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An epoxy resin (diglycidyl ether of bisphenol-A) was blended with different loadings of a glycidyl-polyhedral oligomeric silsesquioxane (POSS) and isothermally cured with an amine hardener at varying temperatures and times. The glass transition temperature (T g) of the samples was measured at different chemical conversions (α) using differential scanning calorimetry (DSC). Time-temperature shifts were made for T g vs. ln(time) data to be superposed at an arbitrary reference temperature in the kinetically controlled reaction regime, and these shift factors were used to obtain an Arrhenius activation energy. The influence of POSS on different reaction systems was investigated in terms of the T g-α relationship, which was fitted with two models; DiBenedetto and Venditti/Gillham equations. It was found that POSS molecules played different roles at different stages of the curing process. At lower conversions, the inorganic cage of the incorporated POSS (up to 20 wt%) reduced the mobility of the molecular segments, giving rise to an increase in T g. However, above the 20 wt% POSS, there was a depression of T g, which may be associated with a plasticizing effect of organic substituents of the POSS molecules. Moreover, the effect of POSS on T g became less pronounced when the conversion reached 0.8.

Poly(p-phenylenebenzobisoxazole) (PBO) composite fibers containing small amounts (~2 wt.%) of carbon nanofibers (CNFs) were successfully prepared by in-situ polymerization and dry-jet wet spinning. Polarized optical microscopy images displayed a lyotropic liquid-crystalline phase in the as-polymerized dopes. Solution viscosity measurements revealed that the molecular weights of the composite fibers were in the range from 1.81×104 gmol-1 to 2.2×104 gmol-1. Field emission scanning electron microscopy images of the composite fibers etched by UV irradiation showed that CNFs embedded in the PBO matrix were individually dispersed, and well oriented along the fiber direction. Tensile tests indicated that the tensile moduli of the PBO/CNF composite fibers were higher than those of the pristine PBO fibers, whereas the tensile strengths were lower or similar to those of the pristine PBO fibers. The elastic loop test was carried out to measure the compressive strength of the fibers. The compressive strength of the pristine PBO fiber was 0.3 GPa, whereas that of a PBO composite fiber containing 1.0 wt.% CNF increased to 0.92 GPa, which is about twice the compressive strength of Zylon (0.43 GPa). Moreover, a heat-treated PBO composite fiber containing 2.0 wt.% CNFs exhibited the high compressive strength of 1.17 GPa, which is the second highest value among all reported values for organic polymers.

Sulfonic acid-functionalized graphene (S-graphene) is employed as a promising inorganic filler as well as a solid acid proton conducting medium to realize a composite membrane with Nafion for polymer electrolyte fuel cell (PEFC) applications under reduced relative humidity (RH). The functionalization of graphene is performed by sulfonic acid-containing aryl radicals to increase the number of sulfonate groups per unit volume of a domain. A Nafion–S-graphene composite membrane is obtained by embedding S-graphene in Nafion, which provides high absorption of water and fast proton-transport across the electrolyte membrane under low RH values. The proton conductivity of the Nafion–S-graphene (1%) composite membrane at 20% RH is 17 mS cm–1, which is five times higher than that of a pristine recast Nafion membrane. PEFCs incorporating the Nafion–S-graphene composite membrane deliver a peak power density of 300 mW cm–2 at a load current density of 760 mA cm–2 while operating at optimum temperature of 70 °C under 2...

Multi-walled carbon nanotubes (MWNTs) were functionalized with benzoic acid groups via an “on water” technique and further derivatized with norbornene groups. The norbornene groups grafted onto the MWNT surface were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FE-SEM) to confirm covalent functionalization. Observations of suspensions and transmission electron microscopy (TEM) and SEM images of nanocomposites suggested improved dispersibility of norbornene-functionalized MWNTs (nMWNTs) in dicyclopentadiene/5-norbornene-2-carboxylic acid (DCPD/NCA) monomers relative to pristine MWNTs (pMWNTs). Cure kinetics and mechanical properties of MWNT/poly(DCPD/NCA) nanocomposites with various functionalized nanotube loadings (0.1–0.6 wt%) were investigated by means of differential scanning calorimetry (DSC), a universal testing machine (UTM), and dynamic mechanical analysis (DMA). It was found from DSC that the functionalized nanotubes have an acceleration effect on the cure process, which is likely related to enhanced heat transfer from the carbon nanotubes. The swelling ratio increased with increasing nanotube loading, revealing that the formation of crosslinks was hindered by the addition of nanotubes. The incorporation of the functionalized nanotubes resulted in improved Young’s modulus and yield strength compared with neat poly(DCPD/NCA), far beyond the enhancement with pMWNTs. Although a decrease in the elongation at break was observed as the nanotube loading increases, the tensile toughness remained almost unchanged up to 0.4 wt% nMWNT loading. Furthermore, the addition of the nMWNTs also shifted the glass transition toward higher temperatures. These enhancements are presumably attributed to better nanotube dispersion and stronger nanotube-matrix interfacial affinity.

Blends of poly(lactic acid)s (PLAs) containing three different concentrations of d -isomer (i.e., 1, 4, and 10 mol%; referred to as PLA1, PLA4, and PLA10, respectively) with poly( dl -lactic acid) (PDLLA) were prepared via solution blending. The three PLAs were miscible with PDLLA, as determined by dynamic mechanical analysis. Drawn films of PLA1/PDLLA, PLA4/PDLLA, and PLA10/PDLLA blends exhibited endothermic peaks just above the glass transition temperature, which is evidence of strain-induced enthalpy relaxation. A thermodynamic model for the miscible blend system was applied to determine contributions of intramolecular and intermolecular energy changes to strain-induced enthalpy relaxation for PLA1, PLA4, and PLA10; the resultant values suggested that intramolecular energy changes are mainly responsible for strain-induced enthalpy relaxation.

