Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Investigation of the effect of ozone on the PHB structure as an approach to control the degradation rate of products.

ABSTRACT
An urgent task today is a detailed study of the effect of oxidation of biopolymers on their properties. The purpose of the work was to study the impact of ozone on poly(3-hydroxybutyrate) (PHB). The manuscript presents DSC, XRD, EPR, FTIR, SEM, AFM and GPC data. It was shown that the microrelief of the PHB films changes after 5 h of ozonation without accumulating new chemical groups on the surface. Also, the crystalline phase remained completely unaffected. All the changes occurred in the amorphous region, which became significantly denser with a decrease in radical mobility by 45%. As a result, the strength of the films increased by 60% with constant elongation. The ozonized films were characterized by a decrease in polydispersity by 41%, an increase in the proportion of medium-length macromolecules by 80% and an increase in molecular weight by 5%, which shows that ozone reacts most actively with low molecular weight fragments of PHB in the direction of their rupture and with medium-length chains in the direction of crosslinking. These changes lead to an increase in the degradation period of films in the soil from 200 to 400 days. The prospect of using ozone for surface modification, in particular for controlling the rate of biodegradation, is very attractive due to its simplicity and low cost of implementation.