ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 5, pp. 833!837. + Pleiades Publishing, Ltd., 2007. Original Russian Text + B.A. Zhubanov, R.M. Iskakov, R.B. Sarieva, M.J.M. Abadie, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 5, pp. 856 !861.

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MACROMOLECULAR CHEMISTRY ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ AND POLYMERIC MATERIALS

New Film Composites Based on Alicyclic Polyimide B. A. Zhubanov, R. M. Iskakov, R. B. Sarieva, and M. J. M. Abadie Institute of Chemical Sciences, Almaty, Kazakhstan University of Montpellier, France

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Received June 19, 2006; in final form, November 2006

Abstract New film composites based on alicyclic polyimide with polyethylene terephthalate and polycarbonate plasticizers were prepared. The thermodynamic parameters of mixing of film materials were determined by differential scanning calorimetry and thermogravimetry. The structure and composition of the resulting materials were studied by IR spectroscopy and X-ray diffraction analysis. DOI: 10.1134/S1070427207050278

Polyimides (PIs) are of particular importance owing to the development of nanotechnologies which are widely used in production of light plastics applied in instrument-making industry, e.g., in design of large devices to be unrolled in the outer space [1]. Films based on aromatic polyamides (produced by Du Pont, the United States), which exhibit high thermal and radiation resistance, are most often used as supports for further metal plating of their surface. However, these films do not promote rapid and profound penetration of metal ions into the polymer [23 4]. Therefore, to obtain materials with improved physicochemical properties, new polymeric films were prepared, which are based on alicyclic polyimide prepared by high-temperature single-stage polycondensation of tricyclododecenetetracarboxylic acid dianhydride (adduct of benzene and maleic anhydride) with oxydianiline in m-cresol and DMF [5]. The choice of plasticizers is governed by the fact that the degree of crystallinity in polyethylene terephthalate (PET) and polycarbonate (PC) reaches 60 and 40%, respectively, which strongly improves the material strength [6]. Moreover, PET and PC are filmforming, thermally stable, and frost-resistant compounds and can operate in a wide temperature range from 3 60 to 200oC and from 3150 to 200oC, respectively [7]. The aim of this work was to prepare film polymeric composites with improved mechanical properties based on an alicyclic polyimide.

acid (4.2.2.02,5)dec-7-ene-3,4,9,10-tetracarboxylic (adduct of benzene and maleic anhydride) with oxydianiline in m-cresol3DMF (40%) solution with pyridine catalyst [8, 9] at gradual heating to 140 3170oC over a period of 5 h:

EXPERIMENTAL

The films on a support were fixed in a holder which was placed in a spinner of a D8 Advance (Bruker AXS) diffractometer (CuKa radiation, l 1.5406 A). When the Kapton films were inelastic or

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Commercial PET and PC (Aldrich and Bayer Material 5 brand, respectively) stabilized with phosphine (3%) were used. The composites were prepared by reaction and mechanical mixing at various initial component ratios [10, 11].

The viscosities of the polymer solutions in m-cresol were determined on an Ubbelohde viscometer at 20oC [12]. The IR spectra were recorded on a NexusNicolet 5700 Fourier spectrometer.

Initial PI was prepared by high-temperature singlestage polycondensation of dianhydride of tricyclo833

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ties of PI3PET and PI3PC systems and initial PI in m-cresol and DMF. From the temperature dependences of the heat capacities (Fig. 1), the glass transition points Tg were determined (Table 1).

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T, C Fig. 1. Heat capacity C of PI3PET composites as a function of temperature T. PI : PET, wt % : wt %: (1) 85 : 15, (2) 95 : 5, (3) 98 : 2, (4) 99 : 1, and (5) pure PI.