A vertically aligned carbon nanotube (VA CNT) membrane created from the successful fusion of nanotechnology and membrane technology has been stated to be a next generation membrane due to its fast water transport and antimicrobial properties. Although previous studies of the VA CNT membrane reported the potential for fast water transport or desalination by molecular dynamics simulation, this study is the first to report on the feasibility of using the VA CNT membrane for water purification. The VA CNT membrane (4.8 nm of pore diameter and 6.8×1010 #/cm2 of pore density) was fabricated and its flux, rejection performance, and membrane biofouling tendency were evaluated in comparison to the commercial ultrafiltration (UF) membrane. The VA CNT membrane appeared to have a water flux approximately three times higher than the UF membrane and water transport approximately 70,000 times faster than conventional no-slip flow. This higher flux was peculiarly observed in water, the most hydrophilic solvent, while other solvents showed that permeate flux decreased with higher viscosity. The rejection property of the VA CNT membrane as examined by the MWCO measurement was similar to the commercial UF membrane. Additionally, the VA CNT membrane showed better biofouling resistance with approximately 15% less permeate flux reduction and 2 log less bacterial attachment than the UF membrane. This study reports the high potential of the VA CNT membrane with antifouling property in the water purification process.

Two different sets of polyamide 66(PA66)-based composite films containing 2.0-10.0 wt% acid-treated multiwalled carbon nanotubes (MWCNT) were manufactured by solution mixing and casting method in the presence or absence of a nonionic surfactant. For the improved dispersion and interfacial interaction of MWCNTs in the PA66 matrix, carboxylic acid-functionalized MWCNTs were prepared by the acid-treatment of pristine MWCNTs. The uniform dispersion of the acidtreated MWCNTs in the PA66 matrix was confirmed from FE-SEM images of the fractured composite film surfaces. DSC thermograms supported that the acid-treated MWCNTs served as nucleating agents for the melt-crystallization of PA66 in both composite films prepared with/without the addition of the surfactant. The electrical and tensile mechanical properties of the composite films prepared with the surfactant were ~20 % higher than those of the composite films manufactured without the surfactant. For both composite films, sheet resistivity and tensile mechanical properties were found to be highly decreased and increased, respectively, with the increment of the acid-treated MWCNT content.

The endothermic heat just above glass transition for the drawn poly(lactic acid)s (PLAs) films with four different d -isomer contents (1, 4, 10, and 20 mol%: named as PLA1, PLA4, PLA10, and PLA20) was observed on differential scanning calorimetry (DSC) heating scan. The amount of endothermic heat increases with increasing the draw ratio, which means that the endotherm is undoubtedly caused by stretching the PLAs films. The endotherm is clearly seen in the drawn films of amorphous PLAs (PLA10 and PLA20). In the crystalline PLA4, the endothermic heat decreases with increasing crystallinity. Hence, it is considered that the endotherm is closely related to some events occurring in the amorphous phase of the drawn PLAs films. In order to verify an association between endothermic event and macroscopic shrinking deformation, two types of dimensional constraints during DSC measurement, which are effective in restraining the sample shrinkage, were imposed on a drawn PLA10 monofilament. The endothermic temperature of PLA10 with draw ratio of 4 moves from 62 °C for a free filament to 67 °C for an ends-fixed one. For a filament ends-fixed and very tightly rolled up with aluminum sheet, a sharp endothermic peak does not appear. Instead, a very broad endothermic curve ranging from 90 °C to 172 °C shows up, suggesting that the stretched chains in a filament with severe dimensional constraint relax slowly toward isotropic state over broad range of temperature. This result implies that the heat-absorption is contemporaneous with the macroscopic shrinkage of drawn filament. It was also visually confirmed that a drawn sample is shrunk above the endothermic peak. The conformational energy change during macroscopic shrinking deformation, determined by using Raman spectroscopic method, is comparable to the endothermic heat. Hence, the main origin of endothermic heat seems to be the conformational energy change during shrinking deformation.

We have prepared the blends of poly(pentamethylene 2,6-naphthalate) (PPN) with poly(heptamethylene 2,6-naphthalate) (PHepN) by solution blending method and investigated their glass transition behaviour, melting behaviour, and tensile properties. It was observed that the blends of PPN/PHepN(9/1) and PPN/PHepN(1/9) have a single glass transition, reflecting a homogeneous phase, whereas those of PPN/PHepN(7/3), PPN/PHepN(5/5), and PPN/PHepN(3/7) exhibit double glass transitions, representing the existence of two phases. The PPN homopolymer annealed below 90 °C shows triple melting peaks (Tm1, Tm2, and Tm3). It was proved that Tm1 is attributed to melting of thin lamellar formed during secondary crystallization process, Tm2 to melting of thick lamellar created during primary crystallization, and Tm3 to melting of crystals recrystallized after melting the primary crystals at Tm2. For the annealed PHepN homopolymer, double melting endotherms (Tm1 and Tm2) were observed, caused by dual lamellar population with different thickness, i.e. Tm1 corresponding to the melting of secondary crystal and Tm2 to primary one. The Hoffman-Weeks plots, applied to the melting of primary crystals (Tm2s), indicate that the equilibrium melting temperatures of PPN homopolymer, PPN/PHepN(9/1), and PPN/PHepN(7/3) blends are same to be 147 °C, and those of PHepN homopolymer, PPN/PHepN(1/9), and PPN/PHepN(3/7) blends to be 145 °C. Both the glass transition and melting behaviours demonstrate that the PPN/PHepN blend system is partially miscible. In addition, both the modulus and strength for the blends almost follow additive rule against blend composition, indicating that the PPN/PHepN blends are mechanically compatible over all blend compositions.

