The possible contamination of the environment by surfactants arising from the widespread use of detergent formulations has been reviewed. Two of the major surfactants in current use are the linear alkylbenzene sulphonates (LAS) and the alkyl phenol ethoxylates (APE). These pass into the sewage treatment plants where they are partially aerobically degraded and partially adsorbed to sewage sludge that is applied to land. The biodegradation of these and a range of other surfactants both in wastewater treatment plants and after discharge into natural waters and application to land resulting in sewage sludge amended soils has been considered. Although the application of sewage sludge to soil can result in surfactant levels generally in a range 0 to 3 mg kg(-1), in the aerobic soil environment a surfactant can undergo further degradation so that the risk to the biota in soil is very small, with margins of safety that are often at least 100. In the case of APE, while the surfactants themselves show little toxicity their breakdown products, principally nonyl and octyl phenols adsorb readily to suspended solids and are known to exhibit oestrogen-like properties, possibly linked to a decreasing male sperm count and carcinogenic effects. While there is little serious risk to the environment from commonly used anionic surfactants, cationic surfactants are known to be much more toxic and at present there is a lack of data on the degradation of cationics and their fate in the environment.

Liposomes have been prepared by the vesicle extrusion method (VETs) from mixtures of dipalmitoylphosphatidylcholine (DPPC), phosphatidylinositol (PI) and dipalmitoylphosphatidylethanolamine with covalently linked poly(ethylene glycol) molecular mass 5000 and 2000 (DPPE-PEG 5000 and DPPE-PEG 2000) covering a range of 0-7.5 mole%. The encapsulation of D-glucose has been studied and found to be markedly dependent on the mole% DPPE-PEG. The permeability of the liposomes to D-glucose has been measured both as a function of temperature and liposome composition. The permeability coefficients for D-glucose increase with mole% DPPE-PEG 5000 and with temperature over the range 25-50 degrees C. The activation energies for glucose permeability range from 90 to 23 kJ mol(-1). The decrease in activation energy with increasing temperature is attributed to an increasing number of bilayer defects as the liposome content of PEG-grafted lipid is increased. The dependence of D-glucose encapsulation as a function of PEG-grafted lipid content is discussed in terms of the conformation of the PEG molecules on the inner surface of the bilayer. For liposomes containing DPPE-PEG 5000 the relative percentage encapsulation of glucose, assuming that the PEG surface layer excludes glucose, is comparable to that predicted from the mushroom and brush conformational models.

No abstract

No abstract

During the studies towards the development of pentafluorophenyldimethylsilanes as a novel organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our previous report focused on the synthesis and base induced cross coupling of aryl substituted vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our research, studies into the factors which influence the successful outcome of the cross coupling reaction with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism discussed. Further investigation into expanding the breadth and diversity of substituted vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical trans-stilbenes and cyclic structures containing the trans-alkene architecture.