INTRODUCTION:

Allyl polymers, owing to their improved physical and electric properties, high hemo- and thermal stability, cause a great interest of researchers [1-3]. However, initial monomers, including allylamine, possess low reactionary ability in polymerization reactions. Sufficiently severe conditions are necessary: high temperature (above 300-400°C), high pressure, g-radiation. It limits their application.

It is known that introduction of electron acceptor substitutes in their structure essentially raises ability of monomers to polymerization [4]. We as such compounds have used 1,4-benzoquinone. The quinone-hydroquinone system is the most known and well studied oxidation-reduction system, and is widely used for the synthesis of redox-polymers [5].

MATERIALS AND METHODS:

Monomers – mono- (AA-Q) and disubstituted (AA-Q-AA) derivatives of allylamine (AA) and 1,4-benzoquinone (Q) were synthesized by methods [6].

Thermal polymerization of monomers was carried out in ampoules in the range of temperatures 160-220 ^oC and duration of process – 7 h. Content of sulphur in reaction medium was 5-50% from the monomer mass. Yield of gel-fraction was determined by the method of extraction in Sohxlet apparatus. Samples of polymers were washed from unreacted monomers and sulphur by mixture of dimethylformamide and acetone (1:1) [7].

Thermal stability of allyl redox-polymers linear and reticular structure was studied by the method of thermogravimetric analysis (TGA) on the air at the interval of temperatures 20-400 ^oC with constant velocity of heating 4^oC/min.

Stability linear and reticular redox-polymers to thermal hydrolysis was determined by the way of their boiling in water for a different time by [8] with subsequent control of static exchange (SEC) and oxidation-reduction (ORC) capacity.

RESULTS AND DISCUSSION:

Studying of polymerization of monomers on the basis of АА and 1,4-Q has shown that for them is equally successful either radical [6,7] or, cation [9] initiation. Thus formed linear and weakly branched redox-polymers. However, in many cases it is more preferable to use spatially linked polymers.

In this connection we investigate thermal polymerization of AA-Q and AA-Q-AA in the presence of sulphur. The choice of sulphur as the linking agent is caused by two reasons: first, necessity of its recycling caused by annual growth of dumps of sulphur in connection with rapid development of the oil-extracting industry in Republic of Kazakhstan. Secondly, introduction of thyol groups in addition to quinoid provides alongside with oxidation-reduction properties an ability to selective extraction of ions of silver [5].

Thermal polymerization of monomers AA-Q and AA-Q-AA is investigated in the presence of sulphur of a deposit of Zhanazhol of the Aktyubinsk area (Fig. 1, curve 1), elementary sulphur (curve 2), UOS "Tengizshevroil" (curve 3).

Fig. 1 Influence of quantity of sulphur on the yield of gel-fraction at АА-Х-АА polymerization (200⁰С, 5 h) (1 – Zhanazhol, 2 – elemental sulphur, 3 – “Tengizshevroil”)

Atoms of sulphur possess high ability to incorporate with each other with formation of ring or chain figures. If elementary sulphur is presented basically in a kind of octahedron cycles S₈ as a part of a product of sulphur cleaning the oil and gas raw materials alongside with forms S₈, S₆ there are active low-molecular forms S_2-, S_3-, S_4-, S_5- - forms [10]. But apparently from figure 1, these distinctions do not render essential influence on character of the received curves and a gel-fraction yield at polymerization of disubstituted quinoid derivative of allylamine. Reaction of linking in the course of monomer polymerization at temperature of 200°С and durations of heating 5 h proceeds on the maximum depth equal to 91-93 %, in the presence of 10 % of Zhanazhol sulphur and 20 % of elementary sulphur and Open Society "Tengizshevroil" sulphur. Thus, the sulphur taken from oil deposits, despite their various modifications, can be used with success in linking processes, in processes of sulphuric vulcanization of macromolecules.

The highest content of sulphur in polymerization products is observed at 200°С (Fig. 2).

Fig. 2 Influence of temperature of polymerization of monomers АА-Х (1) and АА-Х-АА (2) on the yield of gel-fraction in the presence of 10% S (5 h)

In the presence of sulphur in an initial monomeric mix the gel-fraction yield (to 93-96 %) essentially raises. Depending on its content by results of the element analysis into structure of polymers enters to 26 % of sulphur. For lack of sulphur in an initial mix of reagents the yield of gel-fraction for AA-Q and AA-Q-AA reaches only 56 and 64 % accordingly (Table 1).