buckled, they were glued to the support using a Ramsay paste invisible in X-ray diffraction. The thermogravimetric (TGA) analysis and evaluation of the heat capacity of the polymers in question were performed by the procedures of thermal degradation and differential scanning calorimetry (DSC) on a Mettler Toledo TGA/SDTA 851c and an FP85 TA Cell devices at constant heating rates of 4 and 8 deg min31, respectively. The mechanical properties of the film samples (60 0 10 mm) determined out on a Com-Ten Testing Equipment tensile-testing machine (the United States). The polymer blends based on PI and PET were prepared in m-cresol solutions by the reaction mixing at PET concentration varied from 1 to 20 wt %. The reaction mixing provides preparation of the polymers completely thermodynamically compatible with formation of molecularly homogeneous blends [13]. However, owing to specific smell, m-cresol cannot be widely used as high-temperature solvent for mechanical mixing of the initial components. The polymeric composites based on PI and PC were prepared by mechanical mixing of the components in DMF at PC concentration varied from 0.5 to 2 wt %. Such narrow concentration range is due to relatively low solubility of PC in DMF; moreover, at PC concentration higher than 5 wt % the films become thermodynamically incompatible with PI.

The observed decrease in Tg in the PI3PET system with increasing PET content is probably due to the nature of the plasticizer, which in the presence of water released above 100 3120oC in the course of cyclization of the amide groups is partially hydrolyzed with breakdown of the ester group, thus decreasing the degree of crystallinity and glass transition point of the polymer. With increasing PC content in the PI3PC composites, the glass transition point of the polymeric films increases. This increase in the glass transition temperature Tg with increasing PC content in the PI3PC composites is probably due to the fact that these polymers are characterized by strong interchain interaction through H bonds owing to high polarity of the carbonyl groups in PC [7]. As a result, the crystal structure in the PI3PC polymers is more stable as compared to the PI3PET composites. It is known [5] that PI is an amorphous polymer whose morphology is described as an ideal melt with irregular supramolecular structure. On transformation from hyperelastic into rigid glassy state, amorphous polymers remain in the disordered glassy state. Mutual transformations of amorphous polymers from one state into another are not phase transitions. In contrast to real phase transitions, these transformations proceed gradually and continuously within a given temperature range and only in the transition area the behavior of the polymer glasses resembles the thermodynamic transition of the second kind when an abrupt change in the thermodynamic properties is observed [13]. Temperature dependences of the heat capacity of the polymer blends given in Fig. 1 involve no breaking points, which corresponds to the thermodynamic transition of the first type, e.g., given polymers are characterized by the short-range ordering.

The data on the polymeric compositions of PI and PET showed that the compatible films are formed at a PET concentration of 135 wt %; with increasing PET content to 15 wt %, the polymeric material becomes turbid, but its physicomechanical properties remain, on the whole, unchanged.

It should be noted that the heating rate can strongly affect Tg of the amorphous polymers [6], and this is probably typical for their blends when the content of the additive is relatively small. For example, at a heating rate of 4 deg min31 no Tg is observed on the DSC curves for PI in m-cresol (Fig. 1), whereas at a heating rate of 8 deg min31 (Fig. 2) certain jump at 114oC in the curve of the weight loss is observed, which corresponds to Tg of PI.

To evaluate the thermodynamic compatibility of the polymers (films), we determined the heat capaci-

Also, the glass transition point is an important criterion for evaluating the compatibility of the poly-

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Table 1. Physicochemical properties of the PI PET and PI PC composites

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ ³ Tg Tm ³ [ ], ³ Tensile strength, , ³ Relative elongation, ³ Initial component ratio t ³ ³ ³ ÃÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄ !1 PI : P2, wt % : wt % MPa % ³ dl g ³ ³ ³ C ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ 100/0 (m-cresol) ³ 1.51 ³ 100 ³ 15.4 ³ 380 ³ 114 100/0 (DMF) ³ 1.44 ³ 71 ³ 30 ³ 393 ³ 93.7 PI PET: ³ ³ ³ ³ ³ 0/100 ³ [4] ³ 14 29 ³ ³ 255 265 ³ 70 80 99/1 ³ 1.50 ³ 106 ³ 15.2 ³ 368 ³ 98/2 ³ 1.49 ³ 101.5 ³ 17.2 ³ 363 ³ 92 95/5 ³ 1.46 ³ 91 ³ 15.3 ³ 360 ³ 85 85/15 ³ 1.42 ³ 80 ³ 13.3 ³ 355 ³ 78 PI PC: ³ ³ ³ ³ ³ ³ ³ ³ ³ 0/100 ³ [4] 99.5/0.5 ³ 1.42 ³ 100 ³ 9.0 ³ 390 ³ 97.0 99/1.0 ³ 1.4 ³ 95 ³ 10.4 ³ 387 ³ 97.5 98.5/1.5 ³ 1.35 ³ 85 ³ 11.0 ³ 384 ³ 98.0 98/2 ³ 1.33 ³ 72 ³ 11.6 ³ 380 ³ 98.7 ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄ

