Substrates Sulphonic acid polymers

The discovery of mediators (small molecules which when oxidised by peroxidases or laccases form highly reactive species), which have the abihty to oxidise high redox potential substrates difficult to be oxidised by the enzyme alone, has further expanded the applications of these enzymes in modifying inert polymers. Examples of widely investigated mediators are 1-hydroxybenzotriazole (HBT), violuric acid (VA), A-hydroxyacetanilide (NHA) and 2,2 -azinobis-(3-ethylbenzothiazoline)-6-sulphonate (ABTS). Alternatively, active research is aimed at developing natural cost-effective lignin-derived mediators [10]. 

Systematic studies of the acid-catalysed hydrolysis of esters in the presence of sulphonated polystyrene showed an increase in the value of q with decreasing solubility of the esters in water [17, 22]. Correspondingly, for soluble macromolecular acids the values of q have been found to decrease with increasing degree of sulphonation of the polymer. These effects are consistent with hydrophobic interaction between resin and substrate and its effect on the value of Ar. The importance of hydrophobic interaction can be reduced if, for example, acetone is added to the solvent. Such solvent changes have the opposite effect on hydrophilic substrates [26]. 

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