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Mechanical Properties and Structure of Poly(p-phenylenevinylene) Films Prepared by the Zone-Reaction Method Hidenori Okuzaki,* Norihiro Ikeda, Isamu Kubota, and Toshio Kunugi Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Yamanashi University, 4-3-11 Takeda, Kofu 400-8511, Japan Received November 17, 1998; Revised Manuscript Received June 15, 1999 ABSTRACT: The “zone-reaction method”, consisting of zone drawing (ZD) and zone reaction (ZR), was applied to chemically synthesized poly(p-phenylenevinylene) (PPV) precursor films under various applied tensions (σ) and heater temperatures (Th). The changes in the structure, tensile, and viscoelastic properties of the resulting films were investigated. It was found that orientation function (f) of the ZD films increased with draw ratio (DR), regardless of the Th and σ values, and attained 0.862 (DR ) 9). ZR was subsequently performed on the ZD film. The molecular orientation and PPV content were strongly affected by the Th: The film obtained at Th ) 240 °C exhibited the highest f value, as high as 0.894, while a further increase in the Th resulted in a disorientation of molecular chains. On the other hand, the absorption ratio between 632 cm-1 (C-S stretch) and 965 cm-1 (trans-vinylene C-H out-of-plane bend) (A632/A965) became almost zero at Th above 240 °C. The Young’s modulus and tensile strength for the resulting ZR film respectively increased to 69.4 and 1.3 GPa from 2.1 and 0.04 GPa of as-cast original film. The dynamic storage modulus for the ZR film was the value as high as 74.7 GPa and held 40 GPa even at 350 °C, which were considerably higher than those of the typical engineering plastics.
Introduction Much attention has been paid to poly(p-phenylenevinylene) (PPV) due to its potential applications in electrical and optical devices. Most of the previous work has focused on the electrical conductivity,1,2 electro- or photoluminescence,3 and nonlinear optical response.4 The physical properties such as thermal properties,5,6 crystalline structure, and morphology7,8 have also been investigated. A few reports on the mechanical properties suggest that PPV is a high-performance polymer because of its rigid structure consisting of alternating phenylene and vinylene groups.9,10 It is of great importance to produce high-performance PPV not only for the practical use but also from the fundamental viewpoints for approaching the intrinsic thermal or mechanical properties. Machado and Karasz investigated tensile properties of PPV films prepared by a uniaxial stretching/annealing method.11 They found that Young’s modulus and tensile strength of the resulting film respectively attained 40 and 0.5 GPa, which were much higher than those of commercial polymers. We have succeeded in preparing high-performance films or fibers from conventional polymers such as polyolefins,12 polyesters,13 and polyamides14 by the zonedrawing/zone-annealing method developed in our laboratory. Previously, we have reported on the mechanical properties of PPV films prepared by the zone-drawing/ heat treatment method.9 It was found that the resulting film had a dynamic storage modulus of 33.7 GPa at room temperature and 11.5 GPa at 300 °C. We developed here the “zone-reaction (ZR) method” and applied it to chemically synthesized PPV precursor films under various applied tensions and heater temperatures. The present work deals with changes in the structure, tensile, and viscoelastic properties of the resulting films. The experimental results allow us to * To whom correspondence should be addressed. Phone and Fax +81-55-220-8554; e-mail
[email protected].
Figure 1. Schematic illustration of the zone-reaction (ZR) method applied to PPV precursor film.