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mer blends. If a composite is characterized by two glass transition points corresponding to the polymeric components, then this system is incompatible; and the system is compatible if it is characterized by a single glass transition point. As seen from experimental results (Fig. 1, Table 1), the polymeric composites based on PI and containing PET (1315 wt %) or PC (0.532.0 wt %) exhibit only one glass transition point, which indicates that all the polymeric films are thermodynamically compatible. Thus, we succeeded in preparing compatible polymeric films based on PI containing the above amounts of PET and PI plasticizers; Tg of PI3PET composites is lower than that of PI3PC composites. The main parameters affecting Tg are the chain flexibility and the nature of intermolecular packing [6]. With a decrease in the chain flexibility, Tg increases owing to steric hindrance, which is typical for PI3PC systems. The observed decrease in Tg for PI3PET composites is probably due to higher degree of freedom in macromolecules causing higher mobility and flexibility of the polymer sections owing to the plasticizing affect of PET. Based on the resulting thermodynamic parameters we assumed that the composites with PET plasticizer show more promise for further modification of the film material, namely, for implantation of metal ions such as Ag+, Cu2+, Ni2+, or Co2+ [15]. In this work we studied the structure and physicochemical properties of the film materials, because addition of partially crystalline PET and PC into the amorphous PI matrix improves the composite morRUSSIAN JOURNAL OF APPLIED CHEMISTRY

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phology [16] and probably enhances the strength of the polymer film. The assumption that the packing in PI3PC composites is more rigid than in PI3PET systems is confirmed by X-ray diffraction data, namely, by the presence of PC crystallites in PI halo (Fig. 3). This fact confirms the presence of a crystalline area in the polymer, in contrast to the PI3PET films, for which the crystalline area is rather diffuse. The presence of the PET ester group in the PI3PET polymers is confirmed by the IR spectra. As seen from Fig. 4a, with increasing content of PET from 1 to 5 wt % the intensity of the stretching vibrations of the ester group nC3O at 1000 cm31 increases, and at 15 wt % content of the PET plasticizer in the polymer blend the intensity of these vibrations is close to that m, g min!1

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T, C Fig. 2. DTG curves of composites based on (1) neat PI and PI3PET with PET content of (2) 2, (3) 5, (4) 10, (5) 15, and (6) 20 wt %. (m) Weight loss rate and (T) temperature. No. 5

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ZHUBANOV et al. Table 2. Composition of polyimide systems

ÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ Content, wt % ³Content of PET, wt % Composite ÃÄÄÄÄÄÂÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄ ³ imide ³amido acid³ gravimetry ³TGA data ÄÄÄÄÄÄÄÄÅÄÄÄÄÄÅÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ PI ³ 89.8 ³ 10.2 ³ ³ PI PET, ³ ³ ³ ³ PET, %: ³ ³ ³ ³ 1% ³ 86.1 ³ 12.4 ³ 1.05 ³ 1.15 2% ³ 83.8 ³ 12.0 ³ 2.1 ³ 2.25 5% ³ 80.5 ³ 11.8 ³ 5.1 ³ 7.7 15% ³ 74.0 ³ 10.9 ³ 15.3 ³ 14.9 ÄÄÄÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄ

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2 , deg Fig. 3. Diffraction patterns of (1) pure PI and its composites containing (2) 5 wt % PET and (3) 1.5 wt % PC, sliding angle 2 deg. (A) Intensity and (2q) Bragg scattering angle.

