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Section 15. Chemistry
Garayeva Shabnam Hamid gizi, senior laboratory assistant, Sumgait State University, Department of chemistry and methods of its training, E-mail: [email protected] Shahnazarli Rita Zeynal gizi, candidate, of Chemistry, leading researcher, Institute of Polymer Materials of Azerbaijan National Academy of Sciences, Ramazanov Gafar Abdulali oglu, doctor, of Chemistry, professor of department Sumgait State University, "Petrochemistry and chemical engineering" Guliyev Abasgulu Mamed oglu, doctor, of Chemistry, professor, Institute of Polymer Materials of Azerbaijan National Academy of Sciences, Corresponding member of Azerbaijan National Academy of Sciences
SYNTHESIS OF CYCLIC ACETALS OF VINYLOXYCYCLOPROPANES AND PHOTOSENSITIVE POLYMERS ON THEIR BASIS
Abstract: The synthesis of cyclic acetals of cyclopropane-containing vinyl ethers has been carried out and their homopolymerization and copolymerization with maleic anhydride in the radical conditions have been carried out. The interrelation between copolymerization process and formation of the complexes of donor-acceptor type between comonomers in the system has been studied. By a method of PMR-spectroscopy the formation of donor-acceptor complexes between comonomers has been revealed. The photosensitivity of the films of the synthesized copolymers has been investigated and it has been shown that it depends on MW, solubility of polymer, nature of functional substituent and a number of other factors.
Keywords: substituted vinyloxycyclopropanes, copolymers with maleic anhydride, donor-acceptor complexes, photosensitivity, negative photoresist.
Introduction with given properties (strength, thermal stability, plasticity,
The vinyl ethers have proven themselves as active adhesion, etc) from them [1, 16-19]. The copolymers of monomers for preparation of technically valuable materials these monomers with maleic anhydride possess also wide
spectrum ofimportant characteristics and has a large scientific-practical value. Such copolymers are very interesting and attractive macromolecular compounds for their use as a base in making of the photosensitive materials.
It has been known that the polymers, macromolecules of which contain unsaturated or cyclic groups both in main and in side chain, easily pass into three-dimensional net-like structure at their thermal treatment or in action of radiation, electron beam or UV-irradiation on them [2, 606]. They can be also structured with various vinyl monomers in their interaction in the presence of initiator. Therefore, the polymers containing such chemically active groups as vinyl, allyl and also cyclic groups of carbocyclic and epoxide type in macromolecules is proposed to use in making of photoresists of negative type. In addition, the cyclic acetals and their derivatives are widely used in organic synthesis as reagents, semiproducts, initial substance in preparation of biologically active drugs.
Experimental
The IR-spectra of the synthesized monomers and homo- and copolymers prepared from them were taken on apparatus "Cary 630 FTIR" of firm Agilent Technologies (crystal ZnSe). The PMR-spectra were taken on spectrometer "Fourier" (frequency 300MHZ) of firm "Bruker" in various solvents, internal standard - hexa-methyldisiloxane. The chemical shifts of signals are presented in a scale S (ppm).
The purity of the synthesized compounds was determined by a method of gas liquid chromatography on chromatograph of mark LKhM-8 MD.
The characteristic viscosities of the polymer products were determined in Ostwald viscosimeter.
The parameters of MWD of homopolymers were determined on highly effective liquid chromatograph "Kovo" (Czech Republic) with refractometric detector. Two columns by size 3.3 x 150 mm were used, "Separon-SGX" with size of particles 7 mcm and porosity 100A served as immobile phase. The calibrating dependence lgM on VR was measured in the range ofM = (3-100)l02 with use of polyethylene glycol standards, temperature -20-25 ° C, 1 account - 0.13 ml.
The photostructurization process of the polymers was studied by irradiation of UV-light of the films applied on glass substrates of the polymer solution in methyl ketone or acetone (film thickness 0.4-0.5 mcm) for 5-30 min at room temperature.
The synthesis of monomers 1-4 has been carried out by interaction reactions of 1.1-dichloro-2-vinylox-ycyclopropane with corresponding alcohols or glycols [3, 1099-1111].
