Pohang University of Science and Technology^* Department of Polymeric and Organic Material, Graduate School of Science and Engineering, Tokyo Institute of Technology^**
○Sangwoo Jin^* Tomoya Higashihara^** Kyeong Sik Jin^* Jinhwan Yoon^* Kyuyoung Heo^* Jehan Kim^* Kwang-Woo Kim^* Akira Hirao^** Moonhor Ree^*

Star-shape polymers have gained great attention because of their interesting properties and potential applications. In the present study, a series of star-polystyrenes with 6-57 arms were synthesized. In addition, linear polystyrenes were purchased. Solutions of each polystyrene sample were prepared at a concentration of 1-4 wt% in tetrahydrofuran, a good solvent and cyclohexane at 35C, a theta solvent. Small-angle X-ray scattering (SAXS) measurements were conducted at the 4C1 beamline (BL) of the Pohang Accelerator Laboratory. The scattering profiles of the linear polystyrenes were confirmed to reveal the characteristics of a Gaussian coil, which has a Gaussian sphere behaving self-avoiding random walk in the solvent but excluded volume effect in the theta solvent. In comparison, the 6-armed polystyrene reveals scattering profiles varying with a power law of q^-2 in the Debye region, and the 57-armed polystyrene exhibits scattering profiles following a power law of q^-4 in the Debye region regardless of the good solvent and theta solvent. The other armed polystyrenes show scattering profiles which follow an intermediate power law between those observed for the 6- and 57-armed polystyrenes over the Debye region. All the structural details, which were extracted from the SAXS profiles, will be discussed with considering the chemical nature of the inner and outer parts in the multi-armed polystyrene and the number of arms.