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Single-Crystal Linear Polymers Through Visible Light–Triggered Topochemical Quantitative Polymerization

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Science  17 Jan 2014:
Vol. 343, Issue 6168, pp. 272-277
DOI: 10.1126/science.1245875

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Topochemical Polymerization

In a topochemical reaction, chemical changes start at active sites in the solid and then proceed autocatalytically to neighboring regions. If one starts with a monomer that can form ordered structures similar to the final polymer, it is possible to polymerize chains in a fully ordered state and thus make very long single chains. Dou et al. (p. 272; see the Perspective by Goroff) describe an unexpected visible-light–induced polymerization of derivatives of a dye. Two of the derivatives underwent photoinduced single-crystal-to-single-crystal topochemical polymerization.

Abstract

One of the challenges in polymer science has been to prepare large-polymer single crystals. We demonstrate a visible light–triggered quantitative topochemical polymerization reaction based on a conjugated dye molecule. Macroscopic-size, high-quality polymer single crystals are obtained. Polymerization is not limited to single crystals, but can also be achieved in highly concentrated solution or semicrystalline thin films. In addition, we show that the polymer decomposes to monomer upon thermolysis, which indicates that the polymerization-depolymerization process is reversible. The physical properties of the polymer crystals enable us to isolate single-polymer strands via mechanical exfoliation, which makes it possible to study individual, long polymer chains.

  • * Dedicated to M. Prato on the occasion of his 60th birthday.

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