Faculty Profiles - UCHIDA Tetsuya

Papers - UCHIDA Tetsuya

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Single wall carbon nanotube dispersion and exfoliation in polymers Reviewed

T Uchida, S Kumar

JOURNAL OF APPLIED POLYMER SCIENCE 98 ( 3 ) 985 - 989 2005.11

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Dispersion and exfoliation of single wall carbon nanotubes (SWNTs) have been studied in poly(acrylonitrile) (PAN), poly(p-phenylene benzobisoxazole) (PBO) solutions, and composite fibers using transmission electron microscopy. As a result of polymer assisted dispersion and exfoliation, the average SWNT bundle diameter in SWNT/ PAN (5/95) was 11 nm, while the average diameter for the pristine SWNT bundles was about 30 nm. High resolution TEM of SWNT/PBO (10/90) composite fibers did not reveal the presence of SWNT aggregates or bundles, suggesting SWNT exfoliation as individuals. On the other hand, both oriented and unoriented nanotube bundles have been observed in SWNT/PBO samples containing 15 wt % nanotubes. Carbon nanotubes are 10(5) times more radiation resistant than flexible polymers such as polyethylene, and 10(5) times more resistant than highly radiation resistant polymers such as PBO. Therefore in the high resolution TEM study of nanotube/polymer composites, nanotubes can be observed long after the polymer has been damaged by electron radiation. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/app.22203

A comparison of reinforcement efficiency of various types of carbon nanotubes in poly acrylonitrile fiber Reviewed

HG Chae, TV Sreekumar, T Uchida, S Kumar

POLYMER 46 ( 24 ) 10925 - 10935 2005.11

Language：English Publisher：ELSEVIER SCI LTD

Polyacrylonitrile (PAN)/carbon nanotubes (CNTs) composite fibers were spun from solutions in dimethyl acetamide (DMAc), using single wall (SWNTs), double wall (DWNTs), multi wall (MWNTs) carbon nanotubes, and vapor grown carbon nanofibers (VGCNFs). In each case, CNT content was 5 wt% with respect to the polymer. Structure, morphology, and properties of the composite fibers have been characterized using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, tensile tests, dynamic mechanical tests, as well as thermal shrinkage. While all nanotubes contributed to property improvements, maximum increase in modulus (75%) and reduction in thermal shrinkage (up to 50%) was observed in the SWNT containing composites, and the maximum improvement in tensile strength (70%), strain to failure (110%), and work of rupture (230%) was observed in the MWNTs containing composites. PAN orientation is higher in the composite fiber (orientation factor up to 0.62) than in the control PAN fiber (orientation factor 0.52), and the PAN crystallite size in the composite fiber is up to 35% larger than in the control PAN (3.7 nm), while the overall PAN crystallinity diminished slightly. Nanotube orientation in the composite fibers is significantly higher (0.98 for SWNTs, 0.88 for DWNTs, and 0.91 for MWNTs and VGCNFs) than the PAN orientation (0.52-0.62). Improvement in low strain properties (modulus and shrinkage) was attributed to PAN interaction with the nanotube, while the improvement in high strain properties (tensile strength, elongation to break, and work of rupture) at least in part is attributed to the nanotube length. Property improvements have been analyzed in terms of nanotube surface area and orientation. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2005.08.092

Development of a new hybrid gel phantom using carrageenan and gellan gum for visualizing three-dimensional temperature distribution during hyperthermia and radiofrequency ablation Reviewed

M Kuroda, H Kato, K Hanamoto, K Shimamura, T Uchida, Y Wang, S Akaki, JI Asaumi, K Himei, M Takemoto, S Kanazawa, K Shibuya, S Kawasaki, Y Hiraki

INTERNATIONAL JOURNAL OF ONCOLOGY 27 ( 1 ) 175 - 184 2005.7

Language：English Publishing type：Research paper (scientific journal) Publisher：SPANDIDOS PUBL LTD

