The effect of solvents on the radiation-induced polymerization of ethyl and isopropyl vinyl ethers

The radiation-induced cationic polymerization of ethyl and isopropyl vinyl ethers was studied in a variety of solvents. The propagation rate constants were estimated and found to vary widely with the nature of the solvent. In particular, a good linear relationship existed between the logarithms of the rate constants and the reciprocal of the dielectric constants. The lowest rates were those of the highest dielectric constant solvents. These results have been interpreted in terms of the Laidler and Eyring theory of ion-molecule reactions. Isopropyl vinyl ether polymerizes much faster than ethyl vinvl ether, although the rates approach the same value at infinite dielectric constant. In contrast, “free” carbenium ion polymerizations initiated by stable carbenium ion salts in methylene chloride solution had similar values for both monomers. A comparison is made between the rate constants obtained with both methods of initiation.     

Note on the paper by T. Andersen entitled “the differential equations of the Voigt functions” (JQSRT 19, 169 (1978))

Solutions in terms of quadratures are presented for two differential equations defining the Voigt function.     

Scattering of ice coupled waves by a sea-ice sheet with random thickness

Arctic sea-ice contains imperfections such as cracks, leads and pressure ridges that scatter flexural-gravity waves. Models for predicting scattering have been described in the literature, concentrating mainly on singular isolated features with simplified shapes or on arrays of such features. In reality ridges are seldom simple and leads are rarely entirely free of ice. Here we describe a model in which the scattering by a sheet of arbitrary thickness can be simulated. Linear wave theory and Green's functions are used to derive the governing equations for a numerical model of a two-dimensional (in the vertical) system. We examine wave scattering by random ice sheets, identifying trends in behavior as the wave period and the length, median thickness and variance of the sheet are changed. It has been suggested that wave scattering could be used to identify sea-ice thickness, a task which is difficult or expensive by other methods, and here we examine a technique by which this could potentially be achieved. However, a large data base is necessary for this to work and this may limit the practicality of the approach.