Document Type

Article

Publication Date

5-15-1992

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

Department

Department of Biological Sciences

Abstract

Transmission electron microscope images were obtained of fractions of poly(1-tetradecene sulfone) and poly(cyclohexene sulfone) cast from very dilute solutions (0.007%, wt/vol) and rapidly freeze-dried on a mica surface. The samples were then vertically platinum-carbon (Pt-C) replicated with 9 +/- 0.3-A Pt-C and held together with 128 A of electron-transparent evaporated carbon. The Pt-C coating enlarges the molecular chain diameters by approximately 5 A, so that a single polysulfone chain has an apparent diameter of 9-12 A in the transmission electron microscope. Poly(1-tetradecene sulfone) forms short helical regions that show irregular helical turns of pitch 7-18 A, two to eight turns long with apparent helix diameters of 16-22 A. The n-C12H25 side chains were not obvious on the helices, but a few were visible on extended chain sections. In contrast, poly(cyclohexene sulfone) appears as a collection of Pt-C-coated single chains 10-12 A in diameter with no side-chain projections. The presence and absence of helical regions in these freeze-dried polysulfones thus reflects their solution conformations as long ago inferred on the basis of dielectric measurements.

Original Citation

Ruben GC, Stockmayer WH. Evidence for helical structures in poly(1-olefin sulfones) by transmission electron microscopy. Proc Natl Acad Sci U S A. 1992;89(17):7991-7995. doi:10.1073/pnas.89.17.7991

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