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1.
Poly(p-phenylene pyromellitamic acid)s were synthesized over the weight-average molecular weight range 8,000 to 22,000. The polymers were recovered as amorphous powders composed of 3–4 × 1–2 μ platelets 0.1–0.2 μ thick containing 20–30% associated solvent. Consumption of reactants and attainment of the ultimate molecular weight of the polymer were found to occur within the first few minutes of reaction. The polymers were characterized by scanning electron microscopy; ultraviolet, visible, near-infrared, and infrared spectroscopy; x-ray analysis; viscometry; and light-scattering photometry. The intrinsic viscosity–molecular weight relation for the polymer in DMF was \documentclass{article}\pagestyle{empty}\begin{document}$ [\eta ] = 25.2 \times 10^{ - 4} \bar M_w^{0.56} $\end{document}. 相似文献
2.
Motowo Takayanagi Teruo Katayose 《Journal of polymer science. Part A, Polymer chemistry》1981,19(5):1133-1145
N-substituted poly(p-phenylene terephthalamide)s (PPTA), such as N-alkylated, N-aralkylated, and N-carboxymethylated poly(p-phenylene terephthalamide), were synthesized from PPTA and the corresponding halides by the polymer reaction via the metalation reaction in a solution of sodium methylsulfinylcarbanion in dimethyl sulfoxide at low temperature. The introduction of various substitutional groups into the amide groups of PPTA increased their solubilities, but decreased their thermal stabilities compared with PPTA. The effects of various substitutional groups on the thermal properties and the solubilities are discussed. Liquid crystal formation was noticed for PPTA substituted with bulky groups such as 9-anthrylmethyl group. 相似文献
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Dirk Marsitzky Thorsten Brand Yves Geerts Markus Klapper Klaus Müllen 《Macromolecular rapid communications》1998,19(7):385-389
This paper describes a new way to synthesize rod-coil block copolymers consisting of poly(p-phenylene) (PPP) as rigid rod and either polystyrene (PS) or poly(ethylene oxide) (PEO) as flexible coil. The Suzuki-coupling of the AB-type monomer 4-bromo-2,5-diheptylbenzeneboronic acid (1) under strictly proton-free conditions leads to the control of PPP endgroups and hence allows the synthesis of a variety of differently end-functionalized poly(p-phenylene)s. The poly(2,5-diheptyl-p-phenylene)-block-polystyrene (7) is then prepared via condensation via condensation of anionically polymerized living polystyrene ( 6 ) with α-(4-formylphenyl)-ω-phenyl-poly(2,5diheptyl-p-phenylene) ( 4 ). Toluenesulfonic acid catalyzed condensation of α-methyl-ω-amino-poly(oxyethylene) ( 8 ) with PPP 4 yields poly(2,5-diheptyl-p-phenylene)-block-poly(ethylene oxide) ( 9 ). 相似文献
5.
Thierry Granier Edwin L. Thomas David R. Gagnon Frank E. Karasz Robert W. Lenz 《Journal of Polymer Science.Polymer Physics》1986,24(12):2793-2804
Electron diffraction patterns of highly oriented poly(p-phenylene vinylene) films obtained by the soluble polymeric precursor route are interpreted on the basis of a monoclinic unit cell containing two monomer units: c (chain axis) = 0.658 nm, a = 0.790 nm, b = 0.605 nm, α ? 123°. The molecules are nearly perfectly oriented along the stretching direction but exhibit partial axial translational disorder. 相似文献
6.
