661.72.88 Hemostatic resorbent polymeric materials have been synthesized from water-soluble acetylceUulose, lagochilin, and lagohirsin. The substances obtained possess an effective hemostatic action and have a water-soluble form.It is known that by adding (low-molecular-mass) physiologically active substances to the macromolecule of a highmolecular-mass compound it is possible to obtain a prolongation of their action, to decrease their toxicity, to improve their solubility, and to achieve directed transport into determined organs [1].We have previously [2] reported the results of investigations on the production of a hemostatic material from watersoluble acetylcellulose by the "inclusion" in its structure of a drug --lagoden (homogeneous mixture). Low-molecular-mass a natural compounds such as lagochilin and lagohirsin, isolated from plants of the genus Lagochilus, possess only a weak hemostati6 activity because of their insolubility in water. In order to impart solubility to them and to prolong their action, and also to create polymeric medicinal forms, we have investigated the addition of molecules of lagochilin or lagohirsin to the aldehyde groups of oxidized ,/vater-soluble acetylcellulose (OWSAC).As is known, the molecule of water-soluble acetylcellulose (WSAC), obtained by the procedure of [3], contains two functional groups, -OH and -OCOCH 3, which greatly restrict the possibility of polymer-analogous transformations. With the aim of forming in it a new reactive -HC = O group we have carried out the directed oxidation of WSAC with periodic acid, which is capable of oxidizing the two hydroxy groups present at the second and third carbon atoms of the anhydroglucose unit of WSAC [4].To confirm the formation of an aldehyde group in the WSAC macromolecule we recorded IR spectra of control and oxidized specimens. In view of the fact that the absorption band of the aldehyde group coincides with the absorption band of the acetyl group, to demonstrate the formation of aldehyde groups we recorded IR spectra of saponified samples of WSAC and OWSAC. Saponification was performed with a 0.5 N solution of sodium methanolate in anhydrous methanol [5]. The IR spectra of the OWSAC specimens revealed an absorption band relating to an aldehyde group, the intensity of which depended on the time of oxidation.The number of aldehyde groups in the product was determined by titrating an aqueous solution of the OWSAC with sodium thiosulfate. The OWSAC contained 100-110 aldehyde groups per 1000 anhydroglucoside units (AGUs) and had retained its solubility in water. A further increase in the number of aldehyde groups led to the formation of intermolecular acetal bonds, as a result of which the OWSAC became insoluble.To add lagochilin or lagohirsin to the aldehyde groups of OWSAC, a definite amount of the substance was dissolved in dimethylformamide to give a concentration of 5-6%, and lagochilin or lagohirsin was added in a ratio to the polymer of 1:4. As a water-abstracting agent we used anhydrous copper sulfate or phosphoric anhydr...

The phenomenon of an increase in the hydrophilic properties of such a polyhydroxy compound as cellulose on a limited substitution of its hydroxy groups by other radicals is due to the existence of a system of strong hydrogen bonds blocking the interaction of cellulose with water but breaking down on partial substitution. However, hydrophilicity is connected not only with the" substitution itself but also with the properties of the substituting radical [1, 2]. It was therefore desirable to study the sorption properties and the thermodynamics of the interaction of mixed cellulose esters with water.We have investigated a water-soluble cellulose acetate (WSCA) with a degree of substitution Fac = 0.72; a watersoluble cellulose acetophthalate (WCAP) with Fac = 0.72, Fph t = 0.08, OH group content 2.2; a water-soluble acetomaleate (WCAM) with Fae = 0.71, Fma I = 0.06, OH group content 2.2, and a water-soluble cellulose aminoacetate (WCAA) with Fae = 0.65, Famin o = 0.51, OH group content 1.84. The degree of polymerization of all the specimens studied was -200.The sorption of water vapor was studied by means of a McBain spiral balance with a sensitivity of -1.3-10 -3 m/kg at 293 K and a residual pressure of 10-3-10 -4 Pa. When the equilibrium values of the amount of water sorbed had been reached, the equilibrium vapor pressure was measured and sorption isotherms were plotted. The heat of mixing was determined in a modernized DAK-I-IA calorimeter. Before the beginning of the experiments, the samples were dried to constant weight and were placed in the working cell of the microcalorimeter. After thermal equilibrium had become established the samples were brought into contact with water vapor. The heat effect was shown on the panel of the integrator and recorded in the form of curves in a diagram. Figure 1 shows isotherms of the sorption of water vapor for all the samples investigated. As has been shown in [3], the sigmoid form of the curves, with a convex initial section, is due to the simultaneous occurrence of two processes: physical adsorption in the pores of the polymer, and its swelling. It follows from Fig. I that mixed cellulose esters have a high sorption capacity in water and that the magnitude of the equilibrium sorption depends on the nature of the substituting radical, decreasing in the sequence WCAM > WCAP > WSCA > WCAA.The sorption isotherms were used to calculate the thermodynamic affinities of water for the mixed cellulose esters. The difference in the chemical potentials of 1 g of water in the phase of a swollen polymer, A/~I, and of pure water, A/~ ~ was calculated by means of the equation

