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Zeolite composite membranes were prepared for the separation of VOCs by the pressurized coating method. On the top of the composite membrane, TiO2, polyimide or polyethersulfone were coated by the same tech-100 nm-sized nique.ZSM-5 coated membranes show higher selectivity for n-hexane in n-hexane/benzene mixture than 500 nm sized ZSM-5 coated membrane. Composite membrane coated with 100 nm zeolite and polymer showed the highest selectivity (44) for n-hexane/benzene.

Copolyimide thin films, which has the low level stress and stress relaxation induced by water sorption, were characterized for potential application as encapsulant, stress-relief buffer, and interlayer dielectrics. The polyimides studied are poly(p-phenylene pyromellitimide) (PMDA-PDA), poly(p-phenylene 4,4′-hexafluoroisopropylidene diphthalimide) (6FDA-PDA) and their random copolyimides with various composition. These copolyimide films exhibited good combinations of physical and mechanical properties with low thermal expansion coefficient (TEC) and residual stress behavior by appropriately selecting the ratios of the acid dianhydride component. For these copolyimides, residual stress increased in the range of −5 to 50 MPa, whereas stress relaxation induced by water uptake decreased in the range of 20.5–4.5 MPa at 30°C, 100% relative humidity with increasing 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) composition, respectively. The degree of in-plane chain orientation was directly correlated to the residual stress and stress relaxation coefficient (S) in the film, which is an in-plane characteristic. However, the stress relaxation caused by the water uptake was significantly influenced by packing order induced by chain mobility, which might occur during thermal imidization. Overall, the candidate for the low level stress buffer application from the PMDA/6FDA-PDA copolyimide was both the 90/10 (=PMDA/6FDA in molar ratio) and 70/30 copolyimides.

The effect of film thickness on the water-sorption behaviors of poly(3,4′-oxydiphenylene pyromellitimide) (PMDA-3,4′ODA) films was gravimetrically investigated and interpreted with a Fickian diffusion model in films. The diffusion coefficient increased with increasing film thickness, whereas the water uptake and the activation energy decreased. Overall, the water-sorption behaviors of PMDA-3,4′ODA films are strongly dependent on the changes in morphological structure, which originated from the variation in the film thickness. As the film thickness increased, the molecular in-plane orientation decreased, consequently leading to the increased diffusion coefficient and decreased activation energy. In contrast, the water uptake decreased with increasing film thickness because of the increase in the out-of-plane packing order. The diffusion coefficient and activation energy were strongly dependent on the in-plane orientation in the films. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 669–676, 2001

Copolyimide thin film, which has low-level stress and stress relaxation induced by water sorption, was characterized for potential applications as an encapsulant, a stress-relief buffer, and in interlayer dielectrics. The polyimides examined were poly(p-phenylene pyromellitimide) (PMDA-PDA) and poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) as well as their random copolyimides with various compositions. These copolyimide films exhibited good combinations of physical and mechanical properties with low thermal expansion coefficients, residual stress, and moisture-induced stress-relaxation behavior by appropriately selecting the ratios of the dianhydride component. For these polyimides, the residual stress increased in the range of -8.1-7.5 MPa, whereas stress relaxation induced by water uptake decreased in the range of 10.3-4.7 MPa with increasing BPDA contents, respectively. The major factor in determining the magnitude of the stress behavior induced by both the thermal mismatch and water uptake in films should be the morphological factors such as chain rigidity, chain orientation, crystallinity, and microvoids. Their morphological structures were examined by wide angle X-ray diffraction and a prism coupler, and the thermal properties were measured using a dynamic mechanical thermal analyzer as well as thermomechanical analysis. Overall, the candidate for the low level stress buffer application from the PMDA/BPDA-PDA copolyimide was the 30/70 (= PMDA/BPDA in molar ratio) copolyimide. This copolyimide showed no residual stress after curing at 400 °C and relatively insensitive stress relaxation to ambient humidity.

Four different polyimides: rodlike poly( p -phenylene pyromellitimide) (PMDA-PDA), pseudo-rodlike poly( p -phenylene biphenyltetracarboximide) (BPDA-PDA), semiflexible poly(4,4-oxydiphenylene pyromellitimide) (PMDA-ODA) and poly(4,4-oxydiphenylene biphenyltetracarboximide) (BPDA-ODA) were prepared from two different precursors, poly(amic diethyl ester) (PAE) and poly(amic acid) (PAA). For polyimides prepared from the PAE precursors, stress relaxation coefficient at 25°C, 100% RH was 14.76×10 −10 cm 2 /s for PMDA-PDA, 3.29×10 −10 cm 2 /s for BPDA-PDA, 24.91×10 −10 cm 2 /s for PMDA-ODA and 9.34×10 −10 cm 2 /s for BPDA-ODA. For polyimides prepared from the PAA precursors, stress relaxation coefficient at 25°C, 100% RH was 10.50×10 −10 cm 2 /s for PMDA-PDA, 1.91×10 −10 cm 2 /s for BPDA-PDA, 28.84×10 −10 cm 2 /s for PMDA-ODA and 9.10×10 −10 cm 2 /s for BPDA-ODA. The effect of bulky ethyl ester group on the stress relaxation behavior is significantly high in rodlike PMDA-PDA or pseudo-rodlike BPDA-PDA having high chain rigidity and intermolecular packing order. The decreased birefringence, crystallinity and the looser packing in amorphous region of rigid polyimide derived from PAE may induce fast stress relaxation compared to flexible polyimide. Specially, the different chain mobility of polyimide also induced significant effect on the stress relaxation.