conclude that the ZR method is capable of resulting in high orientation of molecular chains and mechanical properties. Experimental Section Preparation of PPV Precursor Film. The PPV precursor films were prepared using the method of Karasz and coworkers.15 p-Xylene-bis(diethylsulfonium chloride) monomer was synthesized by reacting R,R′-dichloro-p-xylene (0.6 mol L-1) with diethyl sulfide (1.8 mol L-1) in methanol solution at 50 °C for 24 h. The methanol was evaporated, and the monomer was precipitated from cold acetone, filtered, and then dried overnight in a vacuum. Polymerization was carried out by mixing the monomer (0.2 mol L-1) and sodium hydroxide (0.2 mol L-1) at 0 °C for 1 h in a nitrogen atmosphere. After polymerization, the solution was neutralized by addition of an aqueous solution of 0.1 N HCl and then purified by dialysis in deionized pure water for 3 days. The precursor film was prepared by casting the dialyzed solution on a glass plate and allowing it to solidify by evaporation of solvent at 50 °C for 12 h. Apparatus for Zone Reaction. The apparatus employed for the zone reaction of PPV precursor film is schematically
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shown in Figure 1. The zone heater (2 mm thick), consisting of Nichrome wire and a thermocouple placed between two asbestos plates, was mounted on the cross-head of a tensile tester, where the heater temperature was controlled by a thermoregulator. The upper end of the precursor film (40 mm long, 2 mm wide, and 28 µm thick) was fixed to the strain gauge of the tensile tester, and then the desired tension was applied to the lower end by mounting a dead weight. The zone heater was moved in the direction from lower to upper end at a constant speed of 20 mm min-1 in air. Measurements. The draw ratio (DR) was determined by measuring the distance between marks put on the surface of the film prior to drawing. The PPV content (x), defined as the ratio of PPV repeated unit, was evaluated by elemental analysis. The orientation function (f) was evaluated with a FTIR spectrometer, Pargamon 1000 (Perkin-Elmer Co. Ltd.). The dichroic ratio (D), defined as the ratio of absorption between parallel (A|) and perpendicular (A⊥) to the drawing direction, was estimated as follows16
f)
[(
)(
)]
D - 1 D0 + 2 D + 2 D0 - 1
(1)
where D0 ) 2 cot2 R, and R is the angle of the absorption transition moment to molecular chain axis. The estimation of f was carried out using the absorption of the trans-vinylene C-H out-of-plane bend16 at 965 cm-1 where the absorption transition moment R was 84°.17 The degree of crystallinity (Xc), defined as the ratio of the peak area of the diffraction from crystallites to total diffraction, was measured from wide-angle X-ray diffraction patterns, and the orientation factor of crystallites (fc) was evaluated by using the Wilchinsky method.18 The apparent crystallite size normal to the (hkl) plane (Dhkl) was estimated from Scherrer’s equation
Dhkl )
0.9λ β cos θhkl
(2)
where λ, β, and θhkl were the wavelength of the Cu KR beam (1.542 Å), the half-width of the diffraction peak in units of radians, and one-half of the diffraction angle, respectively. The wide-angle X-ray diffraction photographs were taken with a Ni-filtered Cu KR radiation (40 kV, 20 mA) by an X-ray generator (Rigaku Co. Ltd.). The distance between the sample and X-ray film was 40 mm, and the exposure time was 8 h. Thermogravimetric (TG) analysis was performed with a TGDTA 2000S (MAC Science Co. Ltd.). About 10 mg of dry film was weighed in an aluminum pan, and the measurement was carried out at a heating rate of 3 °C min-1 in an argon atmosphere. The thermal shrinkage was measured with a TMA system (Rigaku Co. Ltd.) in air at a heating rate of 5 °C min-1 under a constant tension of 5 g mm-2 that was the minimal value to tense the film. The tensile properties were measured with a tensile tester, Tensilon II (Orientec Co. Ltd.), at a constant strain rate of 10% min-1 (chuck distance 20 mm, head speed 2 mm min-1) under the thermostatic conditions (temperature 25 °C, 65% relative humidity). Young’s modulus, tensile strength, and elongation at break were calculated from the stress-strain curves and represented average values of at least 10 tests. The dynamic viscoelastic properties, storage modulus (E′), loss modulus (E′′), and loss tangent (tan δ) were measured with a dynamic viscoelastometer, VIBRON DDV-II (Orientec Co. Ltd.), at 110 Hz over a temperature range from room temperature to 400 °C at a heating rate of 2.5 °C min-1 in a nitrogen atmosphere.
