Polyacetylenes, crystallinity structure

Copolymers with longer polyene segments were found to be insoluble in the reaction solvent (toluene). In these materials, the polyacetylene fraction was crystalline (97). Copolymers with a low acetylene content were composed of a variety of isolated crystalline structures within an amorphous matrix, whereas those containing 50% or more polyacetylene had a morphology that resembled fibrillar polyacetylene. Dried copolymer solutions and suspensions gave blue films with the mechanical properties characteristic of the carrier polymer. No increase in environmental stability was observed. 

Conducting polymers such as polyacetylene, polypyrrole, polyaniline, polythiophene, etc. have been actively studied for use in various fields due to their interesting properties batteries,46 electrochromic displays,47 materials for supercapacitors,48 corrosion protection,49 protecting layers for static electricity,50 materials for organic electroluminescence displays,51 sensing materials,52 etc. Polypyrrole is reported to be extremely rigid, with a semi-crystalline structure. 

Optical properties are related to both the degree of crystallinity and the actual polymer structure. Most polymers do not possess color site units, so are colorless and transparent. But, some phenolic resins and polyacetylenes are colored, translucent, or opaque. Polymers that are transparent to visible light may be colored by the addition of colorants, and some become opaque as a result of the presence of additives such as fillers, stabilizers, moisture, and gases. 

Five aspects of the preparation of solids can be distinguished (i) preparation of a series of compounds in order to investigate a specific property, as exemplified by a series of perovskite oxides to examine their electrical properties or by a series of spinel ferrites to screen their magnetic properties (ii) preparation of unknown members of a structurally related class of solids to extend (or extrapolate) structure-property relations, as exemplified by the synthesis of layered chalcogenides and their intercalates or derivatives of TTF-TCNQ to study their superconductivity (iii) synthesis of a new class of compounds (e.g. sialons, (Si, Al)3(0, N)4, or doped polyacetylenes), with novel structural properties (iv) preparation of known solids of prescribed specifications (crystallinity, shape, purity, etc.) as in the case of crystals of Si, III-V compounds and... 

Polythiophene is a highly crystalline polymer with the chain analog to cis-polyacetylene. The sulfur atoms stabilize the structure and interacts poorly with... 

Table 26 shows X-ray diffraction data of polyacetylenes and those of polyethylenes for comparison. The ratios of half-height width to diffraction angle (A28/28) for the substituted polyacetylenes are all larger than 0.20. The value for amorphous polyethylene is similar to these values, while those of crystalline polyethylene and cis-polyacetylene89) are much smaller. Therefore, it is concluded that the present polymers are amorphous. This must be due to the presence of bulky substituents and/or the non-selective geometric structure of the main chain. 

As another example of a helical polyacetylene, the single-handed helical polyacetylene fibril, whose structure was studied by SEM, was prepared by the polymerization of acetylene within a chiral nematic liquid crystalline phase.192... 

Table 2 contains idealized structures of some CPs with typical dopants and values for the conductivities of thin films. The exact structures of PPy and poly thiophene (PT) are unknown. Polyacetylene is the most crystalline and PANi can exist in several oxidation states with electrical conductivities varying from 10 S/cm to the values reported in Table 2. In its undoped state, PPS is an engineering thermoplastic with a conductivity of less than 10 S/cm. Upon doping with ASF5, conductivities as high as 200S/cm have been obtained after casting a film from a solution of AsFsP ...

To a large extent, current interest in solid-state polymerization of monoacetylenes derives from the observation of interesting electrical, magnetic, and optical phenomena in polyacetylene, (CH)j (45), a pEutially crystalline material unstable to ambient conditions typically synthesized by Ziegler-Natta techniques. The fundamental study of (CH), and its electron-transferred ( doped ) forms has been retarded by the lack of fully ordered materials. Ftilly ordered polyacetylenes are also of interest because it is conceivable that their crystal structures could allow significant interchain interactions, a situation precluded in most PDA by side chains. 

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