The water diffusion behaviors and activation energies of PDA- and ODA-based polyimide thin films were quite dependent on both the chemical structure and the morphological structure in the films. The water diffusion coefficients of polyimide thin films increased with increasing temperature. The activation energies varied in the range of 5.81 to 9.27 kcal/mol and were relatively higher for the PDA-based polyimide thin films than for the corresponding ODA-based polyimide thin films. For the PDA- and ODA-based polyimide films, the differences in the morphological structures and the chemical affinity to water molecules might be reflected directly on the water diffusion behaviors. The PDA-based polyimide films exhibited a relatively more ordered morphological structure (high crystallinity and good in-plane orientation) than that of the corresponding ODA-based polyimide thin films, which may serve as impenetrable obstacles for the water diffusion in the out-of-plane direction. Consequently, it may lead to a relatively slower water diffusion and high activation energy in the PDA-based polyimide thin films. Additionally, the PDA-based polyimide films with relatively lower chemical affinity showed relatively low diffusion coefficients and high activation energies. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 731–737, 2001

For the biphenyltetracarboxylic dianhydride (BPDA)-based polyimide thin films, the water sorption behaviors were gravimetrically investigated by using a thin film diffusion analyzer. The water sorption behaviors of the polyimide thin films are quite different and strongly dependent upon the sort of polyimide. The diffusion coefficients of the polyimide thin films vary in the range of 1.6 × 10−10 to 12.4 × 10−10cm2/s and the water uptakes vary from 1.52 to 5.25 wt %. Both the diffusion coefficient and water uptake of the polyimide thin films are in the increasing order: BPDA-pPDA < BPDA-p,p′ODA < BPDA-p,m′ODA < BPDA-mPDA ∼ BPDA-p,p′DDS < BPDA-m,m′DDS. Specifically, the polyimide films with para-oriented linkages in backbone structure showed relatively lower diffusion coefficient and water uptake than the corresponding polyimide films with meta-oriented linkages because of the well-developed crystalline structure and good intermolecular chain ordering. In addition, the polyimide thin films having higher chain order showed relatively lower diffusion coefficient and water uptake. The crystallinity and intermolecular chain ordering in the morphological structure are critical parameters in controlling the water sorption behaviors of the polyimide thin films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2121–2127, 2001

The dependence of the water sorption behavior of polyimide thin films upon different diamine fragments was gravimetrically investigated. It was found that the diffusion coefficient and water uptake were strongly dependent upon the internal linkage in the diamine fragment, and varied in the range of 1.6×10−10 13.5×10−10 cm2/s and 1.52 ∼ 5.63 wt.%, respectively. The water sorption behavior of the polyimide films decreased with increasing bulkiness of the internal linkages in the diamine fragments: BPDA-PDA

Effects of Diamines (1,4-Phenylene Diamine and 4,4′-Oxydianiline) on Water Sorption Behavior of Polyimide Thin Film

Four different p-PDA–based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400°C: poly(p-phenylene pyromellitimide) (PMDA-PDA); poly(p-phenylene biphenyltetra carboximide) (BPDA-PDA); poly(p-phenylene 3,3′,4,4′-oxydiphthalimide) (ODPA-PDA); and poly(p-phenylene 4,4′-hexafluoroisopropylidene diphthalimide) (6FDA-PDA). Water-sorption behaviors of polyimide films were gravimetrically investigated at 25°C and 22–100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 × 10−10 cm2/s, and are in the increasing order: BPDA-PDA < PMDA-PDA ∼ ODPA-PDA < 6FDA-PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA-PDA < ODPA-PDA < 6FDA-PDA < PMDA-PDA. The water-sorption behaviors for the p-PDA–based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p-PDA–based polyimide thin films are closely related to the in-plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1315–1323, 2000

The pore-forming behavior in polyimide membranes was investigated by varying the amounts of N , N ′-dimethylacetamide (DMAc, wt.% versus water as a nonsolvent) in coagulation baths. The pore-forming behavior was explained by phase diagrams, coagulation values, diffusion coefficients of nonsolvents, and solubility parameters. The nonsolvent induced phase inversion (NIPI) process prepared the asymmetric polyimide membranes. Increasing the amount of DMAc delayed the demixing phase inversion, increased the stability of the polymer ternary system, and reduced the pore specific volume of sub-layers and the pore size in the skin layers. The diffusion coefficient, D e , of the nonsolvents into the PAA solutions were in the range of 0.39–2.97 × 10 −5 cm 2 /s. Adding DMAc in a coagulation bath resulted in a small difference of the solubility parameter, Δ δ S,NS , and also making the delayed demixing easier. A less porous structure is formed by strong interactions between solvent and nonsolvent; nonsolvent penetration is delayed in the polymer solution. The sub-pore shape in polyimide membranes, which were a finger-like structure, did not change as the amount of DMAc increased. Overall, the DMAc in the pore-forming process had significant effects on the membrane morphology. The choice of solvent as the role of counter additive to a nonsolvent could be an important factor in the membrane preparation.

