Syndiotactic Polystyrene ε Cocrystals With n-Alkanes: Guest Uptake and Crystal Structure

Abstract

s-PS ε-clathrates with different n-alkanes, ranging from n-hexane to n-dodecane, have been obtained for the first time and their structure has been investigated by means of X-ray diffraction, FT-IR spectroscopy, and molecular mechanics calculations. The diffraction data of all the s-PS/n-alkane ε-clathrates are in agreement with the orthorhombic unit cell with axes a = 1.62 nm, b = 2.20 nm, and c = 0.79 nm and the space group Pbcn, proposed for the nanoporous ε form, indicating that the crystal packing of the chains in the clathrate forms remains substantially unaltered independently of the length of the n-alkane. Molecular mechanic calculations provided conclusions that the n-alkanes' guest, independent of their length, are arranged in the channels in fully trans-planar conformation with their main molecular axis almost parallel to the axis of the cavity. The possibility of having n-alkane guest with a bent conformation in the channels was also ruled out. A detailed structural study was carried out for the cocrystalline form containing n-octane. Supplemental materials are available for this article. Go to the publisher's online edition of Soft Materials to view the free supplemental file.

Keywords:

• Co-crystal
• n-alkane
• Syndiotactic polystyrene

ACKNOWLEDGMENTS

Financial support of the “Ministero dell'Istruzione, dell'Università e della Ricerca” (PRIN2007), and of the Consortium INSTM (PRISMA01/2007 project) is gratefully acknowledged.