Hideroh Takahashi

Preparation of nylon 66/mesoporous molecular sieve composite under high pressure

Nylon 66/mesoporous molecular sieve (pore diameter: 2.7 nm) composites were prepared by annealing mixtures of nylon 66 and mesoporous molecular sieve (FSM) powders under high pressures and high temperature (FSM content: 0-60 wt %; pressure: 0.5-30 MPa; temperature: 300°C; time: 1 h). X-ray diffraction and TEM measurements indicated the presence of the pores of FSM in the composite. Above 2 MPa, nylon 66 was charged in the pores of FSM. The fraction of the charged nylon 66 increased with pressure and was independent of the FSM content (pressure: 2-30 MPa; fraction of charged nylon 66: 54-66%). The infrared spectrum of the composite showed the bands based on Si-O, C-H, N-H, C=O. DSC measurement indicated that the heat of fusion of nylon 66 crystallite in the FSM pores was low compared with that of nylon 66. The composites prepared above 2 MPa were found to be superior in storage modulus to nylon 66. The modulus increased with an increase in the fraction of charged nylon 66 and the amount of FSM.

Optical limiting property of fullerene-containing polystyrene

Buckminsterfullerene, such as C60 and C70, is a soluble new form of carbon [1] and can be obtained by evaporating graphite electrodes in helium at 1.3 3 10 Pa [2]. This C60 and its n-doped derivatives exhibit outstanding electrical and non-linear optical properties [3±5]. In most materials, transmittance of visible laser pulses increases with incident intensity. However, optical-limiting materials exhibit a decrease of the transmittance with increasing incident intensity [4]. The materials were also termed reverse saturable absorbers [6] and can serve to protect sensors and eyes. The toluene solution of fullerene such as C60 shows the optical limiting property with saturated output ̄uence lower than those reported for other optical-limiting materials in use [4]. The polymeric fullerene derivatives have been reported in previous papers [7±12]. We have shown that polystyrene-bound C60 was synthesized by reaction of styrene in the presence of C60 under high pressure [12]. The polymer showed the optical limiting property in the solid state. In the present work, the high-pressure synthesis of fullerene-containing polystyrene (mixture of polystyrene and polystyrene-bound fullerene) was carried out and the optical limiting property of a toluene solution of the polymer was investigated. Fullerene (C60:92%, C70:8%) from MER Corporation (USA) was used without further puri®cation. Fullerene was soluble in styrene at room temperature [12]. Reaction of styrene solution of fullerene under high pressure was carried out using a high hydrostatic pressure reactor, as shown in a previous paper [13]. The styrene solution of fullerene with 0.5 wt % (about 2 g) packed into a polytetra ̄uoroethylene cell (inside diameter: 8 mm, length: 40 mm), was introduced into the high pressure vessel. The specimen solution was compressed at 0.1 GPa by a handoperated oil pump, reacted at 250 8C for 5 h with a pressure transmitting medium (silicone oil). After reaction under high pressure, the fullerene-containing polystyrene was cooled to room temperature, decompressed and removed from the cell. The molecular weight of the fullerene-containing polystyrene was determined using a liquid chromatograph consisting of a refractive index detector and a column. The molecular weight of the polystyrene was between 200 and 50 000 based on the polystyrene calibration. The experimental arrangement to characterize the optical limiting property was as reported earlier [14]. The optical limiting tests were performed with a Continuum frequency doubled Nd:YAG laser that produces about 400 mJ=pulse of 8 ns pulse width. The beam had a near Gausian transverse pro®le. The laser was operated at 10 Hz. The quartz cell which contained the solution was irradiated with pulses 8 mm diameter from the Nd:Yag laser at 532 nm. Apertures and focusing optics were not used. The optical limiting property was obtained by varying the input energy with increase in delay time of the Qswitch from 304 to 434 ìs. Input and output energies per pulse were obtained from a power meter (Gentec: PSV-3103) and the energy transmitted through the toluene was identi®ed as an input energy. Fig. 1 shows the input-output response of the toluene solutions of the fullerene-containing polystyrene. At low input ̄uence, the transmittance of the solution, obtained by the ratio of the input ̄uence to the output ̄uence, is constant and obeys the Beer±Lambert law. At high input ̄uence, the transmittance decreases with input ̄uence. Input and output response did not depend on raising and lowering the input ̄uence. This observation indicates that there is no photodegradation of the product by irradiation of the laser beam. We observe an optical limiting property with the saturated output ̄uence. The saturated output ̄uence of the toluene solution of the polymer is estimated by the output ̄uence at an input ̄uence of 0.58 J cmÿ2. The saturated output ̄uence decreases from 0.22 to 0.05 J cmÿ2 with increase of the fullerene concentration (0.025±0.075 wt %). The reverse saturable absorption mechanism by an energy level diagram yielded a reasonable explanation for optical limiting of ð-electron conjugated systems such as fullerene (C60, C70) [15, 16] and polyacene-based oligomer [14]. As the fullerenecontaining polystyrene also has a ð-electron conjugated system, the optical limiting behaviour can be

