CC BY
16
ISSN 0005*2531 (PrirtT AZERBAIJAN CHEMICAL JOURNAL № 3 2022 45
UDC 541.64:512.678
COPOLYMERS ON THE BASIS OF (p-CHLOROPHENOXYCARBONYL)-CYCLOPROPYL STYRENE WITH STYRENE AND METHYL METHACRYLATE
A.I.Sadygova
Azerbaijan Medical University Institute of Polymer Materials, NAS of Azerbaijan
alvina.sadigova@mail.ru
Received 16.03.2022 Accepted 29.04.2020
The radical copolymerization of (p-chlorophenoxycarbonyl)cyclopropyl styrene with styrene and methyl methacrylate has been carried out. New cyclopropane-containing copolymers have been obtained. It has been established that the synthesized copolymers due to peculiarities of their structure and polyfucntionality, namely with content of carbonyl and cyclopropane groups sensitive to UV irradiation in the macromolecule have photosensitivity. The constant values of relative activity of monomers have been determined and Q-e parameters on Alfrey and Price have been calculated. The copolymerization constants of this compound (r2) with styrene and methyl methacylate (r2), calculated on Fineman-Ross method are: r2 = 1.1 and1.05, but r2 = 0.56 and 0.48, respectively; Q and e parameters values: Qi = 3.1 and 2.4, ei = -1.4 and -0.8, respectively. The photochemical structuring has been investigated and it has been shown that the structuring process proceeds due to of cyclopropane ring opening and carbonyl group. The composition and structure of these copolymers have been established and their some characteristics (heat resistance, hardness, adhesive strength, water absorption) have been investigated. The structuring process has been also studied and it has been established that the synthesized copolymer has relatively high photosensitivity (50-55 cm2-J-1).
Keywords: microstructure, monomers, copolymerization, (p-chlorophenoxy)cyclopropyl styrene, photosensitivity.
doi.org/10.32737/0005-2531-2022-3-45-50 Introduction
One of the first polymer materials investigated as electronoresists were negative photoresists on the basis of polyvinylcinnamate and cy-clo-rubber. A review of these works is presented in [1]. Now, the use of synthetic polymers in the field of microelectronics as photo-and electron-resists does not sufficiently meet the requirements of this industry, namely, high photosensi-tivity, satisfactory resolution, resistance to chemical influences, good adhesion of the photoresist film to the substrate, and good deformation and strength characteristics.
This explains the great interest of researchers to preparation of new types of photosensitive polymers for microelectronics [2-8]. We have solved this problem by polymerization of functionally substituted cyclopropyl styrenes [9-11].
The interest in the preparation of such polymers has been stipulated by the fact that the forming macromolecules contain reactive functional groups of various nature in the form of
hangers in the main macrochain. As a result of copolymerization of functional cyclopropane-containing vinyl compounds, being one of the most perspective reactive monomers, the polymers containing cyclopropane groups, regularly located in the side hangers or macrochains have been synthesized [12, 13].
This work has been devoted to the study of copolymerization of (p-chlorophenoxycarbo-nyl)-cyclopropyl styrene (CPhCCS) with styrene and methyl methacrylate (MMA) and es-tablisment of the structure and properties of co-polymers obtained on their basis with the aim of creation of new photosensitive copolymers. The choice of this monomer has been stipulated by the fact that the concentration of double bonds and their chemical nature, and also the availability of cyclopropane ring in combination with carbonyl group in the monomer decisively influence on such important photolithographic parameters of the resist as photosensitivity and resolution, as evidenced by sufficiently large experimental material accumulated to now.
The choice of this compound for investigation of copolymerization with vinyl monomers (styrene and MMA) has been stipulated by availability of strongly absorbing the light energy of groups (carbonyl, chlorine and cyclopropane) in molecule of new monomer. For copol-ymerization of the investigated systems, it is important to choose conditions under which the polymerization would occur only along the vinyl group, and the reactive fragments would remain unchanged in the side chain.