This study investigated the main origin of the thermochromism of a novel compound, 1,3-bis(hydroxyethylamino)-4,6-dinitrobenzene (BDB). In order to unravel the relative dependence of reversible color change between yellow and orange on proton transfer reaction and crystal-crystal phase transformation, kinetic experiments were executed. The recovery rates of thermochromic transition, proton transfer reaction, and crystal-crystal phase transformation were calculated from the data measured through UV-vis spectrophotometry, IR spectrometry, and X-ray diffractometry with a lapse of time at fixedtemperatures (30, 40, and 50 °C) after cooling from heated temperature (150 °C). The kinetic experiments revealed that the recovery takes place more quickly at lower temperature. At each fixed-temperature, the recovery rate is in the order of the crystal-crystal phase transformation > the proton transfer reaction > the thermochromic transition. It is concluded that the proton transfer reaction is the main origin for thermochromism of BDB in solid state and the crystal-crystal phase transformation is a collateral one.

We have prepared a series of poly(lactic acid)/hydroxyapatite (PLA/HAp) composite foams by a supercritical CO2 foaming process and investigated the lead ion (Pb2+) removal performances of the foam samples in batch aqueous solutions (foam sample of 5 g, aqueous solution of 500 ml, initial Pb2+ ion concentration of 275 mg/l, pH values of 2.0–6.0) at 25°C. It is characterized that the porosity of the foams decreases from 96.3% to 50.3% as the HAp content increases from 0 to 40 wt%, although all the foam samples exhibit well-developed open porous structures. The maximum capacity of Pb2+ ions removed by the composite foams increases from 81.2 to 140.5 mg/g with increasing the HAp content from 10 to 40 wt%, due to the increased adsorption sites of HAp for Pb2+ ions. However, the removal kinetic analysis based on the pseudo-second order model demonstrates that the Pb2+ ion removal rate is slightly faster for the composite foams with higher porosity (i.e., lower HAp content). The maximum Pb2+ ion removal capacity of a given composite foam increases from 20.2 to 140.5 mg/g with increasing the initial pH value from 2.0 to 5.0 but it decreases slightly to 111.7 mg/g at the initial pH value of 6.0. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

We herein report the effects of interfacial reinforcement on mechanical and electrical properties of nanocomposites based on polylactide (PLA) and multi-walled carbon nanotube (MWCNT). For this purpose, a series of MWCNTs grafted with PLA chains of various lengths (MWCNT- g -PLAs) were prepared by ring-opening polymerization of l -lactide with carboxylic acid-functionalized MWCNT (MWCNT-COOH). MWCNT- g -PLAs were then mixed with commercial PLA to obtain PLA/MWCNT- g -PLA nanocomposites with 1.0 wt.% MWCNT content. It was revealed that morphological, mechanical, and electrical properties of PLA/MWCNT- g -PLA nanocomposites were strongly dependent on the PLA chain length of MWCNT- g -PLAs. FE-SEM images exhibited that the nanocomposites containing MWCNT- g -PLA with longer PLA chain length exhibited better dispersion of MWCNTs in the PLA matrix. Initial moduli and tensile strengths of PLA/MWCNT- g -PLA composites increased with the increment of chain length of PLA grafted on MWCNTs, which attributes to the improved interfacial adhesion between the grafted PLA chains of MWCNT- g -PLA and the PLA matrix. As a result, the experimental initial modulus (2775 ± 193 MPa) of the nanocomposite including MWCNT- g -PLA with PLA chains of average molecular weight of 530 g/mol was quite close to the theoretical value (2911 MPa) predicted for the nanocomposite with perfect interfacial adhesion. Unexpectedly, electrical resistivities of PLA/MWCNT- g -PLA nanocomposites were found to increase from ∼10 4 to ∼10 12 Ω/sq with increasing the PLA chain length of MWCNT- g -PLA, which is due to the fact that the PLA chains grafted on MWCNTs prevent the formation of the electrical conduction path of MWCNTs in the PLA matrix.

We report the isothermal enthalpy relaxation behavior, gas permeability, and dynamic mechanical properties of melt-quenched amorphous polylactide (PLA) films with various D-isomer contents (1, 4, and 9 mol%) as a function of the aging temperature (Ta) and time (ta). It was found that the enthalpy relaxation peak area (ΔHrelax) and glass transition temperature (Tg) of all PLA samples aged at a given Ta increased initially and then remained relatively unchanged with increasing ta. The experimental ΔHrelaxvs. ta plots were fitted well with the Cowie-Ferguson equation incorporating the Kohlrausch-Williams-Watts (KWW) function. A comparison of the PLA samples aged at a similar degree of subcooling (ΔT = Tg−Ta) showed that the ultimate ΔHrelax was somewhat higher for a PLA film with a lower D-isomer content. In addition, the oxygen permeability of all PLA films decreased linearly with increasing ta, which is due to the densification of glassy PLA films during physical aging. The dynamic mechanical data demonstrated that for the aged PLA films, the storage moduli around glass transition region increased significantly and the loss moduli peak corresponding to the glass transition region shifted to higher temperatures and became narrower.

