Hexyl methacrylate (HMA)-based monolithic semi-micro columns were prepared by in situ polymerization within the confines of 1.02-mm-i.d. silicosteel tubing for reversed-phase and/or precipitation-redissolution liquid chromatography. Practically useful monolithic columns with adequate separation efficiency, high permeability, and good mechanical strength were successfully obtained using a polymerization mixture comprising 24% hexyl methacrylate (HMA), 6% ethylene dimethacrylate (EDMA), 44.5% 1-propanol, and 25.5% 1,4-butanediol. The column performance was evaluated through the separations of a series of alkylbenzenes. At a normal flow rate of 50 microL min(-1), the produced HMA-based monolithic columns typically exhibited 3,000 theoretical plates for a 20-cm-long column, and the pressure drop was generally less than 1 MPa per 20 cm. The monolithic columns were resistant to at least 15 MPa, and could be properly operated at 15-20 times higher flow rate than normal, reducing the separation time to 1/15-1/20. The HMA-based monolithic columns were applied to rapid and efficient separations of proteins such as ribonuclease A, cytochrome c, transferrin, and ovalbumin in the precipitation-redissolution mode. Using a CH(3)CN gradient elution at a flow rate of 1,000 microL min(-1), four proteins were baseline separated within 20 s.
Surface of natural rubber was modified by radiation-induced grafting of hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA), to improve the properties of surface hardness, dry friction, wiping performance, and wear duration. The ratio of grafted-HEMA to the rubber near the surface layer of HEMA-grafted rubber was analyzed by FT-IR and expressed as composition ratio. The composition ratio was controlled from 0.29 to 0.93 by changing HEMA concentration and dose in graft polymerization. When this composition ratio was higher than 0.8, the surface hardness was higher than 70 and the coefficient of dry friction lower than 0.65. Those values became better than those of commercially available chlorinated-rubber in terms of wear and friction against glass. The surface hardness in wet state became very close to natural rubber since grafted-HEMA was softened by contacting with water. As a result, the grafted-HEMA rubber realized 95% and higher wiping performance of water on glass. Additionally, the wear resistance was eight times higher than chlorinated rubber.
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