1999 Fiscal Year Final Research Report Summary
Viscoelastic Properties and Dynamics of Model Comb Polymers : A Fundamental Research for Metallocene-Catalyzed Polyolefin
| Project/Area Number |
10450366
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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 |
高分子構造・物性(含繊維)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
WATANABE Hiroshi Kyoto University, Institute for Chemical Research, Associate Profes, 化学研究所, 助教授 (90167164)
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| Co-Investigator(Kenkyū-buntansha) |
INOUE Tadashi Kyoto University, Institute for Chemical Research, Instructor, 化学研究所, 助手 (80201937)
OSAKI Kunihiro Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (00027046)
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| Project Period (FY) |
1998 – 1999
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| Keywords | comb chains / two-step anionic coupling / entanglement relaxation / tube model / constraint release / tube dilation / viscoelastic relaxation / dielectric relaxation |
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| Research Abstract |
Slow relaxation of metallocene-catalyzed polyolefins is significantly affected by small amount of long branches. However, the effect of branching has not been clearly understood because of competing effects of molecular weight distribution. In this study, model comb polybutadienes without this distribution were synthesized via two-step anionic coupling (utilizing a selective reactivity of pyridine groups). Viscoelastic tests of this material revealed that the terminal relaxation corresponds to the relaxation of the trunk in the comb chains and proceeds via the constraint release (CR) mechanism considered in the tube model.
In the current tube models, the tube motion results in not only the CR motion (retarded Rouse-like motion) but also the dynamic tube dilation (DTD), the latter also inducing the viscoelastic relaxation of the chain in the tube. Specifically, the DTD mechanism is assumed to dominate the relaxation of branched chains (including the comb chains). However, the DTD process has not been experimentally verified. Thus, for deeper understanding of the comb relaxation, the DTD process was experimentally tested for chains having simpler topological structures, the linear and star-branched chains.
For this purpose, this study focused its attention on a fact that the motion of type-A chain is differently averaged in the viscoelastic and dielectric properties. On the basis of this difference, a relationship between these properties was derived. This relationship, being valid whenever the tube dilates in the time scale of chain relaxation, actually held for monodisperse linear chains. However, for blends as well as monodisperse starbranched chains, the DTD relationship failed and the chain actually relaxed via the CR mechanism before the DTD process was completed. This result is consistent with the relaxation behavior of the comb chains explained above.
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