TY - JOUR
T1 - Viscoelastic Properties of Dumbbell-Shaped Polystyrenes in Bulk and Solution
AU - Doi, Yuya
AU - Takano, Atsushi
AU - Takahashi, Yoshiaki
AU - Matsushita, Yushu
N1 - Funding Information:
The authors acknowledge Prof. H. Watanabe at Kyoto University, Prof. T. Inoue at Osaka University, and Prof. Y. Masubuchi at Nagoya University for their helpful discussion. The authors thank Dr. J. Roovers for providing the rheological data for four-arm star polystyrenes. This work was supported by JSPS Research Fellowships for Young Scientists (No. 14J03393 for Y.D.) and Grant-in-Aid for Scientific Research (No. 24350056 for A.T. and No. 25248048 for Y.M.) from the Japan Society for the Promotion of Science. This work was partly supported by the Collaborative Research Program of the Institute for Chemical Research, Kyoto University (Grant No. 2015-58), and A.T. is grateful for the support. This work was also supported by the Program for Leading Graduate Schools at Nagoya University entitled “Integrate Graduate Education and Research Program in Green Natural Sciences”.
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/2/9
Y1 - 2021/2/9
N2 - This study examined viscoeslastic properties of two flexible dumbbell-shaped polystyrene (PS) samples, D-30/120/30 and D-30/240/30, which possess the same ring size (MR ∼30 kg/mol) and different lengths of central linear chains (ML ∼120 and 240 kg/mol) in bulk and solution. In bulk, both dumbbell PS samples exhibited an extremely long entanglement plateau in dynamic oscillatory measurements, and their terminal relaxation behavior was not observed in our experimental window. In stress relaxation measurements, dumbbell samples in bulk exhibited considerably slower terminal relaxation than high-molecular-weight linear PS samples (M ∼106 g/mol), and a clear difference between two dumbbell PS samples was observed in the long time regime, i.e., terminal relaxation of D-30/240/30 is much slower than that of D-30/120/30. These results suggest that (i) the dumbbell polymer forms a characteristic "network"where two rings on both ends in a molecule spontaneously thread the ring part of other dumbbell chains and (ii) this type of interchain interaction resulting in network formation becomes more dominant than usual entanglements similar to linear chains. The network of dumbbell chains starts to relax their stress when the intermolecular threading is released, and this release process tends to occur more frequently for the dumbbell with a shorter central chain, D-30/120/30, than that with a longer one, D-30/240/30. In dioctyl phthalate (DOP) solutions of D-30/240/30, where DOP is known as a θ-solvent for PS at 22 °C, in a relatively high concentration regime (i.e., 20-30 wt %), the solutions exhibited an entanglement plateau and higher viscosity than the corresponding linear PS solutions, suggesting that the characteristic entanglement originating from intermolecular threading of dumbbell chains is still dominant in the solution. On the contrary, in a lower-concentration regime (≤8 wt %), the D-30/240/30 solutions exhibited similar viscosities to the linear PS ones, wherein the dumbbell molecules behave like unentangled/isolated chains.
AB - This study examined viscoeslastic properties of two flexible dumbbell-shaped polystyrene (PS) samples, D-30/120/30 and D-30/240/30, which possess the same ring size (MR ∼30 kg/mol) and different lengths of central linear chains (ML ∼120 and 240 kg/mol) in bulk and solution. In bulk, both dumbbell PS samples exhibited an extremely long entanglement plateau in dynamic oscillatory measurements, and their terminal relaxation behavior was not observed in our experimental window. In stress relaxation measurements, dumbbell samples in bulk exhibited considerably slower terminal relaxation than high-molecular-weight linear PS samples (M ∼106 g/mol), and a clear difference between two dumbbell PS samples was observed in the long time regime, i.e., terminal relaxation of D-30/240/30 is much slower than that of D-30/120/30. These results suggest that (i) the dumbbell polymer forms a characteristic "network"where two rings on both ends in a molecule spontaneously thread the ring part of other dumbbell chains and (ii) this type of interchain interaction resulting in network formation becomes more dominant than usual entanglements similar to linear chains. The network of dumbbell chains starts to relax their stress when the intermolecular threading is released, and this release process tends to occur more frequently for the dumbbell with a shorter central chain, D-30/120/30, than that with a longer one, D-30/240/30. In dioctyl phthalate (DOP) solutions of D-30/240/30, where DOP is known as a θ-solvent for PS at 22 °C, in a relatively high concentration regime (i.e., 20-30 wt %), the solutions exhibited an entanglement plateau and higher viscosity than the corresponding linear PS solutions, suggesting that the characteristic entanglement originating from intermolecular threading of dumbbell chains is still dominant in the solution. On the contrary, in a lower-concentration regime (≤8 wt %), the D-30/240/30 solutions exhibited similar viscosities to the linear PS ones, wherein the dumbbell molecules behave like unentangled/isolated chains.
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U2 - 10.1021/acs.macromol.0c02050
DO - 10.1021/acs.macromol.0c02050
M3 - Article
AN - SCOPUS:85101488848
SN - 0024-9297
VL - 54
SP - 1366
EP - 1374
JO - Macromolecules
JF - Macromolecules
IS - 3
ER -