We have measured and compared ATR/FT-IR spectra of aqueous dispersions of colloidal silica, and aqueous suspensions of particulate silica, over ranges of bulk concentrations using CIRCLE® and Contact Sampler™ cells. Procedures are described for quantitative analyses of each silica type. Detection limits are approximately 0.001% for the particulate species. The spectra of particulates are distorted by refractive-index effects to low frequency of the main analytical bands around 1090 cm-1, but the distortions are proportional to concentration and do not interfere with the precision of analyses. We recommend either ATR cell, but the Contact Sampler™ is more convenient.

In this letter, we report high electro-optic methylene di(phenylene isocyanate) (MDI)/DR19 side-chain polymer film polymerization by vapor deposition polymerization. For samples deposited at substrate temperatures from 10 to 30 °C, the electro-optic (EO) coefficient, r33, was measured to be 5 pm/V after poling. A lifetime of about one week was obtained. The highest EO effect observed were films deposited at −40 °C and polymerized after poling. The EO coefficient of these samples is about 24 pm/V while the lifetime is only about 30 min. The effect of substrate temperature, the ratio of monomers, and the poling temperature on the nonlinearity of the films are studied.

TRUIS SMITH-PALMER and CHERYL ROBERTS. Can. J. Chem. 69, 1516 (1991). The tensammograms of several sets of cationic polyacrylamide copolymers are discussed and compared. Tensammograms are not affected by molecular weight, but plots of capacitive current at a chosen potential versus charge density give regular curves.