Conductivity and dielectric properties of the monomer and polymer of the bis(p-toluene sulfonate) of 2,4-hexadiyne-1,6-diol

The electrical conductivity of single crystals of the bis(p-toluene sulfonate) of 2,4-hexadiyne-1,6-diol (TS) and its polymer (PTS) was measured in a temperature range 77–373 K (to 353 K for TS), dielectric properties were measured from 123 to 283 K. Anomalies of the conductivity and the real part of the complex dielectric permittivity of TS and PTS along the molecular stacking direction at the temperature corresponding to the low-temperature phase transitions were observed. The dependence of phase transitions on the polymerization conversion of the monomer TS was examined. The phase diagram of the TS-PTS mixed system was constructed.     

Solid-state thermal polymerization of 2,4-hexadiyne-1,6-diol

The solid-state thermal polymerization of 2,4-hexadiyne-1, 6-diol has been studied by a variety of methods. Pure monomer heated under vacuum or in an inert gas atmosphere is found to polymerize readily, unlike material heated in air. X-ray diffraction reveals that samples anneal during polymerization. Initially, a long chain polymer is formed, but above 20% conversion a less perfect product is obtained. Measurements suggest a complex molecular rearrangement during the nonideal phase of polymerization. Possible models for this process are discussed.     

An ESCA-study of solid 2,4-hexadiyne-1,6-diol bis(toluenesulfonate) and its constituents before and after polymerization

ESCA spectra of 2,4 hexadiyne-1,6-diol, toluenesulfonic acid and 2,4-hexadiyne-1,6-diol bis(toluenesulfonate) in monomeric and polymeric form are reported. It is shown that in the energy range of predicted deeper valence states of the polymer carbon chain the spectrum is dominated by the phenyl ring- and SO₂O-orbitals. Upon in situ-polymerization a deep valence band, 42 eV below vacuum, is formed and the highest monomer-π-orbitals constitute a 5 eV wide valence band. The ionization energy is 7 ± 1 eV.     

Observation of paramagnetic triplet species during the thermal polymerization of bis(p-toluene sulphonate) of 2,4-hexadiyne-1,6-diol

ESR observations of single crystals of bis(p-toluene sulphonate) of 2,4-hexadiyne-1,6-diol during solid state thermal polymerization at 60°C reveal spectra characteristic of paramagnetic triplet species. One centre has large values of the fine structure tensor and maximum intensity at maximum polymerization rate. The other has small fine structure values and anneals out slowly after the period of rapid polymerization. The nature of these centres is discussed.     

The solid-state thermal polymerization of bis(p-toluene sulphonate) of 2,4-hexadiyne-1,6-diol. III. An ESR study

Electron spin resonance (ESR) observations of the solid-state thermal polymerization of bis(p-toluene sulphonate) of 2,4-hexadiyne-1, 6-diol at 60°C, 70°C, and 80°C are reported. The weak paramagnetism observed in polycrystalline samples is interpreted in terms of departures of the polymer chain from an equilibrium conformation. Decomposition occurs at 70°C and 80°C during the final phase of polymerization producing additional paramagnetic centers. Lineshape parameters measured during polymerization show changes which we attribute to changes in the delocalization and mobility of the paramagnetic center. We conclude that the nature of paramagnetism in crystalline conjugated diacetylene polymers is a chain defect property characteristic of interband electronic states close to the valence band.     

Carbon nanotube/poly(2,4-hexadiyne-1,6-diol) nanocomposites prepared with the aid of supercritical CO2

Poly(2,4-hexadiyne-1,6-diol)(poly(HDiD)) was coated on the outer walls of carbon nanotubes (CNTs) with the aid of supercritical CO(2), resulting in poly(HDiD)/CNT nanocomposites, which possess optical properties originated from poly(HDiD).     

