Semicrystalline and superlattice structures in linear and branched oligomers

PMSE 487

Xiangbing Zeng, x.zeng@sheffield.ac.uk1, Fangning Xie1, Goran Ungar, g.ungar@sheffield.ac.uk1, and Stephen M. King2. (1) Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom, (2) Rurherford-Appleton Laboratory, ISIS, Chilton, Didcot, OX11 0QX, United Kingdom
Melt crystallization of a linear end-deuterated, and a methyl-branched, monodisperse ultralong alkane, C12D25C192H384CHDC11D23 and C192H385CH(CH3)C99H199, has been studied by real-time small-angle neutron (SANS) and X-ray (SAXS) scattering. It was possible to study the structure and the transformation of the transient non-integer folded (NIF) form into the folded-extended triple-layer superlattice in hitherto unprecedented detail. Furthermore, the rich layer polymorphism in the asymmetrically branched alkane was found to be due to the anchoring of the methyl branch at the crystal surface. Two semicrystalline and two superlattice forms were found. The exceptionally high chain tilt angle (46 deg) was caused by the inability of surface overcrowding to be resolved by chain folding. Both materials give valuable new insights into chain folding, 50 years after its discovery.
 

50 Years after the Discovery of Polymer Single Crystals: A Look Back, Current Discoveries and Future Opportunities
1:30 PM-5:20 PM, Wednesday, August 22, 2007 Westin Boston Waterfront -- Alcott, Oral

Division of Polymeric Materials: Science & Engineering

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007