I generally do believe that a picture is worth a thousand words (or more), but sometimes, they can be misleading. Here's a perfect example of an image in a recent research paper (open access).
But in fact the research was actually looking at the mechanisms of photo-conductivity in poly(3-hexylthiophene), (P3HT) which beside being conductive, is also a semicrystalline polymer.
The researcher found that the existence of the crystalline and amorphous regions in the solid is critical to conductivity. The absorbed photons created a charge separation, with the electron being trapped near the crystalline/amorphous interface and the hole being in the crystalline phase. Lower molecular weight materials, being mostly crystalline, do not have both of these regions and therefore lower electrical activity. The results were able to explain a wide range of conductivity results that had been previously reported without explanation.
So now the fringed micelle model is not only able to explain crystallization in polymers and mechanical properties, but also photoconductive behavior. Triple duty for a model – that's some heavy lifting. But this also suggests that the photoconductive properties of a given grade of P3HT can be adjusted by altering the crystallinity, albeit at the same time that the mechanical properties are being adjusted. I can see some contradictory optimizations in the future for some engineers. After all, what are the odds that the ideal crystallization scheme for the mechanical properties is identical to that for the photoconductivity?
Hat tip to Matteo Cavalleri (twitter @ physicsteo) for the lead.
Obadiah G. Reid, Jennifer A. Nekuda Malik, Gianluca Latini, Smita Dayal1, Nikos Kopidakis, Carlos Silva, Natalie Stingelin, & Garry Rumbles (2011). The influence of solid-state microstructure on the origin and yield of long-lived photogenerated charge in neat semiconducting polymers Journal of Polymer Science Part B: Polymer Physics : DOI: 10.1002/polb.22379
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