Results and Discussion Principle and Characteristics of the Zone-Reaction Method. The zone-reaction method consists of two processes: zone drawing (ZD) and zone reaction (ZR). The ZD is carried out on the original precursor film at low temperatures (100-220 °C) for the purpose of
orienting the molecular chains. Indeed, the precursor film was drawn easily and quickly, producing a neck at the zone heater.9,16 The ZR is subsequently performed on the ZD precursor film at a higher heater temperature (220-280 °C) and higher applied tension to convert the diethylsulfonium unit to PPV by elimination of diethyl sulfide and hydrochloric acid simultaneously with further drawing (Figure 1). Although the apparatus is simple and the procedure is quite easy, this method has the following advantages: (1) the heat and tension act uniformly and effectively on the quite narrow area of the specimen; (2) the thermal decomposition or oxidation of the specimen can be minimized even in air because the heating time is very short, about a few seconds; (3) various thermal reactions or removal of solvent can be performed; (4) a high orientation of molecular chains is obtained because the chemical reaction takes place simultaneously with drawing; (5) the dimensional stability of the resulting films or fibers at elevated temperatures can be improved. Optimum Conditions for ZD and ZR. To determine the optimum conditions for the ZD, the original films are zone drawn at different heater temperatures (Th) under various applied tensions (σ). At Th below 100 °C the film cannot be drawn uniformly, and at Th above 220 °C the neck goes out above the zone heater. Thus, the ZD is performed at a Th range from 100 to 220 °C. The draw ratio (DR) increased with increasing σ at each Th, and under the same σ values the DR rose as the Th became higher. Figure 2 shows wide-angle X-ray diffraction photographs (through view) of the original (a) and ZD films (b) (DR ) 9). The original precursor film exhibits a diffuse Debye-Scherrer ring, indicating that the film is isotropic having low crystallinity. A diffraction ring for the original film changes into sharp and intensive spots in the equatorial direction for the ZD film, indicating that crystalline orientation and crystallinity increase during the ZD. A clear indication of the increase in the molecular orientation by the ZD is demonstrated in Figure 3. It is seen that the orientation function (f) increases with DR, regardless of the Th and σ values, and tends to level off at DR values above 5. This indicates that the orientation of molecular chains significantly increases even at low DR values, and a further increase of the DR does not significantly improve it.14 Since the purpose of the ZD is to obtain higher orientation of precursor chains, the conditions giving the highest f value of 0.862 (DR ) 9) is chosen to be optimum. The ZR is subsequently performed on the resulting ZD film in the same manner at higher Th and σ values for the purpose of eliminating diethyl sulfide and hydrochloric acid simultaneously with further drawing. The films having the highest f value at each Th are shown in Figure 4. The ZR brings about slight increase in the DR, and the film obtained at Th ) 240 °C exhibits the highest f value as high as 0.894. On the other hand, the ZR performed at Th higher than 260 °C results in a decrease of the f value, indicative of disorientation of molecular chains. This may be associated with rapid elimination of low molecular compounds, which increases the structural disorder. A clear indication of the elimination is also demonstrated in Figure 4. The A632/ A965, defined as the absorption ratio between 632 cm-1 (C-S stretch) and 965 cm-1 (trans-vinylene C-H outof-plane bend), decreases as the Th becomes higher, and
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Figure 2. Wide-angle X-ray diffraction photographs (through view) for the original (a) and ZD films (b) (Th ) 200 °C, σ ) 5 MPa, DR ) 9).
Figure 3. Relation between DR and orientation function (f) for the ZD films obtained at different heater temperatures (Th) under various applied tensions (σ).
the value becomes almost zero at Th above 240 °C. This is clear evidence that the precursor is successfully converted into PPV at Th above this temperature. It seems to be rather surprising because the heating time is very short, about 6 s, and the actual temperature the sample experiences during the ZR will be lower than the Th.19 These experimental results, however, allow us to consider that the heating time is enough to draw and convert to PPV, which is presumably due to the heat and tension acting effectively and uniformly on the quite narrow area of the sample. Thus, the film with the highest molecular orientation containing no precursor is selected as optimum for the ZR. The optimum conditions for the ZD and ZR are summarized in Table 1. To clarify the role and effect of the ZR on structure and mechanical properties of the resulting films, the ZD films were subsequently converted to PPV by heat treatment with a conventional method. The ZD film (10 cm long, 0.5 mm wide, and 9 µm thick) was tightstretched and placed at the center of an electric furnace (12 cm long and 3 cm in diameter). The heat treatment was performed at 240 °C, the same temperature as the
Figure 4. Dependence of orientation function (f) and absorption ratio between 632 and 965 cm-1 (A632/A965) on Th for the ZR films. The films have the highest f value at each Th. Table 1. Optimum Conditions for Zone Drawing (ZD) and Zone Reaction (ZR) film
Th (°C)
σ (MPa)
heater speed (mm min-1)
ZD ZR
200 240
5 75
20 20
Th for optimal ZR, for 2 h under the isometric conditions where no additional tension was applied. The films heattreated in air and in a nitrogen atmosphere were designated as ZD-HT(air) and ZD-HT(N2), respectively. Structure. Figure 5 shows FT-IR spectra of various films without polarizers. The original film has absorption at 632 cm-1 corresponding to the C-S stretch of precursor and at 965 and 3024 cm-1 to the transvinylene C-H out-of-plane bend and stretch bands of PPV. This clearly shows that the original film already contains PPV unit that formed during the film casting.20 The absorption at 632 cm-1 disappears for the ZR film, while those at 965 and 3024 cm-1 increase in height. This demonstrates the conversion of diethylsulfonium to PPV, which is consistent with the data shown in Figure 4. A similar spectrum to that of the ZR film is obtained for the ZD-HT(N2) film, whereas the ZD-HT-
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Poly(p-phenylenevinylene) Films 5609
Figure 6. TG thermograms of the original, ZD, ZR, and ZDHT films measured in an argon atmosphere at a heating rate of 3 °C min-1. The thermogram of the ZR film measured in air was designated as ZR(air).