High-pressure synthesis of C60-containing polystyrene

Abstracts are not published in this journal

Annealing of polyacene-based oligomer synthesized under high pressure

A polyacene-based oligomer was synthesized by reaction of diphenyldiacetylene under high pressure (pressure: 0.1 GPa; temperature: 250°C; time: 5 h). Annealing of the polyacene-based oligomer was carried out (temperature: 300–800°C; time: 5 h). Gas analysis, BET surface area measurement, Raman scattering, X-ray diffraction, elemental analysis, 13C-NMR, and conductivity measurements were performed to characterize the structure of the product. The oligomer was annealed with the appearance of mainly hydrogen. The H/C of the product decreased with increasing annealing temperature. The Raman band is observed at 1610 cm−1 assigned to a doubly degenerate deformation vibration of the carbon hexagonal ring. The additional band observed at 1340 cm−1 is attributed to the size effect. X-ray diffraction indicated that the product had no sharp peak because of the disordered carbon structure.

High-pressure synthesis and optical limiting property of cyclic diphenylacetylene oligomer

New conjugated oligomers were synthesized by reacting diphenylacetylene under high pressure of 0.13–0.76 GPa at 250 and 300°C for 1–10 h. The number-average molecular weight Mn, and the weight-average molecular weight Mw increased with pressure, but those values were independent of temperature and time (Mn, 320–490; Mw, 350–580). Elementary analysis, field desorption mass spectrometry, Fourier transform infrared, and 13C nuclear magnetic resonance experiments revealed that the oligomer above and including pentamer was a new compound having cyclic structure. Toluene solutions of the oligomer (400 Mn) contained within a quartz cell were irradiated with the pulse from a frequency-doubled Nd : Yag laser at 532 nm. The transmittance of the solution decreased with input fluence, and we observed an optical limiting property with saturated output fluence. As the concentration of the oligomer increased, the saturated output fluence decreased. The optical limiting property was analyzed according to the reverse saturable absorption mechanism.

High-pressure synthesis of polyphenylacetylene

Polyacetylene is an insoluble conjugated polymer that can be obtained by using conventional ZieglerNatta catalysts [1-3]. Substituted acetylenes, having bulky phenyl groups such as phenylacetylene, produce oligomers not exceeding the number-average molecular weight of 7500 and insoluble polymers by the use of the Ziegler-Natta catalyst [4, 5]. Masuda et al. found in 1974 that group 5 and 6 transition metal catalysts (W and Mo based catalysts) are effective for phenylacetylene polymerization [4, 6]. These polyacetylenes with substituents have attracted much attention as electrical and non-linear optical materials [7-9]. The application of pressure is well known to influence the structure, properties and reactions of substances [10-15]. Acetylene was polymerized at room temperature by a reaction-induced high pressure [11]. A previous paper reported the synthesis of a phenylacetylene oligomer under high pressure (0.11-0.92 GPa) and high temperature (100-200 °C) [16]. In the study reported here, the polymerization of phenylacetylene was carried out at room temperature under high pressure (1.5 GPa). Visible absorption spectroscopy and gel permeation chromatography (GPC) were utilized to characterize the structure of the product. Phenylacetylene (molecular weight 102.14, liquid) in the form H--C=--C--CoH 5 (Wako Pure Chemical Industries Ltd, Japan) was used for the reaction without further purification [purity >99% (gas chromatography)]. The reaction of phenylacetylene under high pressure was performed with a specially designed super high hydrostatic pressure reactor (Hikari High Pressure Machinery Co., Japan). The block diagram of the reactor is schematically illustrated in Fig. 1. Paraffin was used as a pressure transmitting medium. The pressure in the super high pressure vessel was increased ten times compared with that in the high pressure vessel through the hydraulic intensifier. Pressure was measured using a Bourdon gauge (Heise gauge) and a manganin coil gauge. The pressure was displayed on a digital manometer and was recorded on a recorder. The specimen (about 2 g) was packed into a polytetrafluoroethylene cell (inside diameter 8 mm, length 40 mm). After closing the cell, it was introduced into the super high pressure vessel. The specimen was compressed at 1.5 GPa by a motor driven oil pump and substantially reacted at room temperature (2225 °C) for constant times of 1-300 h. After reaction under high pressure, the product was decompressed and removed from the cell. Visible absorption spectra of the products in a quartz cell (specimen path length 10mm) were recorded on an Ultraviolet (UV)-visible recording spectrophotometer (Shimadzu UV-2100). The spectrum was measured in the 400-800 nm region. The molecular weight of the product was determined using a liquid chromatograph (Japan Analytical Industry Co., Ltd, LC-08) consisting of a UV absorption detector (wavelength 254nm) and a column. Chloroform was used as a mobile phase at