M. Panar P. Avakian R. C. Blume K. H. Gardner T. D. Gierke H. H. Yang 《Journal of Polymer Science.Polymer Physics》1983,21(10):1955-1969
Fibers of poly(p-phenylene terephthalamide) (PPTA) have a fibrillar morphology, the individual fibrils having a high proportion of extended chains passing through periodic defect layers. A pleat structure is superimposed. The fibers are fully crystalline (within the limits of determination) with a small fraction of randomly oriented crystalline material. The major distinction between PPTA and conventional fibers lies in the high level of extended chains passing through the defect layers of the former structure. These extended chains result in crystallographic register being maintained between adjacent ordered zones. Quantitatively, a measure of this order is obtained from a comparison of the correlation length, obtained from meridional x-ray peak widths, and the defect spacing. In conventional fibers the defect spacing, i.e., long period, is longer than the correlation length (i.e., crystal size). In PPTA, the analog of the long period, the defect spacing (about 35 nm) is smaller than the correlation length, which is over 80 nm. 相似文献
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Marcus Remmers Margit Schulze Gerhard Wegner 《Macromolecular rapid communications》1996,17(4):239-252
The synthesis and properties of soluble, conjugated polymers consisting of oligo(p-phenylene) sequences linked by ethylene, vinylene, or ethylene, units are reported. Benzene-, stilbene-, diphenylacetylene- and 1,2-diphenylethane derivatives serve as monomers and are connected by the Suzuki-coupling method. A wide range of poly-(p-phenylene)-related polymers are available by the combination of different AA/BB-type monomers in various concentrations. The optical properties of the resulting polymers can therefore be tailored. Number-average degrees of polymerization of up to X̄n = 137 were reached under optimized conditions. Photoluminescence quantum yields of these materials in solution are nearly one. 相似文献
9.
Infrared spectroscopy has been used to determine the relative amount, location, and orientation of residual water and acid molecules in poly(p-phenylene benzobisthiazole) films. By analyzing the relative absorbance of reflected polarized infrared radiation from highly oriented films, the indices of refraction parallel and perpendicular to the chain axis were also obtained. 相似文献
10.
H. Mazurek D. R. Day E. W. Maby J. S. Abel S. D. Senturia M. S. Dresselhaus G. Dresselhaus 《Journal of Polymer Science.Polymer Physics》1983,21(4):537-551
Ion implantation of impurities into thin films of poly(p-phenylene sulfide) (PPS) is found to increase the conductivity of the material by up to 12 orders of magnitude. The increase is stable under exposure to ambient conditions, in contrast to the instability of the conductivity increases in PPS produced by chemical doping with AsF5. PPS films 0.1–0.2 μm thick are spin cast from solution onto interdigitated electrodes patterned on an oxidized silicon substrate. The room-temperature interelectrode resistance is measured as a function of implantation fluence. An estimate of film conductivity is obtained from this resistance with a simple model for the electrode and film geometry. A first experiment yielded similar conductivity increases for implantation of either arsenic or krypton. At a fluence of 1 × 1016cm?;2, which corresponds to an average impurity concentration of 2.5 × 1021cm?3, the conductivity reaches an apparently saturated value of 1.5 × 10?5 (Ω cm)?1. Infrared spectra of the films before and after implantation suggest that crosslinking may be present in the implanted films, and Auger studies show stoichiometric changes throughout the implanted layer. These results suggest that the observed conductivity changes are the result of molecular rearrangements produced by the implantation rather than the result of specific chemical doping. Specific chemical doping may, however, explain the results of a second experiment in which implantation of bromine resulted in substantially larger conductivities found to increase at an approximate linear rate from a value of 1.0 × 10?4 (Ω cm)?1 at a fluence of 1 × 1016 cm?2 to a value of 4.0 × 10?4 (Ω cm)?1 at a fluence of 3.16 × 1016 cm?2. 相似文献
11.
Wilfried Hatke Horst-Tore Land Hans-Werner Schmidt Walter Heitz 《Macromolecular rapid communications》1991,12(4):235-243
The substitution of poly(p-phenylene terephthalate) and poly(p-phenylene terephthalamide) with phenyl and biphenylyl substituents (4-biphenylyl and 2-biphenylyl) in the terephthalic acid unit lowers the melting temperatures and crystallization tendency and increases the solubility. The melting temperatures of the polyesters are in the range of 285–350°C. Melting of the polyamides occurs between 440–490°C. The polyamides begin to decompose in the same temperature range. In polyesters as well as in polyamides the 2-biphenylyl substituent was found to be more effective in decreasing the crystallinity, lowering the melt transition temperatures and increasing the solubility. 相似文献
12.