Figure 5. FT-IR spectra of the original, ZD, ZR, and ZD-HT films without polarizers. Table 2. Thickness (L), Draw Ratio (DR), PPV Content (x), Orientation Function (f), Orientation Factor of Crystallites (fc), Degree of Crystallinity (Xc), and Apparent Crystallite Size Normal to the (110) Plane (D110) for Various Films film
L (µm)
original ZD ZR ZD-HT(N2) ZD-HT(air)
28 9 6 6 6
a
xa
DR
fb
fcc
0.584 9.0 0.667 0.862 0.995 10.3 0.968 0.894 0.994 9.0 0.974 0.782 0.995 9.0 0.769 0.994
Elemental analysis.
b
Xcc (%) D110c (Å) 26.4 68.8 75.2 71.5 71.3
11.3 62.1 67.3 62.2 62.2
FT-IR. c Wide-angle X-ray diffraction.
(air) has large absorption at 1691 cm-1 for the CdO stretch band due to oxidation of polymers during the heat treatment. It should be noted here that the ZR film undergoes no notable oxidation, even though the ZR is carried out in ambient air. This can be explained by the characteristic of this method: the oxidation can be minimized because the heating area is very small and the heating time is very short, about a few seconds. Thickness (L), draw ratio (DR), PPV content (x), orientation function (f), orientation factor of crystallites (fc), degree of crystallinity (Xc), and apparent crystallite size normal to the (110) plane (D110) are summarized in Table 2. As suggested from the FT-IR spectra, elemental analysis indicates that the original film has an x of 0.584, meaning that the film includes about 58% of the PPV unit. In fact, Karasz et al.16 demonstrated that a freshly cast film had the ratio between the diethylsulfonium unit and the PPV unit of 4:1, which stabilized to a ratio about 1:2 after 3 weeks at room temperature. The x value increases with the processes and finally attains 0.968 for the ZR film, indicating that less than 1% sulfur remained. According to the literature,6,7,21 the thermal conversion at lower temperatures about 200 °C usually leaves about 2% of residual sulfur and that at 380 °C results in the complete PPV containing less than 0.1% sulfur. Thus, compared with the conventional method, the ZR technique can cause a similar elimination reaction within a few seconds in ambient air.
Figure 7. Temperature dependence of thermal shrinkage for the original, ZD, ZR, and ZD-HT(N2) films measured in air at a heating rate of 5 °C min-1.
A similar observation has been made by TG analysis performed on various films, and the results are shown in Figure 6. The original film has two major steps of weight loss: at 100-250 °C and above 300 °C. The first step corresponds to the elimination of diethyl sulfide and hydrochloric acid, and the second one may be associated with decomposition of polymers.6,22 It is found that the weight loss of the first step decreases for the ZD film, indicating that the precursor unit is partially converted to PPV during the ZD as expected from slight increase in the x. However, the x calculated using the weight loss of the first step (xTG) by assuming that all of the precursor units are converted to PPV is considerably larger than those calculated by the elemental analysis: the xTG for the original, ZD, and ZR films are 0.819, 0.878, and 0.996, respectively. The reason is not clear, but the xTG value for the original film seems to be so large compared with those obtained by other authors6,16 that we have employed the values from the elemental analysis. It is seen from Figure 6 that the ZR film has a similar thermogram to the ZD-HT(N2) film with less weight loss over the whole experimental temperature range, demonstrating that the precursor unit is effectively changed into PPV by the ZR. To elucidate the second step of the weight loss, the TG analysis has been performed on the ZR film in air where the thermogram
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Figure 8. Wide-angle X-ray diffraction photographs of the through view (a), side view (b), and end view (c) for the ZR film (DR ) 10.3).
