Semi-interpenetrating polymer networks of chitosan and poly(ethylene glycol)

Abstract

Chitosan is a natural polycationic polymer that possesses useful properties such as bioactivity, biocompatibility, non-toxicity and non-antigenicity. On the other hand, its mechanical properties are not good for some biomedical application. They may be improved by preparing semi-interpenetrating polymer networks (semi-IPNs), when the hydrogel network is prepared in the presence of a previously made polymer such as poly(ethylene glycol). This paper deals with synthesis and characterization of the semi-interpenetrating polymer networks of chitosan and poly(ethylene glycol) with different Ch/PEG ratio and crosslinking degree. The degree of deacetylation of chitosan was determined by potentiometric titration, titration and elemental analysis. The semi-IPNs were characterized by swelling kinetics, mechanical properties and thermal analysis. It was found that PEG content and crosslinking agent concentration significantly influence the swelling behaviour of semi-IPNs. Water uptake was higher for lower crosslinking agent concentrations and PEG contents, up to PEG/Ch = 0,75. Better mechanical strength of semi-IPNs was obtained for higher PEG content and crosslinking agent concentration. SEM analysis confirmed the porous structure of semi-IPNs. Increasing the degree of crosslinking and PEG content up to PEG/Ch = 0,75, the pore size decreased. Based on the pore size, the investigated semi-IPNs can be regarded as macroporous. Thermogravimetric analysis showed that thermal stability of the semi-IPNs depends on the degree of crosslinking, as well as on the PEG content.

Tema ovog rada je sinteza i karakterizacija semi-interpenetrirajućih polimernih mreža (semi-IPM) hitozana (Ch) i poli(etilen glikola) (PEG) sa različitim odnosom PEG/Ch i stepenom umreženja. Ispitana je kinetika bubrenja u rastvoru pH 2,2, mehanička svojstva, termička stabilnost i morfologija sintetisanih semi-IPM. Utvrđeno je da stepen umreženja i sadržaj PEG u semi-IPM utiču na bubrenje i termičku stabilnost semi- IPM. Dodatak PEG-a poboljšava mehanička svojstva za sve ispitane odnose PEG/Ch, pri čemu se stepen bubrenja semi-IPM nije mnogo promenio. Na taj način su dobijeni hidrogelovi koji dovoljno bubre i istovremeno imaju dobra mehanička svojstva, što ih čini pogodnim za primenu u medicini i farmaciji. SEM analiza je pokazala da sintetisane semi-IPM imaju poroznu strukturu. Na osnovu veličine pora, izračunate primenom teorije ravnotežnog bubrenja, ispitivane semi-IPM se mogu klasifikovati kao makroporozne.