Preparation And Rheological Properties Of Konjac Glucomannan/Ethyl Cellulose Emulsions

This paper was intended to prepare sustained release polysaccharide blend matrixby using the water-soluble konjac glucomannan (KGM) and water-insolubleethylcellulose (EC) as primary materials to explore a new biological controlled releasematerial approach. The blend process were monitored by using the static andrheological instrumment and atomic force microscopy, after that the changes ofmolecular structure and aggregation state in solution on the stability, aggregation, andthe phase separation of systems were analyzed; Rheological properties of the blendmatrix were analyzed by using the rheometer. The main results are as follows:1. The konjac glucomannan (KGM)/ethyl cellulose (EC) emulsion was preparedby mixing KGM aqueous solution with EC ethyl acetate solution. The phase diagram ofKGM/EC mixtures was established through centrifugation and visual observation byadjusting the ratio of KGM and EC at25°C and pH7.0, the results showed threeregions:(I)phase separation region,(II) compatible region and (III) gelation region.2. In the compatible region, the KGM/EC emulsion was prepared through thesingle factor experiment and orthogonal experiment optimization. The viscosity ofKGM/EC emulsion decreased with the increase of shear rate, which reflected thecharacteristic of a typical pseudo plastic fluid of the emulsion. Dynamic viscoelasticproperties indicated that linear viscoelastic region of KGM/EC emulsion was between0.5%and100%when the angular frequency was1.0rad/s. With the increase ofconcentration of KGM and sweep frequency, storage modulus (G’) and loss modulus(G″) increased, G’ was smaller at low frequency but larger than G″at high frequency. Itindicated that KGM chains was easy to disentangle at low frequency, but resisted thedisentanglement at high frequency.3. The stability of the KGM/EC emulsion and the influence of the emulsionimpacted by different HLB values were also researched in this article. The resultsindicates that, the droplet size of emulsion could be reduced which would make theemulsion more stable when a certain amount of Tween-80and Span-80were added intothe solution. The optimum concentration of Tween-80is0.6%and0.5%for Span-80relatively. Z-potential and viscosity of KGM/EC complex solution rarely influenced byadding emulators.4. AFM results revealed that, KGM molecular chains in emulsion formed porousmesh structure under the action of shear force. KGM molecular formed continuousphase and EC molecular uniformly dispersed in KGM continuous phase as dispersedphase, which presented a structure of sea-island.