is designated as ZR(air). Compared with the ZR measured in an argon atmosphere, the ZR(air) exhibits a large weight loss above 300 °C, suggesting that the second weight loss is associated with the decomposition of polymers owing to residual oxygen. Furthermore, a similar behavior is observed for the ZD-HT(air) film even thought the measurement is performed in an argon atmosphere, which indicates that its poor thermal stability is ascribed to the oxidation during the heat treatment. The thermal weight loss should also reflect on the dimensional stability of films. Figure 7 shows the temperature dependence of thermal shrinkage for various films measured in air. The original film undergoes elongation during heating to 140 °C, which is associated with plastic deformation, while a further heating brings about shrinkage of the film corresponding to the weight loss. On the other hand, the ZD film has less shrinkage up to 310 °C, even though the film loses the weight of about 14% at this temperature. This can be explained by anisotropic contraction of the film: since the molecular chains are highly oriented, the contraction occurs in the lateral direction while minor changes in axial dimension are observed. Indeed, the thickness of the ZD film decreases by 33% during the ZR or heat treatment though the DR values are nearly the same (Table 2). The dimensional stability is improved with the processes, and the resulting ZR film has a thermal shrinkage of only 0.34% even at 350 °C. A significant shrinkage at the elevated temperatures is due to the decomposition by oxidation as indicated by the TG measurements. It is noted that the ZR film exhibits higher dimensional stability than the ZD-HT(N2) film. This will be associated with the large crystallinity and crystallite size for the ZR film, where the crystallites behave as crosslinking points and strongly suppress the relaxation of molecular chains. Figure 8 shows X-ray diffraction photographs of the through view (a), side view (b), and end view (c) for the ZR film. The diffraction patterns of the through (a) and side views (b) (perpendicular to the stretching direction) are substantially the same; the intensive spots are observed around an equator at 2θ ) 20.6° (d ) 4.3 Å) and 27.9° (d ) 3.2 Å) corresponding to the diffraction from (110) and (210) planes of the monoclinic unit cell of the PPV crystal.23 On the other hand, a homogeneous
diffraction is observed in the end view (parallel to the stretching direction), indicative of no apparent planar alignment of PPV chains in the film. It is found that the diffraction peak at 2θ ) 18.8° for the original film shifts to higher diffraction angle with the processes, indicative of a decrease in the d-spacing (d). This suggests a precursor-to-PPV crystal-crystal transition by the elimination reaction. More importantly, the broad and continuous layer lines in the photographs of Figure 8a,b indicate that the PPV chains are not registered perfectly in the stretching direction, resulting in axial disorder. Lenz et al.7 demonstrated that the axial disorder was associated with axial translational disorder of PPV chains and registration fluctuation of molecular chains in a fibrous crystal system, which brought about diffusing and broadening of layer lines. Table 2 provides us information about changes in the molecular orientation and crystallinity during the processes. The f and fc remarkably rise for the ZD film, demonstrating that the crystallites can easily be aligned in the drawing direction and/or the precursor chains are converted into oriented crystallites by the initial process of the drawing as indicated in Figure 2. Indeed, the values of Xc and D110 are significantly increased by the ZD. On the other hand, the f values of both ZD-HT(N2) and ZD-HT(air) films decrease, though the fc values are considerably high. Since the PPV film will contain transvinylene C-H groups in both the amorphous and crystal regions because of the paracrystallinity,7 we suppose that the absorption of the trans-vinylene C-H out-ofplane bend in both regions appears near the same wavenumber of 965 cm-1. Indeed, the isotropic PPV film prepared by heat treatment of the original film (Xc ) 26.4%) exhibits the same absorption intensity at 965 cm-1 as the ZR film (Xc ) 75.2%), indicating that this absorption is less sensitive to the crystallinity. On the basis of these considerations, the IR-derived f may represent the average orientation of molecular chains in both the amorphous and crystal regions, while the fc indicates the orientation of the crystallites. Thus, the experimental result suggests the disorientation of amorphous chains during the heat treatment, posing a problem for further improvement of the mechanical properties.9 Mechanical Properties. In general, the mechanical properties such as Young’s modulus and tensile strength
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Poly(p-phenylenevinylene) Films 5611
Table 3. Tensile Properties for Various Films film
Young’s modulus (GPa)
tensile strength (GPa)
elongation at break (%)
original ZD ZR ZD-HT(N2) ZD-HT(air)
2.1 27.3 69.4 56.9 7.60
0.04 0.65 1.30 1.27 0.14
6.53 6.42 2.70 4.48 2.43
Figure 10. Temperature dependence of loss tangent (tan δ) for the original, ZD, ZR, and ZD-HT films measured in a nitrogen atmosphere. Frequency 110 Hz, heating rate 2.5 °C min-1.
