Extrinsic instability

Polythiophenes in the neutral state are stable in the dark under atmospheric conditions but the conductivity of doped polythiophene and poly(3-alkylthiophene)s decreases rapidly. This lack of stability is one of the major barriers to industrial application of polythiophenes as conductive materials. Extrinsic and intrinsic factors determine the stability of a conductive polymer. Extrinsic instability is mainly due to the reaction of the charged defects with water vapor and oxygen. A... 

Tliis class of material comprises structures with D = 3 or 2 (thus, more thermally stable than the D = 0 structures discussed in Section 7.6.2) containing intrinsic protonic species (H, OH, H3O, or NH4), in contrast to extrinsic proton conductors (as discussed in Section 7.6.3). Therefore, their protonic conductivities are independent of the surrounding atmosphere, although their decomposition temperatures (as listed below in this section) should be increased at high partial pressures of water and/or ammonia. In addition, they do not contain basic components such as SrO or BaO that cause the instability of perovskites in CO2 and steam. 

A gradual decrease in efficiency and catastrophic failure represent two polar cases of instability commonly observed in OLEDs. Such classification is not particularly useful from a mechanistic point of view because it does not reflect the multitude of processes responsible for the instabilities of OLED devices. It also does not reflect the distinction between intrinsic and extrinsic causes of instability. Here we define the intrinsic degradation processes as inherent and qualitatively unavoidable for a certain type of OLED device. By... 

In standardized tests, a-8 plots are most conunonly obtained from the testing machines with the first maximum corresponding to an instability in deformation and neck formation. This point if often called extrinsic yield point, and it depends on the loading geometry. Quite often, extrinsic and intrinsic yield points are very close to each other, and the extrinsic yield point is referred to as the yield point in most literature on deformation behavior of polymers. 

There are a number of routes to self organization in reaction transport systems. The types of linear instability resulting in the monotonic growth of perturbations has been discussed [ 3 ] and are summarized in Fig. 1. Shown are four cases of the dependence of stability eigenvalues for perturbations, of wave vector k, from the uniform state. The first two cases were distinguished in [4] where the extrinsic type of instability was introduced. In the intrinsic case patterns arise at a well defined wave vector... 

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