Polymer

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

Because of their mechanical properties and low density, flax fibers seem to be competitive with glass fibers. However, these fibers present a non-uniformity in many of their characteristics (non-constant diameter along the fiber, variable length, presence of defects). This leads to a dispersion of their mechanical properties. This study focuses on the development of fully biodegradable green composites based on poly (lactic acid) (PLA) and poly (butylene succinate) (PBS) matrix reinforced by flax fibers to determine their elastic characteristics and to analyze their tensile and flexural failure in order to evaluate the influence of the processes on the mechanical properties. The main task is to incorporate flax fibers of several millimeters into the polymer matrix and study of the influence of the twin-screw extrusion and single-screw extrusion which are used for the elaboration of the compound and after the injection of the materials. The first objective is to identify the optimal parameters of the manufacturing processes which permit to elaborate satisfactory products presenting acceptable mechanical properties. The study aims to understand the effect of the introduction of flax reinforcements from a thermal and mechanical point of view. From the main results, the thermal analyses show that the introduction of 20% PBS into the PLA matrix improves the thermal stability of PLA and increases the onset temperature of decomposition. The mechanical characterizations have shown that the stiffness of the resulted composites has been improved after the incorporation of the flax fibers from 1457MPa to 4353MPa compared to the matrix. On the contrary, a decrease in deformation rate was observed owing the addition of flax fibers from 4.4% to 1.9%. These preliminary results show the possibility to develop new bio-composites which are thermoplastic, recyclable, with configurable mechanical properties depending on the selected matrix.

Lignin powder, obtained from an abundant and low cost source, straw, through a low environmental impact process, the steam explosion, is used for the preparation of blends with low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and atactic polystyrene (PS).

Structural relaxation of polyvinyl acetate (PVAc) was studied by mercury dilatometry and differential scanning calorimetry. Tool-Narayanaswamy-Moynihan (TNM) and Adam-Gibbs-Scherer (AGS) models were used to fit numerous experimental data. Single set of volume and enthalpy relaxation parameters describing all performed experiments was found for each model. Comparison of volume and enthalpy relaxation was made on the basis of TNM parameter values. The famous volume relaxation measurements made by Kovacs [Fortschr Hochpolym Forsch 1963;3:394-507] were successfully fitted using the same set of parameters. Furthermore, several non-fitting methods of TNM parameters' estimation (including, e.g., peak-shift method or inflectional analysis) were applied to our data and their critical comparison is outlined. For most methods a good agreement with curve-fitting results was achieved.

Electrospinning was utilized to create lightweight, electrically responsive wing skins for micro-air vehicle (MAV) wing frame designs. Various compositions of an electroactive polymer were investigated to determine the appropriate electrospinning conditions for these materials. Electrospun mats of these materials were characterized via optical microscopy and scanning electron microscopy. Tensile properties of the electrospun fibers were also measured. An optimal polymer composition was electrospun onto MAV wing frames to create a bird wing-like texture. Preliminary testing of electroactivity of these prototype MAV wings is reported here. q

The effects of g irradiation on polymers used in food packaging have been studied by NMR. In order to assess the presence of a threshold dose for an observable effect, the whole range of 1-100 kGy was investigated. Polystyrene, poly-butadiene, styrene-acrylonitrile, highimpact polystyrene and acrylonitrile-butadiene-styrene were studied before and after the g irradiation treatment and in the presence or in the absence of antioxidants and stabilizers. In the absence of stabilizers, the effect of g irradiation on polystyrene is negligible even when operating at high doses. In contrast, the role of antioxidants and stabilizers is crucial in poly-butadiene and butadiene-containing copolymers. High-resolution NMR, dynamic mechanical analysis, impact analysis and gel permeation chromatography performed on irradiated polystyrene samples do not show any detectable effect, confirming polystyrene as an ideal polymer for food packaging use.