M. Campos E. M. Cavalcante J. Kalinowski 《Journal of Polymer Science.Polymer Physics》1996,34(4):623-629
The conductivity of poly(p-phenylene sulfide) (PPS) amorphous samples sandwiched between metallic electrodes has been studied as a function of applied voltage, temperature, and electrode material. The voltage (U) dependence of the currents for electric fields within the range 103–106 V/cm exhibits exp βU1/2 behavior with β = βSchottky below the glass transition temperature (Tg ≊ 90°C), and β = βPoole-Frenkel above Tg. Coordinated temperature measurements of dc currents with different metallic contacts and thermally stimulated currents (TSC) indicate, however, that the conductivity at T < Tg is consistent with the so-called “anomalous” Poole-Frenkel effect rather than the Schottky effect. Consequently, the p-type conductivity in amorphous PPS is proposed to be a bulk-limited process due to ionization of two different types of acceptor centers in the presence of neutral hole traps. © 1996 John Wiley & Sons, Inc. 相似文献
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《Chemical physics letters》1986,130(3):155-159
Ultraviolet photoelectron spectra were measured for films of poly(p-phenylene sulfide) (PPS) prepared by vacuum evaporation. The threshold ionization potential was determined to be 6.0 ± 0.1 eV. The peaks in the photoelectron spectra are assigned by comparison with theoretical calculations, and the π bandwidths of PPS and related compounds are discussed. 相似文献
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Methods are described for obtaining conformational and packing information about para-linked phenylene polymers from wide-angle X-ray scattering. On the basis of these procedures, together with conformational energy calculations, a random chain conformation is determined for non-crystalline poly(p-phenylene sulphide), in which the phenylene groups are rotated away from the coplanar position by 40° and the conformation persists for ~15 Å. Whilst there is no evidence for parallel chain packing at any level, it is necessary to invoke local pairwise correlation of phenylene groups within an otherwise random chain packing system, to obtain satisfactory agreement with the experimental results. 相似文献
16.
The effects of drawing temperature on the physical and mechanical properties of poly(p-phenylene sulfide) have been studied. A melt-quenched film was drawn by solid-state coextrusion both below (75°C) and above (95 and 110°C) the glass transition temperature Tg (85°C) of PPS. The maximum extrusion draw ratio (EDRmax) increased from 3.4 to 5.6 with increasing extrusion temperature Te from 75 to 110°C. It was found that extrusion drawing just above the Tg of PPS (95°C) produced more stress-induced crystals. A high efficiency of draw in the amorphous region was achieved by extrusion at Te-75°C. The tensile modulus at EDRmax decreased from 5.1 to 3.5 GPa with increasing Te from 75 to 110°C. The low efficiency of draw for the samples extruded at 110°C is explained in terms of disentanglement and chain slippage during drawing due to a less effective network. 相似文献
17.
E. P. Socci B. L. Farmer W. W. Adams 《Journal of Polymer Science.Polymer Physics》1993,31(13):1975-1982
We have studied the conformation and coefficient of thermal expansion in the poly(p-phenylene) oligomer p-sexiphenyl (C36H26) by molecular dynamics simulations. Studies of the backbone phenyl–phenyl torsion angle in a simulated p-sexiphenyl crystal at room temperature indicate the presence of torsional librations of approximately ±20°. Further analysis of the phenyl–phenyl backbone torsion angle in less closely packed regions of the simulated crystal (crystal ends) indicate the presence of 180° phenyl ring flips, in agreement with solid-state deuterium NMR data on poly(p-phenylene oligomers). The linear coefficient of thermal expansion was also calculated and found to be negative, in qualitative agreement with experimental data on rigid-rod compounds. © 1993 John Wiley & Sons, Inc. 相似文献
18.