The effects of thickness on the residual stress behavior of the hinged structure poly(4,4-oxydiphenylene pyromellitimide) (PMDA-ODA) and rigid planar structure poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide were studied. Depending on the polyimide chemistry, residual stress behavior of polyimide film with thickness variation was significantly different. For fully cured BPDA-PDA polyimide at 400°C, residual stress of polyimide film increased from 5.4 MPa to 45 MPa. For fully cured PMDA-ODA polyimide at 400°C, residual stress of polyimide film with thickness variation changed from 29.1 MPa to 40.2 MPa. The effect of thickness on the residual stress for the rigid structure BPDA-PDA was significant, but relatively not for the semiflexible structure PMDA-ODA. Residual stress behavior was quite related to the morphology of fully cured polyimide as shown WAXD analysis. Higher molecular anisotropy leads to lower residual stress of polyimide film. Residual stress behavior of polyimide films with thickness variation is thus closely related to chain rigidity and chain anisotropy associated with polyimide chemistry and morphological structure.

The effect of high boiling point solvent on the residual stress behaviors of semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA-ODA) and pseudo-rodlike poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide was investigated. As a solvent, a mixed solution of 20 wt % cyclohexyl-2-pyrrolidone (CHP; bp = 307 °C) and 80 wt % n-methyl-2-pyrrolidone (NMP; bp = 202 °C) was used. The effects of solvent system and imidizing history on the morphological structure, as well as residual stress, were significantly high in the BPDA-PDA having high chain rigidity, but relatively low in the semiflexible PMDA-ODA with low chain rigidity. In addition, rapidly cured films prepared from PAA (NMP/CHP) showed higher residual stress and a lower degree of molecular anisotropy than slowly cured film imidized from PAA (NMP). This was induced by high chain mobility in polyimide thin films prepared from PAA (NMP/CHP) during the thermal cure process. Therefore, molecular anisotropy, depending on the solvent system and imidizing history, might be one of the important factors leading to low residual stress in polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2879–2890, 2000

The water sorption behavior and the activation energy were investigated for various chemical structure polyimide thin films; BPDA-PDA, BPDA-ODA, PMDA-ODA, and 6FDA-ODA. The activation energy for the water diffusion varied in the range of 5.53 to 9.27kcal/mol, and was in the increasing order: BPDA-PDA < BPDA-ODA < PMDA-ODA < 6FDA-ODA. BPDA-PDA and BPDA-ODA polyimide films showed relatively well-ordered morphological structure, which results in relatively low diffusion coefficient and high activation energy. It was found that the diffusion coefficient and the activation energy are significantly related to the in-plane orientation, crystallinity, and packing order in the polyimide thin films. The morphological structure was predominant factors for the water diffusion coefficient and activation energy in the polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2714–2720, 2000

The effect of curing history on the residual stress behaviors in semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA–ODA) and rigid structure poly(p-phenylene biphenyltetracarboximide) (BPDA–PDA) polyimide was investigated. Depending upon the curing history and different structures of polyimide, the residual stress behaviors and the morphology of polyimide thin films were detected in situ by using a wafer bending technique and wide angle X-ray diffraction (WAXD), respectively. For the rigid structure BPDA–PDA polyimide, the residual stress and the slope decreased from 11.7 MPa and 0.058 MPa/°C to 4.2 MPa and 0.007 MPa/°C as the curing temperature increased, and the annealing process is done. However, for the semiflexible structure PMDA–ODA, the change of the residual stress and the slope was relatively not significant. In addition, it was found that the cured polyimide prepared at a higher temperature with a multistep curing process showed a higher order of chain in-plain orientation and packing order than does the polyimide film prepared at a lower temperature with a one-step curing process. These residual stress behaviors of polyimide thin films show good agreement with WAXD results, such as polyimide chain order, orientation, and intermolecular packing order, due to curing history. Specifically, it shows that the effect of curing history on residual stress as well as morphological change was significant in rigid BPDA–PDA polyimide but, not in semiflexible PMDA–ODA polyimide. Therefore, it suggests that the morphological structure depends upon curing history, and the polyimide backbone structure might be one of important factors to lead the low residual stress in polyimide thin films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3287–3298, 1999

Effect of Poly(amic diethyl ester) Precursor on Residual Stress Behavior of Aromatic Polyimides