We developed a new hybrid gel phantom using carrageenan and gellan gum for the purpose of visualizing three-dimensional temperature distribution. The phantom, which contains carrageenan, gellan gum, non-ionic surface active agent, potassium chloride, n-butanol, sodium azide, and water, shows good transparency at room temperature, and has the advantage that the heated region becomes white and opaque due to segregation of the surface active agent. Carrageenan and gellan gum were added to improve the transparency and fragility of the hybrid gel. Potassium chloride was used to adjust the electrical conductivity of the gel to a range of 5-130 MHz, so that it would be equivalent to that of muscle tissue for each frequency used by electromagnetic heating devices. N-butanol was used to adjust the clouding temperature to a range between 45 and 55 degrees C. In the present study we clarified the important properties of the new phantom, and developed formulae for easy determination of the amounts of ingredients necessary for the desired clouding temperature and electric conductivity. The characteristics of this phantom are: a) a solid form to avoid convection by heat conduction; b) sufficient strength without fragility to form a torso without the use of a reinforcing agent; c) high transparency at room temperature and visualization of the heating area as a white turbidity; d) time-lapse and accurate visualization of the changing temperature area without thermal hysteresis; e) electrical properties similar to those of human tissues; f) ease of production; and g) low cost and good safety. This phantom might assist oncologists in their routine checking and study of the performance of electromagnetic heating devices for hyperthermia and radiofrequency ablation.

Carbon nanotube core-polymer shell nanofibers Reviewed

J Liu, T Wang, T Uchida, S Kumar

JOURNAL OF APPLIED POLYMER SCIENCE 96 ( 5 ) 1992 - 1995 2005.6

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Single-walled carbon nanotube (SWNT)/ poly(methyl methacrylate) and SWNT/polyacrylonitrile composite nanofibers were electrospun with SWNT bundles as the cores and the polymers as the shells. This was a novel approach for processing core (carbon nanotube)-shell (polymer) nanofibers. Raman spectroscopy results show strain-induced intensity variations in the SWNT radial breathing mode and an upshift in the tangential (G) and overtone of the disorder (G') bands, suggesting compressive forces on the SWNTs in the electrospun composite fibers. Such fibers may find applications as conducting nanowires and as atomic force microscopy tips. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/app.21662

Novel network morphology of poly(p-oxybenzoyl) Reviewed

K Kimura, S Kohama, S Kondoh, T Uchida, Y Yamashita, T Oohazama, Y Sakaguchi

JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 43 ( 8 ) 1624 - 1634 2005.4

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS INC

Polymerization of 4-acetoxybenzoic acid (ABA) with 3,5-diacetoxybenzoic acid (DABA) was examined to control the morphology of poly(p-oxybenzoyl) (POB). Polymerizations were carried out at a concentration of 1.0% in an aromatic solvent Therm S-1000 (R) (mixture of dibenzyltoluene) at 320 degrees C. Polymerization of ABA yielded the POB fibrillar crystals, but the polymerization with DABA at a concentration in the feed (chi(f)) of 0.10-0.15 afforded novel network structures comprised of spheres connected by fibrillar crystals. The diameter of the spheres prepared at chi(f) of 0. 15, which were 0. 7 and 5.0 mu m, showed bimodality. The network distance, fibril length, and fibril width were 6.1, 2.6, and 0.1 mu m, respectively. They possessed high crystallinity. The network structure was formed as follows. Co-oligomers were first precipitated in the beginning of the polymerization by liquid-liquid phase separation to form the microdroplets. The fibrillar crystals were formed in the coalesced spheres by the crystallization of oligomers induced by the increase of molecular weight. The fibrillar crystals connecting the spheres gradually appeared owing to the shrinkage of the spheres. The fibrillar crystals grew from the surface of the spheres with the crystallization of homo-oligomers of 4-oxybenzoyl units, and finally the network structure was completed. (c) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/pola.20639

