| Research activity |
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Our main research theme is the development of various new
silicon-containing functional polymeric materials based on organic
chemistry of silicon compounds. Silicon-oxygen bonds, for
example, have high heat resistance and a low rotational energy
barrier, and silicon-silicon bonds and silicon-carbon bonds show
specific optoelectronic characteristics. We are using these
characteristics of silicon compounds to design polymers, and
developing new functional polymeric materials as outlined below.
１）Insulating material with high heat resistance
Polymers containing siloxane bonds show low dielectric
constant and high heat resistance, and are now highly desired
materials for interlayer insulation film to be incorporated in futuregeneration
semiconductor circuits. The conventional synthetic
method had the disadvantages of troublesome processes and
emission of hydrogen chloride as a by-product. We succeeded in
the development of an original synthetic process using stable
bis(silane) monomers and water as starting materials, which only
generate hydrogen as a by-product. We are now engaged in the
development of highly functional heat-resistant insulation material,
taking advantage of the characteristics of siloxane bonds.
２）Polysilsesquioxane with new structures
Polysilsesquioxane is a compound consisting of three siliconoxygen
bonds and one silicon-carbon bond. We discovered that it
is possible to generate polyhedral oligomeric silsesquioxane with
closed-cage structure and open-cage structure by controlling the
synthetic conditions. These compounds acquire high heat
resistance and hardness, and are expected to be used not only as
general-purpose materials, but also as a sealing material or
reflective film for next-generation semiconductors.
３）Polymeric liquid crystal and aero-permeable film
materials
We discovered that flexible siloxane bonds, even those of
polymeric structures, can give rise to a liquid crystalline phase at
ambient temperatures when incorporated into the spacer group of
a side-chain liquid crystalline polymer. They can be used as a new
material for liquid crystal displays. The polymers containing
branched oligodimethylsiloxane in the side chains allow easy
permeation of gas molecules due to high mobility of the side
chains. This feature has been used in the production of contact
lenses with high oxygen permeability. The material that we
developed has already been put to practical use.
４）Interface modification and liquid crystal
holography material
Silicon compounds tend to be incompatible with other organic
compounds. For example, in a polysiloxane graft polymer, the
carbonaceous main chain structure and polysiloxane side chain
tend to be phase-separated off, and as a result, the polymer
shows peculiar interface characteristics. We discovered that this
property can be controlled by modifying the length of the
polydimethylsiloxane side chain, and succeeded in applying a
polydimethylsiloxane side chain of a specific length to the
production of pressure-sensitive adhesive used for sticky notes. In
recent years, we have been developing liquid crystal holographic
material that takes advantage of the incompatibility of silicon
compounds with organic compounds. In liquid crystal holography,
the separation efficiency of the low-molecular weight liquid crystal
from polymer matrix formed in the photo-polymerization process
has a direct influence on the resolution of images. We are now
involved in the design and synthesis of photo-polymeric monomers
containing siloxane units with higher separation efficiency to
develop liquid crystal holographic materials. |
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■Equipment
500MHz (Varian UNITY 500plus, multinuclear, for LC-NMR),
400MHz (Varian UNITY 400plus, multinuclear, for solid state
NMR), 300MHz (Varian Gemini 2000, 1H, 13CNMR) nuclear
magnetic resonance spectrometers, gas chromatograph (Yanaco
G6800), high-performance liquid chromatograph (JASCO
GULLIVER series, optically-active column (for analysis: 2, semipreparative:
1, preparative: 1)), gel permeation chromatograph
(JASCO GULLIVER series), gas chromatograph mass
spectrometer (SHIMADZU QP-5000), molecular weight
measurement system (CORONA 114 VPO), differential scanning
calorimeter (Seiko Instruments SSC/5220), supercritical fluid
extraction / chromatography system (JASCO SUPER-200).
The following equipment is also managed by our laboratory:
reflection/transmission microscopic infrared spectrometer (MICR-
20), circular dichroic spectrometer (JASCO J-720), polarimeter
(JASCO DIP-370S), time-of-flight charge mobility measuring
equipment (OPTEL), UV-visible/near-infrared spectrophotometer
(JASCO V-570), spectrofluorometer (JASCO FP-6500),
electrochemical analyzer (HOKUTO DENKO HZ-3000), vacuum
deposition system (ULVAC EBX-1000) |
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| The main research achievements in the past five years |
| 1: |
Y. H. Cho, Y. Kawakami, High Performance Holographic Polymer
Dispersed Liquid Crystal Systems Using Multi-functional Acrylates And Siloxane-containing
Epoxides As Matrix Components, Appl. Phys. A. Mater. 83, 365-375(2006). |
| 2: |
I. Imae, Y. Kawakami, Unique electrochemical and optical
behavior of a novel POSS-based material having carbazole unit, J. Mater. Chem.
15, 4581-4583(2005). |
| 3: |
C. Pakjamsai, Y. Kawakami, Tendency of loop formation of
oligosilsesquioxanes obtained from (4-substituted phenyl)- trimethoxysilane catalyzed
by benzyltrimethylammonium hydroxide in benzene, Polym. J., 33, 445-464(2004). |
| 4: |
T. TSURUTA, Y. KAWAKAMI, Design of Polymers (Kobunshi Sekkei
in Japanese, Nikkan Kougyou Shinbunsha, 2004). |
| 5: |
Y. Kawakami, Mitsubishi Chemical Award from Society of Polymer
Science Japan on Precision Synthesis of Silicon-containing Polymers and Development
of Interfacial Functional Materials(2003). |
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