Two diaminocalix[4]arene monomers were synthesized from p-tert-butylcalix[4]arene through a 4-step reaction sequence. New copoly(amic acid)s containing calix[4]arene moieties on the polymer backbone were successfully synthesized in N-methyl-2-pyrrolidone by polycondensations of 4,4′-oxydiphthalic anhydride (ODPA) with the diaminocalix[4]arene monomers using 4,4′-oxydiphenylene diamine (ODA) as a comonomer. These copoly(amic acid)s were soluble in aprotic polar solvents, so that they can be processed in various ways. The copoly(amic acid) precursors were thermally converted to the corresponding copolyimides in films. The copolyimide films are amorphous, but insoluble in common solvents. They are thermally stable up to 366°C. The copolyimides exhibit relatively high TEC's, low Tg's, low refractive index, low dielectric constant, low optical anisotropy, low dielectric anisotropy, and low water uptake, compared to those of conventional ODPA-ODA polyimide. These property characteristics were interpreted in regard to bulky, cone-like calix[4]arene moieties and their effects on the chain conformation and morphological structure. The processability and property characteristics support that both of the copolyimides containing calix[4]arene moieties are potential candidate materials suitable for membranes, antioxidant additives, chemical sensor devices, and microelectronic devices. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2013–2026, 1999

Poly(amic diethyl ester) [PAE] precursors of four different polyimides with various chain rigidities were synthesized and thermally converted to the polyimides in thin films: rodlike poly( p -phenylene pyromellitimide) [PMDA-PDA] and poly(4,4′-biphenylene pyromellitimide) [PMDA-BZ], pseudo-rodlike poly( p -phenylene biphenylenetetracarboximide) [BPDA-PDA] and semiflexible poly(4,4-oxydiphenylene pyromellitimide) [PMDA-ODA PAE]. For the polyimide films, water sorption behaviors were investigated by gravimetry and then compared with those of the polyimides prepared from the corresponding poly(amic acid) [PAA] precursors. In addition, their morphological structures were examined by X-ray diffraction. For all the polyimides, both water sorption and morphological structure were dependent upon the history of precursor origin. All the polyimides except PMDA-ODA revealed relatively higher diffusion coefficient of water, higher water sorption, lower intermolecular packing order and lower population of a more ordered phase in the PAE-derived polyimide films than the corresponding PAA-derived polyimide films. For PMDA-ODA, the variations in the water diffusion and sorption due to the precursor origin were relatively small in spite of a relatively large change in the morphological structure. Overall, the effect of precursor origin on the water diffusion and sorption is significantly high in the rodlike or pseudo-rodlike polyimides having a high chain rigidity and high intermolecular packing order, but relatively low in the semiflexible polyimide with a relatively low chain rigidity. In comparison, regardless of the precursor origins, the diffusion coefficient of water was in the decreasing order PMDA-ODA>PMDA-PDA>PMDA-BZ>BPDA-PDA and, however, the water sorption was in the decreasing order PMDA-PDA>PMDA-BZ>PMDA-ODA>BPDA-PDA. These water diffusion and sorption behaviors were understood by considering their chemical affinities to water in addition to the morphological structures.

The effects of isomeric oxydiphenylene diamines (ODA), 3,4'ODA and 4,4'ODA, on the water sorption behavior in pyromellitic dianhydride (PMDA)-ODA, biphenyltetracarboxylic dianhydride (BPDA)-ODA, 3,3',4,4'-benzo phenonetetracarboxylic dianhydride (BTDA)-ODA, and 4,4'-hexafluoroisopropylidenediphthalic anhydride (6FDA)-ODA polyimides were gravimetrically investigated. Water sorption curves were reasonably well fitted by Fickian diffusion despite their morphological heterogeneities in the polyimide thin films. However, the effects of isomeric ODA on the water sorption were quite different depending upon the sort of polyimide. The mutual diffusion coefficient of water and 4,4'ODA based polyimide films varies in the range of 3.0 x 10 -10 cm 2 s to 15.2 x 10 10 cm 2 s -1 . and is in the increasing order: BPDA-4,4'ODA < BTDA-4,4'ODA-PMDA-4,4'ODA < 6FDA-4,4'ODA. The water uptake varies from 1.62wt% to 3.25 wt%, and is in the increasing order: BPDA-4,4'ODA < 6FDA-4,4'ODA < PMDA-4,4'ODA < BTDA-4,4'ODA. However, the diffusion coefficient for 3.4'ODA based polyimide films varies in the range of 6.7 × 10 -10 cm 2 s - to 8.6 × 10 -10 cm 2 s - 1 , and is in the increasing order: BPDA-3,4'ODA < 6FDA-3,4'ODA-BTDA-3,4'ODA-PMDA-3,4'ODA. The water uptake varies from 2.02wt% to 2.98wt%. and is in the increasing order: 6FDA-3,4'ODA < BPDA-3,4'ODA < BTDA-3,4'ODA < PMDA-3,4'ODA. Polyimides having higher chain order, highly crystalline structure, and smaller mean intermolecular distance revealed relativcly lower diffusion coefficients and water uptakes in equilibrium.

