Polymer hydrolysis, monitoring

Figures I and II show a comparison of the reaction profile for PPY and polymer catalyzed hydrolysis for p-nitrophenylacetate and p-nitrophenylcaproate monitored by the appearance of p-nitro-phenoxide absorption by UV-VIS spectroscopy. These results confirm the effectiveness of the interactions between the hydro-phobic polymer chain and the hydrocarbon portion of the substrate, as it was previously mentioned, in accordance with the observations of Overberger et al (20).

Table 1 Monitoring enzymatic surface hydrolysis of polymers...

The filtered solution is sent into vacuum distillation tank 9. There a residual pressure of 15-30 GPa is created at a temperature not exceeding 50 °C the solvent (a mixture of toluene and acetone) is distilled. The distillation is carried out until the polymer concentration is 85-90% and monitored by solid residue. The distillation of the solvent is accompanied by the polycondensation of the hydrolysis product and forms polypentenylhy-droxysiloxane. 

Another method of following the rate of urea hydrolysis is based on a specific-ion electrode for ammonium ions (see Section 21D). Here, the production of NH4 is monitored potentiometrically and is used to obtain the reaction rate. In yet another approach, the urease can be immobilized on the surface of a pH electrode and the rate of change of pH monitored. Many enzymes have now been immobilized onto supports such as gels, membranes, tubing walls, glass beads, polymers, and thin films. Immobilized enzymes often show enhanced stability over their soluble counterparts. In addition, they can be reused often for hundreds or thousands of analyses. 

Enzymatic hydrolysis of PAN was first shown by Tauber et al. who monitored the formation of ammonia during hydrolysis of nitrile groups [99, 100]. Considering the fact that only a low 1.1% of nitrile groups are displayed on the polymer... 

As previously mentioned, part of our work was dedicated to the study of bio-activity of the enzyme used to prepare bioartificial hydrogels the enzyme activity was monitored, in a phosphate buffer containing starch substrate (0.2 mg/ml), by measuring the substrate concentration remaining in the batch solution at different times. The results, compared with free a-amylase behaviour, indicated that the catalytic hydrolysis of starch was the same for free a-amylase and a-amylase delivered from bioartificial blend no deactivation of the enzyme because of the presence of PVA was observed either in solution or after the preparation through casting procedure. On the contrary, a-amylase seemed slightly more stable in the polymer network. 

In the first step, isocyanate 119 was attached to the support affording urethane derivative 120. Subsequent treatment with 6 different amines furnished the corresponding polymer-bound sulfonamides 121. Basic hydrolysis released analytically pure products 122 in high overall yields (95-97%) and purities. Reactions were monitored by NMR spectroscopy. 

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