Epoxy network hydrophilicity

Hydrogen Peroxide has been shown to be efficiently electroreduced at an electrode modified with a hydrophilic, penneable film of horseradish peroxidase covalently bound to a 3-dimensional epoxy network having polyvinyl pyridine (PVP)-complexed [Os(bpy)2Cl] - redox centers. Four peroxide sensing cathodes based on peroxidases from Arthromyces ramosus, horseradish and bovine milk are compared. Their sensitivity at O.OV (SCE) ranges from 0.1 - 1.0 A cm - M"1, and their limiting currents relate to the enzyme s ability to complex with the redox epoxy network. 

Glassy carbon None 0.0 10-2 HRP covalently bound to a hydrophilic epoxy network. Polyvinyl pyndine-dcrivcd polyamine crosslinked with PEGDE. 1... 

Glassy carbon Osmium bipyridine 0.0 1 0.1-100 HRP covalently bound to a hydrophilic redox epoxy network crossinked with PEGDGE 1... 

The degradation of the matrix in a moist environment strongly dominates the material response properties under temperature, humidity, and stress fatigue tests. The intrinsic moisture sensitivity of the epoxy matrices arises directly from the resin chemical structure, such as the presence of hydrophilic polar and hydrogen grouping, as well as from microscopic defects of the network structure, such as heterogeneous crosslinking densities. 

Not only can the water molecule pass through gaps in the network because of its small size, but also because it is compatible with (i.e. effectively soluble in) the polymer. Thus polar adhesives are naturally hydrophilic whereas non-polar plastics, such as PVC and Polythene, are not i.e. like permeates like . The solubility of water in epoxies is of the order of a few mass per cent, and the coefficient of diffusion of water at 20 °C is around 10 m s . 

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