Figure 9. Temperature dependence of dynamic storage modulus (E′) for the original, ZD, ZR, and ZD-HT films measured in a nitrogen atmosphere. Frequency 110 Hz, heating rate 2.5 °C min-1.
of conventional polymers are considerably low compared with theoretical values. The main cause of low mechanical properties lies in the folding of molecular chains, leading to chain loops or lamellae in the films or fibers, which are not useful for improving the mechanical properties. The ideal structure of the high-modulus and high-strength polymer is a bundlelike crystal that has an extremely high molecular orientation in one direction. From this point of view, the resulting ZR film is expected to have superior mechanical properties because of its large crystallinity and high molecular orientation in the drawing direction. Table 3 shows tensile properties of various films. The Young’s modulus and tensile strength for the ZR film respectively attain 69.4 and 1.3 GPa from 2.1 and 0.04 GPa of the original film. These values are much higher than those obtained by Machado and Karasz11 (40 and 0.5 GPa) and close to those of the high-performance rigid polymers such as poly(phenyl-1,4-phenylene terephthalate) (PHQT) (60 and 2.9 GPa)24 and poly(p-phenylene terephthalamide) (Kevlar) fibers (83 and 3.6 GPa).25 It is noted that the Young’s modulus of the ZR film is much higher than that of the ZD-HT(N2) film, even though the fc values are nearly the same. This fact suggests that the orientation of amorphous chains and/or crystallinity are crucial to improve the mechanical properties. On the other hand, the drop of tensile properties for the ZD-HT(air) film is probably due to the oxidation and decomposition of polymers: the stress concentrates and deformation or breakdown will take place at various structural defects such as microvoids or microfractures formed during the heat treatment. Figure 9 shows the temperature dependence of storage modulus (E′) for various films, where the E′ increases stepwise with the processes over the whole experimental temperature range. The E′ of the ZR film
at room temperature attains a value as high as 74.7 GPa and holds 40 GPa even at 350 °C, which are considerably higher than those of the typical engineering plastics such as poly(p-phenylene sulfide)26 (E′ ) 7.2 GPa at 25 °C and 2.5 GPa at 200 °C, DR ) 6) and poly(ether ether ketone)27 (E′ ) 13.3 GPa at 25 °C and 5 GPa at 300 °C, DR ) 4.4) prepared by the zone-drawing/zone-annealing method. On the other hand, the ZD-HT films exhibit lower E′ values as well as the Young’s modulus values. The temperature dependence of loss tangent (tan δ) for various films are shown in Figure 10. The original film has a clear mechanical dispersion at 120 °C corresponding to micro-Brownian motion of amorphous chains of the precursor. The dispersion can be interpreted in terms of a “plasticizing effect” by the volatile gases evolved because the temperature well coincides with that of the first step weight loss process.14 In fact, the dispersion decreases in height and broadens for the ZD film and finally disappears for the ZR and ZD-HT films. On the other hand, the ZD-HT(air) film has a large and broad dispersion in the temperature range from 200 to 350 °C, which may be related with the motion of the oxidized chains or thermal decomposition. Conclusions We developed the “zone-reaction method” and applied it for converting PPV precursor film to high-performance PPV. The following results were obtained. 1. The elimination of diethyl sulfide and hydrochloric acid was successfully performed by the ZR, and the resulting film underwent no notable oxidation even in air. 2. The draw ratio, orientation function, crystallinity, and apparent crystallite size for the ZR film were 10.3, 0.894, 75.2%, and 67.3 Å, respectively. 3. The Young’s modulus and tensile strength for the ZR film reached 69.4 and 1.3 GPa, respectively. The dynamic storage modulus attained 74.7 GPa at room temperature and held 40 GPa at 350 °C. References and Notes (1) Murase, I.; Ohnishi, T.; Noguchi, T.; Hirooka, M. Polym. Commun. 1984, 25, 327.
