2006 Fiscal Year Final Research Report Summary
Study of Relationship between Loop Fraction and rheological Behavior of Multiblock Copolymer Systems
| Project/Area Number |
17350108
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Polymer/Textile materials
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
WATANABE Hiroshi Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (90167164)
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| Co-Investigator(Kenkyū-buntansha) |
INOUE Tadashi Osaka University, Graduate School of Science, Professor, 理学研究科, 教授 (80201937)
MATSUMIYA Yumi Kyoto University, Institute for Chemical Research, Assistant Professor, 化学研究所, 助手 (00378853)
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| Project Period (FY) |
2005 – 2006
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| Keywords | multiblock copolymers / bridge / loop conformation / thermodynamic barrier for mixing / dipole inversion / dielectric relaxation / entanglement / constraint release / bead-spring model |
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| Research Abstract |
Structures and rheological properties were examined for (BSB)_p-type multiblock copolymers of butadiene (B) and styrene (S) blocks (p=1-3) dissolved in a S-selective solvent, dibutyl phthalate. The systems formed lattices of precipitated S domains bridged by the B blocks and exhibited the static elasticity due to this lattice-type network structure at equilibrium. Under steady flow, the bridges connecting the S domains across the flow plane were converted to loops and the elasticity vanished. The reformation of the bridges was found to be the rate-determining step for the elasticity recovery at rest after cessation of flow. The time required for this recovery was found to be strongly dependent on not only the thermodynamic barrier of transient B/S mixing but also the entanglement among the block chains.
Structures and rheological/dielectric properties were examined for (SIS)_p-type multiblock copolymers of styrene (S) and isoprene (I) blocks (p=1-5) dissolved in an I-selective solvent,
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tetradecane. The I blocks, having dielectrically active type-A dipoles, took either bridge- or loop-type conformations in the multiblock systems. The dipole-inversion was introduced in particular I block(s) of respective multiblock copolymers, which enabled selective detection of the dielectric signal of this dipole-inverted I block(s) reflecting its large-scale motion. The loop/bridge fractions were estimated from this signal. It turned out that the loop fraction was smaller for the I block located at center of the copolymer chain than for the off-center I block and that the loop fraction slightly increased with increasing total block number and then approached an asymptotic value of 60%. Furthermore, the bridge-type I block was found to exhibit an enormously high extensibility (up to the maximum stretch ratio of=30). This behavior of the bridge was attributed to an osmotic stretching due to the coexisting loops that became significant under large extension of the system.
Viscoelastic and dielectric measurements were conducted for star-branched polyisoprene systems to examine the importance of the constraint release (CR) mechanism in the entanglement relaxation of the star chains. It turned out that the CR mechanism governed the relaxation because the star chains have a broad distribution of the motional modes and the fast modes easily activated the local CF hopping.
For the bead-spring chain model, the most fundamental molecular model for flexible polymers, theoretical analysis was made to calculate the orientation function. The analysis indicated that the orientational correlation emerged for all segments during the creep process under a constant stress. This correlation was found to be a natural consequence of the stress-optical rule. Less
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Research Products
(30 results)
