Synthesis and characterization of novel polyureas based on benzimidazoline‐2‐one and benzimidazoline‐2‐thione hard segments

Six novel polyureas were prepared from benzimidazolin‐2‐one and benzimidazolin‐2‐thione, which acted as hard segments, with two aromatic diisocyanates (4,4′‐diphenylmethane diisocyanate and toluene 2,4‐diisocyanate) and one aliphatic diisocyanate (hexamethylene diisocyanate). The polymers that formed were fully characterized with Fourier transform infrared spectroscopy, ¹³C‐NMR cross‐polarization/magic‐angle spinning, differential scanning calorimetry, and thermogravimetry. X‐ray diffraction revealed that the polymers contained crystalline and amorphous regions that varied with the nature of the backbone structures. All the polyureas were insoluble in common organic solvents, and this made it difficult to investigate their solution properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 576–583, 2006     

Synthetic preparations and physical and electrical properties of main chain type thermotropic liquid crystalline polyimide/SiO2 nanocomposites

Two kinds of monomers, 1,3‐bis[4‐(4′‐amino‐Phenoxy)cumyl]benzene (BACB) and pyromellitic dianhydride were used to synthesize the Liquid Crystalline Polyamic acid—a precursor (LCPAA) of Liquid Crystalline Polyimide (LCPi). The nanohybrid films were successfully prepared by the sol–gel reaction. Tetraethoxysilane (TEOS) (99%)–ethanol (99.8%) solution was added to LCPAA solution. The hybrid films were made by the hydrolysis–polycondensation of TEOS–ethanol in the LCPAA solution. When water and the solvent were removed completely, the hybrid films were obtained. The functional group and chemical structure were characterized by FTIR. We employed a number of instruments to understand whether the nano‐SiO₂ particle was introduced into the polymer matrix and enhanced the thermal properties and mechanical strength. The liquid crystalline phase of the LCPi and LCPi/SiO₂ hybrid films was observed by POM. TGA and DSC were used to test the thermal properties. The crystallization and liquid crystal phase analyses were carried out by XRD. The elemental analysis was employed to measure the 1,3‐bis[4‐(4′‐nitrophenoxy)cumyl)]benzene and BACB monomers. Besides, the cross section at morphology of the materials was observed with an FESEM. The electrical properties of hybrid films were measured by the high resistance analysis and dielectric constant analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1688–1704, 2006     

Asymmetric membranes fabricated from poly(acrylonitrile‐co‐N‐vinyl‐2‐pyrrolidone)s with excellent biocompatibility

Poly(acrylonitrile‐co‐N ‐vinyl‐2‐pyrrolidone)s (PANCNVPs) show excellent biocompatibility. In this work, PANCNVPs with different contents of N‐vinyl‐2‐pyrrolidone (NVP) were fabricated into asymmetric membranes by the phase inversion method. The surface chemical composition of the resultant membranes was determined by Fourier transform infrared spectroscopy–attenuated total reflection. Field emission scanning electron microscopy was used to examine the surface and cross section morphologies of the membranes. It was found that the morphologies hardly change with the increase of NVP content in PANCNVP, while the deionized water flux increases remarkably and the bovine serum albumin (BSA) retention decreases slightly. Experiment of dynamic BSA solution filtration was carried out to evaluate the antifouling properties of the studied membranes. The relative flux reduction of PANCNVP membrane containing 30.9 wt % of NVP is 25.9%, which is far smaller than that of the polyacrylonitrile membrane (68.8%). Results deduce that this improvement comes from the excellent biocompatibility of NVP moieties instead of the hydrophilicity change, because the water contact angles of these membranes fluctuate between 60 and 70°. Results from the membranes using poly(N‐vinyl‐2‐pyrrolidone) (PVP) as an additive confirm that, to a certain extent, the PANCNVP membranes show the advantages of antifouling compared with the polyacrylonitrile/PVP blending membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4577–4583, 2006     

Narrow‐disperse or monodisperse crosslinked and functional core–shell polymer particles prepared by two‐stage precipitation polymerization