Polymer whiskers based on p-mercaptobenzoyl and p-oxybenzoyl blocks Reviewed

K Kobashi, K Kimura, T Uchida, Y Yamashita, K Shimamura

POLYMER 46 ( 7 ) 2191 - 2200 2005.3

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

Preparation of polymer whisker based on p-mercaptobenzoyl (S) and p-oxybenzoyl (0) blocks was examined by the polymerization of Sacetyl-4-mercaptobenzoic acid (AMBA) and the following addition of 4-acetoxybenzoic acid (ABA). Polymerization of AMBA was carried out in liquid paraffin at 300 degrees C for 3 h yielding poly(p-mercaptobenzoyl) (PMB) whisker, and then ABA was added stepwise at 3-hour intervals into the solution. Initial polymerization concentration was 1.98%. The length of the whisker increased with the addition and it became 26.7 mu m from 20.1 mu m after third ABA addition. The width increased very slightly. Both length and width increased with polymer yield but the length increased preferentially rather than the width. The number of whiskers was constant even after the addition of ABA and poly (p-oxybenzoyl) (POB) whisker was not newly formed by the addition. Microscopic FT-IR and selected area electron diffraction measurements revealed that polymer molecules were aligned along the long axis of the whiskers, and the center and tip parts were comprised of PMB crystal and POB crystal, respectively. The polymer whisker based on S and 0 blocks was successfully prepared as grafting POB crystal on PMB whisker with stepwise addition of ABA. Thermal property of the resulting whiskers was also discussed. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2005.01.016

Direct synthesis of poly(4 '-oxy-4-biphenylcarbonyl) and poly(2-oxy-6-naphthoyl) under nonstoichiometric conditions Reviewed

S Kohama, K Kimura, T Uchida, S Umehara, Y Ikemoto, Y Yamashita

POLYMER INTERNATIONAL 54 ( 2 ) 471 - 480 2005.2

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS LTD

Direct synthesis of poly(4'-oxy-4-biphenylcarbonyl) (POBP) and poly(2-oxy-6-naphthoyl) (PON) was examined by polycondensation of 4'-hydroxy-4-biphenylcarboxylic acid (HBPA) and 2-hydroxy-6-naphthoic acid (HNA) in the presence of 4-ethoxybenzoic anhydride or 2-naphthoic anhydride as condensation reagents. Polymerizations were carried out at 320degreesC in aromatic solvents and liquid paraffin. POBP, having a number-average degree of polymerization (DPn) of 38, was obtained as plate-like crystals at the molar ratio of HBPA and anhydride of 50 mol%. PON was also obtained as plate-like crystals but the DPn was only 13. HBPA and HNA were first converted to reactive acyloxyaromatic acid intermediates. Then the DPn was increased by means of reaction-induced crystallization of oligomers and subsequent solid-state polymerization via an acid-ester exchange under nonstoichiometric conditions caused by the monocarboxylic acid by-product. Even though the DPn of PON was not as high, direct polycondensation of HBPA and HNA proceeded successfully with aromatic anhydrides. (C) 2004 Society of Chemical Industry.

DOI： 10.1002/pi.1728

Morphology of poly(p-oxybenzoyl) prepared in perfluoropolyether Reviewed

K Kimura, H Ohmori, T Uchida, Y Yamashita

POLYMERS FOR ADVANCED TECHNOLOGIES 16 ( 1 ) 6 - 10 2005.1

Language：English Publishing type：Research paper (scientific journal) Publisher：JOHN WILEY & SONS LTD

Solvent effect on the morphology of poly(p-oxybenzoyl) (POB) prepared by the reaction-induced phase separation of oligomers was examined by the polymerization of p-acetoxybenzoic acid in perfluoropolyether Aflunox(TM) (AFL2507 and AFL606). Polymerization was carried out at 320degreesC for 6 hr. POB microspheres were formed in AFL2507 by the liquid-liquid phase separation of oligomers due to the low miscibility of oligomers in AFL2507. The molecular weight of the solvent influenced the morphology, and the polymerization in AFL606 of which the molecular weight was lower than AFL2507 yielded whiskers formed by crystallization of oligomers induced by the increase in miscibility compared with that in AFL2507. The solvent structure and its molecular weight influenced the miscibility of oligomers and ultimately controlled the morphology from whisker to microsphere. Copyright (C) 2004 John Wiley Sons, Ltd.

