A graphical method for the determination of the mode of hydrolysis of biodegradable polymers.

PURPOSE

To develop a qualitative method for the determination of the mode of scission in the hydrolysis of biodegradable polymers.

METHODS

The method requires determination of the molar fraction of monomer (m1) by 1HNMR or HPLC, and the degree of polymer degradation (alpha) determined by 1HNMR.

RESULTS

If the scission of the backbone bonds is completely random, the molar fraction of the monomer must equal the square of the degree of degradation as predicted by Kuhn (1). If the degradation follows an exclusive chain-end "unzipping" mechanism then, m1 = alpha. Experimental data falling on the theoretical curves (m1 vs. alpha) confirm the corresponding mode of scission. If the data fall between the two curves, it suggests a faster chain-end scission than random scission. When data fall below both of these curves, it suggests the chain-end bonds are less reactive than the internal bonds.

CONCLUSIONS

The acid catalyzed hydrolysis of a poly(ortho ester) and the base catalyzed hydrolysis of poly(D,L-lactide) (PLA) were by a random scission mechanism, while acid catalyzed hydrolysis of PLA demonstrated faster chain-end scission.