Narrow‐disperse and monodisperse cross‐linked core–shell polymer particles containing different functional groups, such as esters, hydroxyls, chloromethyls, carboxylic acids, amides, cyanos, and glycidyls, in the shell layers in the micrometer size range were prepared by a two‐stage precipitation polymerization in the absence of any stabilizer. Commercial divinylbenzene (DVB), containing 80% DVB, was precipitation polymerized in acetonitrile without any stabilizer as the first‐stage polymerization and was used as the core. Several functional monomers, including methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2‐hydroxyethyl methacrylate, glycidyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, t‐butyl acrylate, i‐octyl acrylate, acrylic acid, acrylamide, acrylonitrile, styrene, and p‐chloromethyl styrene, were incorporated into the shells during the second‐stage polymerization. The resulting core–shell polymer particles were characterized with scanning electron microscopy and Fourier transform infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1776–1784, 2006     

Influence of the cross‐sectional shape on the structure and properties of polyester fibers

The effects of the fiber cross‐sectional shape on the structure and properties of polyester fibers were investigated. Fully drawn yarn (FDY) polyester fibers (167 dtex and 48 filaments) were produced under the same spinning conditions used in a spinning plant. The only difference between the fibers was their cross‐sectional shapes. Four different cross‐sectional shapes were chosen for the experimental work: round, hollow‐round, trilobal, and hollow‐trilobal. The crystallinity and values of the maximum stress, maximum strain, modulus, yield stress, shrinkage in boiling water, and unevenness of the fibers were determined. The difference in the cross‐sectional shapes influenced the modulus, maximum strain, yield stress, and shrinkage in boiling water. No effects on the crystallinity and maximum stress were observed. The results suggested that the hollow fibers had higher amorphous orientation than the full fibers. The hollow‐round fiber had the highest unevenness value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2615–2621, 2007     

Cross‐linked Poly(arylene ether ketone) Proton Exchange Membranes with High Ion Exchange Capacity for Fuel Cells

Sulfonated poly(arylene ether ketone) (SPAEK) possessing the pendant carboxylic acid groups was synthesized. The carboxylic acid groups of SPAEK were reacted with a cross‐linking reagent to prepare a cross‐linked membrane with a high ion exchange capacity (IEC), a high oxidative stability, and an excellent mechanical strength. The cross‐linking hindered the mobility of the polymer chains and thus strongly affected the water uptake and the methanol permeability of the membranes. Also, as the cross‐linker used in this study bore sulfonic acid groups, cross‐linking did not lead to a noticeable loss of the proton conductivity. The cross‐linked SPAEK membrane with 20% cross‐linking density, CSPAEK‐20% membrane, exhibited a high proton conductivity of 0.045 S cm^–1 associated with a high IEC value of 1.78 mmol g^–1 but a low methanol permeability of 4.3 × 10^–7 cm² s^–1. The CSPAEK‐20% membrane also showed excellent cell performance and oxidation resistance.     

Preparation of poly(4‐methyl‐1‐pentene) asymmetric or microporous hollow‐fiber membranes by melt‐spun and cold‐stretch method

Poly(4‐methyl‐1‐pentene) (PMP) hollow fibers were prepared and fabricated into gas separation or microporous membranes by the melt‐spun and cold‐stretched method. PMP resin was melt‐extruded into hollow fibers with cold air as the cooling medium. The effects of take‐up speed and thermotreatment on the mechanical behavior and morphology of the fibers were investigated. Scanning electronic microscope (SEM) photos were used to reveal the geometric structure of the section and surface of the hollow fibers. It was found that the original fiber had an asymmetric structure. A “sandwich” mode was used to describe the formation of this special fine structure. And a series of PMP hollow‐fiber membranes were prepared by subsequent drawing, and it was found that there was a “skin–core” structure on the cross section of these hollow‐fiber membranes. Asymmetric or microporous PMP hollow‐fiber membranes could be obtained by controlling posttreatment conditions. The morphology of these membranes were characterized by SEM, and the gas (oxygen, nitrogen, and carbon dioxide) permeation properties of the membranes was measured. The results indicate that the annealing time of the original fiber and the stretching ratio were the key factors influencing the structure of the resulting membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2131–2141, 2006     

Bubble coalescence in foaming process of polymers

This paper investigates the effect of rheological behavior on dynamics of bubble coalescence. In situ observations on polymers with different rheological behaviors were conducted to study coalescence dynamics. Four patterns of interface deformation were observed. Deformation during coalescence was analyzed by applying image‐processing schemes and rheological models to the in situ observations. Polymer with Newtonian behavior showed nucleation and coalescence of spherical bubbles that created a planar interface. The planar interface was deformed by a combination of biaxial and planar elongational flows. Coalescence in polymers with non‐Newtonian behavior is characterized by penetration with a parabolic shaped interface. The deformation of parabolic interface was due to biaxial elongational flow. However, the interface deformation of the polymer with cross‐linked structure was due to an integration of biaxial and elongational flow. Further, cross‐linking was also observed to have an effect on coalescence time. POLYM. ENG. SCI. 46:680–690, 2006. © 2006 Society of Plastics Engineers     

