Preparation Of Carboxymethyl Starch And Its Stability In Aqueous Solution

Starch is a kind of carbohydrate polymer and polyglucose. Because of its insolubility in cold water, gelation, retrogradation at low temperature and formation of poor model, the application of starch has been limited in food, paper, oil and pharmaceutical industries. In order to improve the properties of starch and enlarge the range of application, the chemical modification is studied to improve application.Carboxymethyl starch(CMS) is a class of water-soluble anionic polymer, which can be obtained by chemical modification of starch. CMS has good hydrophilicity, solubility in water at room temperature, viscosity stability, retrogradation and freeze-thaw stability. CMS is harmless and easy to be absorbed in vivo. It can also inhibit the growth of tumor and raise immunity of human body. CMS is a kind of environmentally friendly polymer and with low cost. It is widely used in food, medicine, papermaking, printing and dyeing, daily chemicals, petroleum and so on. Therefore, the research of carboxymethyl starch has important commercial value. In this thesis, firstly, potato starch is used as raw material and carboxymethyl starch(CMS) is prepared in ethanol/water mixtue solvent. The optimization of the reaction conditionswere also discussed. Secondly, carboxymethyl starch aqueous solution properties were expored by ultraviolet-visible spectrometer. Finally, CMS microspheres have been preparaed by inverse emulsion, and were investigated their controlled release behavior for acetylsalicylic acid. This thesis consists of four chapters.The first chapter introduced structure of starch and basic properties, modified starch.Reviews the research progress and application of carboxymethyl starch.The second chapter about the preparation of carboxymethyl starch. High degree substitution of carboxymethyl starch was obtained in ethanol-water solvent. Several reaction conditions have been discussed about the potato starch carboxy methylation reaction, they are ethanol concentration, molar ratio of sodium hydroxide and chloroacetic acid, molar ratio of chloroacetic acid and anhydrous glucose unit in potato starch, reaction time of alkaline and etherification reaction and temperature of etherification. The optimum process conditions are obtained by this method for the preparation of carboxymethyl starch.The degree substitution of carboxymethyl starch is characterized by the ultraviolet-visible spectrometer. The structure of potato starch and carboxymethyl starch characterized by Fourier Transform Infrared Spectrometer(FTIR), which shows that 1100cm-1 is the ether bond absorption peak, 1613cm-1, 1420cm-1 and 1325 cm-1 is the characteristic absorption peak of carboxyl group(-COOH).The morphology of potato starch and carboxymethyl starch was characterized by Scanning Electronic Microscope(SEM). Crystal structures of potato starch and carboxymethyl starch were characterized by X-ray diffractometer( XRD).The Thermo Gravimetric(TG) analyzer has also been used for characterizing the weight loss of potato starch and carboxymethyl starch in the high temperature.The third chapter, study on stability of Carboxymethyl starch. Influencing factors of the aqueous solution stability of Carboxymethyl starch is studied. Influence factors on the stability of carboxymethyl starch aqueous solution have been studied, and they are carboxymethyl starch concentration, degree of substitution, p H, Calcium ion concentration, sodium chloride concentration, citric acid and sucrose concentration has been discussed. And a stable system of Carboxymethyl starch aqueous solution was obtained under specific conditions. Suspension stability and light transmittance of carboxymethyl starch solution were measured by ultraviolet spectrophotometer.The fourth chapter is about the preparation of carboxymethyl starch microsphere and its controlled release of aspirin.Epichlorohydrin was used as crosslinking agent, and carboxymethyl starch microspheres were prepared by reverse microemulsion method. Effects of drug dosage ratio, dosage of activating and cross linking agent, and reaction time on the drug loading ability were investigated by using L9(34) orthogonal test. And using aspirin as a model drug, it has been studied that the carboxymethyl starch microspheres drug release behavior in simulated gastric fluid and simulated intestinal fluid.The morphology of carboxymethyl starch and carboxymethyl starch microspheres are were characterized by SEM.