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The above data suggest that there are no chemical interactions in the PI3PET polymer films, which are physical blends associated through hydrogen bonds.

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perature dependence of the heat capacity of the PI3 PET composite (Fig. 1). In the IR spectra of the PI3 PET composite, the bands of the carbonyl group of the initial PET at 1735 cm31 and of the carbonyl group of PI at 1700 cm31 are shifted by 35 and 20 cm31, respectively, probably due to the formation of a hydrogen bond between the carbonyl group of PET and hydroxy group of the amido acid fragment [17] formed in the course of PI synthesis. The presence of this acid in the PI3PET systems is confirmed by thermogravimetric analysis. The content of the imide groups and amido acid fragment appearing in the polymer with addition of PET is shown in Table 2. These results correspond to the theoretical ratio of the components.

No chemical interactions were observed in the PI3 PC composites. The characteristic band belonging to the PC carbonyl group at 1740 cm31 is found in all the IR spectra of PI3PC composites with various component ratios (Fig. 4b). No shifts by more than 200 cm31 were observed. Hence, PI3PC composites are also probably formed due to the hydrogen bonds. This is indirectly confirmed by the fact that after heating at temperatures higher than 50oC the film becomes turbid and brittle. 1

Fig. 4. IR spectra of (1) neat PI and (a) PI3PET composites with PET content of (2) 1, (3) 2, (4) 5, and (5) 15 wt % and (b) PI3PC with PC content of (2) 0.5, (3) 1.0, (4) 1.5, and (5) 2.0 wt %. (A) Adsorption and (n) wavenumber.

in the initial PI. This is probably due to the fact that at 15 wt % content of PET the polymer blend undergoes phase segregation making the polymer film turbid; this corresponds to the second weak peak in the tem-

We also tested the mechanical properties of new PI3PET and PI3PC composites; the data on the tensile strength and relative elongation at constant deformation rate are listed in Table 1. As seen, the tensile strength of the PI3PET composites decreases with increasing PET content (similarly to Tg) but remains significantly higher than that of the individual PET (14 329 MPa). As for PI3PC systems, Tg and dt vary in the opposite directions. This is probably due to the

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fact that, in contrast to PET with linear polymeric structure and more compact packing, PC contains bulky side groups, which make the polymeric films brittle. Nevertheless, addition of partially crystalline PET and PC polymers improves the strength of the polymer films; upon mixing of PI and PC, dt increases from 71 to 100 MPa. For PI3PET (99 : 1) composites dt increases from 100 to 106 MPa; at the other component ratios, when the tensile strength of the polymer films slightly decreases, their relative elongation remains fairly high (15.2317.2%), i.e., all the PI3PET polymer films are characterized by high rupture strength and relative elongation. Since the melting points of the composite materials are 3553393oC at high reduced viscosities of the polymer solutions, these polymers can be classed with thermally stable composites with high physicochemical and mechanical properties. Thus, polymeric films with thermally controlled and high strength properties were prepared using PI3PET and PI3PC polymer blends with various ratios of the initial components. CONCLUSIONS (1) The thermodynamic parameters of mixing of the film materials were determined by differential scanning calorimetry and thermogravimetry; these data show that the films based on polyimide containing polyethylene terephthalate (1.0 315.0 wt %) or polycarbonate (0.532.0 wt %) have a single glass transition point, i.e., the resulting polymer films are thermodynamically compatible. (2) The absence of chemical interaction between polyimide and polyethylene terephthalate or polycarbonate was confirmed by IR spectroscopy. (3) Addition of polyethylene terephthalate (1.0 3 15.0 wt %) or polycarbonate (0.532.0 wt %) into the polyimide matrix enhances the film strength. Their tensile strength increases from 71 to 100 and from 72 to 106 MPa for PI3PET and PI3PC systems, respectively, whereas the thermal properties of the composites (Tm 3553393oC) remain essentially unchanged. ACKNOWLEDGMENTS This study was financially supported by the International Science and Technology Center (project no. K-1117). RUSSIAN JOURNAL OF APPLIED CHEMISTRY

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