Experimental part
Synthesis of 2-chlorophenoxycarbonyl 1-(p-vinyl phenol) cyclopropane (CPhCCS) (I). 12.85 g (0.1 mol) of p-chlorophenol dissolved in ethylmethyl ketone (EMK, 150 ml) was added into a three-neck flask equipped with mechanical stirrer, thermometer, and drop funnel, the contents were cooled to 00C. Then 20.65 g (0.1 mol) of 2-chlorocarbonyl-1-(p-vi-nylphenyl) cyclopropane in 30 ml of EMK was added dropwise for 30 min at constant stirring and cooling. The reaction mixture was stirred for 30 min and for another 20 min at room temperature.
The obtained residue was extracted with ether and the ether solution was washed consequently with 0.5% NaOH solution and distilled water to remove the unreacted contents.
The ether layer was dried with anhydrous Na2SO4 and then evaporated using a rotary evaporator. The product was recrystallized from ethanol and obtained with yield 25.97 (87%), m.p.=50-520C.
Elemental analysis (%): C=72.36; H= 5.10, Cl=11.90 (calculated); C=72.20; H=5.0; Cl=11.70 (found).
The copolymerization of the synthesized CPhCCS with styrene and MMA was carried out in ampoules in benzene solution in the presence of 0.5% of dinitrilazoisobutyric acid (AIBN) (from total monomer mass) at 70°C. The forming copolymer was purified by twofold reprecipitation from benzene solution and dried in vacuum (15-20 mm merc.c.) at 300C to constant mass. The copolymers being white powder are well soluble in aromatic and chlo-
rinated hydrocarbons. The characteristic viscosity was determined in benzene in Ubbelode vis-cometer. The molecular weight value (MW) (300000-450000) was estimated on characteristic viscosity ([n]= 0.95-1 dl/g).
The composition of copolymers was determined according to the data of elemental analysis of the chlorine atom.
The IR spectra of copolymers were registered on spectrometer "Agilent Cary 630 FTIR", PMR spectra - on spectrometer BS-487B Tesla (80 MHz) in solution of deuterated chloroform.
For investigation of the photochemical structuring of the copolymer there have been made 2-10% copolymer solutions, which were applied on glass substrate with size of 60*90 mm. The application was carried out by a method of centrifugation at 2500 rev-min-1. The thickness of the resist layer after its drying for 10 min.at room temperature and for 20 min. at 250C/10 mm merc.c. was 0.15-0.20 mcm.
A mercury lamp DRT-220 (current strength - 2.2 A, distance from radiation source - 15 cm, rate of the mobile shutter of the expo-nometer - 720 mm-h'1, exposure time - 5-10 seconds) was used as a source of UV irradiation. The content of the insoluble copolymer was calculated on the residue mass.
Results and discussion
With the aim of establishment of the structure of the synthesized copolymers the spectral analyses (IR and PMR spectroscopy) of the synthesized monomer and polymer samples have been carried out.
Due to the fact that CPhCCS is a poly-functional compound, during its radical copol-ymerization with styrene and MMA, it should be expected the formation of new reactive poly-functional copolymers.
It has been established by comparison of IR spectra of copolymers with spectra of the initial monomer that the absorption band in the IR spectrum of the initial monomer at 990 and 1640-1645 cm-1, referring to deformation and valence vibration of double bond of the vinyl group after copolymerization disappear. The
absorption bands characteristic for benzene ring and cyclopropane groups are kept after copoly-merization. The absorption bands at 1030-1035 cm-1, referring to vibrations of cyclopropane ring at 1720 and 1110 cm-1 of ether bond remain unaffected, respectively.
In the PMR spectra of copolymer the resonance signals referring to protons of benzene nucleus (5 = 6.60-7.30 ppm) and cyclopropane ring (5 = 0.65-1.66 ppm.) are clearly appeared, and the signals referring to
The copolymerization was carried out at various ratios of the initial monomer. In any initial ratio of the monomers a copolymer enriched with links of CPhCCS is always formed (Table 1).
The initial composition is a main factor determining the characteristics of the polymers. It has been revealed that the composition of forming copolymers depends on composition of the initial monomer mixture.
