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Gulamova Iroda Botirjonovna, National University of Uzbekistan, Scientific Researcher the Faculty of Chemistry E-mail: iroda0917@mail.ru Mukhamediyev Mukhtarjan Ganiyevich, National University of Uzbekistan, Associate Professor the Faculty of Chemistry E-mail: mmuxamediev@mail.ru
Synthesis of polymers on the basis of citric acid
Abstract: Studying the influence of pH and the temperature of the environment to viscosity of water solutions, swelling kinetics and collapse of cross-linked polymers and copolymer on the basis of natural ox acids there are founded the presence of pH and heat-sensitive qualities. It is revealed that the existence of polymers as a form of amides and as well as carboxyl groups leads to the appearance of a unique quality of having a little interval of temperature of two critical mixed temperatures.
Keywords: acrylamide -N- methylene citric acid (AA-N-MCA), citric acid, N acryl amide, hydrophilic polymer, polymerization, ionic monomers,
In recent years, interest on water-soluble and water-swelling polymers with various reactive functional groups is growing. These polymers demonstrate large possibilities of usage in medicine, pharmacy (controlled release of the drugs), biotechnology, electronics, environmental protection and other fields ofhuman activity [1; 2; 3]. A special group of monomers capable of forming a hydrophilic polymer systems are substituted N acrylamides, containing non-ionic and ionic functional groups. Thus polymerization of substituted N-acrylamides and meth-acrylamides containing weak acid groups is practically not explored. Therefore, the study of radical polymerization of substituted N-acrylamides, with carboxyl groups and further their conversion into water-soluble and water-swelling polymers make interest from the theoretical and practical standpoint. It is known that the polymerization of ionic monomers is strongly influenced by the reaction ofenvironment. As in comparison with the polymerization of nonionic monomers, in ionic monomers there appears whole range of additional factors (dissociation, specific and non-specific binding of ions, electrostatic and hydrophobic interactions and etc), which can dramatically affect the process of polymerization in solution. Therefore,
the goal of this work is to conduct research in the field of synthesis of monomers of substituted N acrylamide series with ionic groups, and the studying their polymerization to obtain a hydrophilic polymer. In the research asone of the components for the synthesis of substituted N acryl-amide containing an ionic functional group has been chosen natural oxyacid — citric acid. Interest in this subject has grown due to the fact that, depending on the method employed we may obtain monomers of having functional carboxyl or simultaneously active hydroxyl and carboxyl groups. The presence ofsuch groups would produce polymers with a wide range ofproperties, and the study of the kinetics of the polymerization and copolymerization of these monomers would facilitate the development of representations of the reactivity of the functionalized monomers.
Previously in the department, polymers based on otheroxyacid's — glycolic acid and lactic acid, in particular, such as theacrylic glycolic monomers, methacrylate glycolic, acrylamide-N-methylene-glycolic acid, acryl-amide-N-methylene-lactic acidwere obtained [4; 5; 6]. Abstract-radical polymerization of these monomers in aqueous solutions of various pH values and could ionic
Section 11. Chemistry
strength of solution were researched. This work is a continuation of the research in this area.
Synthesis of acrylamide -N- methylene citric acid (AA-N-MCA) is held by the reaction of Mannikha. In
oh
I
this reaction interaction of acrylamide with formaldehyde, in this way forms methyl acrylamide, which interacts with citric acid and as a result of water release forms AA-N-MCA. AA-N-MCA can be represented as follows:
ch2=ch + ch2o + hooc-h2c-c-ch2-cooh 2 i 2 i 2
c=o cooh
I
nh2
ch2=ch
I
During studying the dependence of the ratio of the monomers of reactants we found that the highest yield (up to 62-75% of theoretical) of the monomer is observed at equimolar ratios of the source components. The most suitable conditions for the synthesis of monomers is the simultaneous loading of the initial components and heating the reaction mixture at 60°C for three hours with continuous stirring. Purification was carried
Table 1. - Some physical and chemical
c=o
I
nh
I
ch2
I
0
1
hooc-h2c-c-ch2-cooh
i 2
cooh
out by repeated washing of the monomer the reaction mixture with diethyl ether and chloroform, as it was found that the resulting monomer is subjected to dis-tillative decomposition. AA-N-MCA is a light yellow, viscous liquid, soluble in water, alcohol, and in many polar solvents but not soluble in nonpolar solvents and hydrocarbons. Some physical and chemical parameters of derivedmonomersare shown in the table.