The solid-state polymerization and physical properties of bis(ethyl urethane) of 2,4-hexadiyne-1,6-diol. II. Resonance Raman spectroscopy

Resonance Raman spectroscopy has been used to measure the frequencies of the vibrational modes of the polymer backbone of fully and partially polymerized crystals of an ethyl urethane diacetylene. The data have assisted in the assignment of crystallographic structures to the different modifications of the crystals. Effective interatomic force constants have been derived and used to estimate the Young's modulus. For fully polymerized crystals a value of approximately 76 GPa was found. The dependence of the frequencies on elastic tensile strain parallel to the polymer chain direction was determined. By comparing the strain dependence of frequencies of partially polymerized singlecrystal fibers with those expected for model composites, it was concluded that the polymer chains in thermally polymerized crystals are considerably longer than in those polymerized using γ rays.     

The role of dislocations in the solid-state polymerization of monomers having conjugated triple bonds: A study of 2,4-hexadiyne-1,6-diol bis(p-toluene sulfonate)

The crystal structure of the monomer bis(p-toluene sulfonate) ester of 2,4-hexadiyne-1,6-diol (pT) is conducive from the viewpoint of both the separation distances and molecular configuration, to polymerization, irrespective of whether initiation is thermal, photochemical, or mechanical. The dislocations present in the monomer and polymer structures have been characterized by employing optical microscopic techniques. The slip system (102)[010] is found to be present in both monomer and polymer crystals but the (010)[001] system is found only in the monomer. On this basis a crystal structure for the monomer is proposed based on existing crystallographic information relating to the structure of the polymer. Dislocations are thought, on energetic grounds, to facilitate nucleation of product in the thermal polymerization but have no observable influence on the photoinduced reaction which proceeds homogeneously through the bulk.     

Studies on partially polymerized 2,4-hexadiyn-1,6-bis(p-toluenesulfonate)

An improved procedure for the synthesis of high-purity 2,4-hexadiyn-1,6-bis(p-toluenesulfonate) (PTS) is described. The melting point of partially polymerized PTS increases monotonically with increasing polymer conversion (<12%). The increase in melting point is due to formation of a solid solution of unreacted monomer and polymer chains. The relation between the melting point and polymer conversion can be used for determination of polymer conversion. The low-conversion (<12%) poly PTS is soluble in dimethylformamide. The solution is yellow (λ_max ? 450 nm) and does not undergo a color change when the temperature is lowered or a nonsolvent is added. Gel permeation chromatography (GPC) studies show that the molecular weight distribution of poly PTS is very broad and does not change with increasing polymer conversion up to <12%. The degree of polymerization for the low-conversion polyPTS is very low, about 20 repeat units. The G value for initiation centers (radicals) is about 2. The properties of the low-conversion partially polymerized PTS are compared with the corresponding properties of poly(diacetylene diurethanes).     

Structural evidence for an incommensurable modulated structure in single crystals of bis-p-toluene sulphonate of 2,4-hexadiyne-1,6-diol

X-ray scattering from monomer crystals of bis-p-toluene sulphonate (PTS) diacetylene at low temperatures reveal the existence, between 206 K and 163 K, of an incommensurable modulated structure, just above the already reported low temperature superstructure.     

A highly conductive and crystalline graphite-like polymer from 2,4-hexadiyn-1,6-diol

Poly-(2,4-hexadiyn-1,6-diol) (PHDO), prepared by NbCl₅/(n-Bu)₄Sn catalyzed metathesis of HDO, was pyrolyzed at various temperatures and electrical and structural properties of resulting polymers were investigated by FT-IR, Laser Raman, CP/MAS ¹³C-NMR and X-ray diffraction methods. The polymer obtained by pyrolysis of PHDO at 800°C showed a conductivity of about 10 S/cm at room temperature. The structure of the polymer seems to be a graphite-like crystal consisting of condensed aromatic layers. © 1994 John Wiley & Sons, Inc.     

The mass spectral rearrangements of 1,6-bis(arylsulfenyl)-2,4-hexadiynes and 1,6-bis(arylsulfonyl)-2,4-hexadiynes

The mass spectral. behavior of 1,6-bis(arylsulfenyl)-2,4-hexadiynes and 1,6-bis(arylsulfonyl)-2,4-hexadiynes were examined. The sulfenyl derivatives extruded the hexadiynyl moiety with the formation of Ar? S? S? Ar fragments. The sulfonyl derivatives, on the other hand, showed no extrusion of the hexadiyne fragment but an expulsion of SO₂ and even two SO₂ units.     