Synthesis of 1,1-dichloro-2-vinyloxycyclopro-pane
The aqueous solution of NaOH (66.0 g, 1.65 mol) in constant mixing on dropwise was added to solution containing divinyl ether (210 g, 3.0 mol), chloroform (1.79 g, 1.5 mol) and TEBA-Cl (6.84g, 0.03 mol) in di-chloromethane (400 ml). The reaction was carried out at room temperature. Thereafter the reaction mixture was mixed for 12 h. The prepared reaction mixture was firstly washed with water, then with 1M solution of HCl and again with water. The organic layer was separated, dried over anhydrous Na2SO4, and the solvent was distilled off. The residue was distilled in low pressure. A yield of the purposeful product (colorless oily substance) was 23%, T = 70 ° C/120 mm.merc.c., (48 ° C /40 mm merc.c.), 1HH-NMR - S(ppm.): (CDCl3) 1.26-1.90 (2H,m), 2.08-2.6 (1H,m), 5.03-5.58 (3H,m), IR - wave number v(cm-1): 3060, 2980, 2810, 1630, 1420, 1220, 915, 760, 665 cm1.
Synthesis of cyclic acetals of vinyloxycyclopro-pane
Synthesis of 1-vinyloxy-4.7-dioxaspiro-[2, 4]-hep-tene (1).
The solution of ethylene glycol 4.66 g(0.07 mol) in DMF(20 ml) and then the solution of 10.7g(0.07 mol) of 1.1-dichloro-2-vinyloxycyclopropane in DMF(40 ml) at 0°C constantly mixing on dropwise was added to mixture consisting of 4.08 g(0.17 mol) NaH in DMF(75 ml). Thereafter the reaction mixture was mixed at room temperature for 12h. Then the water (300ml) was slowly added to the reaction mixture. The mixture was extracted with ether (160ml), the organic layer was washed with saturated solution of NaHCO3(twice on 350ml), separated, dried by anhydrous Na2SO4 the solvent was distilled off. The residue was distilled under low pressure. A yield of the purposeful product (colorless oil) - 44%, T = 100-102/135 mm.merc.c., 1H-NMR - S(ppm): (CDCl3)1.03-1.37(dd), 4.85-4.95(m), 5.44-5.80 (m), 1.68-1.90(m), 3.75-4.20(m).
On analogous methodology by interaction of 1.1-dichloro-2-vinyloxycyclopropane with propane-diol-1.3, butanediol-1.4 and methanol there have been
synthesized 1-vinyloxy-4.8-dioxaspiro-[2.5]-octane (2), 1-vinyloxy-4.9-dioxaspiro-[2.6]-nonane (3) and 1.1-di-methoxy-2-vinyloxycyclopropane (4), respectively.
Radical polymerization of cyclic acetals of vi-nyloxycyclopropanes
The polymerization of the compounds 1-4 was carried out in one-chamber ampoule in the presence of 2.2'-azo-bis-isobutyronitrile (AIBN), benzoyl peroxide (BP) and di-tertiary butyl peroxide (DTBP) at various temperatures (60, 80 and 120 ° C), depending on type used initiator both in solution (benzene or toluene) and in mass. The polymerization duration - 30 hours.
Cationic polymerization of cyclic acetals of vi-nyloxycyclopropanes
The cationic polymerization of cyclic acetals of vi-nyloxycyclopropanes was carried out as follows: the so-
lution BF3-0(CH2CH3)20.28g(0.002 mol) in 1.0 ml of tolune in constant mixing was added on dropwise to solution 2.84 g (0.02 mol) of vinyloxycyclopropane 1-4 in toluene (10 ml). The mixture was thermostatted at -70 ° C and mixing was continued for 3h. The polymerization was interrupted introducing small quantity of triethyl-amine. Then the solution was poured out into methanol, the precipitate was separated, twice reprecipitated from THF to methanol and dried in vacuum at 50 ° C. The soluble and insoluble products were divided by filtration of solution to THF.
Results and discusssion
With the aim of preparation of the linear polymers with side reactive groups we have synthesized the vinyl ethers with functional groups in geminal position at cyclopropane ring.
TEBA, NaOH
h2o / ch2ci2 ]
Na/DMF
O
« si
Cl-- /
Cl HO-(CH2)n-OH ^ O
(CH2)
oJ
2^m
xs
O
OMe OMe
m = 2-4 1-3
It should be taken into account that the cyclopro- In the IR-spectra of the synthesized compounds
pane group due to its specific structure gives the elec- there are the absorption bands characteristic for corre-
tron influence of substituent [4, 223]. The synthesized sponding groups, and the PMR-spectra (Table 1) char-
vinyloxycyclopropyl ethers contain various heterocyclic acterize the proposed structures. and non-cyclic substituents at three-membered cycle.
