Abstract

The primary alcohol groups of four kinds of polysaccharides (com starch, rice starch, sweet potato starch, and cellulose), with different structures and water solubilities, were oxidized to carboxyl groups using 2,2,6,6-tetramethyl-1-piperidine oxoammonium ion (TEMPO) at $25^{\circ}C$. The optimum pH, TEMPO content, and NaBr content for the TEMPO/hypobromite-catalyzed oxidation of the polysaccharides were $10.5{\sim}11.0$, 10 mmol/mol primary alcohol, and 0.49 mmol/mol primary alcohol, respectively. The oxidation degree for the primary alcohol group was more than 90% for all four kinds of the polysaccharides. The oxidation process greatly increased the water solubility of the polysaccharides. Water-insoluble polysaccharide such as cellulose became water-soluble to the extent of 8.42% (w/v). And also, the polysaccharides with very low water solubility (less than 0.10% (w/v)) such as com starch, rice starch, and sweet potato starch had high water solubility of approximately 45%(w/v). The gel-forming abilities with calcium ion were determined. The oxidized polysaccharides are new anionic polymers with unique structures that could have application as gums, gels, and films.

구조와 용해도가 다른 4종류의 다당류(옥수수전분, 쌀전분, 고구마전분 및 셀룰로오스)내의 1차 alcohol group을 $25^{\circ}C$에서 2,2,6,6-tetramethyl-1-piperidine oxoammunium (TEMPO)을 사용하여 carboxyl group으로 산화, 전환하였다. TEMPO/bromite 촉매를 이용한 산화반응계에서 최적 pH, TEMPO함량 및 NaBr 함량은 각각 $10.5{\sim}11.0$, 10 mmol/mol of primary alcohol, 0.49 mol/mol primary alcohol이였으며, 반응 최적조건하에서의 산화율은 4종류의 다당류 모두 90%이상이였다. 산화반응은 다당류의 물에 대한 용해도를 매우 증가시켰는 바, 물에 불용성인 셀룰로오스의 경우 산화에 의하여 8.42% (w/v)로 증가되었으며, 옥수수전분, 쌀전분 및 고구마전분과 같이 물에 거의 불용성인(0.10% (w/v) 이하) 다당류들도 약 45% (w/v) 수준으로 물에 대한 용해도가 증가하였다. 또한 본 실험에서의 산화공정에 의하여 제조된 산화물질은 $Ca^{2+}$이온과의 겔 형성능을 갖게됨을 확인하였는 바, 각종 gum, gel 및 film의 새로운 소재로 활용될 수 있을 것으로 기대되었다.

Keywords

• primary alcohol oxidation;
• water solubility;
• gel-forming ability