Poly(4,4′-oxydiphenylene pyromellitimide) (PMDA-ODA) and poly(1,4-phenylene pyromellitimide) (PMDA-PDA) polyimides were prepared from poly(amic acid) (PAA) and poly(amic ester) (PAE) precursors, respectively. Water sorption and diffusion behavior in films were measured at 90% R.H. and 25°C using the water sorption method and stress relaxation analysis. Regardless of the method, the diffusion kinetics of water in polyimide thin films was well fitted to Fickian diffusion. For rigid rodlike PMDA-PDA film having high Tg (>400°C), film prepared from PAE precursor with less chain relaxation and poor stacking efficiency induced higher stress relaxation and diffusion coefficient of water than with the PAA precursor. For semi-flexible PMDA-ODA polyimide film, film prepared from PAE precursor having higher ordered arrangement, higher chain orientation, and well packing structure, had relatively lower diffusion coefficient of water and less stress relaxation than with the PAA precursor. Water diffusion and stress relaxation for the rigid rodlike PMDA-PDA films are relatively slower than for the semi-flexible PMDA-ODA films due to morphological differences.

Flip chip bonding technique using Pb/In solder bumps was applied to packaging of a 10 Gbps laser diode (LD) submodule for high speed optical communication systems. The effect of the flip-chip bonding interconnection technique instead of conventional wire bonding was investigated for high speed broad band devices. The broad band performance of 10 Gbps LD submodule was simulated using SPICE S/W and compared with experimental results. In this simulation, the 10 Gbps LD was modeled in a parallel RC circuit. The values of R and C used for the equivalent circuit were 5ω and 1 pF, respectively. The LD was placed in series with a 18ω thin film resistor to prevent the impedance mismatch between the LD and a 25ω transmission line. The dependence of parasitic parameters on the small signal modulation bandwidth and the scattering parameters of the LD submodule was investigated and analyzed up to 20 GHz. A small signal modulation bandwidth of 14 GHz at 10 mA dc bias current and the clean modulation response up to 20 GHz were found for the flip-chip bonded submodule. The bandwidth of flip-chip bonded 10 Gbps LD submodule is wider than that of the wire-bonded LD submodule by a difference of 3.8 GHz.

Several photosensitive polyimide (PSPI) precursors were synthesised by the acid/base complexations of conventional poly(amic acid) precursors with photochemically cross-linkable 2-(dimethylamino)ethyl methacrylate. PSPIs in films were prepared from the photosensitive precursors by thermal imidisation, whereas the corresponding PIs in films were prepared from the conventional poly(amic acid)s: rod-like poly(p-phenylene pyromellitimide) (PMDA-PDA), rigid (poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), semi-flexible poly(4,4′-oxydiphenylene biphenyltetracarboximide) (BPDA-ODA), semi-flexible poly(4,4′-oxydiphenylene pyromellit-imide) (PMDA-ODA), and flexible poly(4,4′-oxydiphenylene benzophenonetetracarboximide) (BTDA-ODA). Water sorption and diffusion behaviours in the PSPIs were gravimetrically measured at 25°C in 100% relative humidity and compared with those of the corresponding PIs. For the PSPIs as well as the PIs, the water sorption and diffusion behaviours were nearly Fickian, regardless of the backbone chemistry. However, those were strongly dependent upon the polyimide backbone chemistry and precursor origin. In addition, those in polyimides were affected by the bulky photosenistive groups, even though they were temporarily linked to the precursor polymers and then debonded from the backbones and ultimately outgassed during the thermal imidisation process. For PMDA-PDA, BPDA-PDA and BPDA-ODA, the PSPIs absorbed water more quickly than the corresponding PIs, whereas for PMDA-ODA and BTDA-ODA, the PSPIs absorbed water less quickly than the corresponding PIs. In contrast to the water diffusion, all the PSPIs absorbed slightly more or a great deal more water than the corresponding PIs, depending on the backbone chemistry. All the measured water sorption and diffusion behaviours in the PSPIs were understood by considering changes in the morphological structure (namely, chain order and orientation), voids, and residues possibly induced by the bulky photosensitive groups, in addition to the Tg as well as the chemical affinity to water.

Many mathematical techniques have been developed to determine the geometry of articular joint surfaces, because of its so importance to the study of human joint biomechanics. However, a three-dimensional geometric model of the articular joint, which is essential to solid modelling, contact area measurement, and load bearing analyses, has not been well developed. This study proposes to define the articular geometry of the distal femoral joint of the human knee. A mathematical method based on the influence surface theory of plates is established to generate representations of three-dimensional articular surfaces. A mathematical cone and the surface of the human distal femur are accurately recreated, allowing their geometric properties to be determined. Results suggest that this method can be an effective tool for representing articular surfaces.

In this contribution, composite membranes (CM-D and CM-S) of 2,5-polybenzimidazole (PBI) were synthesized by adding inorganic heteropoly acids (IHA-D and IHA-S). IHA-D and IHA-S were synthesized by condensation reaction of silicotungstic acid with tetraethyl orthosilicate (TEOS) in the absence and presence of mesoporous silica (SiO2), respectively. The synthesized composites were structurally and morphologically characterized and further investigated the functional relationships between the materials structure and proton conductivity. The proton conductivity as well as thermal stability was found to be higher for composite membranes which suggest that both properties are highly contingent on mesoporous silica. The composite membrane with mesoporous silica shows high thermal properties and proton conductivity. IHA-D shows proton conductivity of almost1.48×10-1 Scm−1while IHA-S exhibited2.06×10-1 Scm−1in nonhumidity imposing condition (150°C) which is higher than pure PBI. Thus introduction of inorganic heteropoly acid to PBI is functionally preferable as it results in increase of ion conductivity of PBI and can be better candidates for high temperature PEMFC.