Michael A. Masse Joseph B. Schlenoff Frank E. Karasz Edwin L. Thomas 《Journal of Polymer Science.Polymer Physics》1989,27(10):2045-2059
Poly(p-phenylene vinylene) (PPV) undergoes a first-order crystal-crystal phase transition when chemically doped with AsF5, SbF5, or H2SO4 or electrochemically oxidized with ClO-4 as the counterion. These structures have been observed using wide-angle x-ray diffraction. Doping with these agents does not disrupt the original orientation of the PPV crystallites. The crystalline phases obtained with all dopants employed here are similar in character, indicating a closely related family of electrically conductive structures having orthorhombic symmetry. An electrically conductive phase consisting of layers of polymer chains separated by a layer of the chemical dopant is proposed. 相似文献
19.
Ravindranath R Vijila C Ajikumar PK Hussain FS Ng KL Wang H Jin CS Knoll W Valiyaveettil S 《The journal of physical chemistry. B》2006,110(51):25958-25963
A homologous series of polyhydroxylated poly(p-phenylene)s with different alkoxy groups (C6PPPOH, C12PPPOH, and C18PPPOH) were synthesized with use of the Suzuki polycondensation reaction. Comparative studies of the structure correlation between their photophysical properties and film morphology is described. The absorption and emission spectra of polymers in solution and thin films showed similar features indicating that the electronic properties in solution were retained in the film state. Compared to the polymer with the short alkoxy chains (C6PPPOH), the polymers with long alkoxy groups (C12PPPOH and C18PPPOH) showed improved film forming properties with continuous and smooth film morphology. The absorption properties of the C12PPPOH showed an enhanced effective conjugation length and high quantum yield implying planarization of the backbone through alkoxy chain packing (C12H25O-) and potential hydrogen bonds. No overlap in the absorption and emission spectra was observed, which indicated minimized excimer formation or excitation energy transfer in the films. Time-resolved fluorescence measurements showed that the decay times increased from 43 ps (C6PPPOH) to 78 ps (C12PPPOH) and 99 ps (C18PPPOH). Electrochemical studies were performed for all polymers and the observed oxidation potential for C6PPPOH was higher than that of C12PPPOH and C18PPPOH. In addition, the C12PPPOH has the lowest band gap of DeltaE = 2.59 eV when compared to the 3.1 (C6PPPOH) and 2.61 eV (C18PPPOH) gaps. The optical band gaps estimated from the absorption onset of the polymers are significantly higher than those obtained from electrochemical data. C12PPPOH was chosen for investigating the charge carrier mobility by the time-of-flight (TOF) technique. The observed results also showed negative field dependent values of the drift mobility for the polymer C12PPPOH. 相似文献
20.
Akihiro Suzuki Takafumi Kohno Toshio Kunugi 《Journal of Polymer Science.Polymer Physics》1998,36(10):1731-1738
A zone-drawing and zone-annealing treatment was applied to poly(p-phenylene sulfide) fibers in order to improve their mechanical properties. The zone-drawing (ZD) was carried out at a drawing temperature of 90°C under an applied tension of 5.5 MPa, and the zone-annealing (ZA) was carried out at an annealing temperature of 220°C under 138.0 MPa. The differential scanning calorimetry (DSC) thermogram of the ZD fiber had a broad exothermic transition (Tc = 110°C) attributed to cold-crystallization and a melting endotherm peaking at 286°C. The Tc of the ZD fiber was lower than that (Tc = 128°C) of the undrawn fiber. In the temperature dependence of storage modulus (E′) for the ZD fiber, the E′ values decreased with increasing temperature, but increased slightly in the temperature range of 90–100°C, and decreased again. The slight increase in E′ was attributable to the additional increase in the crosslink density of the network, which was caused by strain-induced crystallization during measurement. The resulting ZA fiber had a draw ratio of 6.0, a degree of crystallinity of 38%, a tensile modulus of 8 GPa, and a tensile strength of 0.7 GPa. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1731–1738, 1998 相似文献