Polymer organogelation with chitin and chitin nanocrystals

Abstract

In this paper, we show that biodegradable and biocompatible organogels can be formed with chitin as the filler material and triglycerides as the continuous hydrophobic phase. When crude chitin was used, a large degree of aggregation was observed that prevented the formation of stable organogels. Two approaches were used to diminish this degree of aggregation and increase the stability. Either surfactants were used to increase the dispersability of the crude chitin, or the crude chitin was transformed into smaller rod-like nanocrystals by acid hydrolysis. Both approaches led to the formation of stable organogels with storage moduli up to 10⁶ Pa for high chitin concentrations (20 wt%). Three different types of surfactants were used, namely phosphatidylcholine, enzymatically modified phosphatidylcholine and sorbitan monostearate (Span 60). The choice of surfactant has a large influence on the gel strength and the temperature sensitivity of the gels. With chitin nanocrystals, in the presence of surfactants, larger gel strengths were observed for lower concentrations (1–10 wt%), indicating more efficient packing of the particles. Gels were stable even after addition of considerable amounts of water up to 25 wt%. The increase in gel strength in the presence of water (storage modulus) was most likely an effect of the water absorption ability of chitin that increased the effective volume fraction of the fillers.