Poly(p-phenylene biphenyltetracarboximide) films with various thicknesses were prepared from the poly(amic acid) precursor by thermal imidization at 230-400°C for 1-10 h under a nitrogen atmosphere. The water sorption in the films was measured at 25°C over 22-100% relative humidity using a Cahn microbalance as a function of film thickness and thermal imidization history. The water diffusion in all the films followed nearly Fickian process despite the morphological heterogeneity due to the ordered and less ordered phases. The diffusion coefficient and water uptake varied in 0.85×10 -10 -7.50×10 -10 cm 2 /s and 0.12-2.4 wt %, respectively, depending upon humidity, film thickness, and imidization history. Both diffusion coefficient and water uptake increased with increasing humidity, but decreased as imidization temperature and time increased. With increasing film thickness, the diffusion coefficient increased whereas the water uptake decreased. The water sorption behavior was interpreted with the consideration of morphological variations, such as polymer chain order, in-plane orientation, and intermolecular packing order due to the film thickness and imidization history

Poly(4,4′-oxydiphenylene pyromellitimide) (PMDA—ODA) films of 10–109 μm thickness were prepared from its poly(amic acid) precursor by thermal imide-ring-closure formation at various temperatures. Water sorption in the films was measured at 25°C over 22–100% relative humidity using an electromicrobalance. Water diffusion in all the films was a nearly Fickian process despite the morphological heterogeneity due to the ordered and less ordered phases. Depending upon humidity, film thickness and imidization history, the diffusion coefficient and water uptake varied in the ranges of 1 × 10 −9 to 3 × 10 −9 cm 2 s −1 and 0.4 to 4.5 wt%, respectively. Overall, both the diffusion coefficient and the water uptake increased with increasing humidity and film thickness, but decreased as the imidization temperature and time increased. The water sorption results were interpreted by consideration of morphological variations (molecular order, chain orientation and microvoids) due to film thickness and imidization history.

PMDA-ODA and BPDA-PDA polyimides in 10-50 Atrn thick films were prepared from the respective poly(amic acid) precursor by thermal imidization for 1-10 h at various temperatures over 230-400C. Their water sorption behaviours were studied in detail by gravimetry. Water sorption in both PMDA-ODA and BPDA-PDA followed a nearly Fickian process in spite of the morphological heterogeneity due to the ordered and less ordered phases. Water clustering or plasticization was very weakly evident on the water uptake versus humidity plots. Water sorption in both polyimides was highly dependent upon imidization history. Both diffusion coefficient and water uptake are decreasing functions of imidization temperature and time. This resulted mainly from the enhancement of overall crystallinity by high-temperature imidization because of their high-rT nature. The diffusion coefficient and water uptake were (1.0-3.0) x 10-9 cm2 s-1 and 0.4-4.5 wt% for PMDA-ODA and (0.9-3.0)x 10-cm2s-' and 0. I2-2.40wt%, depending on humidity,/iihidization history and film thickness. The differences between the water sorptions of the p'olyimides are interpreted by considering the differences in their morphologies and chemical affinities to water.

In this contribution, chemical sensor for the detection of aqueous ammonia has been fabricated using UV-curable polyurethane acrylate (PU) and nanohybrids (NH-1, NH-3 and NH-5). PU has been prepared by reacting polycaprolactone triol (PCLT) and isophorone diisocyanate (IPDI) while the nanohybrids, NH-1, NH-3, and NH-5 have been synthesized by solution blending method using PU with 1, 3, and 5 wt% loading levels of C-20B. PU and their nanohybrids showed higher sensitivity investigated by I-V technique using aqueous ammonia as a target chemical. All the nanohybrids showed higher sensitivity as compared to neat PU. The sensitivity increased with increase in clay content and the nanohybrid containing 5 wt% of clay showed the highest sensitivity (8.5254 μA cm(-2) mM(-1)) with the limit of detection (LOD) of 0.0175 ± 0.001 μM, being 7.8 times higher than pure PU. The calibration plot for all the sensors was linear over the large range of 0.05 μM to 0.05 M. The response time of the fabricated sensor was10.0 s. Therefore, one can fabricate efficient aqueous ammonia sensor by utilization of nanohybrid as an efficient electron mediator.