DOI： 10.1002/pat.540

Processing, structure, and properties of carbon nano fiber filled PBZT composite fiber Reviewed

T Uchida, T Dang, BG Min, XF Zhang, S Kumar

COMPOSITES PART B-ENGINEERING 36 ( 3 ) 183 - 187 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The poly(p-phenylene benzobisthiazole) (PBZT)/carbon nano fiber (CNF) composite was prepared by in situ polymerization in polyphosphoric acid (PPA), and fibers spun by dry-jet wet spinning. The liquid crystalline PBZT/CNF dope in PPA exhibited excellent spinnability. The PBZT/CNF weight ratio was 90/10. The transmission electron microscope images show isolated and well oriented CNFs with no aggregation. CNF graphite layer stacking in the composite fiber have been observed using high resolution transmission electron microscopy, and showed that graphitic structure of CNFs was not damaged during polymerization in PPA and subsequent fiber spinning and drawing. High resolution transmission electron microscopy also shows that there is no debonding between CNF and the PBZT matrix. Tensile and compressive properties of the composite fibers have been determined and discussed. (c) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compsitesb.2004.04.015

Morphology control of poly(p-mercaptobenzoyl) by modification of oligomer end-group Reviewed

K Kimura, D Nakajima, K Kobashi, S Kohama, T Uchida, Y Yamashita

POLYMER JOURNAL 37 ( 7 ) 471 - 479 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：SOC POLYMER SCIENCE JAPAN

Influence of acyl end-group of oligomers on morphology of poly (p-mercaptobenzoyl) (PMB) was examined by the polymerization of S-acyl-4-mercaptobenzoic acids having the different acyl groups and their dimers in liquid paraffin at 260-300 degrees C. The polymerization of S-acetyl-4-mercaptobenzoic acid afforded PMB whiskers, whereas the polymerization of S-propionyl-4-mercaptobenzoic acid, S-butyryl-4-mercaptobenzoic acid and S-valeryl-4-mercaptobenzoic acid yielded PMB microspheres. The microspheres were formed by the liquid-liquid phase separation of oligomers induced by the longer acyl end-groups than acetyl group of the oligomers due to the reduction of freezing point of oligomers. In contrast to this, the polymerizations of their dimers afforded needle-like and slab-like crystals instead of microspheres. In these polymerizations, the crystallization was induced due to the increase of the molecular weight of the phase-separated oligomers, leading to the increase of the freezing point of oligomers. The morphology of PMB could be controlled by the chemical modification of oligomer end-groups.

DOI： 10.1295/polymj.37.471

Oxidative stabilization of PAN/SWNT composite fiber Reviewed

BG Min, TV Sreekumar, T Uchida, S Kumar

CARBON 43 ( 3 ) 599 - 604 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

PAN/SWNT composite fibers have been spun with 0, 5, and 10wt% single wall carbon nanotubes (SWNTs). Tensile fracture surfaces of polyacrylonitrile (PAN) fibers exhibited extensive fibrillation, while for PAN/SWNT composite fibers, tendency to fibrillate decreased with increasing SWNT content. The reinforcing effect of SWNTs on the oxidized polyacrylonitrile (PAN) fiber has been studied. At 10wt% SWNTs, breaking strength, modulus, and strain to failure of the oxidized composite fiber increased by 100%, 160%, and 115%, respectively. Tensile fracture surfaces of thermally stabilized PAN and the PAN/SWNT fibers exhibited brittle behavior and well distributed SWNT ropes covered with the oxidized matrix can be observed in the tensile fracture surfaces of the fibers. No de-bonding has been observed between unoxidized or the oxidized PAN matrix and the nanotube ropes. Higher strain to failure of the oxidized composite fiber as compared to that of the oxidized control PAN fiber also suggests good adhesion/interaction between SWNT and the oxidized matrix. Thermal stresses generated on the composite fiber during the oxidation process were lower than those for the control fiber. The potential of PAN/SWNT composite fiber as the precursor material for the carbon fiber has been discussed. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2004.10.034

Alignment of SWNTs in lyotropic rigid-rod polymer compositions

Thuy D. Dang, Satish Kumar, Tetsuya Uchida, Karla L. Strong, N. Venkatasubramanian

POLYIMIDES AND OTHER HIGH TEMPERATURE POLYMERS: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS, VOL 3 3 517 - 533 2005

