1995 Fiscal Year Final Research Report Summary
Structural Fluctuations and Crystal Growth in Ultra-thin Polymer Films
| Project/Area Number |
06452069
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理学一般
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
MIYAJI Hideki Kyoto Univ., Fac.of Sci., Assoc.Prof., 大学院・理学研究科, 助教授 (90025388)
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| Co-Investigator(Kenkyū-buntansha) |
TODA Akihiko Hiroshima Univ., Int.Arts & Sci., Assoc.Prof., 総合科学部, 助教授 (70201655)
IZUMI Kunihide Kyoto Univ., Fac.of Sci., Instructor, 大学院・理学研究科, 助手 (50025376)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Polymer / Ultra-thin Film / Crystal Growth / Structural fluctuation / Diffusion |
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| Research Abstract |
1.Ultra-thin polystirene films from 20 to several hundreds of nm in thickeness were prepared by a water casting method. Since the radius of gyration is given to be 0.03*M^<1/2> nm for a poly-stirene chain with molecular weight of M,the chains with molecular weight of more than 100,000 are to be squeezed in the ultra-thin films ; accordingly chains shows structures and dynamics different from those in bulk. 2.The X-ray amorphous halo observed with use of PSPC has shown no difference between the thin film and bulk ; the structure of the most of chains in the film has the same structure as in bulk. 3.Atomic force microscopy shows that the fluctuation of height on the surface of the amorphous film is about 1 nm. The fluctuation was observed also on the crystal surface after crystallization of the film, and hence crystais are coverd with amorphous layr. 4.The effect of substrate are conspicuous on primary nucleations. Above 210ﾟC of crystallization temperature, lemellar crystals perpendicular to a carbon substrate were observed at the center of grown crystals ; a screw dislocation was at the center for mica substrate. Below 150ﾟC,observed were 2-dimensional spherulites with branched lemellae perpendicular to the substrate. 5.Film thckness dependence of lateral growth rates wrere measured as a function of molecular weight M,crystallization temperature T_C and substrate materials. For the lamellar crystals parallel to the substrate, the growth rate G decease linearly with the inverse of the thickness D : G/G_*=1-a/D where G_* is the growth rate in bulk, a is a constant of about 5 nm, independent of T_C, M and substrate materials. For the 2-D spherulites, G remains unchanged with decreasing D.We therefore conclude that the part of a polymer chain at a distance less than 5 nm from a substrate "feels" the absorption of chain segments on the substrate, and hence suffers the delay of diffusion for crystallization to give rise to G decreasing linearly with 1/D.
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