title: Perforated layer structures in liquid crystalline rod-coil block copolymers.
abstract: We report a novel observation of the tetragonal perforated layer structures in a series of rod-coil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer structure was observed at f(PMPCS) approximately 0.37 in relatively low molecular weight (M(w)) samples and approximately 0.5 in high M(w) PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod-coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The "onset" of perforation was also observed in real space in sample PS(272)-b-PMPCS(93) (f(PMPCS) approximately 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in f(PS), by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at f(PMPCS) approximately 0.48.
authors.affiliation: A. J. Drexel Nanotechnology Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Kishore K
authors.initials: KK
authors.lastname: Tenneti
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Chen
authors.forename: Christopher Y
authors.initials: CY
authors.lastname: Li
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Tu
authors.forename: Xinhua
authors.initials: X
authors.lastname: Wan
authors.forename: Qi-Feng
authors.initials: QF
authors.lastname: Zhou
authors.forename: Igors
authors.initials: I
authors.lastname: Sics
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Hsiao