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.
Highlights
Star-shaped polymers are structurally intriguing materials that consist of several linear polymer chains connected at one point
17-armed star polymers have been subjected to synchrotron solution X-ray scattering in order to get insights into their molecular structure and and armarm chain characteristics
17-armed star polystyrenes in various molecular weights were investigated in the Θ
Summary
Star-shaped polymers are structurally intriguing materials that consist of several linear polymer chains connected at one point (i.e., a central core). Crystalline star polymers revealed lower melt temperatures, lower crystallization temperatures and lower degrees of crystallinities than the linear counterparts [7] These unusual properties might originate basically from the compactness of molecular structures and the geometrical constrain of arm chains in such compact structure. Despite the compact molecular structures, star polymers can own peripheral end groups and additional internal groups, depending on their molecular designs [3,4,5,6,7,8] Both arm end groups and internal groups could be active due to either their own chemical natures or functionalizations [3,4,5,6,7,8]. The star polymers all exhibit fuzzy ellipsoidal shapes They reveal interesting 3D structural characteristics based on the individual arms’ unique behaviors. Molecular characteristics and thermal properties of 17-armed star polystyrenes
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