For estimation of polymerization activity of CPhCCS there have been calculated the constant values of relative activity of monomers on compositions of the initial monomer mixture on Fineman-Ross method [14] Q-e parameters - on Alfrey and Price. The parameters of microstructure of copolymers were determined on the basis of copolymerization constants [15]. The obtained data are presented in Table 1.
The constant values of relative activity (Table 1) indicate to greater reactivity of CPhCCS in comparison with styrene and MMA, which has been connected with influence of substituent at p-chlorophenoxycarbo-nyl)cyclopropyl styrene of cyclopropane ring on electron density of double bond of the vinyl group [16]. The ester group is included in the general conjugation system, causing electron
protons of the vinyl group (5 = 5.10-6.65 ppm) are absent. According to the data of spectroscopy the copolymerization of CPhCCS with styrene and MMA proceeds only due to opening of double bonds of the vinyl groups with conservation of remaining reactive functional fragments of p-chlorophenoxycarbonyl)cyclopropyl styrene. Thus, on the basis of analysis of IR spectra of copolymers obtained by copolymerization of CPhCCS with styrene and MMA, the following structure of copolymers is assumed:
density redistribution both in the monomer and in the radical center formed from it. As a result, the energy necessary for appearance of the transition state is decreased, leading to an increase of the reactivity of the monomer.
The calculated values of Q1 and e1 parameters during copolymerization with both styrene and MMA indicate to an increased conjugation in the monomer (CPhCCS) connected with the influence of a substituent of p-chlorophenoxy-carbonyl)cyclopropyl styrene stipulating high reactivity of the monomer and lower reactivity of radicals. In calculation of e1 factor it was chosen the negative sign on the basis that the electron density of double bond of the vinyl group at CPhCCS should be less than at styrene and MMA, because the influence of substituent at CPhCCS leads to redistribution of electron cloud density of the double bond of the vinyl group, changing the radical polarity. The greater reactivity of CPhCCS in comparison with styrene and MMA confirmed by the copolymeri-zation constants (r1 =1.1 and 1.05, but r2= 0.56 and 0.48, respectively) has been also connected with it. The data of microstructure of copolymers have been obtained on the basis of calculated copolymerization constants (Table 1).
ch2=ch
AIBN / w „TT \
+CH2=^R'-- -fcH2-^CH2-CH-|-
Ï__^O R
QHCH C^OC6H4C1 CH,
CH,
H
-X
(1)
x_c R=—C6H5; —COOCH,
^0C6H4C1 6 5
Table 1. Copolymerization of CPhCCS (MQ with styrene (M2) and MMA (M2).
Composition of the initial mixture, mol.% Composition of copolymers, mol.% r1 r2 Q1 e1 rrr2 Microstructure of copolymer
M1 М2 m1 m2 LMj Lm2 R
CPhCCS -Or
10 90 15.62 84.38 1.12 6.04 38.74
25 75 33.77 66.23 1.35 2.68 49.38
50 50 57.40 42.60 1.10±0.03 0.56±0.02 3.1±0.01 -1.4±0.02 0.61 2.08 1.56 54.64
75 25 78.35 21.65 4.24 1.18 49.40
90 10 98.15 8.85 10.72 1.06 16.72
CPhCCS- -MMA
10 90 19.36 80.64 1.12 4.60 35
25 75 37.90 62.10 1.35 2.20 56
50 50 59.35 40.65 1.05±0.03 0.48±0.02 2.4±0.01 -0.8±0.02 0.50 2.05 1.40 58
75 25 78.54 21.46 4.15 1.13 38
90 10 90.91 9.09 10.45 1.04 17
LM and Lm - average length of blocks of monomer links; R - Harwood blocking coefficient
A length of blocks LMl in increased with increase of fraction of PhCCPS in the composition of copolymer. It is seen from Table 1 that R and LMl are maximum (57.42 and 42.63; 2.1
and 54.64 units, respectively) at ratio of the initial monomers 50:50, 75:25. It follows that the selection of certain compositions of the monomer mixtures one can use the directed formation of the microstructure of copolymers, which is one of the most perspective ways of modification of their properties.