Language：English Publishing type：Research paper (scientific journal) Publisher：VSP BV-C/O BRILL ACAD PUBL

Rigid-rod polymeric fibers, fabricated from their lyotropic mesophase in strong acid solutions, are known to have exceptional tensile strength and high stiffness besides exhibiting remarkable thermal and thermooxidative stabilities. Mechanical and electrical properties of Single-Wall Carbon Nanotubes (SWNTs) are also predicted to be quite extraordinary. The potential benefits of reinforcing a rigid-rod polymer, such as P130, with SWNTs as the dispersed phase are demonstrated in this study. The general methodology involves in situ polycondensation to form the rigid-rod polymer in polyphosphoric acid medium in an environment of SWNTs, followed by the dry-jet wet spinning of the hybrid fibers from the lyotropic liquid crystalline solution. The tensile strength of the PBO/SVv'NT fibers incorporating 10 wt% SWNT was found to be 50% higher than that of the control P130 fibers, while only relatively moderate enhancements in the measured values of the tensile modulus and compressive strengths resulted for the hybrid fibers. Morphological studies of the fibers by TEM analysis showed that SWNTs were very well-dispersed in the 90/10 PBO/SWNT heat-treated composite fibers but the presence of SWNT bundles or ropes, 20-50 nm diameter, aligned parallel to the fiber axis, was observed at higher levels of incorporation of SWNTs as was indeed the case for 85/15 PBO/SWNT heat-treated fibers. Recent efforts to effect the sidewall modification of SWNT with phenylbenziraidazole groups to enhance the potential for SWNT dispersion/solubility in acidic media are also discussed.

Carbon nanofiber and carbon nanotube/polymer composite fibers and films

Chae, H.G., Uchida, T., Kumar, S.

Nanoengineering of Structural, Functional and Smart Materials 2005

Morphology control of poly(azomethine ester) by using reaction-induced oligomer phase separation

Yasuhide Yakushi, Shinichi Yamazaki, Tetsuya Uchida, Kunio Kimura

Polymer Preprints, Japan 54 ( 2 ) 4777 - 4778 2005

Language：Japanese Publishing type：Research paper (international conference proceedings)

Spindle-like crystals of poly(azomethine ester) (PAME) were formed by the polymerization of 4-(4-acetoxybenzylidenamino)benzoic acid (ABBA) in liquid paraffin (LPF) at 300°C via reaction-induced crystallization of oligomers. But the trace of lamellae stacking structure was observed on the surface of crystals due to the lack of post-polymerization between the oligomers in the crystals. In order to induce the crystallization at 350°C to accelerate the post-polymerization, the polymerization of ABBA was carried out in the mixed solvent of LPF and aromatic solvent. This polymerization afforded the fibrillar crystals having smooth surface. One-pot polymerization of 4-acetoxybenzaldehyde and 4-aminobenzoic acid yielded ribbon-like PAME crystals besides spherical precipitates. These ribbon-like crystals showing the larger width than the fibrillar crystals prepared from ABBA were formed by the crystallization of oligomers through the stepwise formation of azomethine linkage and ester linkage during the elevated temperature polymerization. These crystals possessed quite high crystallinity as well as the fibrillar crystals. The morphology of PAME was controllable by means of precipitation during solution polymerization.

Crystal structure and composition of poly(ethylene terephthalate-co-4,4 '-bibenzoate) Reviewed

HM Ma, T Uchida, DM Collard, DA Schiraldi, S Kumar

MACROMOLECULES 37 ( 20 ) 7643 - 7648 2004.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The crystal structure in random copolymers poly(ethylene terephthalate-co-4,4'-bibenzoate) (PET/BB) was studied using wide-angle X-ray diffraction (WAXD). The composition of crystalline and amorphous regions has been studied by FTIR spectroscopy using the amorphous peaks at 1580 and 1560 cm(-1) for terephthalate (T) and bibenzoate (B) units, respectively. Further, PET/BB55 was hydrolyzed to selectively etch the amorphous regions. The hydrolyzed products were further studied by FTIR and H-1 NMR spectroscopy, wide-angle X-ray diffraction, and transmission electron microscopy. Results show that crystal structures are very close to that of the respective homopolymer, PET and poly(ethylene bibenzoate) (PEBB) for the low and high BB content samples, respectively. The crystalline region of high BB content fibers is composed of mainly PEBB units. In PET/BB55 fiber, among the 30 wt % of the copolymer which was not etched, there is only one terephthalate unit for every five repeat units of bibenzoate. The crystal size of B type crystals along the c axis was found to be around five repeat units long. Short chain segments rich in BB are sufficient to induce crystallization, to form PEBB-like crystals.

