Methylene chain defects, temperature

It is well-known that the occurrence of chain defects, in the form of for example small methylene sidegroups, could reduce this Tm-value [4J. This offered the possibility to reduce the relative high processing temperature of PK copolymers. The effect of addition of small amounts of propylene to the carbon monoxide/ ethylene mixture on the Tm-value is shown in Figure 9.1. A nearly linear decrease of the Tm-value as a function of the weight percentage of C3 was found for propylene concentrations between 0 and about 15 %wt. i.e. for the Tm-value holds ... 

Since the polaron resonance is also observed in dilute methylene dichloride solutions, one may be tempted to assign it to intrachain polaron recombination. Yet this assignment may be incorrect on two counts (i) it is not clear that the polymer chains ate completely separated from each other by the solvent (ii) even if the chains are tnily isolated by the solvent, confonnational defects, typically kinks, may generate interconjugation-segment polaron pairs, which are dynamically similar to interchain pairs [30,49]. Indeed, it should be noted that toluene solutions of P3HT did not yield any ODMR, and in CCI4 solutions the polaron resonance decayed below the noise level after 488 nm photoexcitation at room temperature for a few minutes [23,59.73]. This clearly demonstrates that the polaron resonance is sensitive to the interaction between the polymer and the solvent, and may possibly involve its effect on chain separation and/or formation of kinks in the chains. 

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