Kinetic and statistical aspects of the polymerization of toluene diisocyanate (TDI 80:20) with a commercial polyether polyol based on sorbitol have been analysed. The polymerization kinetics were measured under isothermal and adiabatic conditions, using different amounts of triethylamine (TEA) as catalyst. The kinetics were described by two independent second-order equations giving the reaction of orthoand para-NCO groups. The activation energy for the reaction of o-NCO was significantly higher than that corresponding to p-NCO. Both activation energies decrease on increasing the catalyst concentration. For uncatalysed systems, o-NCO reacts 100 times slower than p-NCO at 25°C, while both reactivities become equivalent at temperatures close to 125°C. A general gelation condition was found using a recursive procedure. Systems polymerized with a high excess of TDI show evidence of isocyanurate ring formation, while OH-terminated prepolymers may be used to decrease the gel conversion and the time to gel at room temperature.

A polyhedral oligomeric silsesquioxane (POSS) tethered imidazolium surfactant was used to exchange montmorillonite for the preparation of polymer nanocomposites in polystyrene, poly(ethylene-co-vinyl acetate), and polyamide-6 using a melt blending technique. Simultaneous temperature resolved small angle X-ray scattering and wide angle X-ray diffraction was used to monitor the surfactant stability and phase behavior of the polyamide-6 nanocomposites. Good thermal stability of the surfactant was in agreement with thermogravimetric analysis. Transmission electron microscopy revealed a mixed intercalated/exfoliated structure, with the presence of small tactoids exhibiting gallery spacings greater than 3.8 nm in all three polymers. Fluorescently tagged organically exchanged montomorillonite was used to assess the quality of nanoparticle dispersion. Exchanging the montmorillonite with lower loadings of the POSS surfactant slightly increased the size of clay tactoids, but did not significantly alter the gallery spacing or overall dispersion. The results suggest that the bulky and rigid structure of POSS, as well as its tendency to aggregate into ordered crystals, form a bilayer structure in the clay galleries and prevent montmorillonite from completely exfoliating, even in polyamide-6.

A wide range of chiral amines and amino alcohols associate with poly(2-methoxyaniline-5-sulfonic acid) (PMAS) in aqueous solution, from which optically active PMAS$(amine) films can be cast. The chiral induction is believed to be initiated by acidebase interactions with ''free'' sulfonic acid groups on the PMAS chains. Chiral amine:PMAS dimer molar ratios as low as 1:4 give PMAS$(amine) films with similar optical activity to those cast from 1:1 molar mixtures, indicating that only one in four of the ''free'' sulfonate groups on the PMAS chains need to be electrostatically bound by chiral ammonium ions to achieve optimal chiral induction. Circular dichroism studies show that the enantiomeric amines (R)-(þ)-and (S)-(À)-1-phenylethylamine induce the opposite helical hands for the supermolecular assemblies of PMAS chains. However, there is no clear correlation between the sign of the CD signals for the PMAS$(amine) films and the configuration of structurally diverse amines.

The melting behavior of restrained isotactic polypropylene fibers is examined quantitatively in terms of the influence the anisotropic structural state of the polymer has on the observed properties. Two endotherm peaks are observed to occur in some of the samples. The formation and location of the multiple peaks are determined by the orientation of the noncrystalline chains, and is independent of the fabrication path used to achieve that orientation. Above a certain minimum orientation of the noncrystalline chains, multiple endotherm peak formation occurs. The high-temperature endotherm (T2M) extrapolates to an ultimate melting point for fully oriented noncrystalline chains of 220°C, while the lower-temperature endotherm (T1M) extrapolates to an ultimate melting point of 185°C. Noncrystalline chain orientation influences the endotherm temperature through its changing configurational entropy. It is shown quantitatively that the noncrystalline polymer must be considered as plastically deformed, since rubber elasticity theory is not followed as predicted. The melting behavior of isothermally crystallized samples are also reported to further elucidate the nature of the observed endotherms.

