Polydiacetylenes polymerization

Finally, synthetic metals made of polymeric organic molecules may also show the property of ferromagnetism. Organic materials of this kind were first demonstrated in 1987 by Ovchinnikov and his co-workers at the Institute of Chemical Physics in Moscow. The polymer they used was based on a polydiacetylene backbone, which contains alternating double-single and triple-single bonds between the carbon atoms of the molecule (10.2). 

It is also shown that the electron-phonon interaction is operative in the polymerization process of the one-dimensional conjugated polymeric crystals a simple dynamical model for the polymerisation in polydiacetylenes is presented that accounts for the existing observations. 

The solid-state polymerization of diacetylenes is an example of a lattice-controlled solid-state reaction. Polydiacetylenes are synthesized via a 1,4-addition reaction of monomer crystals of the form R-C=C-CeC-R. The polymer backbone has a planar, fully conjugated structure. The electronic structure is essentially one dimensional with a lowest-energy optical transition of typically 16 000 cm-l. The polydiacetylenes are unique among organic polymers in that they may be obtained as large-dimension single crystals. 

We first discuss the materials research which includes monomer synthesis, growth of monomer crystalline structures and polymerization in the solid state, yielding the requisite polymer structures. Next, the nonlinear optical experimental research is discussed which includes a novel experimental technique to measure x (w). Linear and nonlinear optical data obtained for the polydiacetylene films is subsequently presented. Detailed theoretical analysis relating the data to x (< >) and subsequently to its molecular basis will be discussed in a later publication. 

The two-step process of epitaxial polymerization has been applied to symmetrically substituted diacetylenes First, the monomers have been crystallized epitaxially on alkali halides substrates from solution and the vapor phase. The oriented monomer crystals are then polymerized under the substrate s influence by gamma-irradiation. The diacetylenes in this study are 2,4-hexadiyn-l,6-diol (HD) and the bis-phenylurethane of 5,7-dodecadiyn-l,12-diol (TCDU). The polydiacetylene crystal structures and morphologies have been examined with the electron microscope. Reactivity and polymorphism are found to be controlled by the substrate. 

The urethane-substituted polydiacetylenes exhibit thermo-chromic transition with low and high temperature crystal phases favoring acetylenic and butatriene backbone, respectively (4-6). Our interest in the application of epitaxial polymerization to diacetylenes has been the possibility of substrate control over orientation, structure, and the single crystal nature of thin films. 

The polymerization of the butadiene monomers (3,4) can also be followed spectroscopically by the disappearance of the strong absorption of the monomers at 260 nm, whereas the absorption of the resulting poly-1,4-trans(butadiene)s is too small to be observed in a single monolayer. The polymers from the butadiene and methacryloyl lipids are probably better model membrane systems, because the polymer chains are still mobile and not excessively rigid as the polydiacetylenes. 

Fig. 8 (top) Liposome with polydiacetylene linked monolayer mixed with ligand for receptor detection. (bottom) Colorimetric detection of influenza virus using polymerized liposomes to which have been added increasing amounts of influenza virus from left to right. [18]... 

Polydiacetylenes are obtained as single crystals by topochemical solid-state polymerization of the monomer single crystal. These compounds have received considerable attention because of their one-dimensionally -conjugated structure. Their unique --electron structures, and therefore superior third-order nonlinear optical properties, have been extensively investigated. 

Hayamizu and coworkers53 reported the polymerization of the octatetrayne monomer 15,17,19,21-hexatriacontatetrayne (HTY) (95) to the polydiacetylene 96 with butadiynyl substituents (R = H) as presented in Figure 35 as an example. 

Figure 12.7 Photographs of electrospun fiber mats embedded with 1 (a) before and (b) after 254-nm UV irradiation (1 mW/cm ) for 3 min. (c) Scanning electron microscopy image of the microfibers containing polymerized 1. (c) Photographs of the polydiacetylene-embedded electrospun fiber mats prepared with various diacetylene monomers after exposure to organic solvent. Reprinted fi om Yoon et al. (2007). Copyright 2007 American Chemical Society. (See color insert.)...

Fig. 5 /d-Tds characteristics for polydiacetylene monolayers, assembled and polymerized on the air-water interface (inset) and transferred to form bottom-contact, bottom-gate p-type FETs... 

LB films have also been prepared from simple (20, for example) [165] and functionalized (21, for example) [166] amphiphatic diacetylenes. Two different approaches were pursued. In the first approach, diacetylenes were polymerized as monolayers and subsequently transferred to substrates to generate LB films. In the second approach, LB films were formed from monomeric diacetylenes and were subsequently polymerized. Strong absorption of polydiacetylenes in... 

Crystalline polydiacetylenes, exhibiting a fully conjugated backbone, can be obtained [113] by thermal or photochemical polymerization of the monomer R C=C C=C R, where R is the organic substituent. The polymeric structures of the type... 

Polyenes and polydiacetylenes 216 Organic superconductors 225 Polymeric semiconducting devices 226... 

Polydiacetylenes are produced by the solid-state polymerization of single crystalline diacetylenes of the form RC=C—C=CR by 1,4-addition (see Fig. 32). The fully conjugated backbone of the polydiacetylenes is a model quasi one-dimensional electronic system being capable of representation by two extremes of bonding, sequence (a) an acetylene structure -fRC—C=C—CR)- and sequence (b) a butatriene structure -fRC=C=C=CR)-A,. There is great current debate as to the best method of representation but, in line with the belief that the nature of the side groups affect the bond lengths (and hence the... 

Any theoretical approach to conduction in polydiacetylene crystals should therefore be capable of explaining these observations (especially 2), and should permit differentiation between the band and excitonic pictures. Numerous optical studies on fully and partially polymerized samples have revealed the following additional phenomena (see for example Bloor et al., 1974, 1976a, b Reimer et al., 1976). 

Polymer industries depend on the spontaneous polymerization of molecules into chains in response to an appropriate trigger. Polymerization reaction under STM was first observed by Grim et al., although the reaction itself was not induced with a current from the tunneling probe [37]. Recently, by using an STM tip, Okawa and Aono have successfully initiated and terminated the linear propagation of the chain polymerization of a diacetylene compound into a polydiacetylene compound at any chosen point with a spatial precision of about 1 nm [38]. 

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