5612 Okuzaki et al. (2) Wnek, G. E.; Chien, C. W.; Karasz, E. F.; Lillya, C. P. Polym. Commun. 1979, 20, 1441. (3) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.; Mackay, K.; Friend, R. H.; Burns, P. L.; Holmes, B. Nature 1991, 347, 539. (4) , Kaino, T.; Kubodera, K.; Kobayashi, H.; Kurihara, T.; Saito, S.; Tsutsui, T.; Tokito, S. Electron. Lett. 1987, 23, 1095. (5) Ohnishi, T.; Murase, I.; Noguchi, T.; Hirooka, M. Synth. Met. 1986, 14, 207. (6) Montaudo, G.; Vitalini, D.; Lenz, R. W. Polymer 1987, 28, 837. (7) Granier, T.; Thomas, E. L.; Gagnon, D. R.; Karasz, F. E.; Lenz, R. W. J. Polym. Sci., Polym. Phys. 1986, 24, 2793. (8) Chen, D.; Winokur, M. J.; Masse, M. A.; Karasz, F. E. Polymer 1992, 33, 3116. (9) Okuzaki, H.; Hirata, Y.; Kunugi, T. Polymer 1999, 40, 2625. (10) Tokito, S.; Smith, P.; Heeger, A. J. Polymer 1991, 32, 464. (11) Machado, J. M.; Karasz, F. E. Polym. Prepr. 1989, 30, 154. (12) Kunugi, T. J. Polym. Sci., Polym. Lett. 1982, 20, 329. (13) Kunugi, T.; Suzuki, A.; Hashimoto, M. J. Appl. Polym. Sci. 1981, 26, 213. (14) Kunugi, T.; Akiyama, I.; Hashimoto, M. Polymer 1982, 23, 1193. (15) Antoun, S.; Gagnon, D. R.; Karasz, F. E.; Lenz, R. W. J.
Macromolecules, Vol. 32, No. 17, 1999 Polym. Sci., Polym. Lett. 1986, 24, 503. (16) Gagnon, D. R.; Karasz, F. E.; Thomas, E. L.; Lenz, R. W. Synth. Met. 1987, 20, 85. (17) Bradley, D. D. C.; Friend, R. H.; Lindenberger, H.; Roth, S. Polymer 1986, 27, 1709. (18) Wilchinsky, Z. W. J. Appl. Phys. 1959, 30, 792. (19) Suzuki, A.; Maruyama, S.; Kunugi, T. Kobunshi Ronbunshu 1992, 49, 741. (20) Jin, J. I.; Lee, Y. H.; Shim, H. K. Macromolecules 1993, 26, 1805. (21) Murase, I.; Ohnishi, T.; Noguchi, T.; Hirooka, M.; Murakami, S. Mol. Cryst. Liq. Cryst. 1985, 118, 333. (22) Lenz, R. W.; Han, C. C.; Lux, M. Polymer 1989, 30, 1041. (23) Masse, M. A.; Schlenoff, J. B.; Karasz, F. E.; Thomas, E. L. J. Polym. Sci., Polym. Phys. 1989, 27, 2045. (24) U.S. Patent 4159365. (25) Flood, J. E.; White, J. L.; Fellers, J. F. J. Appl. Polym. Sci. 1982, 27, 2965. (26) Suzuki, A.; Kohno, T.; Kunugi, T. J. Polym. Sci., Polym. Phys. 1998, 36, 1731. (27) Kunugi, T.; Mizushima, A.; Hayakawa, T. Polym. Commun. 1986, 27, 175.
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