The availability of the synthesized copo-lymers of reactive groups of different chemical nature in the macromolecule links causes interest to investigation of photochemical structuring of this copolymer, i.e. cross-linking under action of UV irradiation.
The photochemical investigations of the synthesized copolymers were carried out on methodology [10]. Owing to the availability of groups strongly absorbing the light energy (cyclopropane, chlorine, carbonyl), the synthesized copolymers are photosensitive and in action by
UV irradiation are subjected to photochemical conversions leading to the formation of net structures. The structuring process of the obtained cyclopropane-containing copolymers has been studied with IR spectral investigations. Depending on irradiation duration (3-5 min) the intensity of maxima of the absorption bands characteristic for cyclopropane ring (1030-1035 cm-1), carbonyl group (1720 cm-1) and chlorine atom (650-680 cm-1) falls considerably or disappear completely.
Probably, these groups take part in photochemical reactions leading to the structuring of carbonyl group of the copolymers.
Thus, the availability of cyclopropane ring, chlorine atom and carbonyl groups in the macromolecules of the obtained copolymer allowed to create a material with high photosensi-tivity on the basis of the copolymer.
In Table 2 the comparative characteristics of properties of the synthesized copolymers, polystyrene and poly-MMA are presented.
Table 2. Some characteristic of the obtained copolymers (content of CPhCCS in the com
Index CPhCCS+St CPhCCS+MMA poly-St poly-MMA poly-CPhCCS
Refractive coefficient 1.56 1.60 1.59 1.49 1.6
Vicat heat resistance, 0O 125 120 103 115 130
Brinell hardness, kg-mm-2 18.0 15.0 14 13 20.5
Specific impact strength, kg-cm-cm-2 18.0 18.8 18 12 21.0
Tensile strength, MPa 34.6 52.0 35.0 60.0 45.0
Adhesion strength, MPa 4.2 5.4 - - 8.3
Water absorption for 24 h, % 0.08 0.16 0.1 0.3 0.08
position of copolymers - 30 mol. %)
It follows from the data shown in Table 2 that the copolymers containing CPhCCS being photosensitive have higher heat-physical and physical-mechanical properties in comparison with polystyrene and poly-MMA. These qualities allow to use them in making of photosensitive materials with improved lithographic characteristics.
It has been established in investigation of physical-mechanical properties of copolymers (CPhCCS+St and CPhCCS+MMA) that in the temperature range -20+800C they retain higher tensile strength and practically do not decrease elasticity in the field of low temperature.
The synthesized polymers possess also good optical indices (n£°=1.5935-1.6054). It has been revealed that the obtained polymers retain transparency up to 1000C during their holding for 1-1.5 hours. It has been shown that the light transmission in the visible part of the spectrum is 85-90% and does not depend much on the thickness of the sample up to 6-8 mm, at a relatively high thickness, the optical properties are partially deteriorated, which is typical for all known transparent materials.
It has been established that the photosensi-tivity of the copolymer depends on the content of CPhCCS in the copolymer, i.e. with an increase of the proportion of CPhCCS in the macro-molecule, the total photosensitivity is increased. The evidence of this fact is shown in Figure.
Dependence of photosensitivity (Ph) of CPhCCS+St copolymer on composition.
Thus, the availability of the obtained co-polymer of cyclopropane ring and carbonyl groups in the macromolecules of the obtained copolymer allowed to create a material with high photosensitivity on the basis of the copolymer.
As a result of carried out work the new cyclopropane-containing copolymers of negative type has been synthesized. It can be concluded on the basis of carried out investigations that the availability of cyclopropane ring and other fragments in the structure of the synthesized copoly-mer provides high photosensitivity for this copoly-mer (50-55 cm2/J). It has been shown that the created photoresists are characterized with high lithographic parameters, good adhesion to substrates and few microdeficiencies of the polymer films.
The synthesized polymers can be used as photosensitive polymer materials for microelectronics, and also in optics as an optically transparent material.