A series of amorphous poly(lactic acid) (PLA) monofilaments with various D-isomer contents of 1∼9 mol% have been prepared and then elongated uniaxially at 25∼65 °C in the glass transition region. Both initial modulus and maximum strength of PLA monofilaments are appreciably decreased with increasing the temperature, especially at ∼50 °C, and they were somewhat lower for the monofilament with higher D-isomer content. Structural evolution, chain orientation, and thermal properties of PLA monofilaments drawn uniaxially with various draw ratios at 65 °C were then investigated by using wide-angle X-ray diffraction, polarized Raman spectroscopy, and differential scanning calorimetry, respectively. X-ray diffraction patterns clearly exhibited the development of chain orientation and stain-induced crystallization of the monofilaments as a function of draw ratio (DR). The dichroic ratio, a measure of the chain orientation, was quantitatively evaluated from the polarized Raman spectra. It was revealed that the dichroic ratios increased up to DR=4 and decreased slightly at DR>4 owing to the strain-induced crystallization for PLA monofilaments with D-isomer contents of 1 and 4 mol%. The glass transition and cold-crystallization temperatures of PLA monofilaments increased and decreased, respectively, with the increment of DR. The strain-induced enthalpy relaxation endothermic peak appearing in glass transition region became intense with increasing the DR.

We prepared a series of polyurethane(PU)/chitosan composite foams with different chitosan content of 5∼20 wt% and investigated their adsorption performance of acid dye (Acid Violet 48) in aqueous solutions with various dye concentrations and pH values. It was observed that PU/chitosan composite foams exhibited well-developed open cell structures. Dye adsorption capacities of the composite foams increased with the increment of chitosan content in composite foams, because amine groups of chitosan serve as the binding sites for sulfonic ions of acid dyes in aqueous solutions. In addition, dye adsorption capacities of composite foams were found to increase with decreasing the pH value, which stems from the fact that the enhanced chemisorption between protonated amine groups of chitosan and sulfonic ions of acid dye is available in acidic solutions. The dye adsoption kinetics and equilibrium isotherm of the composite foams were well described with the pseudo-second order kinetic model and Langmuir isotherm model, respectively. The maximum adsorption capacity (qmax) for the PU/chitosan composite foams with 20 wt% chitosan content is evaluated to be ca. 30 mg/g.

In this paper, a simple optical method that uses an infrared(IR) cut filter is proposed to minimize variation of eye image by external infrared(IR) sources in a video based head mounted eye tracking system that is used in the field of sports. For this, the IR cut filter is attached to a head mount of the eye tracking system, and the camera with an IR LED is located between the IR cut filter and eye. In this structure, external IR is blocked by the IR cut filter, and the IR intensity on the eye can be controlled by the IR LED. Therefore, the illumination condition of the camera to capture the eye can be stable without being affected by external IR illuminations. To verify the proposed idea, variation of the eye image and intensity of the IR with/without the IR cut filter is measured under various illumination conditions. The measured data show that the IR cut filter method can block external IR effectively, and complex pupil detection algorithms can be replaced by a simple binarized method.

We have synthesized poly(octamethylene terephthalate) (POT), poly(octamethylene 2,6-naphthalate) (PON), and poly(octamethylene terephthalate- co -octamethylene 2,6-naphthalate)s [P(OT- co -ON)s] with various comonomer composition by melt-polycondensation reaction and investigated their chain structures, crystalline structures, melting and cocrystallization behavior by using 1 H NMR spectroscopy, wide angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively. It was observed that P(OT- co -ON)s exhibit clear melting and crystallization peaks in DSC thermograms and sharp diffraction peaks in WAXD patterns throughout the copolymer composition, resulting from the cocrystallization behavior of OT and ON units in copolymers. When the melting and crystallization temperatures of P(OT- co -ON)s are compared as a function of the copolymer composition, there exists an eutectic point at around 23 mol% ON, where the crystal transformation from POT-type to PON-type occurs. It was confirmed from WAXD patterns of the melt-crystallized samples that the crystal transformation from POT-type to PON α-type to PON β-type occurs with the increment of the comonomer ON content in copolymers, i.e., POT-type crystals for POT and P(OT- co -ON) with 11 mol% ON, PON α-type crystals for P(OT- co -ON)s with 23–48 mol% ON, and PON β-type crystals for PON and P(OT- co -ON)s with 62–87 mol% ON. Both DSC and WAXD results demonstrate the isodimorphic cocrystallization of P(OT- co -ON)s. Based on the Wendling–Suter model for cocrystallization thermodynamics, it was found that the average defect free energy for the inclusion of OT units into PON β-type crystals is much lower than the value of the incorporation of ON units into POT-type crystals.

Poly(octamethylene terephthalate) (POT), a semicrystalline aromatic polyester, is synthesized by melt-condensation reaction, and its thermal property and crystal structure are investigated by using differential scanning calorimetry, X-ray diffraction, and molecular modeling methods, respectively. It is revealed that the synthesized POT sample has comparably low melting temperature of 131 °C and forms one crystalline phase. Based on two-dimensional X-ray fiber diagram and molecular modeling analyses, the crystal structure of POT is identified to be triclinic with dimensions of a = 4.560 A, b = 5.597 A, c = 18.703 A, α = 104.87°, β = 119.45°, and γ = 100.32°, in which one chemical repeating unit of POT with all-trans conformation of octamethylene group is packed according to the space group of . © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 276–283, 2009

