stable tertiary alkoxy radicals. Kitroxide formation is inhibited by secondary, but not by tertiary, hydroperoxides.

Dielectric measurement on a polymer‐dispersed liquid crystal (PDLC) has been carried out in the frequency range from 10 Hz to 1 MHz and over the temperature range from 100 to 330 K. The PDLC sample was prepared by thermally induced phase separation of a 50% mixture by weight of commercially available liquid crystal E7 with PMMA and was sandwiched between two indium tin oxide glass plates separated by 40 μm spacers to form a “window.” The dielectric spectrum at low temperature (220–250 K) shows two distinct relaxation processes. Which occur at about 5 K lower than those in pure E7 having Tg ≈ 209 K. From differential scanning calorimetry data, the nematic transition of LC droplets in the PDLC is at 258 K, about 6 K lower than that of pure E7. The Maxwell‐Wagner effect has been observed in the low‐frequency side as the temperature increases from 280 to 320 K. At room temperature, the loss peak associated with the Maxwell‐Wagner effect shows an amplitude dependence with excitation level but no frequency shift. The effect of different concentrations of E7 in PDLC samples at a given temperature shows the 50% mixture has the “fastest” relaxation frequency in such a dispersed heterogeneous system. © 1992 John Wiley & Sons, Inc.

Sumnzary Differences in the rate constants for the selfreact ions of t-alkylperoxy-radicals are due to differences in the rate constants for irreversible decomposition of the initially formed tetroxides and not to differences in the equilibrium constants for tetroxide formation.

The results of several investigations of solvent-free polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted by the authors and other groups are reviewed. 23Na NMR spectra of a wide variety of amorphous polymer electrolytes are characteristic of the second-order quadrupole broadened central ± 1/2 transition with a distribution of quadrupole couplings. The temperature dependence of the linewidth is similar across a wide range of materials, and highlights the importance of polymer segmental motions above the glass transition temperature to ion mobility. Strong cation-anion interactions in poly(propylene oxide) complexes are indicated by measurements of mobile ion concentrations and, in some cases, the observation of salt precipitation at elevated temperature.

Differential scanning calorimetry (d.s.c.) and electrical conductivity measurements of poly(propylene oxide), PPO, complexed with the salts NaI and KSCN are reported. In addition, 23Na n.m.r. measurements on PPO‐NaI (x = 8), both at ambient and elevated pressure (2 kbar), have been performed. The d.s.c. data clearly indicate that the salt precipitates out of the complexes at about 85°C for NaI and 60°C for KSCN. These effects are manifested by a dramatic departure of the conductivity from Vogel‐Tammann‐Fulcher (VTF) behaviour, and a relatively sharp drop in mobile Na+ concentration, as deduced from n.m.r. measurements, above about 80°C. High pressure n.m.r. linewidth measurements are consistent with a pressure‐induced increase in glass transition temperature.