UV polymer coating

High adhesion and sensitivity to UV irradiation of these polymer coatings allow one to use them as a base for the preparation of polymer resistance of a negative type. 

Such sol-gel derived and ultraviolet (UV)-curable hybrids afford enhanced corrosion and mechanical protection of fibres compared to standard polymer coatings used by the fibre optics industry. These coatings are hard, transparent and impossible to strip since they become intimately bonded to the fibre surface during curing. 

Preliminary conductivity measurements indicate that the polymers based on the anionic system are ionically conductive, whereas the nonionic based polymers are non-conductive. AC impedance tests were done on a thick film ( limn thick) using sodium sulfate as the electrolyte in a specially designed closed cell. The resistivity of polystyrene obtained from middle phase microemulsions was found to be in the rjange of lOMO ohm-cm, compared to lO o -10 2 ohm-cm for bulk polystyrene. A thin film of the polymer was also obtained on graphite electrodes by UV irradiation. Electrochemicd measurements using such polymer coated electrodes also suggest that the film is conductive. SEM micrographs before and after the electrochemical measurements indicate that the polymeric film is stable and porous. 

Indeed, photopolymerization of acrylamide in aqueous solution on cell-GEHMP gives cellulose with the surface covered by a poly acrylamide) gel. Similarly, UV initiated polymerization of 2-hydroxyethyl acrylate, 2-(dimethylamino) ethyl methacrylate and A -vinylpyrrolidone carried out with the above functionalized Si(>2 results in the formation of a surfece polymer coating. 

CEC was demonstrated in the analysis of /i-adrenergic antagonists using capillaries modified with propranolol-imprinted polymer. In situ molecular imprinting was performed via photo-polymerisation at — 20°C within a capillary that was premodified with 3-methacryloxypropyltrimethoxysilane. The time for UV irradiation was carefully determined so as to obtain a polymer coating of appropriate thickness. Enantioseparation of the racemate of propranolol was successfully demonstrated with a separation factor of 1.12 and a resolution factor of 1.26. 

The components of a typical CE apparatus are shown in Fig. 33.3. The capillary is made of fused silica and externally coated with a polymer for mechanical strength. The internal diameter is usually 25-50 pm, a compromise between efficient heat dissipation and the need for a light path that is not too short for detection using UV/visible spectrophotometry. A gap in the polymer coating provides a window for detection purposes. Samples... 

After light absorption by the photocatalyst the next step is photoproduction of free radicals that initiate polymerization of the acrylate unsaturated monomers, oligomers, and polymers contained in the UV-curable coating system. 

Monomeric vinylic metal n complexes undergo polymerisation reactions to form polymers that have limited applications because of their poor thermo-mechanical properties but they absorb UV without degrading in the process. Such polymers can be used as a UV-resistant coating and act as catalysts in other monomer reactions. Metallocene methylene polymers are high temperature resistant materials and have uses as ablative materials for space capsule heat shields. These materials use Fe and Ru in their metal polymers. 

---