acrylamide-N-citric acid characteristics
Monomer The elemental composition,%
MR, cm 3/g nD20 d420 4 g/cm 3 C H N Acid number
found calcu lated found calcu lated found calcu lated found calcu lated found calcu lated
AA-N-MCA 79,56 80,06 1,51 1,31 43,6 48 4,7 4,9 5,1 5,4 172,6 174,7
%T
50.0 -.-.-.-.-.-.-.-.-.-.-.-.-.
4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600 4CI0.0
cm-1
Figurel. IR -spectrum of acrylamide — N — citric acid
Identification of the resulting monomer was performed to determine the elemental composition (C atoms, H, N), acid number, the calculation of molecular refraction and removing the IR and PMR spectra. The table shows the data obtained in the determination of the acid number, elemental composition and calculation of molecular refraction. IR monomer shown in Figure 1.
As can be seen from Figure 1, the IR spectrum ofAA-N-MCA absorption bands in the 1627 cm-1 corresponding to the double bond and 1668 cm-1 stretching vibrations -SONH- group monomer. The intense absorption band at 1345 cm-1 corresponds to OH (carboxyl) group. The presence of hydroxyl groups in the AA-N-MCA confirms same characteristic absorption bands in the IR-spectra in space 3200-3600 (OH) and 1100 cm-1 (C-OH). At 3753 cm-1 absorption band ofhydroxyl groups linked with hydrogen bond, which indicates that the monomer is in solution as a dimer. The absorption band at 1720 cm-1 corresponds to the stretching vibrations of the carbonyl group of the carboxyl monomer.
The structure of the monomer was also confirmed the withdrawal of its H NMR (on the frequency of 400 MHz). The PMR spectrum of the solution of AA-N-MCA in heavy water the group of acrylic signals fragment present at 6.15 ppm (2H) and 5.875 ppm (1H) and two equivalent doublet splitting 14Hz belonging group -NCH2-c protons centered at 2.9 ppm (equivalent 1H) and 2.75 ppm (axial 1H). The signal at 4.88 ppm HD belongs to the proton impurities in D2O. The signals of the protons of the hydroxyl groups and -NH- do not appear because of deuterium exchange in D2O medium.
Thus, spectroscopic study confirms the above obtained compound of formula.
It is obvious that one of the ways of obtaining polymers based on N-substituted amides is free radical polymerization of their unsaturated derivatives. Therefore, in order to obtain poly-AA-N-MLC research was carried out with radical polymerization of AA-N-MCA in aqueous solutions in the presence of a radical polymerization initiator hydroisolubricative dinithryle acid. Polymerization of the monomer was carried out for 10 hours at 60 °C. It was found that the solubility of the obtained polymer is strongly influenced by the monomer concentration in the reaction solution. Increasing monomer concentration in solution is above 10% leads to gelation, the resulting polymers strongly swell in water but do not dissolve. At lower concentrations formed polymers are readily soluble in water.
Thus, in this study we received a new AA monomer N-MCA-containing reactive carboxyl functional group. The structure of the resulting monomer identified a number of chemical and physical-chemical methods. By radical polymerization of AA-N-MCA in aqueous solutions and found that depending on the reaction conditions, may receive a water-soluble and water-swelling polymers.
Summary
new monomer — acrylamide -N- methylene citric acid was synthesized and it is chemical structure was determined by chemical and physico-chemical methods. It was shows abbility of obtain on the base of these monomer some water- soluble and water- swallowing polymers.
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