Polydiacetylene chains

As we can see from the Table all the three chains (and this is the case also for further two other polyacetylene and three polydiacetylene chains (7) which also have been calculated) have broad valence and conduction bands with widths between 4.4 and 6.5 eV-s. Comparing the band structure of the two polyacetylene chains we can find that the position of the bands and their widths is not very strongly influenced by the different geometries. This is again the case if we compare the here not described band structures of the further polyacetylene and polydiacetylene chains. On the other hand the position of the valence and conduction bands and the widths of the valence bands of the polydiacetylene chains is more different from those of the polyacetylene chains. To conclude we can say that due to the broad valence and conduction bands of these systems (which mean rather large hole and electron mobilities,respectively) one can expect that if doped with electron acceptors or donors these systems will become good conductors, which is, as it is experimentally estab-... 

The method has been applied to polyene, polyacetylene and polydiacetylene chains, to formamide chains (both hydrogen-bonded and stacked). Applications have been done also to TCNQ and TTF stacks, to (SN) and to periodic DNA models (the four homopolynucleotides), to the sugar phosphate chain of DNA and to different periodic protein models (homopolypeptides). All these systems have relatively broad valence and conduction bands (bandwidths around or larger than 0.5eV) according to our results. 

Figure 1. Solid-state polymerization of diacetylenes shown schematically (left) an array of monomer molecules in the crystal lattice frightj the resulting polydiacetylene chain.

Figure 4. Temperature dependence of the intense optical absorption for polydiacetylene chains in their monomer matrices at typical concentrations of 1% all samples were crystalline.

In summary, it is well established that the species that initiates exothermic growth of a polydiacetylene chain is a diradical dimer. It can be generated thermally, the activation energy being determined by the energy of the librational motion required to temporarily shorten the C1-C4 reaction distance of a molecular pair to about 2 A, or by electronic excitation of the diacetylene moiety via UV- or y-irradiation. Upon UV-excitation the number of chains initiated is of order 10 per absorbed photon. The active precursor state is likely to be of triplet character. Even in case of optical... 

Table 4. Observed bond lengths of polydiacetylene chains and... 

Two different reaction mechanisms have been postulated for the topochemical polymerization of diacetylenes involving diradical or carbene chain ends The first mechanism leads to a butatriene structure (I), the latter to the acetylene structure (II) of polydiacetylene chains. 

Within these limits the polydiacetylene chain seems to be best represented by the acetylene structure (II). This is especially true for those polymers (PTS, HDU-1, THD) which are obtained thermally under mild conditions. In the other cases devia-... 

Resonant raman spectroscopy has proved to be another valuable tool for the study of the structure of the polydiacetylene chain. Due to the resonance enhancement the spectra are compared to greatly simplified, infrared spectra and show as principle feature only the in-plane modes of the polymer chain. The correlation of the CsC and C = C stretching modes and their temperature dependence have been interpreted as resonances between the mesomeric structures (I) and (II) i32) Hoy(rever, a model using simple anharmonic force constants for the acetylene structure (II) is in good agreement with the experiment, e.g, the temperature and pressure dependence of the vibration frequency and the mechanical properties... 

Two models for the shape of the polydiacetylene chain in solution are schematically presented in Fig. 30. 

Fig. 30. Schematic representation of the shape of polydiacetylene chains. Top planar, fully conjugated chain, middle Kuhn model, bottom woim-like chain...

In conclusion it must be admitted that the spectral changes of polydiacetylene chains in various environments, which are intimately coupled to the electronic structure of the backbone, are still not fully understood and remain one of the unsolved problems in this field. 

Figure 4. Principal triplet and singlet bipolaron configurations of the polydiacetylene chain.

The possibility of ultrahigh electron mobility on polydiacetylene chains was discussed by Wilson" The carrier velocity was estimated to be 2.2 x 10 m s" which was greater than the mobility of any conventional semiconductor. The results were explained in relation to a solitary wave acoustic polaron characteristic of a one dimensional Ti-electron system. 