Four different UV-curable poly(urethane acrylate)s were prepared through the reaction of two diisocyanates [i.e., toluene-2,4-diisocyanate (TDI) and isophorone diisocyanate (IPDI)] and two polyols [i.e., polycaprolactone triol (PCLT) and polycaprolactone diol (PCLD)], and they were characterized with Fourier transform infrared spectroscopy. The mechanical properties, thermal properties, and water sorption of the cured poly(urethane acrylate)s were also investigated with respect to the chemical structures of the polyols and diisocyanates. In comparison with linear PCLD–TDI and PCLD–IPDI, crosslinked PCLT–TDI and PCLT–IPDI with trifunctional PCLT showed relatively high thermal decomposition temperatures. The hardness and modulus of the UV-cured poly(urethane acrylate) films, which were measured by a nanoindentation technique, were in the following increasing order: PCLD–IPDI ∼ PCLD–TDI < PCLT–IPDI ∼ PCLT–TDI. The pencil hardness was 3H for PCLT–IPDI and PCLT–TDI and HB for PCLD–IPDI and PCLD–TDI. Two urethane acrylates prepared from the trifunctional polyol showed better acid and alkali resistances than those made from the bifunctional polyol. These mechanical properties and chemical resistances may have been strongly dependent on the chain flexibility of the molecules and crosslinking density. Regardless of the functionality in the polyol, the change in the yellowness index showed a lower value in the poly(urethane acrylate) coating containing the aliphatic diisocyanate IPDI in comparison with the corresponding poly(urethane acrylate) with the aromatic diisocyanate TDI. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A series of benzoic acid derivatives 1–10 have been synthesised by two different methods. Compounds 1–6 were synthesised by a facile procedure for esterification using N,N’-dicyclohexylcarbodiimide (DCC) as a coupling agent, methylene chloride as a solvent system and dimethylaminopyridine (DMAP). While 7–10 were synthesised by converting benzoic acid into benzoyl chloride by treating with thionyl chloride in the presence of benzene and performing a further reaction with amine in dried benzene. The structures of all the synthesised derivatives of benzoic acid (1–10) were assigned on the basis of extensive NMR studies. All of them showed inhibitory potential against tyrosinase. Among them, compound 7 was found to be the most potent (1.09 μM) when compared with the standard tyrosinase inhibitors of kojic acid (16.67 μM) and L-mimosine (3.68 μM). Finally in this paper, we have discussed the structure–activity relationships of the synthesised molecules.

A series of photoinitiator-free photosensitive polyimides (PSPIs) with lower dielectric constants have been synthesized by reaction of fluorine aromatic diamine, 2,2′-bis(3-amino-4-hydroxyphenyl)hexafluoropropane diamine (AHHFP) with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and a mixture of various mole ratios of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) by using solution poly-condensation reaction at room temperature and further imidization at 180°C. These aromatic polyimides were further acrylated via a reaction with acryloyl chlroride in the presence of triethyl amine to produce negative photoinitiator-free PSPIs. All the photoinitiator-free photosensitive polyimides were characterized by FTIR and NMR while their morphologhy was evaluated by X-ray diffractions study. These newly synthesized PSPIs were evaluated to determine their electrical, thermal, and photolithographic properties. The PSPI (AHHFP-BTDA-6FDA [1 : 0.5 : 0.5]) with high mole ratio of 6FDA showed lower dielectric constants of 2.420 at 1 kHz and 2.170 at 1 MHz in capacitance and optical methods, respectively. Further, the acrylated AHHFP-BTDA showed the highest photosensitivity than other PSPIs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Mesoporous silica fiber was synthesized by sol-gel process and centrifugal spinning method. The spinning process induced lattice contraction and also promoted the oderness of the mesoporous structure. The fiber is 3–10 cm in length and optically transparent. TiO 2 was loaded on the mesoporous silica fiber by simple impregnation method. The volume of 1nm pore was decreased by the formation of TiO 2 particles in the meso-pores of silica fiber. The TiO 2 /mesoporous silica fiber showed the absorption band around 300–350 nm which has been assigned to the crystalline TiO 2 phase. The photocatalytic activity of TiO 2 loaded mesoporous silica fiber was much higher than conventional TiO 2 /mesoporous silica powder and commercial TiO 2 (P-25). The mesoporous silica fiber seems to be promising support for the practical application of photocatalytic reaction.

The mesoporous silica— poly (vinyl alcohol) hybrid polymer electrolyte membranes were successfully synthesized with 140m thickness. The membrane has multiple layered structures, in which the both the top and bottom layers were mainly PVA and middle layer was composed of mesoporous silica hydrogel with PVA. The mesoporous silica - PVA hybrid membranes possessed well-resolved hexagonal mesoporous channel. We found that as increasing the acidity of heteropolyacids, the proton conductivity of the membrane was also increased. The proton conductivities of the hybrid membranes with PW, PMo and SiW at high temperature (70°C ~) were higher than that of Nafion® membrane. Applications of the mesoporous silica PVA composite membranes to DMFC seems to be promising at high temperature (>70°C).

Silica mesoporous/heteropolyacid(HPA)-PVA/SSA hybrid membrane was prepared by sol- gel processes to make a proton conducting membrane. The method involves stabilization of HPA in inorganic-organic hybrid membrane. By adding HPA in the silica mesoporous- PVA/SSA matrix, the membrane showed high proton conductivities of 10-3 S/cm at room temperature. Methanol crossover was decreased with increasing the contents of mesoporous material. This simple method can be applied to make a proton conducting membrane involving mesoporous structure.

