Synthesis of hydrogels based on starch biomaterials and sodium-carboxymethylcellulose kholnazarov Bakhodir

SYNTHESIS OF HYDROGELS BASED ON STARCH BIOMATERIALS AND SODIUM-CARBOXYMETHYLCELLULOSE
Kholnazarov Bakhodir
Senior researcher, Termez State University,
190111, Republic of Uzbekistan, Termez, F.Hojayev St., 43.
E-mail:[e-mail]
Turaev Hayit
Doctor of Chemical Sciences, Professor, Termez State University,
190111, Republic of Uzbekistan, Termez, F.Hojayev St., 43.
E-mail:[e-mail]

ANNOTATION
This polymer material demonstrates a significant proportion of the ability to swell and retain water in its structure, but does not dissolve in water. These hydrogels are highly absorbent and can contain over 90% water. Hydrogels also have a degree of flexibility very similar to that of natural tissues due to their significant water content. The sodium salt of carboxymethyl cellulose was used as the main material, which is a biomaterial for the preparation of a hydrogel with optimal crosslinking.
Keywords: Starch, hydrogel, citric acid, sodium-carboxymethylcellulose, crosslinking, copolymerization solution.
INTRODUCTION
Cellulose is the world's most abundant renewable material. It is insoluble in water, which makes it suitable for hydrogel formation. The introduction of various substituents into the cellulose structure reduces the number of strong hydrogen bonds between hydroxyl groups, so water solubility can be achieved relatively easily. Common groups are alkyl, hydroxyalkyl and carboxymethyl functional groups used to modify cellulose [1]. For gelation purposes, carboxymethylcellulose (CMC) is found in the base material, but a significant amount of research work in the literature is available for other cellulose derivatives. Hydrogels based on carboxymethylcellulose are prepared from aqueous solutions using several cross-linking methods. Crosslinkers such as polycarboxylic acids, epichlorohydrin and N,N'-methylenebisacrylamide (MBA) are commonly used, but gelation can also be achieved using polyvalent cations such as Fe³⁺ [2]. To initiate the cross-linking reaction in pure CMC high-energy irradiation, both electron beam and gamma radiation are often used [3]. The great advantage of irradiation is that gel formation occurs even without cross-linking agents. The presence of cross-linking agents significantly improves the gelation process, resulting in better gelation and milder synthesis conditions required. The gelation process is influenced by several parameters, such as the chemical structure and molecular weight of the polymer, solute concentration, absorbed dose and atmosphere [4]. Starch is also a very low-cost renewable resource that is mainly used as a copolymer in synthetic polymer-based hydrogels. A homogeneous starch structure is obtained by starch pre-gelatinized by heat treatment before copolymerization [5]. Crosslinking of hydrogels can be achieved using an initiator system or high energy irradiation, which produces free radical crosslinking and has very high swelling properties. The properties of hydrogels are influenced by the starch source and different amylopectin/amylose ratio [6]. Starch-based hydrogels are combined with other renewable materials such as starch/chitosan hydrogels, which give hydrogels poor water absorption. Carboxymethyl cellulose is mainly used in copolymers with other cellulose derivatives and mixed with other low-cost renewable materials [7]. Cellulose and its water-soluble derivatives have been used primarily for the preparation of various gelatinized starch composite films. Hydrogels were synthesized with carboxymethyl starch and carboxymethyl cellulose in the presence of MBA cross-linker [8]. The goal of this work is to obtain pure cross-linked CMC and CMC/starch hydrogels with improved superabsorbent properties compared to pure CMC-based gels. Starch/CMC mixture is prepared by taking starch and CMC in different ratios. Citric acid is used as a catalyst. Effect of starch content of gel properties under different synthesis conditions.