Table 1.- Spectral characteristics of gem-disubstituted vinyloxycyclopropanes
H
H2
H3 H4
O
O^
(CH2)m
•oJ
H5 H6
4
1
Code of monomer Chemical shifts of protons and proton-containing groups, 8, ppm
H1 H2 H3 H4 H5 H6 -OCH2,-OCH3 C-CH2-C
1. 4.85 4.95 5.44-5.80 1.68-1.90 1.03 1.37 3.75-4.20 -
2. 4.85 4.97 5.40-5.84 1.86-1.95 1.05 1.39 3.76-4.22 1.82
3. 4.86 5.04 5.45-5.87 1.97-2.25 1.06 1.42 3.88-4.44 1.85
4. 4.82 4.93 5.40-5.74 1.66-1.95 1.06 1.40 3.34-3.72 -
The monomers 1-4, owing to combination of vinyl group with ether oxygen and cyclopropane ring possess specific properties. A substitution of alkyl group for cyclopropane one having p-character in vinyl ether
favors weakening of positive influence of ether group [5, 849-859], as a result of which an inclination of these monomers to polymerization in the conditions of radical initiation is slightly improved.
The results of the model reactions on addition of thiols to vinyloxycyclopropanes in the conditions of radical initiation [6, PK-025] allow to estimate preliminarily the possibility of behavior of the radical
polymerization of the synthesized compounds 1-4 on scheme excluding opening of three-membered cyclopropane ring. The polymerization proceeds only by double bond:
n
O
(CH2)
OJ
2 m
It has been experimentally established that the radi- Table 2), independently of reaction conditions leads to cal polymerization of the synthesized monomers (con- the formation of oligomers with low MW (degree of po-ditions and results of polymerization are presented in lymerization 12-22).
Table 2.- Conditions and results of homopolymerization of vinyloxycyclopropanes 1-4 (solvent - benzene, polymerization duration - 30 h.)
Code of monomers T, ° c Initiator Yield of po ymer,% MW
Type Quantity, mol.% Soluble fraction [n], dl/g
1. 60 AIBN 0.5 42 0.481 2800
80 BP 0.3 37 0.465 2700
120 DTBP 0.3 8 - -
-70* BF3OEt2 0.02 46 0.526 3100
2. 60 AIBN 0.6 38 0.435 2500
3. 60 AIBN 0.6 34 0.356 2000
4. 60 AIBN 0.6 49 0.495 2900
* - the polymerization was carried out for 3h
This is confirmed by viscous characteristics of the a method of the high effective liquid chromatography prepared polymers and determination their MW by (Figure 1 and Table 2).
Figure 1. MWD curves of homopolymer of the compounds 1 prepared in the presence of AIBN (1), BP (2) and BF3-O(C2H5)2 (3)
The comparison of IR-spectra of the synthesized monomers 1-4 and polymers prepared on their basis showed that the absorption bands at 1640-1645 cm-1, characteristic for vinyl group and being in the initial monomers disappear in the polymerization process. The absorption bands characterizing availability of other functional groups and also skeleton vibrations of
cyclopropane ring in this case are kept in the polymer spectrum. The analogous results are prepared in consideration of PMR-spectra of the initial monomers and polymers prepared on their basis. In the PMR-spectra of the polymers two partially overlapping signals with the same intensity are observed. These signals are referred to protons of CH2-groups of cyclopropane ring (S = 1.54 ppm)
and protons of CH2-groups of the polymer chain (S = 1.9 ppm). The analogous signals of equal intensity are also appeared for methine protons of three-membered cycle (S = 3.60 ppm) and protons of CH-groups of the polymer chain (S = 4.12 ppm). These data confirm that the polymerization of the synthesized monomers proceeds due to opening of only double C = C-bond, in this case cyclopropane group with corresponding substituents is kept.
It should be noted that during polymerization in the presence of radical initiators with temperature rise a yield of the polymer is increased. In particular, at temperature rise from 80 to 120 ° C a yield of the polymer for 6 h is increased approximately in 3 times. An increase of initiator concentration doesn't lead to the essential increase of a yield of the prepared polymers; a viscosity and MW remain almost at the same level, and in some cases are even decreased. With increase of the polymerization duration a yield of the polymer is increased, but this is not reflected on increase of MW. Relatively high MW is observed in a case of polymerization of monomer 1.
Thus, in a case of the radical polymerization of monomers 1-4 the process proceeds selectively on
vinyl group with preparation of oligomers of linear structure with side cyclic groups capable for further conversions.
For revealing of dependence between structure of the synthesized compounds 1-4 and their polymerization activity we have carried out the polymerization of these compounds in the same conditions in the benzene solution in the presence of AIBN. It has been found in this case that the monomer 1 show the greatest activity, мономер 3 - the least. With broadening of ac-etal cycle (with increase of m value) MWs of polymers are slightly decreased (Table 2). The least activity of the monomer 3 has been possibly connected with steric hindrances stipulated by large size of cyclic fragment.
