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Surface modification of polydimethylsiloxane (PDMS) based vulcanizate rubber by C02-pulsed laser as the excitation source, without a photosensitizer, was studied at room temperature. The modified surfaces were characterized using a variety of techniques including scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDXA), attenuated total reflectance infrared (ATR-IR) spectroscopy and water drop contact angle analysis. EDXA showed that all of the treated PDMS surfaces contained a higher ratio of O/Si than the base PDMS. SEM micrographs and water drop contact angle variations showed the uniform porosity and high decrease in the wettability of the surface of PDMS respectively. The bulk mechanical properties of PDMS after laser-treatment did not change, as shown by dynamic mechanical thermal analysis (DMTA). The friction coefficient of the surface of the modified silicone decreased drastically, even after only one pulse was delivered to it. Data from in vitro blood compatibility experiments indicated a significant reduction of platelet adhesion and aggregation for the modified surfaces and those platelets which were adherent remained unspread (no activation). The extent of reduction of platelet adhesion was correlated to the number of laser pulses. The attachment of anchorage dependent cells, namely Baby Hamster Kidney (BILK) fibroblastic cells was investigated under stationary culture conditions. The laser treated surfaces showed little adhesion, no spreading and growth properties. This technique can be employed to prepare PDMS samples in which one surface is laser treated and the other is untreated. Such materials may be useful in, for example, medical implants in which one (the treated) surface is in contact with a blood supply and hence does not cause cell aggregation (clotting) and the other side is tissue compatible (allows adhesion of tissue). Acrylamide (AAm), 2-hydroxyethylmethacrylate (HEMA) and hydroxyethylmethacrylate phosphatidyl choline (HEMAPC) were grafted onto preirradiated PDMS. Platelet adhesion and cell attachment studies show that the biocompatibility of the AAm and HEMA grafted PDMS are intermediate between that of untreated PDMS and either the HEMAPC grafted PDMS surface, or PDMS surfaces that had been treated with 10 CO. laser pulses.

This work is devoted to the synthesis, characterization and modification of a class of acrylic-based superabsorbent polymers. The techniques of inverse suspension and solution polymerisations were used for synthesis. Each absorbent was mainly characterised by its equilibrium capacity of water absorption and by the rate of absorption. The swelling characteristics of the polymers were evaluated in terms of change in polymerisation variables which include, type and amount of crosslinker, monomer composition, process of polymerisation, temperature, initiator concentration, monomer concentration and particle size of the product. The swelling dependency on salinity was also examined. In some cases, the base polymer was blended with certain polymers in order to upgrade the swelling properties. A swelling model was devised based on a simple viscoelastic model, i. e. Voigt model, to obtain a better understanding of the effect of the above-mentioned variables on the swelling behaviour. Finally, our materials of choice were compared with some commercial analogues and some further comments have been made for continuing the work.

The major phenolic lipids from natural and technical Cashew Nut-Shell Liquids were isolated by various techniques including precipitation, chemical purification, distillation, phase separation and chromatography. Cardanol, 3-pentadecyl phenol and cardol were polyethoxylated under base catalysed conditions and the products were characterised by both nmr and HPLC. Their surfactant properties were then analysed by surface tension measurements and their rates and extent of biodegradation were evaluated by means of a modified OECD screening test. The synthesis of the biosyntetic intermediate 2,4-dihydroxy-6-pentadecyl benzoic acid, by means of a Horner-Emmons modification to the Wittig reaction, is also reported. Some studies with cavitands are also reported, including the synthesis of some novel macrocycles and some sugar transport studies.