Study On Interaction Functional Groups Of Gelatin And Montmorillonite In Composite

As a natural amphoteric polyelectrolyte, the chains of gelatin possess large amounts of positive and negative charges. Montmorillonite (MMT) is a kind of natural layered silicate and the distribution of charges on its layers is also very complicated. All these characteristics determine that intercalation process of gelatin and MMT is special. In acidic media, the intercalation of gelatin into MMT could be considered as the ion exchange between gelatin molecules with large amounts of positive charges and cations in the interlayer space of MMT. The interaction between gelatin and MMT is electrostatic interaction. Since the intercalation composite could also be prepared in alkalic media, there should be a sort of interaction between gelatin molecules with negative charges and MMT. The dissertation focused on this interaction and the experiments were taken to ascertain the interaction functional groups.In this paper, the interaction between carboxyl functional groups and MMT were simulated by small molecule-sodium laurate. The interaction between carboxyl anions and MMT was ascertained by the means of XRD,FT-IR,TG&DTA和13C CP/MAS/DD NMR. It was found that the interaction between carboxyl anions in gelatin chains and MMT was stronger than the electrostatic interaction between amino cations in gelatin and MMT by comparing the thermal and swelling behaviors of the composites prepared at different pH values.Comparing the mechanical properties of gelatin/MMT intercalation composites prepared at different pH values with the same ratio of gelatin to MMT, it was found that the composite prepared in alkalic media had better mechanical properties. That reflected the interaction between carboxyl anions in gelatin chains and MMT. Since there were less carboxyl groups in the modified gelatin chains, the mechanical properties of modified gelatin/MMT composite was worse than that of gelatin/original MMT composite.The modified MMT (dehydroxylated MMT) was prepared to ascertain the interactive sites on MMT. The diffraction peaks of sodium laurate in sodium laurate/original MMT composite were fairly stronger than those of sodium laurate/modified MMT composite. The mechanical properties of gelatin/modified MMT composite were not as good as those of gelatin/original MMT composite and the dehydroxylated MMT aggregated in the gelatin/modified MMT composite. All these phenomena proved that hydroxyl groups were the interactive sites on MMT.