Polyacetylene-polybutadiene

The Influence of Microstructure on the Properties of Polyacetylene/Polybutadiene Blends... 

In this paper, we explore the morphological features of polyacetylene/polybutadiene (PA/PB) blends in detail via electron microscopic techniques. We have also extended our original study of stress induced property enhancement in blends with polyacetylene compositions in the 40-60% range (Blend paper 1, ref. 5). 

Table 1. Electrical Conductivity of Polyacetylene/Polybutadiene Blends as a Function of Blend Composition and Mechanical Treatment.

Polyhydrocarbon C-H, tertiary carbon or carbon a to the double bond Polyethylene, polyacetylene, polybutadiene, etc. 

Another widely used approach is the in situ polymerization of an intractable polymer such as polypyrrole onto a polymer matrix with some degree of processibil-ity. Bjorklund [30] reported the formation of polypyrrole on methylcellulose and studied the kinetics of the in situ polymerization. Likewise, Gregory et al. [31] reported that conductive fabrics can be prepared by the in situ polymerization of either pyrrole or aniline onto textile substrates. The fabrics obtained by this process maintain the mechanical properties of the substrate and have reasonable surface conductivities. In situ polymerization of acetylene within swollen matrices such as polyethylene, polybutadiene, block copolymers of styrene and diene, and ethylene-propylene-diene terpolymers have also been investigated [32,33]. For example, when a stretched polyacetylene-polybutadiene composite prepared by this approach was iodine-doped, it had a conductivity of around 575 S/cm and excellent environmental stability due to the encapsulation of the ICP [34]. Likewise, composites of polypyrrole and polythiophene prepared by in situ polymerization in matrices such as poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidine chloride-( o-trifluoroethylene), and brominated poly(vi-nyl carbazole) have also been reported. The conductivity of these composites can reach up to 60 S/cm when they are doped with appropriate species [10]. 

There are several approaches to the preparation of multicomponent materials, and the method utilized depends largely on the nature of the conductor used. In the case of polyacetylene blends, in situ polymerization of acetylene into a polymeric matrix has been a successful technique. A film of the matrix polymer is initially swelled in a solution of a typical Ziegler-Natta type initiator and, after washing, the impregnated swollen matrix is exposed to acetylene gas. Polymerization occurs as acetylene diffuses into the membrane. The composite material is then oxidatively doped to form a conductor. Low density polyethylene (136,137) and polybutadiene (138) have both been used in this manner. 

Another exciting developing field is in material science. Chlorination and bromination of fullerenes (refs. 18,19) and solid state bromination of polyacetylenes (refs. 20,21) and of polybutadienes (ref. 22) are typical examples. 

Typical examples of HCP are hydroxy-terminated polybutadiene (HTPB), car-boxy-terminated polybutadiene (CTPB), hydroxy-terminated polyether (HTPE), hydroxy-terminated polyester (HTPS), and hydroxy-terminated polyacetylene (HTPA). The physicochemical properties of various types of HCP are described in Section 4.2.3. 

Indicate cycloolefin monomers that will be polymerised by metathesis catalysts to polymers with a structure equivalent to polybutadiene, an alternating ethylene/ butadiene copolymer, an alternating butadiene / isoprene copolymer and polyacetylene. 

Pleated sheet conformation, 30,31 PLEDs (polymeric light-emitting diodes), 218 Plexiglas, 62 Plunkett, Roy, 65-66 PMMA. See Poly(methyl methacrylate) Polartec (Polar Fleece), 194 Poly(6-aminohexanoic acid), 25 Poly(a methyl styrene), 20 Polyacetylene, 72, 73 Polyacrylamide, 20 Polyamides, 22, 28, 61, 146 biodegradable, 185 Polyaramids, 77, 86 Polybutadiene, 70,109,148,155 Poly butyl acrylate), 20 Poly(butylene isophthalate), 25 Polycaprolactam, 21 Polycarbonate (PC), 17, 48, 86, 140 biodegradable, 185 density of, 247 impact strength of, 143 permeability of, 163 Polychloroprene, 65 Polycondensation, 85, 90-91 interfacial, 91-92... 

As in any other chemical compound, different geometrical arrangements of substituent groups are possible in a polymer where rigid molecular units are involved. This gives rise to trans- and cis-configurational isomerism in polymers containing double bonds in their repeat units, as in polyacetylene and natural and synthetic rubbers. The structures of the trans- and m-isomers of polyacetylene and polybutadiene are illustrated in Fig. 1.8. 

Polyacetylene 1,622 as conducting agent 622 Polybutadiene binders see Binders in composite propellants Polybutadiene binders with carboxylic function 602.60S... 

The mechanical and electrical properties of polyacetylene (PA) were modified by blending it with polybutadiene (PB). Further enhancement of the electrical conductivity of the blends was obtained by stretch elongation of the blends prior to doping. 

A structural model, based on a complex process of stretch induced ordering in the polyacetylene domains, was proposed to account for these observations. Support for this model was obtained using electron microscopic techniques. Low polyacetylene content blends (<20% PA) were found to consist of discrete polyacetylene domains dispersed in a continuous polybutadiene matrix. In the high polyacetylene content blends (>70% PA), both phases were simultaneously continuous, forming an interpenetrating network structure. Blends with intermediate compositions consist of both continuous and isolated domains of polyacetylene distributed throughout the polybutadiene matrix. 

When acetylene gas is polymerized in a solid solution of the Shirakawa catalyst and polybutadiene, a heterogenous blend consisting of a amorphous polybutadiene phase and a crystalline polyacetylene phase is formed. (5) The mechanical and electrical properties of this composite are critically dependent on the composition of the blend components and on their relative arrangement. In our initial Blend paper, (5) for example, we showed that the mechanical properties of PA/PB blends are a function of the blend composition, with low polyacetylene compositions ex-... 

Both of these interpretations are clearly supported by scanning electron microscopy studies of extracted PA/PB blends. For example, Figure 1 shows a sequence of micrographs of a low polyacetylene content blend (<20% PA) extracted for different times with toluene. Figure 1(a) shows the surface texture of a typical unextracted PA/PB blend. The surface exhibits features characteristic of polybutadiene cast from a toluene solution. 

Blending of polyacetylene with polybutadiene provides an avenue for property enhancement as well as new approaches to structural studies. As the composition of the polyacetylene component is increased, an interpenetrating network of the polymer in the polybutadiene matrix evolves from a particulate distribution. The mechanical and electrical properties of these blends are very sensitive to the composition and the nature of the microstructure. The microstructure and the resulting electrical properties can be further influenced by stress induced ordering subsequent to doping. This effect is most dramatic for blends of intermediate composition. The properties of the blend both prior and subsequent to stretching are explained in terms of a proposed structural model. Direct evidence for this model has been provided in this paper based upon scanning and transmission electron microscopy. 

Linear or cyclic oligomers containing some conjugated double bonds can be obtained from allene or its superior homologs, eventually in the presence of 1,3-butadiene or acetylene (in the latter case co-oligomers result)5. Transition metal complexes, in particular low-valence complexes of Group VIII elements, were found to be the best catalysts. Dehydrogenation reactions, carried out on cis-1,4- or tram-1,4-polybutadiene and in the presence of chloranil, quantitatively yielded polyacetylene within 8—15 hours at 130 °C6. ... 

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