No abstract

It is known that the partial substitution of cellulose leads to a disruption of its ordered structure and considerably increases its reactivity in other substitution reactions. It was of interest to investigate how the partial substitution of the hydroxy groups of cellulose by other radicals in the production of mixed cellulose derivatives affects its reactivity in acetylation and the water solubility of the products of their hydrolysis.In the present paper we give for the first time the results of an investigation of the deep hydrolysis at various temperatures of mixed cellulose esters --acetocarboxymethyl-and acetomethycelluloses --obtained by the acetylation of suitable weakly substituted cellulose derivatives.It must be mentioned that the acetylation of carboxymethylcellulose takes place very slowly, with difficulty, and requires a considerably longer time than the acetylation of cellulose itself, although, as has been stated above, a slight loosening of the structure of cellulose facilitates various substitution processes. This contradictory fact can be explained by the assumption that when cellulose is treated with monochloroacetic acid there is, on the one hand, a loosening of the structure and a disruption of hydrogen bonds, while, on the other hand, the introduction of another radical which itself has a polar -COOH group apparently leads to the formation of new hydrogen bonds between the cellulose chain.% which lowers the solubility of the resulting ester in the esterifying medium. Such a molecular structure also has a considerable influence on the process of hydrolyzing an acetyl group.It is interesting to note that, as compared with the acetylation of weakly substituted earboxymethylcellulose, the acetylation of methylcellulose took place readily and rapidly. A viscous transparent syrup of acetomethylceUulose was obtained. In the production of methylcellulose with a high degree of etherifieation of up to 50 the reactivity of the ether obtained increased through the loosening of the structure by the introduction of methoxy groups capable of hydration.The results of hydrolysis are shown in Fig. 1. It can be seen from this that the time of hydrolysis of acetocarboxymethylcellulose obtained from Na-CMC was greater than that for the product obtained from H-CMC. This circumstance is apparently due to the fact that in the case of Na-CMC a certain mount of the catalyst --sulfuric acid --is consumed in the conversion of Na-CMC into H-CMC during the acetylation process and thus retards hydrolysis.The acetocarboxymethylcellulose contained about 0.7 % of carboxymethyl groups (3, = 5). As can be seen from Fig. 1, by the substitution of these radicals in the given numbers of hydroxyls it is possible to obtain water-soluble products with Tashkent Institute of Chemical Technology.

A. S. Sidikov, G. It. Rakhmonberdiev and Sh. S. Arslanov UDC 661.72.88The thermooxidative degradation of water-soluble acetylcellulose and some of its carboxy-containing derivatives has been studied by the methods of thermal analysis. A relationship has been established between the thermostability of the aceto-mixed derivatives and the nature of the substituting group.During synthesis and processing, cellulose derivatives undergo various thermal actions.The study of their thermostability and the determination of the laws characterizing the influence of the functional groups present in mixed acetic esters of cellulose under the action of heat is therefore very important.We have investigated the thermooxidative degradation of water-soluble acetocellulose (WSAC) and its water-soluble carboxy-containing derivatives, such as the acetomaleate (WAMC) and the acetophthalate (WAPC) and also acetocarboxymethylcellulose (WACMC) by thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermal analysis (DTA).WSAC with a degree of substitution by acetyl groups oft = 55 was obtained by the homogeneous hydrolysis of highly substituted cellulose acetate [1]. WACMC was obtained by the acetylation of partially substituted carboxymethylcelluiose with a degree of substitution of 7 = 5, followed by hydrolysis to the water-soluble state [2]. WAMC containing 25% of bound acetic acid (7 = 85) and 5.0% of maleate groups (T = 15) and WAPC containing 24% of bound acetic acid (7 = 70) and 9.5% of phthaloyl groups (7 = 29) were obtained by esterifying secondary acetylcellulose with the appropriate dibasic acid anhydrides followed by hydrolysis of the mixed esters, again to the water-soluble state [3].When the WSAC was heated even at 40~ a loss in mass began at the rate of about l%/minute. As a result, the weight of the sample fell by 9---10%. The process was accompanied by a small endothermic effect (Fig 1, a). It is likely that the volatilization of sorbed moisture and low-molecular-mass products took place in this temperature interval.In the temperature interval from 100 to 240~ there was a section of relative thermostability (SRT) of the sample, where there was no loss in weight and no heat effects. At 240~ and above, a gradually accelerating second process of loss in weight began, at first accompanied by a small absorption of heat (up to 320~ the loss in weight in this section was 6%), and then exothermic degradation reactions superlx~sed on one another with a maximum at 3700C. As a result of this process a loss in weight of the sample of the order of 55-60% took place at an overall rate of 6%/min. According to the available literature information, the degradation of cellulose in this temperature interval proceeds with the evolution of a number of liquid and gaseous products, of which the most frequently mentioned are levoglucosan and its derivatives, and various ethers and esters and also the products of their oxidation as far as CO, CO 2, and water.The final combustion of the residue (about 20---30%) is characteri...