Preparation of polyacrylonitrile and cellulose acetate blend fibers through wet‐spinning

Fibers containing both polyacrylonitrile (PAN) and cellulose acetate (CA) were prepared through wet‐spinning by using N,N‐dimethylformamide (DMF) as a solvent. Compatibility of PAN and cellulose acetate blend (PCB) fibers was investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and infrared (IR) spectrophotometry. The absorptive capacity and mechanical properties of the fibers were measured. It was observed that the surface and the cross section of PAN fibers were quite smooth and free from voids and microcracks, whereas cracks and voids were present on the surface and cross section of blend fibers, which increased with the incorporation of CA in the blend. Moisture regains of blend fibers were quite high while their tensile properties showed a partial decrease. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2000–2005, 2007     

Effect of amino‐functionalization of multi‐walled carbon nanotubes on the dispersion with epoxy resin matrix

Amino‐functionalization of multiwalled carbon nanotubes (MWCNTs) was carried out by grafting triethylenetetramine (TETA) on the surfaces of MWCNTs through the acid–thionyl chloride way. The amino‐functionalized MWCNTs show improved compatibility with epoxy resin and, as a result, more homogenous dispersion in the matrix. The mechanical, optical, and thermal properties of the amino‐functionalized MWCNT/epoxy composites were also investigated. It was found that introducing the amino‐functionalized MWCNTs into epoxy resin greatly increased the charpy impact strength, glass transition temperature, and initial decomposing temperature of cured epoxy resin. In addition, introducing unfunctionalized MWCNTs into epoxy resin was found greatly depressing the light transmission properties, which would affirmatively confine the application of the MWCNTs/epoxy composites in the future, while much higher light transmittance than that of unfunctionalized MWCNTs/epoxy composites was found for amino‐functionalized MWCNTs/epoxy composites. SEM of the impact cross section and TEM of ultrathin film of the amino‐functionalized MWCNTs/epoxy composites showed that the amino‐functionalized MWCNTs were wetted well by epoxy matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 97–104, 2006     

Preparation of polystyrene/poly(vinyl acetate) nanocomposites with a core–shell structure via emulsifier‐free emulsion polymerization

Polystyrene/poly(vinyl acetate) latex nanoparticles with a core–shell morphology in an emulsifier‐free emulsion polymerization system were prepared with purified styrene and vinyl acetate (VAc) as monomers and 2,2′‐azo bis(2‐amino propane) dihydrochloride (ABA,2HCl) as the initiator and emulsifier. The optimized conditions of polymerization of VAc, on top of the already‐formed polystyrene as a core polymer, with a core–shell morphology were obtained using various parameters such as volume ratio of the first and second stages, type of process, and reaction time. The morphologic structure of the nanoparticles was studied by scanning electron microscopy and transmission electron microscopy. The latex nanoparticles and polymers were characterized by differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2409–2414, 2006     

Thermal properties and mechanical characteristics of cationic dyeable poly(trimethylene terephthalate)/metallocene isotactic polypropylene conjugated filaments

Cationic dyeable poly(trimethylene terephthalate) (CD‐PTT) and metallocene isotactic polypropylene (m‐iPP) polymers were extruded (in proportions of 75/25, 50/50, and 25/75) from two melt twin‐screw extruders to prepare three CD‐PTT/m‐iPP conjugated filaments of the island–sea type. This study investigated the thermal properties and mechanical characteristics of the CD‐PTT/m‐iPP conjugated filaments with gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, potentiometry, rheometry, density gradients, wide‐angle X‐ray diffraction, extension stress–strain measurements, and scanning electron microscopy. The rheological behavior of the CD‐PTT/m‐iPP polyblended polymers exhibited negative‐deviation blends, and the 50/50 CD‐PTT/m‐iPP blend showed a minimum value of the melt viscosity. The experimental results from differential scanning calorimetry indicated that CD‐PTT and m‐iPP molecules formed an immiscible system. The tenacity of the CD‐PTT/m‐iPP conjugated filaments decreased initially and then increased as the m‐iPP content increased. Morphological observations revealed that the blends were in a dispersed phase structure. A pore/filament morphology of a larger size (0.5–3 μm in diameter) was observed after a 1,1,1,3,3,3‐hexafluoro‐2‐propanol (CD‐PTT was removed)/decalin (m‐iPP was removed) treatment in the cross section of a CD‐PTT/m‐iPP conjugated filament. The CD‐PTT and m‐iPP polymers were identified as an immiscible system. Blends with 10 wt % compatibilizer exhibited the maximum improvement in the tenacity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2387–2394, 2007     