Poly(lactic acid)-grafted multiwalled carbon nanotubes (MWNT-g-PLA) were prepared by the direct melt-polycondensation of L-lactic acid with carboxylic acid-functionalized MWNT (MWNT-COOH) and then mixed with a commercially available neat PLA to prepare PLA/MWNT-g-PLA nanocomposites. Morphological, thermal, mechanical, and electrical characteristics of PLA/MWNT-g-PLA nanocomposites were investigated as a function of the MWNT content and compared with those of the neat PLA, PLA/MWNT, and PLA/MWNT-COOH nanocomposites. It was identified from FE-SEM images that PLA/MWNT-g-PLA nanocomposites exhibit good dispersion of MWNT-g-PLA in the PLA matrix, while PLA/MWNT and PLA/MWNT-COOH nanocomposites display MWNT aggregates. As a result, initial moduli and tensile strengths of PLA/MWNT-g-PLA composites are much higher than those of neat PLA, PLA/MWNT, and PLA/MWNT-COOH, which stems from the efficient reinforcing effect of MWNT-g-PLA in the PLA matrix. In addition, the crystallization rate of PLA/MWNT-g-PLA nanocomposites is faster than those of neat PLA, PLA/MWNT, and PLA/MWNT-COOH, since MWNT-g-PLA dispersed in the PLA matrix serves efficiently as a nucleating agent. It is interesting that, unlike PLA/MWNT nanocomposites, surface resistivities of PLA/MWNT-g-PLA nanocomposites did not change noticeably depending on the MWNT content, demonstrating that MWNTs in PLA/MWNT-g-PLA are wrapped with the PLA chains of MWNT-g-PLA. Copyright © 2008 John Wiley & Sons, Ltd.

We evaluate and compare the power generating characteristics of the anode supported SOFCs which have been fabricated from KIST and FZ-Julich in Germany. The performance and electrochemical property of each unit cell was characterized at the temperature range of under same operating conditions and its microstructural property was thoroughly investigated via SEM after the performance test. According to the investigation, KIST- and FZJ SOFC showed different power generating characteristics in their temperature dependances due to their different design of electrode microstructure, especially the cathode microstructure. FZJ SOFC showed better performance at high temperature while showed lower performance at lower temperature. From the investigation about the correlation between microstructure and electrochemical property, we found that the superior performance of FZJ SOFC at high temperature was mainly due to its lower cathodic polarization resistance whereas better performance of KIST SOFC at lower temperature was mostly attributed to the lower ohmic resistance.

The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan δ versus temperature: the primary α-relaxation associated with the glass transition and the secondary β-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both α- and β-relaxation temperatures increased with increasing CT content. The activation energy of the α-relaxation increased with increasing CT content, whereas that of the β-relaxation decreased. The sub-glassy secondary β-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.

Nanocomposite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in nitric acid subsequent to sonication. Even though SWNT shows good dispersion visually, the reinforcing effect was not satisfactory. The G-band Raman spectra of the drawn film clearly demonstrated that SWNTs in the film are well-oriented along the drawing axis of the film. The electrical resistivity of the film prepared using nitric acid was lower than that of the film using DMF. Thus, nitric acid is presumably more effective in dispersing nanotubes than DMF.

The present result indicates that the steady-state fluorescence behavior of E7/NOA-65 polymer disperse liquid crystal films prepared by a photoinitiated-polymerization induced phase separation method plays a significant role in understanding electro-photophysical response and hysteresis on varying applied electric fields. The fluorescence technique is sensitive to molecular alignment of LC molecules in the polymer matrix and it also provides useful quantitative information on the rise time, the threshold voltage and the driving voltage of a PDLC system.

We have synthesized poly(1,4-cyclohexylenedimethylene terephthalate-co-hexamethylene terephthalate) [P(CT-co-HT)] random copolymers having various comonomer contents, from 0 to 100 mol% HT, by meltcondensation and have investigated their crystallization behavior by using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). We observed that P(CT-co-HT)s exhibit clear melting and crystallization peaks in their DSC thermograms and sharp diffraction peaks in their WAXD patterns for all of their copolymer compositions as a result of cocrystallization of the CT and HT units, even though the copolymers are statistically random copolymers. When we plotted the melting and crystallization temperatures of P(CT-co-HT)s and thed-spacings of all the reflections against the copolymer composition, we observed a eutectic point at ca. 80 mol% HT, which suggests that a crystal transition occured from a PCT-type crystal to a PHT-type crystal. Both the DSC and WAXD results support the notion that P(CT-co-HT) copolymers undergo an isodimorphic cocrystallization.

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20–30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 cm−1 shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.

Poly(trimethylene terephthalate-co-trimethylene 2,6-naphthalate)s (P(TT-co-TN)s) with various copolymer composition were synthesized, and their chain structure, thermal property and crystalline structure were investigated by using1H-NMR spectroscopy, differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), respectively. It was found from sequence analysis that all the P(TT-co-TN) copolymers synthesized have a statistical random distribution of TT and TN units. It was also observed from DSC thermograms that the glass transition temperature increases linearly with increasing the TN comonomer content, whereas the melting temperature of copolymer decreases with increasing the corresponding comonomer content in respective PTT- and PTN-based copolymer, showing pseudo-eutectic melting behavior. All the samples melt-crystallized isothermally except for P(TT-co-66 mol % TN) exhibit multiple melting endotherms and clear X-ray diffraction patterns. The multiple melting behavior originates from the dual lamellar population and/or the melting-recrystallization-remelting. The X-ray diffraction patterns are largely divided into two classes depending on the copolymer composition, i.e., PTT and PTNβ-form diffraction patterns, without exhibiting cocrystallization.