Table 1. An yield of gel-fraction and the content of the connected sulphur in the reticular redox-polymers obtained by thermal polymerization of monomers AA-Q and AA-Q-AA at various quantities of sulphur in initial reaction medium (Т = 200°С, 5h)

Monomer	S, %		Yield of gel-fraction, %
Monomer	In the initial Mixture	In gel-fraction	Yield of gel-fraction, %
АА-Q	0	0	56,2
	5	4,3	65,4
	20	12,3	96,1
	50	26,6	95,3
AA-Q-AA	0	0	64,1
	5	4,7	75,3
	20	14,9	90,1
	50	25,8	93,0

According to data [11] radical process here takes place. Under the influence of radicals there is a disclosing of octahedron rings of elementary sulphur. Formed instable intermediate compounds break up with allocation of biradicals of sulphurs containing variable quantity of its atoms ^.S_8-х. The last also form cross-section connections in the course of polymerization of monomers. And at the first stages polysulphidic compound are formed which then rearrange in groups with the smaller content of atoms of sulphur. On the other hand, there is an opinion [12] that with the same probability can proceed the ionic processes. The mechanism of these transformations demands special researches.

One of the basic characteristics of redox-polymers is the oxidation-reduction capacity [5]. Presence in allyl redox- polymers of amino groups where the atom of nitrogen has not divided pair of electrons, assumes ability to a complex formation. In this compounds important parameter at use of redox-ionites in practice for extraction of ions of various metals is sorption capacity which is defined by static exchange capacity (SEC) (Table 2). Apparently, the received reticular polymers have lower values ORC (2,7-3,0 mg-equ/g), than their linear analogs

Table 2. Sorption and oxidation-reduction capacity of polymers on the basis of quinoid derivatives of allylamine of linear and reticular structure

Polymer	SEC, mg-equ/g	ORC, mg-equ/g	EC_Ag, mg-equ/g
-(-AA-X-)_n-	7,8	3,5	-
-(-AA-X-AA)_n-	7,3	3,2	-
-(-AA-X-)_n-:S	7,7	3,8	6,5
-(-AA-X-AA)_n-:S	6,9	4,2	5,8

(3,2-3,5 mg-equ/g). However, the method of synthesis of sulphur containing redoxites in one stage is convenient in the technological relation as necessity of preliminary synthesis of macromolecules and their subsequent linking by sulphur disappears. Besides such polymers are perspective for extraction of ions of silver. Allyl polymers do not possess such ability.

The morphology of surfaces of linear and reticular redox-polymers on the basis of AA considerably differs. The surface of linear polymers on the basis of monoreplaced derivative (Fig. 3а, b) consists of layers, more tightly adjoining to each other, than in polymers from disubstituted monomer.

Fig.3 Electronic microphotograph of linear redox-polymer on the basis of AA-Q (a) and Q-AA-Q (b)

Synthesis of the spatially-structured redox- polymers by thermal polymerization of monomers in the presence of sulphur leads to formation of surfaces of other kind. The surface of reticular polymer on the basis of monoreplaced derivative (Fig. 4a) represents a set of craters of various diameter. At use for synthesis of reticular redox-polymer of disubstituted derivative its surface sharply changes (Fig. 4b).

Fig.4 Electronic microphotograph of reticular redox-polymer on the basis of AA-Q (a) and Q-AA-Q (b)

Change of structure of monomers at their thermal polymerization with sulphur is accurately traced at comparison of their IR-spectra. Connections С-S and S-S not so easy to identify, as band of absorption corresponding to them are exclusively little intensive and position of bands very variable [13]. However, occurrence on IR-spectra of redox- polymers a wide absorption band in the field of 400-700 sm^-1 gives the grounds to assume that at their structure of connection – S-S - (400-500 sm^-1) and -С-S- (600-700 sm^-1) are present.

The power system concerns perspective scopes of oxidation-reduction polymers. With their help it is possible to delete the oxygen dissolved in water causing corrosion of equipment of coppers. Thus rigid demands are made to them concerning their thermal stability. High-molecular compounds on the basis of allylic compounds possess a number of the valuable properties one of which is thermal stability.