The Role of Al in Cross‐Linking of Alkali‐Activated Slag Cements

The structural development of a calcium (sodium) aluminosilicate hydrate (C–(N‐)A–S–H) gel system, obtained through the reaction of sodium metasilicate and ground granulated blast furnace slag, is assessed by high‐resolution ²⁹Si and ²⁷Al MAS NMR spectroscopy during the first 2 yr after mixing. The cements formed primarily consist of C–(N‐)A–S–H gels, with hydrotalcite and disordered alkali aluminosilicate gels also identified in the solid product assemblages. Deconvolution of the ²⁷Al MAS NMR spectra enables the identification of three distinct tetrahedral Al sites, consistent with the ²⁹Si MAS NMR data, where Q³(1Al), Q⁴(3Al), and Q⁴(4Al) silicate sites are identified. These results suggest significant levels of cross‐linking in the C–(N‐)A–S–H gel and the presence of an additional highly polymerized aluminosilicate product. The mean chain length, extent of cross‐linking, and Al/Si ratio of the C–(N‐)A–S–H gel decrease slightly over time. The de‐cross‐linking effect is explained by the key role of Al in mixed cross‐linked/non‐cross‐linked C–(N‐)A–S–H gels, because the cross‐linked components have much lower Al‐binding capacities than the noncross‐linked components. These results show that the aluminosilicate chain lengths and chemical compositions of the fundamental structural components in C–(N‐)A–S–H gels vary in a way that is not immediately evident from the overall bulk chemistry.     

Solid state 19F NMR study of crystal transformation in PVDF and its nanocomposites

The polymorphism of poly(vinylidene fluoride) (PVDF) and its nanocomposites was studied by means of solid state nuclear magnetic resonance spectroscopy. ¹³C cross polarization magic angle spinning (¹³C CP MAS) NMR spectra were recorded using simultaneous high‐power decoupling on both the proton and fluorine channels. Both ¹H → ¹³C and ¹⁹F → ¹³C CP experiments were conducted, giving identical results apart from intensity variations due to the CP efficiency. Two main resonances for the CF₂ and the CH₂ groups were observed for both neat PVDF (PVDF‐C0) and the nanocomposite containing 2 wt% clay (PVDF‐C2) samples. ¹⁹F CP MAS spectra were obtained from long proton spin‐lock experiments with a shorter contact time. The results showed two strong resonances at ?84 and ?98 ppm with equal intensities, representing the α‐form crystalline structure of PVDF. It was shown that the clay induces the crystallization of PVDF in β‐form. Our earlier investigations using thermal analysis and X‐ray scattering methods also showed crystal transformation of PVDF in its clay nanocomposites. POLYM. ENG. SCI. 46:1684–1690, 2006. © 2006 Society of Plastics Engineers     

Crosslinking of cotton cellulose in the presence of serine and glycine. II. Pore structures and agent distribution

Serine and glycine are selected as coreactants to combine with dimethylol‐dihydroxyethyleneurea (DMDHEU). We found that the pore structures of DMDHEU‐crosslinked cottons are changed. DMDHEU alone has lower values of equilibrium absorption, structural diffusion resistance constant, and rate constant, but higher value of activation energy than do DMDHEU–serine and DMDHEU–glycine. On the other hand, DMDHEU–serine has higher values of structural diffusion resistance constant and lower values of equilibrium absorption and rate constant than does DMDHEU–glycine; however, the hydroxyl group contained in serine has the higher affinity toward direct dye resulting in the decrease in the value of activation energy. The expansion patterns of cross section show that the degree of the expansion of the DMDHEU‐crosslinked fiber is lower than that of the DMDHEU–serine‐ and DMDHEU–glycine‐crosslinked fibers. The distribution of crosslinking agents on the crosslinked fabrics reveals the slightly higher surface distribution of DMDHEU–serine and DMDHEU–glycine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1578–1584, 2006     

Light‐colored fluorinated polyimides based on 2,5‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl and various aromatic dianhydrides

