과산화수소와 초음파 조사를 이용한 알긴산의 분자량 조절에 관한 연구

Abstract

In this study, we performed molecular weight control of sodium alginate (polysaccharide) derived from seaweed biomass (brown algae, Sacchairna Japonica) using hydrogen peroxide and ultrasound irradiation. Ultrasonic irradiation method was expected to reduce the molecular weight of sodium alginate by degradation which occur breaking of molecular’s chain. Also, oxidative decomposition reaction with hydrogen peroxide can be OH radicals which is possible to reduce the molecular weight by cutting 1,4-glycosidic bond of sodium alginate. The frequency of ultrasonic waves was constantly investigated at 22.5 kHz, and the oxidative decomposition reaction was carried out at reaction temperature (30-60℃), reaction time (5-120 min), and a hydrogen peroxide concentration (0.1-5.0 v/v%), and catalyst amount (molar ratio of hydrogen peroxide and catalyst ratio=10-500 : 1). As a result, we investigated molecular weight and polydispersity index of sodium alginate on the reaction temperature (30-60℃) and the reaction time (5-120 min) under ultrasonic irradiation. As the reaction temperature and time increased, the molecular weight and the dispersity was decreased. It showed a molecular weight of 606,000Da and 3.5 of polydispersity under the conditions at 60℃ for 120 min, it showed molecular weight and the polydispersity are reduced by 33.1% and 37.1%. It was considered that high reaction temperature time were required for reducing the molecular weight of sodium alginate under ultrasonic irradiation. As a result of oxidative decomposition reaction by addition of hydrogen peroxide, the molecular weight and polydispersity of sodium alginate tended to decrease as hydrogen peroxide concentration increased. As increased of hydrogen peroxide concentration from 0.1 to 1.0 v/v%, the decrease of molecular weight of sodium alginate from 3.8-36.1 to 85.3-87.0%, and it showed the decrease sodium alginate from 85.3-87.0% to 98.1-98.2% with increased hydrogen peroxide concentration from 2.0 to 5.0 v/v%. It was considered that hydrogen peroxide is a factor that high influence in the decomposition reaction of sodium alginate. We investigated molecular weight and polydispersity of sodium alginate with iron catalyst and hydrogen peroxide for improve the oxidative decomposition reaction. Molecular weight of sodium alginate was more reduced under the catalyst amount was increased from 500 : 1 to 100 : 1. However, it showed that no efficiency the molecular weight and polydispersity over the catalyst amount of 50 : 1. It was the iron catalyst amount of 100 : 1 was optimum value under the current reaction condition over oxidative decomposition reaction. After the oxidative decomposition reaction of sodium alginate, which was analyzed structures by molecular weight range. As a result, 1,4-glycosidic bond peak was decreased with the peak C=O of carboxyl group (-COOH) peak and hydroxyl gorup (-OH) tended to increased. In addition, we investigated that sodium alginate particles were reduced and well distributed using SEM results. In this results, we expected to increase the availability of sodium alginate by various molecular weights. In order to investigate the utility of alginate which molecular weight was controlled via oxidative decomposition reaction, two kinds of polymer synthesis reactions were carried out. First, copolymer was synthesized by polymerization reaction of polyacrylamide with alginate. However, copolymer was not synthesized by reduced molecular weight of alginate derived from through oxidative decomposition reaction. The production of silver nanoparticles, it was confirmed through TEM and HR-TEM analysis that alginate particles had spherical particles of nanoparticles because of the reducing ability was determined on the OH group of alginate. Silver nanoparticles can be used as antibacterial substances, antistatic agents, cryogenic superconductors and biosensors. In the future, it is possible to utilize as reducing agetns and stabilizing agents from various molecular weights of alginate by oxidative decomposition reaction.