Chemistry

Guiding Polymers with DNA

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Science  09 May 2014:
Vol. 344, Issue 6184, pp. 558
DOI: 10.1126/science.344.6184.558-c
CREDIT: CHEMICAL NANOSCIENCE LABS/NEWCASTLE UNIVERSITY

Insights into how a DNA template can guide the formation of conducting polymer nanowires have been obtained from atomic force microscopy (AFM), and molecular dynamics (MD), and coarse-grained simulations. Watson et al. prepared polypyrrole [poly(Py)] and poly-2,5-bis(2-thienyl)pyrrole [poly(TPT)] nanowires by mixing the oxidized monomers with FeCl3 and bacteriophage lambda DNA templates in solution. The formation process was followed by removing solution at various times and depositing it on trimethylsilane-modified silica for AFM analysis. For poly(TPT), after 10 min, a low density of spherical polymer particles nucleated on the DNA; at 1 hour, the density and size of the particles increased and developed a beads-on-a-string morphology. By 4 hours, polymer particles began to merge and cover all of the DNA, and by 24 hours, a uniform wire with no distinct particles was seen. The process is similar for poly(Py) but is more rapid, and displays eariler elongation. The MD modeling studies show that DNA rotation promotes polymer binding in the initial stage, and the coarse-grained simulation shows that the smooth-wire formation is driven by a balance between adhesion to the DNA template and lowering the surface tension of the polymer.

J. Am. Chem. Soc. 10.1021/ja500439v (2014).

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