The effect of flexible chain length on the thermal and mechanical properties such as melting temperature, glass transition temperature, dynamic mechanical relaxation behavior, and uniaxial tensile deformation for melt-quenched poly(m-methylene 2,6-naphthalate) (PmN) films was investigated using differential scanning calorimeter (DSC), dynamic mechanical thermal analyzer, and universal tensile machine. It was found from DSC thermograms that PmNs with even number of methylene group have higher melting temperatures and faster crystallization rates than PmNs with odd number of methylene group, showing an odd–even fluctuation. The plots of tan δ versus temperature show that all PmN samples have three relaxation processes (β, β∗, and α) regardless of the number of methylene group in their backbone. It was found that both β∗- and α-relaxations are cooperative processes and that the activation energies of both relaxations as well as the glass transition temperature associated with the α-relaxation show odd–even fluctuations as a function of the number of methylene group. The initial tensile modulus at the low drawing rate of 0.15 cm/min also shows an odd–even fluctuation. In summary, the macroscopic thermal and mechanical properties of PmN such as melting temperature, glass transition temperature, crystallization rate, activation energies of α- and β∗-relaxations, and initial modulus measured under a slow drawing rate exhibit odd–even fluctuations as the number of methylene group in PmN increases.

X-ray powder diffraction and molecular modeling are used to identify the crystal structure and chain conformation of poly(trimethylene 2,6-naphthalate) (PTN) β-form crystal. The unit cell of PTN β-form crystal was determined to be a triclinic with dimensions of a=0.4665 nm , b=0.7014 nm , c=2.2177 nm , α=100.85°, β=88.78° and γ=120.63°, and the space group of the crystal is identified as P 1 . The observed crystal density of 1.37 g cm−3 and the determined dimensions of unit cell indicate that the unit cell contains one polymer chain with two repeating units. In the unit cell, each trimethylene unit in PTN backbone is in gauche/gauche conformation and neighboring naphthalene units are in face-to-face type arrangement, forming π-stacks that lead to the lowest energy of the unit cell.

A series of poly(m-methylene 2,6-naphthalate-co-1,4-cyclohexylenedimethylene 2,6-naphthalate) copolymers were synthesized, and their crystallization behavior was investigated using differential sca...

The melting and crystallization behavior of poly(trimethylene 2,6-naphthalate) (PTN) are investigated by using the conventional DSC, the temperature-modulated DSC (TMDSC), wide angle X-ray diffraction (WAXD) and polarized light microscopy. It is observed that PTN has two polymorphs (α- and β-form) depending upon the crystallization temperature. The α-form crystals develop at the crystallization temperature below 140 °C while β-form crystals develop above 160 °C. Both α- and β-form crystals coexist in the samples crystallized isothermally at the temperature between 140 and 160 °C. When complex multiple melting peaks of PTN are analyzed using the conventional DSC, TMDSC and WAXD, it is found that those arise from the combined mechanism of the existence of different crystal structures, the dual lamellar population, and melting–recrystallization–remelting. The equilibrium melting temperatures of PTN α- and β-form crystals determined by the Hoffman–Weeks method are 197 and 223 °C, respectively. When the spherulitic growth kinetics is analyzed using the Lauritzen–Hoffmann theory of secondary crystallization, the transition temperature of melt crystallization between regime II and III for the β-form crystals is observed at 178 °C. Another transition is observed at 154 °C, where the crystal transformation from α- to β-form occurs.

A series of poly(1,4-cyclohexylenedimethylene terephthalate-co-1,4-cyclohexylenedimethylene 2,6-naphthalate) [P(CT-co-CN)] copolymers were synthesized, and their cocrystallization behavior was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). Although the P(CT-co-CN) copolymers synthesized have statistical random distribution of CT and CN units, all the copolymers show clear melting and crystallization peaks in DSC thermograms over entire copolymer composition, and have an eutectic melting temperature in the plot of melting temperature versus copolymer composition. WAXD patterns of all the samples show sharp diffraction peaks, and are largely divided into two classes according to the copolymer composition, that is, PCT-type and PCN-type diffraction patterns. These facts lead us to conclude that P(CT-co-CN) copolymers show isodimorphic cocrystallization. The eutectic composition at which the crystal transition from PCT-type to PCN-type crystal occurs was estimated ca. 40 mol % CN content. When the defect Gibbs free energy was estimated by using the equilibrium inclusion model proposed by Wendling and Suter, the value (7.18 kJ/mol) in the case of incorporation of CT units in the PCN crystals were larger than the case (3.32 kJ/mol) of incorporation of CN units in the PCT crystals. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 177–187, 2004

A series of poly(hexamethylene terephthalate- co -hexamethylene 2,6-naphthalate) (P(HT- co -HN)) random copolymers were synthesized by melt polycondensation and characterized using 1 H NMR spectroscopy and viscometry. Their cocrystallization behavior was investigated using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) method. Even though the P(HT- co -HN) copolymers synthesized are statistically random copolymers, they show a clear melting and a crystallization peak in DSC thermograms over the entire range of copolymer composition and have a minimum melting temperature in the plot of melting temperature versus copolymer composition. WAXD patterns of all the copolymer samples show sharp diffraction peaks and are largely divided into two groups, i.e. PHT type and PHN type crystals. In addition, WAXD patterns of the PHN type crystals are subdivided into two types of PHN α and PHN β according to the copolymer composition. These facts indicate that the P(HT- co -HN) copolymers show isodimorphic cocrystallization. The composition at which the crystal transition between PHT type and PHN type occurs is equivalent to the eutectic composition (22 mol% HN content) for the melting temperature. When the defect free energies were calculated by using the equilibrium inclusion model proposed by Wendling and Suter, the defect free energies in the case of incorporation of HT units in the PHN α and β crystals were higher than the case of incorporation of HN units in the PHT crystal lattice.