Solid-state polymerization of a diacetylene crystal: Thermal,ultraviolet, and γ-ray polymerization of 2,4-hexadiyne-1,6-diol bis-(p-toluene sulfonate)

Results are presented for the thermal, ultraviolet, and γ-ray polymerization of 2,4-hexadiyne-1,6-diol bis-(p-toluene sulfonate) (PTS). Monomer extraction is used to obtain polymer conversion-vs.-time curves at 30, 50, and 80°C. In agreement with previous work over a narrower temperature range, the curves all display a dramatic autocatalytic effect with an onset at about 10% conversion to polymer. Although the polymerization rate undergoes a 200-fold change over this temperature range, the shape of the conversion curves does not change. These data yield an activation energy (E) of 22.2 ± 0.4 kcal/mole when interpreted in terms of the time required to reach 50% polymer. An annealing technique is used to provide a closer look at the autocatalytic region. In that case, E = 22.5 ± 0.8 kcal/mole is determined from measurements of the time required to go from 10 to 50% polymer at temperatures ranging from 23 to 80°C (a 500-fold change in rate). Thermal polymerization rates measured in the low-conversion limit using a spectroscopic method based on diffuse reflectance yield E = 22.8 ± 0.6 kcal/mole. Thus E is independent of polymer conversion and the autocatalytic effect can be best understood as arising from a large increase in the propagation length of the polymer chains. The autocatalytic effect is shown to be present in both UV and γ-ray polymerization. In the case of γ-ray polymerization, conversion-vs.-time and spectroscopic measurements are consistent with inhomogeneities in the polymer concentration caused by particle tracks. Activation energies for UV and γ-ray polymerization are quite low (2-3 kcal/mole) and confirm that the chain initiation event makes the major energetic contribution to E. The polymerization mechanism is discussed in detail. The photopolymerization experiments can be consistently interpreted with a model based on the triplet excited state of the diacetylene monomer as the chain initiation species.     

A differential scanning calorimeter study of the crystal forms and polymerization kinetics of 2,4-hexadiynyl-1,6-bis(p-toluenesulfonate)

The thermal properties of 2,4-hexadiynyl-1,6-bis(p-toluenesulfonate) have been explored by program temperature and isothermal differential calorimetry. The heat of fusion for the rapidly heated pure solid was 8254 cal/mole (34,540 J/mole) at 367.1°K (93.8°C). This amounts to an entropy change of 22.5 cal/mole °K (94.1 J/mole °K). The energy of activation for the thermal polymerizations was 18.97 kcal/mole (79.37 kJ/mole). The thermal polymerization appears to follow a solid–solid phase transition which proceeds by random homogeneous nucleation throughout the process. The kinetics were simple first order over 70% of the reaction. Programmed temperature studies indicate that during the first 10% of the polymerization a new high temperature (mp 375.4°K) solid phase is formed which acts as the monomer form during the bulk of the reaction.     

Wheel-and-axle design as a source of host-guest compounds. The crystal structure of the 2:1 acetone: tetraphenyl-2,4-hexadiyne-1,6-diol complex

The title diyne-diol crystallizes with an “open” structure containing channels, roughly parallel to the long axis of the host, in which the acetone is hydrogen bonded to the anti-oriented hydroxyl groups.     

Mass spectral study of the pyrolysis of tetrakis(trifluoromethyl)allene

Low-energy mass spectrometry and chromato-mass spectrometry have been used to show that major final products of the pyrolysis of tetrakis (trifluoromethyl) allene (TTA) are perfluoro-1,3-cyclopentadiene and hexafluoroethane, formed as a result of the thermal loss of two trifluoromethyl radicals. This indicates the lack of an interaction of the trifluoromethyl substituents with the cumulene bond-electrons.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2655–2657, November, 1990.