Organic -inorganic hybrid materials were prepared starting from tetraethoxysilane and aor a,v-triethoxysilane terminated poly(1-caprolactone) (PCL-Si) using the sol-gel process. In all cases the formation of nanocomposites with a high level of interpenetration between organic and inorganic phases was noted. Poly(methyl methacrylate) slabs were dip-coated with PCL-Si/silica hybrids and a very strong increase of the flame resistance (also after UV irradiation) was noted for all coating compositions without marked differences with respect to hybrid compositions. This behavior was attributed to a preferential segregation of silica onto the outer surface, as evidenced by XPS analysis. q

An investigation about the dependence of the physical properties of styrene -butadiene rubber copolymers (cured with different sulphur content, in order to obtain various networks) on the crosslink density was carried out by means of dynamical mechanical analysis, differential scanning calorimetry and positron annihilation lifetime spectroscopy. SBR specimens were cured with different sulphur content, in order to obtain various networks. On increasing the crosslink density, the glass transition temperature increases and the fractional free volume decreases. The thermal expansion coefficient of the free volume decreases in the rubbery phase by increasing the crosslink density, owing to the slower rate of expansion of nanoholes; furthermore, it seems influenced by the percentage of polysulfide density. The density of nanoholes is independent of the temperature, but decreases on adding sulphur. The results can be framed within the Simha -Somcynsky free volume theory. q

Biomaterials based on synthetic polymers have been explored in medicine since early in the 20th century. The inert nature of polymeric materials and their many fabrication options suggested possibilities in medicine to surgeons having to deal with repair and replacement of diseased or injured organs and tissues. Now the biomaterials/medical device industry is estimated at US$150 billion worldwide and saves the lives of millions and improves the quality of life for millions more. In spite of the success of biomaterials and medical devices, there are issues with 'biocompatible' biomaterials that have an on impact medical practice and stimulate scientific questions. This perspective discusses the fact that although we have been reasonably successful with implants, there is much room for improvement.

Epoxy resins absorb significant quantities of moisture, typically 1 to 7% by weight for various formulations, which can greatly compromise their physical properties. It is known that polarity of the epoxy is a significant factor in determining the ultimate moisture uptake. However, the contribution from molecular topology still remains vague. In this work, the effects of molecular topology are elucidated by synthesizing novel epoxies where the polarity is maintained constant but the topology is systematically altered. The molecular topology is quantified in part via Positron Annihilation Lifetime Spectroscopy (PALS) in terms of the nanometer-sized voids, or nanovoids, that are also commensurate with typical interchain distances. The nanovoids are separated into their absolute zero and thermally fluctuating fractions by performing PALS measurements over a wide range of temperatures. A strong correlation is observed between the absolute zero hole volume fraction and the ultimate moisture uptake. Although the correlation is clear, the absolute zero hole volume fraction alone is not sufficient to predict the ultimate moisture uptake, and network polarity must also be considered. It is surmised that the role of the nanovoids is to open the epoxy matrix and alleviate steric hindrances that may prevent a water molecule from associating with a polar group.

The flow behaviour of xanthan, a biological polyelectrolyte, has widely been reported to be complex, and unlike that of synthetic polyelectrolytes. Most studies have been confined to xanthan concentrations above 0.02% w/w. Using a highly sensitive opposed-jets technique, we have now measured salt concentration effects on the extensional flow behaviour of xanthan in aqueous solution at a concentration of 0.01% w/w. At this low concentration xanthan behaves precisely as expected for a 'normal' polyelectrolyte, collapsing from an extended worm-like conformation to a more compact coil. We suggest that the behaviour at higher xanthan concentrations arises from a disorder-order transition due to intermolecular effects.