A novel trifluoromethyl‐containing aromatic diamine monomer, 2,5‐bis (4‐amino‐2‐trifluoromethylphenoxy)biphenyl (2), was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and phenylhydroquinone in the presence of potassium carbonate to yield the intermediate dinitro compound (1), followed by catalytic reduction with hydrazine and Pd/C. A series of fluorinated polyimides (code 5a–f) were synthesized from diamine (2) with six commercially available aromatic dianhydrides using a standard two‐stage process with thermal or chemical imidization of poly(amic acid). Most of fluorinated polyimides showed good solubility at a concentration of 5–10 wt % and even in pyridine and dioxane. For improving solubility of 5c, copolyimides (5c/a–f) were also prepared from 2 and a pair of dianhydrides (3c/a–f), which were mixed in the molar ratio 1:1. All the polyimide films had a tensile strength in the range from 73 to 112 MPa, an elongation at break within a range of 9–23%, and an initial modulus in the range of 1.6–2.2 GPa. These polyimides exhibited glass transition temperatures of 220–267°C and showed no significant decomposition below 500°C under either nitrogen or air atmosphere. In comparison with the analogous nonfluorinated polyimides based on 2,5‐bis (4‐aminophenoxy) biphenyl (2′), the fluorinated polyimides showed better solubility as well as reduced color intensity, lower dielectric constant, and moisture absorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4101–4110, 2006     

Smart anionic polyelectrolytes based on natural polymer for complexation of cationic surfactant

The thermosensitive polyelectrolytes were obtained by grafting 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) onto hydroxypropylcellulose (HPC), a biodegradable polysaccharide. The interactions of the polymers with dodecyltrimethylammonium chloride (DTAC), a model cationic surfactant, were studied. It was found by the measurements of the surface tension and the analysis of fluorescence emission of pyrene used as a fluorescent probe, that the HPC–AMPS graft polymers strongly interact with DTAC with the formation of polymer–surfactant complexes. The critical aggregation concentrations of these polymer–surfactant systems were found to be of the order of 10^?5 mol/dm³. The polymers were found to be potentially useful in the purification of water from cationic surfactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2401–2407, 2006     

Determination of impurities in industrial caprolactam produced from toluene by SPME and GC–MS

Solid‐phase microextraction (SPME) in combination with gas chromatography‐mass spectrometry (GC–MS) was applied to study the impurities in industrial caprolactam produced from toluene. Various nitriles, lactones, amides, and alcohols were detected to be the main impurities in caprolactam products. Trace amounts of heterocyclic compounds, which had great effects on the quality of caprolactam, were also successfully detected. Those were pyrrole, 2‐ethyl‐3‐methyl pyrazine, 5,6,7,8‐tetrahydroquinoxaline, quinoxaline, 2,3‐dimethyl quinoxaline, 2‐pyridinamide, etc. The effects of some impurities on caprolactam quality and the polymerization of caprolactam as well as the possible origin of the main impurities were also discussed. This could be of great importance to the industrial purity control of caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3141–3144, 2006     

Preparation and characterization of novel semi‐interpenetrating 2‐hydroxyethyl methacrylate‐g‐chitosan copolymeric microspheres for sustained release of indomethacin

A novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Studies of poly(8‐hydroxy‐4‐azoquinolinephenol‐formaldehyde) and its metal complexes

Poly(8‐hydroxy‐4‐azoquinolinephenol‐formaldehyde) resin (8H4AQPF) was prepared by condensing 8‐hydroxy 4‐azoquinoline phenol with formaldehyde (1 : 1 mol ratio) in the presence of oxalic acid. Polychelates were obtained when the DMF solution of poly(8H4AQPF) containing a few drops of ammonia was treated with the aqueous solution of Cu(II) and Ni(II) ions. The polymeric resin and polymer–metal complexes were characterized with elemental analysis and spectral studies. The elemental analysis of the polymer–metal complexes suggested that the metal‐to‐ligand ratio was 1 : 2. The IR spectral data of the polychelates indicated that the metals were coordinated through the nitrogen and oxygen of the phenolic ? OH group. Diffuse reflectance spectra, electron paramagnetic resonance, and magnetic moment studies revealed that the polymer–metal complexes of the Cu(II) complexes were square planar and those of the Ni(II) complexes were octahedral. X‐ray diffraction studies revealed that the polymer metal complexes were crystalline. The thermal properties of the polymer and polymer–metal complexes were also examined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1506–1510, 2006