Factors Affecting The Hydrolysis of Polylactic Acid (PLA)

As a polyester material, the degradation of Polylactic Acid is divided into simple hydrolytic degradation and enzyme-catalyzed degradation. Simple hydrolytic degradation is the inverse reaction of esterification, starting from the absorption of water, small molecules of water moved to the surface of the sample, diffusion into the ester bond or hydrophilic groups around the role of acid and alkali in the medium, the ester bond free hydrolysis fracture, the sample of the molecule, the amount of slow decrease in molecular weight when the molecular weight is reduced to a certain extent, the sample began to dissolve, generating soluble degradation products. Enzymatic degradation of polylactide is indirect, polylactic acid first hydrolysis occurs, hydrolysis to a certain extent, and further metabolism under the action of enzymes, so that the degradation process can be completed.

People change the molecular structure of PLA by copolymerization modification and synthesize various types of copolymers with PLA as the matrix to control its hydrolysis rate. For example, PLGA copolymer, the introduction of PEG not only improves the hydrophilicity of PLA and reduces its crystallinity, which accelerates the degradation of the polymer, but also gives the material new properties and functions. The hydrophilicity of the introduced group plays a decisive role in the hydrolysis process of the Polymers in the blend modification, the better the hydrophilicity, the more significant the hydrolytic degradation.