DOI： 10.1021/ma0486905

Fractionation and crystal morphology of rigid polymer, poly(p-phenylene benzobisthiazole) Reviewed

K Shimamura, N Michiaki, T Ikeda, T Uchida, M Hirao

JOURNAL OF MACROMOLECULAR SCIENCE-PHYSICS B43 ( 5 ) 1015 - 1024 2004.9

Language：English Publishing type：Research paper (scientific journal) Publisher：MARCEL DEKKER INC

Fractionation of the rigid polymer, poly(p-phenylene benzobisthiazole) (PBZT), was carried out in dilute solution in concentrated methane sulfuric acid (MSA) using silica gels as packing material of a column. Several combinations of the average chain length of the fractionating materials and the average pore diameter of the gels were examined to improve fractionation resolution. The gels with average pore diameter near the average chain length resulted in high fractionation resolution. Single crystals of the fractionated and unfractionated PBZTs were observed by transmission electron microscopy (TEM). Both single crystals were fundamentally composed of rod crystals with the chain orienting normal to the rods. The unfractionated PBZT made a cluster of parallel rod crystals, where longer chains penetrated a few rod crystals leaving their chain ends within the crystalline core. On the contrary, with the fractionated polymer, extended-chain rod-like crystals were dispersed, isolated from each other. This morphology enables us to estimate the chain length visibly by TEM, for which a few milligrams of the material is enough for the observation.

DOI： 10.1081/MB-200033280

Preparation of poly(p-oxybenzoyl) microspheres having needlelike crystals on the surface Reviewed

K Kimura, S Kohama, S Kondoh, Y Yamashita, T Uchida, T Oohazama, Y Sakaguchi

MACROMOLECULES 37 ( 4 ) 1463 - 1469 2004.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Polymerization of 4-acetoxybenzoic acid (ABA) with 3,5-diacetoxybenzoic acid (DABA) was examined to create a novel morphology of poly(p-oxybenzoyl) (POB) by means of the phase separation of oligomers during polymerization. Polymerizations were carried out at a concentration of 1.0% in liquid paraffin at 320 degreesC. Polymerization of ABA yielded the POB whiskers. On the other hand, the polymerization of ABA with DABA of which the concentration in the feed (chi(f)) was 0.05-0.20 yielded the microspheres having needlelike crystals on the surface. The average diameter of the microspheres was in the range of 3.4-1.6 mum and the average length of the needlelike crystals was 3.2-0.3 mum. The diameter and length decreased with chi(f). DABA acted as a liquid-liquid phase separation inducer and the liquid-liquid phase separation of co-oligomers comprising 4-oxybenzoyl units and 3,5-dioxybenzoyl units was induced in the beginning of polymerization to form the core microspheres. Then the phase separation mode was changed to the crystallization of the homooligomers of the 4-oxybenzoyl unit and the homooligomers were crystallized as needlelike crystals on the surface of microspheres already precipitated. Solid-state polymerization occurred in the precipitates. The microspheres having needlelike crystals were prepared by the combination of liquid-liquid phase separation and the crystallization of oligomers during solution polymerization. The obtained microspheres having needlelike crystals possessed very high crystallinity and exhibited good thermal stability.