The increasing speed of advanced chip technologies has greatly challenged the interconnection methods and processes in order to achieve enhanced capability. We have successfully fabricated the solder bump and it's reflowing process for flip-chip bonding interconnection technique instead of conventional wire bonding for high speed devices. The lead (Pb: 350/spl deg/C) and the Indium (In: 157/spl deg/C) were used for solder bump and deposited by using thermal evaporation. The thickness of the deposited metal for solder bump was in the range of 5/spl sim/6 /spl mu/m thickness. Specially, to increase the accuracy and the reliability of the flip-chip bonding Technique, 3 layer thick photoresist about 30 /spl mu/m was used to control the deposition area for solder bump. It was also used for the lift-off process of excess deposited metal for solder bump. The height of solder bump through the reflowing process was controlled in the range of 10/spl sim/40 /spl mu/m according to the deposited area and shape. Also, the deposited area and shape was one of the most important parameters for solder bump fabrication. In addition, it was found that an oxidized surface layer effects on the increased melting temperature of deposited metal for solder bump. In this process, the reflowing temperature of PB/In (60:40 wt%) solder bumps was 230/spl plusmn/5/spl deg/C.

The purpose of this paper is to propose a reliability parameter of laser diodes for optical communication system applications. Based on the alarm function in optical communication systems, we have developed a reliability parameter; /spl rho//sub a/(=/spl eta//sub a///spl eta//sub 0/.Ith/sub a//Ith/sub 0/)/spl ges/1.5, which is more applicable to estimate reliability projections and to design LD modules for optical communication systems.

Flip chip bonding technique using Pb/In solder bumps was applied to packaging a 10 Gbps laser diode (LD) submodule for high-speed optical communication systems. Dependence of parasitic parameters on the small signal modulation bandwidth of the LD submodule was investigated through SPICE simulations. Experimentally, a small signal modulation bandwidth of 14 GHz at 100 mA dc bias current and the clean modulation response up to 20 GHz were obtained in the flip-chip bonded LD submodule, which was wider than that of the wire-bonded 10 Gbps LD submodule by a difference of 3.8 GHz.

A facile method for polyimide (PI) coating with enhanced hydrophobicity through the deposition of morphology controlled PI particles is presented. An electrospraying process combined with in situ imidization was employed in the fabrication of the PI particles for controllable morphologies as well as hydrophobic multilayered films. We confirmed that in situ imidization accompanying evaporation of the solvent affected the surface morphology of the PI particles during the reactive electrospraying process. The competition of in situ imidization and solvent evaporation in the heating process induces not only the formation of a dimple structure but also the formation of a hollow structure, which was affected by the droplet size. The multilayered film produced by deposition of the PI particles had a microstructured surface with spherical protrusion, micro-dimples, and micro-channels. The multilayered film of PI particles exhibited a hydrophobic surface with water contact angle of 151° due to the microstructured surface of PI coating which was simply but effectively generated by reactive electrospray technique.

Ethanol chemical sensors have been developed by proficient exploitation of polypropylene carbonate (PPC) and PPC/cloisite 20B (clay) nanocomposite (NC) for the detection and quantification of ethanol in the environment. NC was synthesized by the addition of polypropylene carbonate (PPC) into 5 wt% of cloisite 20B. The physicochemical structure was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The thermal and mechanical properties of PPC and NC were investigated by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and nanoindentation analyzer, respectively. NC displayed high thermal and mechanical properties. TGA results revealed that the thermal decomposition temperature (Td50%) of PPC increased significantly, being 43 °C higher than that of pure PPC, while DSC measurements indicated that NC increased the glass transition temperature from 21 to 32 °C. Accordingly, NC showed a high elastic modulus and hardness as compared to PPC. By applying to ethanol sensing, both PPC and NC performed as the best ethanol chemi-sensors in terms of sensitivity. NC showed 3.24 times higher sensitivity (0.8231 μA cm−2 mM−1) as compared to pure PCC (0.2543 μA cm−2 mM−1).

A membrane architecture that facilitates access from both sides in microfluidic environments provides a flexible platform for the study of biosystems. Here, we report for the first time on a simple and low cost fabrication process via nanoimprint lithography (NIL) for a thin, fully released SU-8 membrane with perforated micro- and sub-micron pores and a modular microfluidic system integrated with the membrane. A modified NIL process which combines thermal and UV NIL was employed to define the pore structures in an SU-8 layer coated on a sacrificial layer. We have demonstrated the production of large area SU-8 membranes of as large as 4 inch diameter that are fully covered with perforated micropores. The released SU-8 membrane was easily integrated as a modular component into a microfluidic system by sandwiching the membrane between two microfluidic chips. Important aspects to reliably produce the membrane architecture such as materials selection and process conditions for fabrication are discussed. After demonstrating selective adsorption of lipid vesicles at the micropore sites of the SU-8 membrane, we have reconstituted lipid bilayers at the micropores within the microfluidic system following the method developed by Suzuki et al (2004 Lab Chip 4 502–5). This implies that the membrane architecture can potentially be used as a microfluidic platform with lipid bilayers that can sustain external mechanical stress for biophysical studies of membrane proteins.

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