Seventeen-Armed Star Polystyrenes in Various Molecular Weights: Structural Details and Chain Characteristics

Jia Chyi Wong; Li Xiang; Kuan Hoon Ngoi; Chin Hua Chia; Kyeong Sik Jin; Akira Hirao; Moonhor Ree

doi:10.3390/polym12091894

Seventeen-Armed Star Polystyrenes in Various Molecular Weights: Structural Details and Chain Characteristics

Polymers (Basel). 2020 Aug 23;12(9):1894. doi: 10.3390/polym12091894.

Authors

Jia Chyi Wong^{1

2}, Li Xiang², Kuan Hoon Ngoi^{1

2}, Chin Hua Chia¹, Kyeong Sik Jin³, Akira Hirao^{4

5}, Moonhor Ree²

Affiliations

¹ Materials Science Program, Department of Applied Physics, Faculty of Science and Technology, University Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia.
² Department of Chemistry and Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea.
³ Pohang Accelerator Laboratory, Pohang University of Science & Technology, Pohang 37673, Korea.
⁴ Department of Chemical Science and Engineering, Graduate School of Materials and Chemical Engineering, Tokyo Institute of Technology, 2-12-1-S1-13, Ohokayama, Meguro-ku, Tokyo 152-8550, Japan.
⁵ Department of Chemical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan.

Abstract

Star-shaped polymers are very attractive because of their potential application ability in various technological areas due to their unique molecular topology. Thus, information on the molecular structure and chain characteristics of star polymers is essential for gaining insights into their properties and finding better applications. In this study, we report molecular structure details and chain characteristics of 17-armed polystyrenes in various molecular weights: 17-Arm(2k)-PS, 17-Arm(6k)-PS, 17-Arm(10k)-PS, and 17-Arm(20k)-PS. Quantitative X-ray scattering analysis using synchrotron radiation sources was conducted for this series of star polymers in two different solvents (cyclohexane and tetrahydrofuran), providing a comprehensive set of three-dimensional structure parameters, including radial density profiles and chain characteristics. Some of the structural parameters were crosschecked by qualitative scattering analysis and dynamic light scattering. They all were found to have ellipsoidal shapes consisting of a core and a fuzzy shell; such ellipse nature is originated from the dendritic core. In particular, the fraction of the fuzzy shell part enabling to store desired chemicals or agents was confirmed to be exceptionally high in cyclohexane, ranging from 74 to 81%; higher-molecular-weight star polymer gives a larger fraction of the fuzzy shell. The largest fraction (81%) of the fuzzy shell was significantly reduced to 52% in tetrahydrofuran; in contrast, the lowest fraction (19%) of core was increased to 48%. These selective shell contraction and core expansion can be useful as a key mechanism in various applications. Overall, the 17-armed polystyrenes of this study are suitable for applications in various technological fields including smart deliveries of drugs, genes, biomedical imaging agents, and other desired chemicals.

Keywords: 17-armed star polystyrene; chain characteristics; dynamic light scattering analysis; molecular size; molecular structure; radial density profile; size distribution; synchrotron X-ray scattering analysis.