The blends of poly(ethylene naphthalate) (PEN) and poly(ethylene terephthalate) (PET) were obtained by melt blending at 3108C for 2 min and quenching into an ice water. Mechanical properties and structural formation of unoriented amorphous PEN/PET blend ®lms during drawing at 85, 100 and 1308C were studied by tensile tests and in situ X-ray measurements. The results obtained were compared with the pure PEN and PET. The PET ®lm could not be drawn due to partial melt at above 1008C and a lower drawing rate but the ®lm blended with PEN was possible to be drawn. The crystallization of PEN/PET blend during drawing proceeded gradually due to the effect of PET at 1008C though the crystalline re¯ections in the crystallization of pure PEN appeared suddenly by necking. This was evidenced by the formation of a-form crystalline re¯ections of PEN as detected by in situ X-ray measurements.

This paper reviews the recent discoveries that were achieved by our group in the field of particle synthesis via ring-opening metathesis polymerization (ROMP). Both polynorbornene and polybutadiene-based particles were prepared by the respective ROMP of norbornene and cyclooctadiene initiated by (PCy 3) 2 Cl 2 RuaCHPh using several methods of polymerization in dispersed media, such as dispersion, suspension and miniemulsion. Depending upon the process implemented, particles size was found to range from 300 nm to 20 mm.

The burning behaviour of three different¯exible polyurethane foam samples covered with wool fabric has been studied in a cone calorimeter operated at a radiant¯ux of 35 kW m À2. One noname retarded and two¯ame retarded polyurethane foams containing melamine and melamine plus a chlorinated phosphate, respectively, have been used. Two wool fabrics were used, one of which was ame retarded using zirconium hexa¯uoride (Zirpro (IWS)). Results for the polyurethane foams indicated that the presence of chlorinated phosphate in the¯ame retardant system results in increased levels of smoke and CO compared to when melamine only was the¯ame retardant. The times to ignition of the foam/fabric combinations were longer than those of the foams alone. The (peak) rates of heat release of the composite samples were dependent on the covering fabric. Smoke and CO release from the composite depended on both the foam and the fabric.

Melt electrospinning is one aspect of electrospinning with relatively little published literature, although the technique avoids solvent accumulation and/or toxicity which is favoured in certain applications. In the study reported, we melt-electrospun blends of poly(ε-caprolactone) (PCL) and an amphiphilic diblock copolymer consisting of poly(ethylene glycol) and PCL segments (PEG-block-PCL). A custom-made electrospinning apparatus was built and various combinations of instrument parameters such as voltage and polymer feeding rate were investigated. Pure PEG-block-PCL copolymer melt electrospinning did not result in consistent and uniform fibres due to the low molecular weight, while blends of PCL and PEG-block-PCL, for some parameter combinations and certain weight ratios of the two components, were able to produce continuous fibres significantly thinner (average diameter of ca 2 µm) compared to pure PCL. The PCL fibres obtained had average diameters ranging from 6 to 33 µm and meshes were uniform for the lowest voltage employed while mesh uniformity decreased when the voltage was increased. This approach shows that PCL and blends of PEG-block-PCL and PCL can be readily processed by melt electrospinning to obtain fibrous meshes with varied average diameters and morphologies that are of interest for tissue engineering purposes.

The synthesis of AB 2 -type miktoarm star polymers using a combination of reversible addition-fragmentation chain transfer (RAFT), ring opening polymerization (ROP) and ''Click'' chemistry was demonstrated in this work. An azide functional RAFT agent was used to polymerize butyl acrylate, polyethylene glycol acrylate and N-isopropylacrylamide monomers. Propargylamine was reacted with glycerine carbonate to obtain a dihydroxy functional alkyne compound which was used for the ring opening polymerization of 3-caprolactone (3-CL) and lactide. The resulting alkyne functional polycaprolactone (PCL) and polylactide (PLA) polymers were reacted with azide functional polymers in the presence of copper bromide (CuBr) catalyst to obtain miktoarm star polymers. The polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The star polymers had low polydispersity (w1.3) with well-defined structures. These polymers have a number of potential applications including crosslinking agents for polyurethane (PU) coatings for biodegradable and fouling release applications.