A series of poly(butylene terephthalate-co-butylene 2,6-naphthalate) (P(BT-co-BN)) random copolymers were synthesized, and their cocrystallization behavior was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The P(BT-co-BN) copolymers, which are found to be statistical random copolymers, show a single melting and a single crystallization peak over the entire range of copolymer composition and have a eutectic melting point in the plot of melting point versus composition. WAXD patterns of copolymers are divided into two groups, i.e., the PBT type crystal and the PBN type crystal. These facts indicate that the P(BT-co-BN) copolymers show isodimorphic cocrystallization. The eutectic composition at which the crystal transition between PBT and PBN type crystal occurs was estimated ca. 35 mol % BN content. When the defect free energy was calculated by using the equilibrium inclusion model, the defect free energy (6.10 kJ/mol) in the case of incorporation of BN uni...

Ternary blends of polysulfone (PSF)/polycarbonate (PC)/Impact modifiers (IM) were prepared to improve the mechanical properties of PSF/PC binary blends. Two different core–shell impact modifiers, methyl methacrylate–butadiene–ethylacrylate (MBE) and acrylonitrile–butadiene–styrene (ABS) terpolymers, were used. Morphology of the blends was very dependent on thc matrix type but independent of the IM type. For PSF matrix PC tends to encapsulate the IM. Whereas, for PC matrix, the IM tends to locate in PC matrix and thus two distinct phases of PSF and IM are observed. The encapsulation of PC onto the IM in PSF matrix was verified from the model blends of PSF/PC/SAN24 and PSF/PC/PMMA, where SAN24 and PMMA are corresponding to the shell of the IM, respectively. Impact strengths of the blends with the IM were slightly increased compared to PSF/PC binary blends, but not significantly. This may be the result of poor PSF/PC interfaces, which are valid from their immiscibility.

A series of novel nitro compounds containing different alkyl chain length (x=2∼5), 1,5-bis(hydroxyalkylamino)-2,4-dinitrobenzene (BDBx), are synthesized and their thermochromic behavior is investigated by using differential scanning calorimetry and optical microscopy. All the BDBx crystals synthesized show yellow color at room temperature. BDBx (x=2∼4) samples display orange color even in the solid when heated above respective thermochromic transition temperature, while the yellow color of BDB5 changes to orange with melting. The orange color of BDBx crystals returns to yellow when cooled down to room temperature, indicating that the thermochromic behavior of BDBx is reversible. The thermochromic transition temperatures of BDBx crystals are found to be decreased with increasing the alkyl chain length, exhibiting evenodd fluctuation.

Interfacial tension between immiscible polymer pairs was predicted by using a square gradient theory in conjunction with the Flory-Orwoll-Vrij equation-of-state expression for the free energy of mixing. The contact interaction parameter was determined by fitting the equation-of-state theory to experimental cloud points taken from the literature, and the square gradient coefficient was estimated from the relation derived from a scattering function. The modified square gradient theory could successfully predict both the magnitude and temperature dependence of interfacial tension between polystyrene and poly(methyl methacrylate), although no adjustable parameters were used in calculating interfacial tension. The molecular weight dependence of interfacial tension was also successfully predicted. The contribution of free volume on interfacial tension is analyzed for two systems: polystyrene/poly(methyl methacrylate) and polystyrene/poly(dimethyl siloxane) blends.

The compatibilizing effect of styrene-co-4-vinylpyridine (SVP) random copolymers on the immiscible polystyrene (PS)–polyethylene-based ionomer (Surlyn) blends was examined by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and tensile test. For the binary SVP–Surlyn and ternary PS–Surlyn–SVP blends, the domain size of dispersed phase decreases dramatically with the increase in the vinyl pyridine (VP) content of the SVP copolymers. The mechanical properties are improved with increasing the VP content in copolymers. FTIR results suggest that the compatibilization in this blend system is attributed to the ion–dipole interaction between the polar VP groups of SVP copolymer and ionic groups of Surlyn. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 807–816, 1998

The melting behaviour of syndiotactic polystyrene (sPS) and its blend with poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) was examined by differential scanning calorimetry (d.s.c.), and the polymorphism of sPS was also investigated by X-ray diffraction. Both pure sPS and sPS/PPO blends showed three melting endotherms under our crystallization conditions. When the d.s.c. results are compared with the X-ray patterns, it is suggested that the lowest and middle melting endotherms are due to the melting of β- and α-forms of sPS, respectively, whereas the highest melting endotherm comes from the melting of recrystallized sPS crystals formed during the d.s.c. scan. It is also observed that the recrystallization of sPS in sPS/PPO blends is disturbed by the presence of PPO.

The effect of transesterification on the phase behaviour in poly(ethylene 2,6-naphthalate) and poly(ethylene terephthalate) blends was investigated by using differential scanning calorimetry. The transesterification between the two polymers was confirmed by 1 H nuclear magnetic resonance. The blend samples heat treated for up to 11 min at 280°C show two glass transitions, which approach closer with the increase of reaction time. After 13 min, a single glass transition is observed, and the glass transition range becomes narrow with the lapse of reaction time. From the glass transition behaviour, the phase compositions and the phase fractions were determined as functions of reaction time at 280°C. The composition difference between ethylene 2,6-naphthalate (EN)-rich and ethylene terephthalate (ET)-rich phases decreases as the transesterification proceeds. On the other hand, though the weight fractions of the EN-rich phase, the ET-rich one and the interfacial zone tend to change with the lapse of time, the changes are small in magnitude.

