Conjugated polymers, bonding

CH = CH — CH = CH — are said to have conjugated double bonds and react somewhat differently from the other diolefins. For instance, bromine or hydrogen is often added so that a product of the type -CHBr-CH=CH-CHBr- is formed. Also, these hydrocarbons participate in the Diels-Alder reaction see diene reactions). They show a tendency to form rubber-like polymers. Hydrocarbons not falling into these two classes are said to have isolated double... 

In addition to thermal polymerization, it is possible to polymerize CPD with inorganic haUdes as catalyst. With trichloroacetic acid as the catalyst, deeply colored, blue polymers that conduct electricity in nonpolar solvents such as benzene in the presence of acid can be obtained. The conductivity and color are caused by blocks of conjugated double bonds present in the polymers (20—21). 

Polymers, large molecules made up of smaller molecules in a repeating pattern, are used for many electrochromic materials. Conjugating polymers, which have alternating single and double bonds, are particularly suitable. Figure B shows the electrochemical oxidation of the conjugated polymer, polythiophene. Oxidation (in which electrons are removed) produces a semiconductive polymer. The neutral (unoxidized) polythiophene is red in color, whereas the semiconductive polythiophene (oxidized) is blue. In their neutral... 

Cesca, S., Priola, A. and Bruzzone, M. Synthesis and Modification of Polymers Containing a System of Conjugated Double Bonds. Vol. 32, pp. 1—67. 

Note Added in Proof This is nicely illustrated by the landmark publication of Protasiewicz et al. [94] who describe derivative (122), the first conjugated polymers featuring phosphorus-phosphorus multiple bonds (Scheme 33). The di-phosphene-PPV (122) exhibits an extended 71-conjugated system as shown by the optical HOMO-LUMO gap that is close to that of related PPV [94]. 

A.P. Monkman, L.-O. Palsson, R.W.T. Higgins, C. Wang, M.R. Bryce, A.S. Batsanov, and J.A.K. Howard, Protonation and subsequent intramolecular hydrogen bonding as a method to control chain structure and tune luminescence in heteroatomic conjugated polymers, J. Am. Chem. Soc., 124 6049-6055, 2002. 

It is quite brittle and is insoluble, because of the right nature of the Polymer chain that is caused by the presence of aromatic rings linked together through parapositions. It can withstand temperatures even up to 560°C. This property is attributed to the presence of resonance-stabilised conjugated double bonds in the aromatic rings. 

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