Polyacetylenes, crystallinity stability

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. 

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

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. 

Some years later the Penn Group [17] reported doping Shirakawa polyacetylene with the electron acceptors I2 or Br2, resulting in charge-transfer complexes with conductivities of 0.5-30 S cm . A comparison of the various types of polyacetylene [11] revealed some astonishing correlations conductivity was directly proportional to crystallinity and inversely proportional to the number of sp orbitals. This discovery was the key to the production of new polyacetylene types with fewer defects and greater stability. 

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