DOI： 10.1021/ma035672z

Diameter control of poly(p-oxycinnamoyl) microspheres prepared by self-organizing polycondensation Reviewed

K Kimura, S Kohama, Y Yamashita, T Uchida, Y Sakaguchi

POLYMER 44 ( 24 ) 7383 - 7387 2003.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD

The diameter control of poly(p-oxycinnamoyl) (POC) microspheres was examined. POC microspheres were prepared by the polycondensation of (E)-4-acetoxycinnamic acid in liquid paraffin at 320 degreesC. The microspheres were formed through the formation of microdroplets by the reaction-induced liquid-liquid phase separation and the subsequent polymerization of oligomers in the microdroplets leading to the solidification. The size of the microspheres was actually governed by the coalescence of the microdroplets in the growth process. In order to control the coalescence of the microdroplets, 4-octadecyloxybiphenyl (ODB) was added to the polymerization solution as a coalescence inhibitor, which exhibited amphiphilicity to liquid paraffin and POC. ODB inhibited the coalescence of the microdroplets. The average diameter decreased with the increase of the ODB concentration, and it was tunable from 0.97 to 4.61 mum. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2003.08.042

Preparation and mechanical properties of rigid polymer network/nylon6 composites Reviewed

T Uchida, K Shimantura, K Kimura

SEN-I GAKKAISHI 59 ( 6 ) 207 - 212 2003.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：SOC FIBER SCIENCE TECHNOLOGY

Rigid polymer networks were prepared by polycondensation of 2,5-diamino-1,4-benzenedithiol with a mixture of tereplithalic acid (TPA) and trimesic acid (TMA). The apparent density was dependent on TPA/TMA ratio and much less than that of linear PBZT (1.57 g/cm(3)), showing existence of many nano voids within the network. As the segment was so rigid, many COOH's were left around the voids. The network swelled twice in weight with E caprolactam, which was polymerized into a composite form of nylon6 impregnated rigid polymer network. Extraction of free nylon6 from the composite with formic acid showed that a quarter of nylon6 grafted directly to rigid polymer network. The grafted nylon6 could not crystallize evidenced by DSC measurements. On the other hand, particles of PBZT network (several hundred nm in diameter) were prepared by stopping the polycondensation just before gelation. A composite film was prepared with the particles swollen with epsilon-caprolactam. The ratio of PBZT network/nylon6 was 1/3 and the apparent density of the composite film was 1.23 g/cm(3) which is higher than that of a pure nylon6 film (1.16 g/cm(3)). Significant improvement in the mechanical property was observed for this composite.

Self-assembling polycondensation for preparation of poly(p-oxybenzoyl-alt-p-mercaptobenzoyl) whisker Reviewed

K Kobashi, K Kimura, Y Yamashita, T Uchida, Y Sakaguchi

MACROMOLECULES 36 ( 12 ) 4268 - 4275 2003.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Self-assembling polycondensation was examined to prepare the whisker of poly(p-oxybenzoyl-alt-p-mereaptobenzoyl). Polymerizations were carried out in liquid paraffin (LPF) and aromatic solvents such as Therm S 800 and 1000 at 300 degreesC for 6 h. Polymerization concentration was 1.0 wt/vol %. The whisker was not obtained by the random copolymerization of p-acetoxybenzoic acid and S-acetyl-4-mercaptobenzoic acid at the molar ratio of 0.5 in feed. However, the whiskers were successfully prepared by the polymerization of S-(4-acetoxybenzoyl)-4-mercaptobenzoic acid (OS) and 4-(S-acetyl-4-mercaptobenzoyl)oxybenzoic acid (SO). The whisker prepared from OS (POS) in LPF was 18 mum in average length and 0.4 mum in average width, and that from SO (PSO) was slightly longer than POS. The whiskers prepared in aromatic solvents were much longer than those in LPF, for which the length was 36-49 mum. These whiskers consist of the alternating polymer chains, and the polymer chains align along the long axis of the whisker. The sequence regularity enhanced the crystallizability of the oligomers, and this led to the formation of whiskers. The oligomer formation rate was much higher than that of transesterfication reaction rate, and this large difference in these two rates made the oligomer precipitate with maintaining the alternating sequence. Further polymerization occurred in the crystals, and the whiskers having the alternating sequence were finally completed. The difference in the two rates increased with the decrease of the miscibility between the oligomer and the solvent, and therefore, OS and LPF were more advantageous to maintain the alternating sequence.

DOI： 10.1021/ma030046n

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