| The petroleum resources are being exhausted gradually and the problem of environmental pollution from nondegradable polymer materials that are mainly derived from petroleum resources becomes more and more serious. Therefore, it is necessary to develop novel polymeric material mainly derived from natural polymer. Konjac is the local resource of China, as a kind of renewable polymer, which has potential to substitute for some petrochemical products because of its environmental friendliness.The main research contents and conclusions in this thesis are as follows:1. The acetylated KGM products with different degree of acetylation were synthesized using acetic anhydride in the presence of zinc chloride as catalyst. The values of DA ranging from 1.82 % to 6.23 % were determined by saponification—titration method. The effect of DA and complex ratios to synergistic interaction of mixture gels of KGM and xanthan were investigated by dynamic viscoelastic measurements. Winter and Chambon criterion was firstly utilized to quantify the critical gelation temperature (Tgel) for the mixture of KGM and xanthan. Compared with the storage modulus (G') and Tgel of native KGM / xanthan mixtures, that of acetylated KGM / xanthan complexes decreased greatly, mostly due to the decrease of molecular weight of KGM caused by degradation of KGM backbone. With the degree of acetylation of KGM increasing, G' and Tgel of acetylated KGM / xanthan complex decreased gradually. This observation indicated that acetylation of KGM would weaken synergistic interaction of KGM / xanthan complexes.2. KGM fractions with widely various molecular weight from 4.0×105 to 2.5×106 were prepared by heterotypic reaction in ethanol using hydrochloric acid as degradation reagent. Rheological properties of mixture systems of xanthan and KGM fractions were investigated by dynamic viscoelastic measurements. Results from dynamic viscoelastic measurements show that molecular weight of KGM obviously influenced on rheological properties of KGM / xanthan mixtures as follows: when molecular weight of KGM was gradually increased from 4.0×105 to 1.91×106, Tgel of the system is steeply shifted to a higher temperature and G' is enhanced greatly; when Mv of KGM shifts from 1.91×106 to 2.5×106, Tgel and G' of the system has some slight increase, even less molecular weight dependence. Furthermore, it is elucidated the mixture systems formed relatively strong gels corresponding to Mv of fractions of KGM above the critical value 1.91×106.3. The sol-gel transition of aqueous mixtures of sodium alginate and carboxymethylated konjac glucomannan (CM-KGM, a charged derivative from KGM synthesized using 6 wt % NaOH / 5 wt % urea as reaction medium was induced by in situ pH-decrease in the presence of glucono-delta-lactone (GDL). The gelation kinetics and the rheological properties of a mixture system were investigated by dynamic viscoelastic measurements. The slow release of protons induced by GDL gave birth to partly uncharged polymer chains and partly shielded electrostatic repulsion, resulting in an interpolymer association. This segregative interaction brought about a significant improvement in elastic modulus of the resulted gel. The strongest synergism occurred at a content of CM-KGM WCM = 29.9 wt%, exhibiting the highest gel strength. Increasing the content or the degree of substitution (DS) of CM-KGM both resulted in slower gelation kinetics. The fractal dimension of the incipient gel, which was not greatly affected by the mixing ratio and the DS of CM-KGM, reflects a rather compact gel structure network.The results of basic research in this thesis concerning the modification of natural polymers and the preparation and characterization of compound gel materials provided important scientific foundation for the further development and application. Therefore, this study has theoretical significance and applied prospect, which is well consitent with the target of environmental protection and the strategy of sustainable development.
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