Processes of destruction of ionites in a dry condition allow to estimate appreciably thermal stability of a matrix and functional groups, and also to define reference temperatures of destruction of macromolecules. Results of the thermo gravimetric analysis linear and linked allyl oxidation-reduction polymers are presented in Fig. 5. Thermal destruction of homopolymers, received on the basis of mono- and disubstituted allyl derivatives of quinone, proceeds almost equally. Thermal stability -[-АА-Q-]_n- is insignificantly higher, than at -[-АА-Q-АА-]_n-. Their reference temperature of destruction is identical, their weight starts to decrease at 170-180°С. Losses for -[-АА-Q-]_n- and -[-АА-Q-АА-]_n- make at 200 °С accordingly nearby 1,0 and 1,2 %, at 300°С - 20,5 and 22,0 %, at 400°С - 28,8 and 29,2 %.

Fig. 5 Curves of mass loss of redox-polymers of linear (1, 2) and reticular (3, 4) structure on the basis of АА-Q (1, 3) and АА-Q-АА (2, 4)

Apparently from figure, higher thermal stability possesses redox-polymer reticular structure on the basis of disubstituted monomer (-[-АА-Q-АА-]_n-:S). Losses of weight for (-[-АА-Q-]_n-:S) and (-[-АА-Q-АА-]_n-:S) make accordingly at 200°С - 9,5 and 7,0 %, 300°С-21,0 and 19,5 %, 400°С - 30,8 and 28,4 %. Thus, in the beginning on curves monotonous reduction of weight of samples to temperatures 230°С for (-[-АА-Q-]_n-:S) and 220°С for (-[-АА-Q-АА-]_n-:S) is observed. Then speed of loss of weight increases, and is sharper for the second redox-polymer, and after 300°С is again slowed down. At heating on air at 300-400°С losses of weight of redox-polymers of linear and reticular structure are almost identical. From what it is possible to conclude that thermal destruction of their matrixes proceeds similarly owing to what they do not differ on the thermal stability.

Research of processes of thermal hydrolysis allows to estimate stability of properties of ionites more precisely. The obtained data plays an important role and for practical application of redox-polymers as them use for clearing of water solutions. Results of thermal hydrolysis of the linear and linked redox-polymers are resulted in Table 3.

As data Table 3 shows, to the SEC and ORC all investigated samples with increase of duration of a boiling in water decrease. Losses to the SEC of the linear redox-polymers received on the basis of both mono- and disubstituted allylic derivatives of quinones, are identical. Similar changes are observed also at redoxites reticular structure. However ORC at a boiling in water during 36 h remains as at linear, so the linked samples synthesized on the basis of disubstituted allylic monomer is better. Stability of reticular structured polymers to thermohydrolysis is higher than at linear as the loss of SEC and ORC linked samples are less.

It is shown that the structure of redoxites does not influence on their thermal stability at heating on air above 300°С and make essential impact on their stability to thermal hydrolysis. At boiling in water thermostability of reticular structured polymers are higher than linear.

CONCLUSIONS:

Thus, synthesis, structure and properties of sulphurcontaining quinoid redox- polymers, obtained by thermal polymerization of allylic monomers in the presence of elementary sulphur and sulphur of various deposits of Kazakhstan, were studied. It was shown that sulphur can be effectively used for structurization of macromolecules of allylamine in the course of their formation at radical initiation of quinoid derivatives of allylamine.

ABBREVIATIONS:

AA allylamine

AA-Q monosubstituted derivatives of allylamine

AA-Q-AA disubstituted derivatives of allylamine

Q benzoquinone

IR- spectra infra red spectra

ORC oxidation-reduction capacity

SEC static exchange capacity

TGA thermo gravimetric analysis

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Received on 18.01.2016 Modified on 05.02.2016

Asian J. Research Chem. 2016; 9(5): 221-225

DOI: 10.5958/0974-4150.2016.00038.9

Polymer	6 h		24 h		36 h
Polymer	SEC,%	ORC,%	SEC,%	ORC,%	SEC,%,	ORC,%
-(АА-Х)_n-	95,9	94,7	89,6	80,0	87,5	68,5
-(АА-Х-AA)_n-	95,4	90,8	90,0	82,4	87,8	79,6
-(АА-Х-:S)_n-	98,3	97,2	92,0	89,5	90,0	84,2
-(АА-Х-AA-:S)_n-	97,2	98,8	92,2	90,5	89,5	90,5