Fig.29 A STM image (27.1 nmx27.1 nm) of a monolayer of TTA-DIA after 30 minutes of UV light irradiation. A pulse (height - 3.2 V, width 500 ns) was applied at the position indicated with a white arrow. B STM image (27.1 nmx27.1 nm) of the monolayer of TTA-DIA at the same area after application of a single pulse. The white arrow in the image indicates the polydiacetylene backbone created by pulsing. C Molecular model of a 2D nanostructure formed by the covalent connection of adjacent parallel polydiacetylene chains. (Reproduced with permission from [89])...

Fig. 5.15 The formation of mechanism of the helical PDA(polydiacetylene) chain in the Lcoi liquid crystal state. Reproduced from Ref. [76] by permission of The Royal Society of Chemistry...

Lapersoime-Meyer, G. 2001. Excitons on a ID periodic conjugated polymer chain Two electronic structures of polydiacetylene chains. Int J Mod Phys 15 28. 

Horvath, A., G. Weiser, C. Lapersonne-Meyer, M. Schott, and S. SpagnoH. 1996. Wannier exdtons and Franz-Keldysh effect of polydiacetylene chains diluted in their single crystal monomer matrix. Phys Rev B 53 13507-13514. 

In 1987 Ovchinnikov et al. announced the discovery of the first ferromagnetic organic polymer based on polydiacetylene chain with dangling nitroxyl radicals [8,9]. The compound was obtained by bulk polymerization of stable paramagnetic biradical BlPO initiated by light. The chemical structure of this compound is shown below. 

Jacquemin, Champagne and Hattig " have investigated the longitudinal component of the frequency-dependent /8-polarizability for small polydiacetylene chains containing terminal amino and nitro donor and acceptor groups. The computations have been carried out at the Hartree-Fock, MP2, MP4 and Coupled Cluster levels and frequency-dependent CC results have been used to test the efficiency of additive and multiplicative corrections to approximate the frequency-dependent correlated values. The multiplicative corrections are found to reproduce the CC values to within a few percent while the additive correction underestimates the values by about 20%. 

Figure 11 (Left) Scheme of the polymerized bilayer assembly. The blue phase polydiyacetylene chromatic detection element is deposited over a support monolayer. The polydiacetylene chain Is asymmetrically substituted with urethane side groups partially terminated with receptor-binding ligands. (Right) Absorption spectrum of the blue and red phase PDA with a schematic representation of their chain with (red phase) and without (blue phase) influenza virus attached. Adapted figures with permission from D.H. Charych, J.O. Nagy, W. Spevak, and M.D. Bednarski, Sc/ence 261, 585 (1993), Figure 2 and 3. Copyright 1993 AAAS.

FIGURE 15 Comparison of the probability densities of the p radical electron distribution in trans-polyacetylene and in polydiacetylenes with finite chain length. Due to the non-degeneracy of the butatriene and acetylene structure the p -radical electrons are localized at the ends of the polydiacetylene chains. 

Therefore the radical electrons are forced to the ends of the polydiacetylene chains. Consequently the shape of the radical electron wavefunction is predominantely determined by e and the boundary conditions. 

TEIE ULTRA HIGH ELECTRON M3BILITT ON POLYDIACETYLENE CHAINS - THE THEORY... 

The low field nobility of a charge carrier on a polydiacetylene chain is ultra high, and yet the drift velocity saturates at a low vaiue comparable to the sound velocity Conventional ideas applicable to conventional semiconductors cannot eiqplain these phenomena The motion is that of a Solitary Wave Acoustic Polaron (SWAP) The SWAP is characteristic of a one dimensional system The properties of the SWAP are described ... 

Donovan, K.J., Freeman, P.D. and Wilson, E.G., The Ultra High Electron Hobility on Polydiacetylene Chains the Facts, previous article. 

This approach is illustrated in Fig. 1 for the solid state pol nnerization of an array of diacetylene monomers to produce a polydiacetylene chain. The parameter 6 is calculated for backbone associated carbon atoms as a function of the packing parameters d and which are defined in Fig. 1. 

The per chain modulus of this pol3nner is about equal to that of diamond in the [110] direction. A polyethylene fiber with the same per chain mechanical properties would have an ultimate tensile strength in excess of one million psi. The theoretical modulus calculated for a defect free polydiacetylene chain using a spectroscopic force field is within 10% of the observed modulus. This contrasts with the case for conventional polymers, where the bulk tensile modulus is typically much less than 50% of the theoretical (spectroscopic) modulus. 

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