THERMORHEOLOGICAL AND THERMOGRAVIMETRIC ANALYSIS OF BIOADHESIVE POLYMER MUCIN MIXTURES/

In this study, the thermal behaviour of bioadhesive polymer hydrogels, a mucin gel and their mixtures, was investigated using thermorheologi cal and thermogravimetric analysis. Three poly(acrylic acid (PAA) poly mers with different cross-linking status (Carbopol 974P, Carbopol 971P and Noveon AA-1) were selected on the basis of their good bioadhesive properties. Rheological scans from 10-90 degrees C were performed in the oscillatory mode. A marked increase in elastic modulus (G') with t emperature was detected above 50 degrees C in all mucin-containing sam ples, as opposed to the pure gels which showed a 'flat' response. Ther mogravimetric (TG) analysis (from 30-150 degrees C, at a rate of 8 deg rees C/min) revealed variations of the pattern of water loss within th e gels which corresponded to the rheological properties of the PAA sys tems. The thermal behaviour of the Noveon AA-1/mucin mixture did not s how the same trends on mixing with mucin as did the Carbopol systems, indicating that the type of cross-linking agent (a tetrafunctional ent ity, as opposite to a bifunctional one in the Carbopols) may have an i mpact on the polymer interaction with mucin. (C) 1997 Elsevier Science B.V.