The crystallization kinetics of poly(butylene 2,6-naphthalate) and its copolyesters has been investigated by differential scanning calorimetry at large undercoolings. Wide angle X-ray diffraction patterns show that the copolymers crystallize purely in crystalline phase of poly(butylene 2,6-naphthalate). In contrast to the typical crystallization behavior of copolymer, the crystallization isotherms follow the Avrami equation up to high degree of conversion, and the Avrami exponents are mostly close to 2, independent of copolymer composition and crystallization temperature. The analysis of kinetic data with a modified Lauritzen-Hoffman equation indicates that the product of the lateral surface free energy and the fold one (σσe) is 1410±100 erg2cm−4 and this value is not dependent on copolymer composition. The surface free energies and the work of chain folding are also discussed in comparison with those of poly(butylene terephthalate) and poly(ethylene terephthalate).

Blends prepared from poly(ethylene 2,6-naphthalate) (PEN) and poly(butylene 2,6-naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed : brittle for the blends 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.

Thermal properties of poly(ethylene 2,6-naphthalate) (PEN)/poly(butylene 2,6-naphthalate) (PBN) blends were investigated by differential scanning calorimetry. Blends containing less than 60 wt% PBN showed double glass transitions, which approach mutually closer with increasing PBN content, whereas a single glass transition was observed for compositions more than 80 wt% PBN. This behavior indicates that the blends with 60 wt% PBN or less separate into two amorphous phases containing both components and the difference in composition between two phases decreases with an increase of PBN content, while a single amorphous phase is formed for compositions more than 80 wt% PBN. This result was supported by melting behavior and crystallization kinetics.

The phase behavior of blends of vinyl chloride-vinyl acetate copolymers with poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PnBMA), was examined as a function of the vinyl acetate (VAc) content in the copolymer. From the variation of cloud points with the copolymer composition, segmental contact energy parameters X ij 's for various monomeric unit pairs have been estimated by using a copolymer model based on Patterson's equation of state theory. It was found that the segemental interaction of VAc with MMA and VC is attractive in each case, indicating that PVAc is miscible with PMMA and PVC

To obtain the superhydrophobic water-repellent cotton fabrics, cotton fabrics were treated with silica nanoparticles and/or a cost-effective water-repellent agent (WR agent). Two different silica nanoparticles were synthesized via a sol-gel process and their shapes, sizes, and compositions were characterized. It was found that silica particles are spherical and have diameters of 143 and 378 nm. For the cotton fabrics treated with the WR agent alone, the water contact angles on the fabric surface remained lower than 20 degrees at the WR agent concentration of 0.3 wt% or less. Silica nanoparticle treatment itself did not change the hydrophilic surface of cotton fabric, indicating that water drops were adsorbed into fabrics due to the hydroxyl groups on both cotton and silica nanoparticle surfaces. However, for the cotton fabrics treated with both silica nanoparticles and the WR agent, a contact angle above 130 degrees can be obtained even at the very low WR agent concentration of 0.1 wt%. Therefore, superhydrophobic cotton fabrics could be obtained via the combined treatment of silica nanoparticle and WR agent, which is cost effective compared with fluorinate silane treatment.

The miscibility of poly(vinylidene fluoride) (PVDF) and poly(styrene-co-methyl methacrylate) (SMMA) blends was examined as a function of copolymer composition. PVDF was miscible with SMMA copolymers having an styrene content less than 13 vol%. The segmental interaction parameters were determined by combining the equilibrium melting point depression of PVDF and the binary interaction model. According to the binary interaction model, the maximum styrene content in SMMA for the blend to be miscible was predicted as 18.5 vol% which agrees well with an experimental result.

The phase behavior of poly (ethylene oxide) (PEO) and poly (styrene-co-sodium sulfonated styrene) (SPS) blends has been examined as a function of copolymer composition. The mixtures show complex coacervation in dilute benzene/methanol (9/1,v/v) solution. The presence of intermolecular interactions between PEO and SPS in solution is verified by viscometry. Interaction between PEO and SPS in the solid state was supported by small-angle x-ray scattering; however, binary blends containing low PEO content show high miscibility, whereas the blends with high PEO content phase separation

Synthetic receptor binding motif mimicking bone morphogenetic protein-2 (BMP-2) was covalently linked to titanium (Ti) surfaces through a chemical conjugation process. The composition and properties of surface-modified Ti were investigated by XPS as well as by measuring surface radioactivity. In vitro tests were conducted with osteoblast-like MC3T3-E1 cells to assess cell attachment, morphology, and expression of osteogenic marker in the cells grown on modified Ti surfaces. In addition, in vivo experiments involved implants in mandibular bone defects of beagles to evaluate the effect of surface modification on bone regeneration. Results of XPS measurements showed a complete and homogeneous peptide overlayer on the Ti surfaces; the content was further measured by gamma counting. Biological evaluations showed that the biochemically modified Ti samples were active in terms of cell attachment behavior. The MC3T3-E1 cell growth rate, marker protein expression, and alkaline phosphatase production of the peptide-modified surfaces were all higher than those of control Ti. Importantly, the implants in the canine mandibles showed significant increase of bone growth when modified with bioactive peptide, thereby confirming that biochemical modifications of Ti surfaces can enhance the rate of bone healing as compared with untreated Ti surfaces.

The extent of transesterification reaction, intrinsic viscosity, weight-average molecular weight and hydrodynamic radius of poly(ethylene 2,6-naphthalate) (PEN)/poly(ethylene terephthalate) (PET) (50/50, w/w) blend were measured as a function of reaction time at 280°C. In PEN/PET blend, the reactions between end groups as well as the transesterification should be considered since the molecular weight of the blend increases with reaction time.