Macromolecules 46, 1470-1476 (2013)

Crystallization of Poly(γ-benzyl L-glutamate) in Thin Film Solutions: Structure and Pattern Formation

Kaiwan Jahanshahi1,2, Ioan Botiz1,3, Renate Reiter1, Ralf Thomann2, Barbara Heck1, Roozbeh Shokri1,2, Werner Stille1, Günter Reiter1,2

1Institute of Physics, Faculty of Mathematics and Physics, Albert-Ludwigs-University of Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany

2Freiburg Materials Research Center (FMF), Stefan-Meier-Strasse 21, 79104 Freiburg, Germany

3Freiburg Institute for Advanced Studies (FRIAS), Albertstrasse 19, 79104 Freiburg, Germany


We have investigated the formation of poly(γ-benzyl L-glutamate) (PBLG) crystals from semidilute thin film solutions. Crystallization was initiated by adding methanol, a nonsolvent. After drying, each PBLG crystal possessed an internal domain structure exhibiting a zigzag pattern consisting of parallel stripes of alternating orientations between domains. X-ray scattering and electron diffraction revealed within these crystals a pseudohexagonal packing of the PBLG α-helices with their axis oriented parallel to the plane of the substrate. On the basis of optical anisotropy studies, it could be shown that the orientation of the helix axis was parallel to the stripes. While forming in solution, the objects are assumed to consist of a hexagonal columnar liquid crystalline phase. Upon drying, lateral packing density of the helices increased and resulted in a net dilative strain perpendicular to the columns, which is supposed to cause the formation of zig-zag patterns.