Hydrolytic Degradation of an Aliphatic Polyester

Safety precautions Before this experiment is carried out, Sect. 2.2.5 must be read as well as the material safety data sheets (MSDS) for all chemicals and products used. 

1 g of a linear aliphatic polyester (e.g., a polyester of succinic acid and 1,6-hexanediol, see Example 4-2) are dissolved in dry tetrahydrofuran in a 100 ml graduated flask and made up to the mark at 30 °C.50 ml of this solution are mixed with 2 ml of 30% sulfuric acid and stored in a closed vessel, separate from the other 50 ml of solution, at 30 °C (e.g., in the viscometer bath).The viscosities of the two solutions are determined immediately and then at hourly intervals in an Ostwald viscometer (capillary diameter 0.3 mm) at 30 °C for this purpose 3 ml of the appropriate solution are pipetted each time from the flask into the viscometer.The two flasks are allowed to stand overnight at 30 °C and the hourly viscosity measurements continued on the next day until the values remain essentially constant over 1 h, which will be the case after a total of 20 h.The viscosity of the sample without the sulfuric acid remains unchanged. 

The specific viscosity (or simply the flow time) is plotted against reaction time. For the calculation of the specific viscosity the flow time of the solvent, fo,must be determined fora mixture of 50 ml of tetrahydrofuran and 2 ml of 30% sulfuric acid the viscosity of pure tetrahydrofuran is considerably raised by the addition of the acid. Finally, 20 ml each of the hydrolyzed and unhydrolyzed solutions are dropped into 200 ml of methanol and the resulting precipitates compared if the hydrolysis of the first sample is complete no precipitate will appear whatsoever. 

Example 5.16 Hydrolytic Degradation of Cellulose and Separation of the Hydrolysis Products by Chromatography 

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