Conclusions
The radical copolymerization of (p-chlo-rophenoxy)-cyclopropyl styrene with styrene and methyl methacrylate has been studied, the copolymerization constants have been determined and Q-e parameters of the Alfray-Price scheme have been calculated.
The structuring process has been studied and it has been established that the synthesized
copolymers have high photosensitivity (51-55
2 1
cm -J-) and high physical-mechanical properties. Due to the availability of photoreactive groups of various chemical nature in the macromolecule, these copolymers can be used as a photosensitive basis of photoresists of negative-type in microelectronics and optics.
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(p-XLORFENOKSi)TSiKLOPROPiLSTiROLUN STiROL УЭ METiLMETAKRiLAT OSASINDA
ALINAN BIRGOPOLiMERLORi
A.i.Sadiqova
(p-Xlorfenoksi)tsiklopropilstirolun stirol va metilmetakrilat ila radikal birgapolimerla§masi prosesi apanlmi§dir. Yeni tsiklopropan tarkibli birgapolimerlar alinmi§dir. Monomerlarin nisbi aktivlik sabitlarinin qiymatlari müayyan edilmi§ va Q-e parametrlari Alfrey va Prays asasinda hesablanmi§dir. Göstarilan birla§manin (ri) stirol va metilmetakrilat (r2) ila Faynman-Ross metodu ila hesablanmi§ birgapolimerla§ma sabitlari: müvafiq olaraq ri = i,i va i,05, r2 = 0,56 va 0,48; Q va e parametrlarinin qiymatlari: müvafiq olaraq Qi = 3.1 va 2.4, ei = -1.4 va -0.8 ta§kil etmi§dir. Fotokimyavi strukturla§ma prosesi öyranilmi§ va strukturla§ma prosesinin tsiklopropan halqasinin va karbonil qrupunun agilmasi hesabina ba§ verdiyi göstarilmi§dir. Bu birgapolimerlarin tarkibi va qurulu§u müayyan edilmi§ va onlarin bazi xüsusiyyatlari (istiliyadavamliliq, barklik, yapi§qanliq möhkamliyi, suudma qabiliyyati) öyranilmi§dir. Birgapolimerlarin strukturla§masi prosesi da öyranilmi§ va müayyan edilmi§dir ki, sintez edilmi§ birgapolimerlar nisbatan yüksak fotohassasliga malikdir (50-55 sm2 ■ J-1).
Agar sözlar: mikrostruktur, monomerer, birgapolimerla^ma, (p-xlorfenoksi)siklopropilstirol, fotohassasliq.
СОПОЛИМЕРЫ НА ОСНОВЕ (п-ХЛОРФЕНОКСИКАРБОНИЛ)ЦИКЛОПРОПИЛСТИРОЛА
СО СТИРОЛОМ И МЕТИЛМЕТАКРИЛАТОМ
А.И.Садыгова
Проведена радикальная сополимеризация (п-хлорфенокси)циклопропилстирола со стиролом и метил-метакрилатом. Получены новые циклопропансодержащие сополимеры. Определены значения констант относительной активности мономеров и рассчитаны параметры Q-e по Алфрею и Прайсу. Константы сополимеризации указанного соединения (r1) со стиролом и метилметакрилатом (r2), рассчитанные по методу Файнмана-Росса, составляют: r1 = 1.1 и 1.05, а r2 = 0.56 и 0.48, соответственно; значения параметров Q и e: Q1 = 3.1 и 2.4, e1 = -1.4 и -0.8, соответственно. Исследовано фотохимическое структурирование и показано, что процесс структурирования протекает за счёт раскрытия циклопропанового кольца и карбонильной группы. Установлены состав и структура этих сополимеров и исследованы их некоторые характеристики (теплостойкость, твердость, адгезионная прочность, водопоглощение). Также изучен процесс структурирования сополимера и установлено, что синтезированный сополимер обладает относительно высокой фоточувствительностью (50-55 см2-Дж-1).
Ключевые слова: микроструктура, мономеры, сополимеризация, (п-хлорфенокси)циклопропилстирол, фоточувствительность.