In our further investigations the synthesized cyclic acetals have been included in radical copolymerization with maleic anhydride (MA). Since in the radical conditions of copolymerization each of comonomers of this system almost is not capable for homopolymerization, the chain growth is possible only due to cross-interaction of comonomers, in which it can be participated both free and connected monomers to complexes.
^xtO + -/Л
(CH2)m
MW; their characteristic viscosity was changed in the ranges from 0.36 to 0.53 cm3/g.
The calculated MW values (taking K = 4.1M0-4 and a = 0.89 [7.2273-2278]) of the copolymers prepared in the various conditions indicate to their relatively low
Table 3.- Copolymerization of cyclic acetals of vinyloxycyclopropanes 1-3 with maleic anhydride ([AIBN]=0.02 mmol/l; T=70 °C)
n
Code of monomer Composition of the initial mixture, mol.% of monomer Copolymerization time, min. Conversion^ Composition of copolymer, mol% of monomer
1 2 3 4 5
1 90.0 20 8.5 49.9
70.0 20 10.6 50.0
50.0 20 15.3 49.8
30.0 20 12.0 50.1
10.0 20 9.9 49.8
2 90.0 20 8.3 49.9
75.0 20 10.2 50.0
1 2 3 4 5
2 50.0 20 14.7 49.7
25.5 30 11.8 50.1
10.0 60 9.7 50.2
3 90.0 20 7.9 49.3
75.0 20 10.1 50.1
50.0 20 14.4 49.9
25.5 30 11.5 49.6
10.0 60 10.1 49.7
4 90.0 20 7.7 50.2
75.0 20 9.7 48.9
50.0 20 14.0 50.1
25.5 30 11.2 49.6
10.0 60 10.0 49.6
The spectral analysis showed that the copolymers prepared both in mass and in solution is identical on composition, intramolecular distribution of links and chemical structure. It has been established on data of IR-spectroscopy and elemental analysis that the composition of the prepared copolymers practically doesn't depend on ratio of the initial monomers and close to equmolar (Table 3).
As a result of copolymerization of cyclic acetals 1-3 and compounds 4 with maleic anhydride there have been prepared the copolymers insoluble in aromatic hydrocarbons being white or light-yellow powdered products. However, the copolymers were well dissolved in polar organic solvents - in acetone, ethers, DMF, and so that the thin films could be poured from them. The maximum yield of copolymer corresponded to ratio of monomers in the initial mixture 1:1. The method of carrying out of copolymerization (in solution or in mass) shows an insignificant influence on yield of the copolymers.
The IR-spectra of the prepared copolymers showed the availability of the absorption bands in the field of 1780 cm-1, characteristic for carbonyl group of anhydride fragment. An availability of the absorption bands at 1020-1050 cm-1 characterizes the skeleton vibrations of three-membered carbon cycle. At the same time in IR-spectra of copolymers the absorption bands in the field of 1640-1645 cm-1, corresponding to valence vibrations of double C=C-bond are absent. Our experiments showed that there are no essential changes in the IR-spectra of the copolymer prepared at various ratios
of the initial comonomers. All these data allow to conclude that: firstly, in the copolymeriztion process only double bond of vinyloxycyclopropane (in this case three-membered cycle is not touched) takes part. Secondly, the copolymerization proceeds with participation of both comonomers with formation of the copolymers of equi-molar composition, and thirdly, a ratio of comonomers in the initial mixture doesn't influence on composition of the prepared copolymers.
It was known that during copolymerization of the vinyl ethers with electron-acceptor monomers, for ex. MA, the donor-acceptor interaction between como-nomers, which extremely increases the polar effect of the reaction arises. In this case, the complex-formation between comonomers in the initial mixture is reflected on characteristic peculiarities of behavior of the copolymerization process [8, 253]. For study of complex-formation process the MR-spectra both pure MA and MA in the presence of comonomers 1-4 in solution CDCl3 were taken.
As shown by data of PMR-spectroscopy, the chemical shift of protons at double bond MA (8=7.25 ppm) in the presence of comonomer ofvinyloxycyclopropane undergoes the displacement to more weak field (8=7.13 ppm). Such change of the chemical shift of MA protons in the presence of above-listed comonomers has been connected with formation of donor-acceptor complex in the system. In other words, in mixing of comonomers in the initial mixture a charge transfer form donor (vinyl ether) to acceptor (MA), which evidences about
formation of complex between them takes place, and as The equilibrium constants (K) of the vinyl ethers
a result a displacement of the chemical shift of protons at with MA (Table 4) were determined analogously to double bond in molecule of MA occurs [9, 398]. methodology presented in work [10, 401-406].
