Selectivity of allylic coagent‐mediated polypropylene maleation

The peroxide‐initiated cografting of maleic anhydride (MAn) and allylic coagents to polypropylene (PP) is described. Both triallyl trimesate (TAM) and triallyl phosphate (TAP) are shown to be compatible with MAn, as the presence of either coagent has no apparent effect on the yield or distribution of anhydride grafts within functionalized PP. Therefore, the influence of chain scission on the melt‐state rheological properties of maleated PP can be mitigated using coagent‐assisted crosslinking. The success of this cografting strategy for controlling melt viscosity is shown to depend on the extent that a bimodal, branched architecture can provide the rheological properties demanded by a given application. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Thermal and mechanical properties of copolymers of methyl methacrylate with N-phenyl maleimide

Structural modification of PMMA was done by copolymerizing it with low mole fraction (≤ 0.1) of N-phenyl maleimide (NPM) using benzoyl peroxide as an initiator. Four copolymers were prepared by changing the mole fraction of NPM in the monomer feed from 0.025 to 0.1. The copolymer composition was determined by ¹H-NMR. An increase in NPM content resulted in an increase in T_g of copolymers. Tensile stress and % elongation decreased, whereas modulus increased with an increase in NPM content. The Flexural strength was not affected by the NPM content. The dynamic mechanical properties were also evaluated in the temperature range of–20 to 100°C. © 1993 John Wiley & Sons, Inc.     

Detection of furocoumarins in plants and plant products with an ultrasensitive biological photoassay employing a DNA-repair-deficient bacterium

The application of an ultrasensitive photobiological assay which detects photosensitizing furocoumarins with sensitivities as high as 1 × 10^–11 g is discussed in relation to these molecules as phytoalexins. Examples of the utilization of this technique, verified by both HPLC and TLC, are the analyses of healthy and diseased celery and carrots, dry seeds, plant extracts and oils, and whole plants and leaves. The usefulness of this method in following the metabolic detoxification of furocoumarins is also illustrated. The extreme sensitivity of the test has permitted the detection, for the first time, of both 5-methoxypsoralen and 8-methoxypsoralen in fresh carrot roots.Supported by the Medical Research Council of Canada and the Natural Sciences and Engineering Research Council of Canada.