Optical-limiting property of cyclic phenylacetylene oligomer synthesized under high pressure

The optical-limiting property of a new cyclic phenylacetylene oligomer was investigated. Toluene solutions of the oligomer contained within a quartz cell were irradiated with the pulse from frequency doubled Nd: Yag laser at 532 nm. At low input fluence, the transmittance of the toluene solution was constant and agreed well with that obtained by spectrophotometer. At high input fluence, the transmittance of the solution above a concentration of 5 wt % decreased with input fluence. The oligomer had an optical limiting property. As the concentration of the oligomer increased from 5 to 20 wt %, the threshold for optical limiting decreased. The threshold was independent of the molecular weight. The optical limiting property was analyzed by the following equation obtained according to the reverse saturable absorption mechanism; log(I0/I) = K(I0 - I) + Ag, where I0 is the input fluence, I is the output fluence, K is a parameter depending on the absorption cross section and the relaxation time, and Ag is the absorbance of the ground state.

Characteristics of Flow Curves for Blends of Immiscible Polymers with Intersecting Flow Curves

and Kunihiro OSAKI*2 *1 Toyota Central Research and Development Laboratories, Inc., Nagakute-cho, Aichi-gun, Aichi-ken 480-11, Japan *2 Institute for Chemical Research, Kyoto University, Uji 611, Japan Characteristics of flow curves for the blends of immiscible polymers , whose flow curves intersect each other, were investigated by computer simulation based on the concentric multi-layer model proposed previously. Flow curves of component polymers were approximated by the power-law. Calculations were performed for a few combinations of power-law indexes and for various blending ratios. Following results were obtained.(1)Flow curves for the blends with various ratios intersect at the same point as those of parent polymers do.(2)Flow curves lie in the order of blending ratio . (3)Flow curves are similar to that of a lower viscosity component at either side of the cross point on flow curves of parent polymers.(4)The region on flow curves, where the conventional blending rules on viscosity are applicable , depends on the ratio of power-law indexes of parent polymers and the value of shear rate and viscosity at the cross point. A good agreement between predicted and experimental results were attained for the blends of polystyrene and high density polyethylene .

High‐pressure synthesis of cyclic mesitylacetylene oligomer

Reaction of mesitylacetylene was carried out by annealing under high pressure (0.13 and 0.52 GPa). The products obtained were classified into soluble and insoluble products in chloroform. The insoluble product reacted under 0.13 GPa was the mesitylacetylene polymer. The soluble product reacted under 0.13 GPa was classified as the monomer and the oligomer [number-average molecular weight (M n ): 390, weight-average molecular weight (M w ): 453, Oligomer yield (O y ): 36%]. The oligomer yield was accelerated by pressure [pressure: 0.13-0.52 GPa, M n : 390-315, M w : 453-968, O y : 36-98%]. Field desorption mass spectrum showed that the oligomer had cyclic structure. The result of the elementary analysis revealed that the insoluble product reacted under 0.52 GPa was a polycyclic aromatic compound.

Molecular Dynamics Simulation of Thermal Motion and Elasticity of a Polymer Chain.

高分子鎖の熱運動とそれに基づく弾性を分子動力学シミュレーションにより解析し, ガウス鎖モデルを用いた統計的な理論と比較した. モデル作成と計算にはPOLYGRAFを使用し, 重合度50のシスポリブタジエンを用いて, 両端を拘束しない自由高分子鎖および両末端間距離を拘束したものについて計算を行った. その結果, 自由高分子鎖の回転半径と温度との関係には屈曲点が現れ, その温度はシスポリブタジエンのガラス転移温度171Kにほぼ一致した. 拘束高分子鎖について, 高分子鎖の自由エネルギー変化から計算した拘束力は, 両末端に働く力を直接に計算した拘束力に一致した. 拘束力は, 高分子鎖が伸びきり状態になる少し前まではガウス鎖モデルとほぼ同じ大きさであるが, そこから急激に立ち上がった. 一方, 両末端間距離の小さいランダムコイル状の場合には, 非結合原子間の相互作用によりエネルギー弾性的な力が働いていることが分かった.