Table 4. Complex-formation constants of cyclic acetals 1-4 with MA (solvent -CDCl3, [MA]- 0.03 mol/l [cyclic acetal]-0.65-2.20 mol/l)
Complex T, °C K, l/mol
Monomer 1 - MA 25 0.240
45 0.185
65 0.150
Monomer 2 - MA 25 0.260
45 0.200
65 0.162
Monomer 3 - MA 25 0.280
45 0.220
65 0.180
Monomer 4 - MA 25 0.220
45 0.187
65 0.160
The investigation of temperature dependence of rameters of complex-formation on Van-Hoff equation complex-formation K was studied at various tempera- (Table 5) [9, 99-102]. tures, which allowed to estimate thermodynamic pa-
Table 5.- Enthalpy and entropy values at complex-formation of monomers 1-4 with MA
Complex -AH, kcal/mol -AS, e.units
Monomer 1 - MA 1.175 6.06
Monomer 2 - MA 1.183 5.84
Monomer 3 - MA 1.105 5.50
Monomer 4 - MA 0.798 5.44
As follows from data of Table, AH values evidence about arising of weak donor-acceptor interactions in the investigated complexes, they almost are not differed and close to the energy of van der Waals interaction energy.
For investigation of photosensitive properties of the prepared copolymers we have carried out the photochemical structurization. The films of the synthesized copolymers poured from solutions and dried at 60 ° C, were irradiated with xenon lamp by capacity 2 kWt for 30 min. In this case, we have detected that at irradiation the films are partially lost their solubility. This was clearly observed in comparison of IR-spectra of these copolymers before and after irradiation. The spectral investigations have revealed the decrease of intensity of the absorption bands of cyclopropane and acetal groups at 1030 cm-1
and 1100 cm-1, respectively. It was simultaneously observed the displacement of the absorption band of car-bonyl of anhydride group from 765 cm-1 to 1780 cm-1 without change of its intensity. The change of intensities of the absorption bands after UV-irradiation of the films has been probably connected with formation of "bridge bonds" between macromolecules due to opening of cyclopropane and acetal groups.
The cross-linking process under action of photoirradiation was investigated by immersion of the irradiated films to solvent (acetone) for 3 min. After drying and weighting of the films a quantity of insoluble part of the film has been determined (fig. 2). Since the mass losses of the film depend on degree of its cross-linking, with increase of degree of cross-linking the mass losses fall.
Figure 2. Dependence of mass loss of the copolymer films 1-4 with MA after irradiation on exposition time (5 - in the presence of sensitizer)
The unirradiated sites of the films were completely dissolved in acetone. On increase of irradiation duration (in this case, a degree of cross-linking increased) the film solubility fallen and after 20 min. of irradiation a mass of soluble part was minimal and constant. It has been also established that an addition of approximately of 1.0 benzoin or cobalt-naphenate as sensitizer to the system led to sharp fall of mass loss. In this case, a degree of cross-linking of the copolymer films reached 58-85% already for 2-5 min. This value depended on nature of the functional substituent at cyclopropane fragment, MW, solubility of polymer and a number of other factors.
Conclusions
1. By interaction reaction of dichlorocarbene with divinyl ether it has been synthesized gem-disubstituted vinyloxycyclopropane, on the basis of which a number of derivatives of cyclic acetals has been prepared. The homopolymerization of the synthesized substituted vinyloxycyclopropanes in the presence of radical initiators both in mass and in solution has been carried out and it has been shown that in polymerization only vinyl group participates. The composition and structure of the synthesized monomers and polymers prepared on
their basis have been established by data of chemical and spectral analyses.
2. The joint polymerization of the synthesized monomers with maleic anhydride has been carried out and it has been show that the process proceeds with formation of complexes of donor-acceptor type. It has been established that the composition of the prepared copolymers doesn't depend on composition of the initial mixture and in all cases corresponds to equimolar composition of comonomers. The complex-formation constants, the values of which evidence about occurrence of the weak complexes between comonomers have been determined. The temperature dependence of complex-formation has been established and thermodynamic parameters of the process have been calculated.
3. Some properties, including photosensitivity of the prepared polymers have been investigated. It has been established that a content of insoluble part of the copolymers films of cyclic acetals with MA after irradiation depends on exposition time, structure, MW and solubility of the copolymer and also on size of cyclic fragment at cyclopropane ring.
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