title: Synchrotron X-ray scattering characterization of the molecular structures of star polystyrenes with varying numbers of arms.
abstract: We have synthesized well-defined multiarmed star polystyrenes, with 6, 9, 17, 33, and 57 arms, and studied their molecular shapes and structural characteristics in a good solvent (tetrahydrofuran at 25 degrees C) and in a theta (Theta) solvent (cyclohexane at 35 degrees C) by small-angle X-ray scattering (SAXS) using a synchrotron radiation source. Analysis of the SAXS data provided a detailed characterization of the molecular shapes, including the contributions of the blob morphology of the arms, the radius of gyration, the paired distance distribution, the radial electron density distribution, and the Zimm-Stockmayer and Roovers g-factor, for the multiarmed star polystyrenes. In particular, the molecular shapes of the star polystyrenes were found to change from a fuzzy ellipsoid, for the 6-armed polystyrene, to a fuzzy sphere, for the 57-armed polystyrene, with an increasing number of arms. The ellipsoidal character of the star polystyrenes with fewer arms may originate from the extended anisotropically branched architecture at the center of the molecule. The arms of the star polystyrenes were found to be more extended than those of the linear polystyrenes. Furthermore, the degree of chain extension in the arms increased with the number of arms.
authors.affiliation: Department of Chemistry, National Research Lab for Polymer Synthesis & Physics, Center for Electro-Photo Behaviors in Advanced Molecular Systems, BK School of Molecular Science, Division of Advanced Materials Science, and Polymer Research Institute, Pohang University of Science & Technology (POSTECH), Pohang 790-784, Republic of Korea.
authors.forename: Sangwoo
authors.initials: S
authors.lastname: Jin
authors.forename: Tomoya
authors.initials: T
authors.lastname: Higashihara
authors.forename: Kyeong Sik
authors.initials: KS
authors.lastname: Jin
authors.forename: Jinhwan
authors.initials: J
authors.lastname: Yoon
authors.forename: Yecheol
authors.initials: Y
authors.lastname: Rho
authors.forename: Byungcheol
authors.initials: B
authors.lastname: Ahn
authors.forename: Jehan
authors.initials: J
authors.lastname: Kim
authors.forename: Akira
authors.initials: A
authors.lastname: Hirao
authors.forename: Moonhor
authors.initials: M
authors.lastname: Ree