The nitric oxide (NO) donor S-nitrosoglutathione (GSNO) was incorporated in solid polymeric films of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP) and blended PVA/PVP. These matrices were found to provide a great stabilization effect on the thermal decomposition of GSNO, leading to 8-16-fold reduction in the first-order rate constants of NO release, compared to aqueous GSNO solutions. PVA/PVP-GSNO released 90% of the NO supply, over a time period of 24 h at 37 C. Differential scanning calorimetry has confirmed the miscibility between the two polymeric components. Stress-strain analysis has shown an improvement of the mechanical property of PVA films in the PVA/PVP blend, which leads to an increase of 25% in the stress at break. Scanning electron microscopy has shown that the PVA/PVP-GSNO blend leads to a smooth coating of metallic surfaces. These properties, allied to the already known good biocompatibility of PVA and PVP, makes GSNO-containing PVA and PVA/ PVP blend films good candidates for the local and controlled release of NO in target areas. r

In this article, the chemistry of interfacial adhesion between different additive systems has been dealt with to develop a high performance nanocomposite and in the process, a comprehensive study on the reinforcing effect of nanosilica has been carried out. The base polymer was considered as the blends of Poly ethersulfone (PES) and thermotropic liquid crystalline polymer (TLCP). A novel polymeric compatibilizer, polyphosphazene elastomer, has been utilized and the interchain crosslinking has been explained. Results of experimental investigations demonstrate that the nanofillers play an important role in reducing the interfacial tension. However, the presence of Polyphosphazene elastomer, acted as compatibilizer further reducing the interfacial tension through the inter-molecular interaction. The nanocomposites, thus developed, have better thermal stability and improved rheological properties. In addition, it has also been observed that Polyphosphazene elastomer impart flexibility in the composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

The aim of this work was to study the effect of the degree of substitution (DS) and the purity of sodium carboxymethyl cellulose (CMCNa) prepared from Tunisian vine stem on the absorption and retention of water. Vine stem was first delignified using souda-anthraquione, then bleached and finally chemically modified, in order to synthesize different CMCNa derivatives. The carboxymethylation reaction was carried out in presence of NaOH (40 %) and monochloroacetic acid (ClCH 2 COOH), in n-butanol as a reaction solvent. The obtained CMCNa derivatives were characterized using different tools such as the DS, Fourier transforms IR techniques, CP-MAS 13 C-NMR, the exchange capacity as well as the determination of modification reaction yield. The performance of the prepared derivatives in term of absorption capacities and retention capacities was established. The performance of CMCNa derivatives was compared with that achieved by commercial counterparts and it was concluded that the prepared ones exerted higher efficiency.

A novel nickel-based complex coordinated with an asymmetric diphosphinoamine ligand was synthesized and fully characterized. Single crystals of good quality were also obtained, and the solid-state structure of the complex was studied via X-rays diffraction. The catalytic activity of this Ni(II) complex in the vinyl-type polymerization of norbornene was studied with methylaluminoxane (MAO) as the cocatalyst/activator. The influence of the reaction time, the equivalents of MAO used, and the concentration of the monomer on: (i) the activity of the catalytic system; (ii) the isolated yield of the polymer; and (iii) the molecular weight and molecular weight distribution of the polymer were investigated. The isolated polynorbornene (PNB) yields are significantly higher compared with those reported for other similar nickelbased systems. The as-obtained PNBs are characterized by high molecular weights and relatively narrow and monomodal molecular weight distributions (amongst the narrowest reported in the literature). The linear dependence of the molecular weight of the obtained PNB on the concentration of norbornene points toward a controlled polymerization reaction.

Two series of aromatic poly(amide-benzoxazole)s have been obtained from 5-chlorocarbonyl-2-(4-chlorocarbonylphenyl)benzoxazole (NBOC) and 6-chlorocarbonyl-2-(4-chlorocarbonylphenyl)benzoxazole (OBOC). NBOC and OBOC were synthesized by a three-step process with high yields, and they were reacted with aromatic diamines by using the in situ silylation method which yielded polymers of high inherent viscosities. The solubility of these polymers was similar to that of aromatic polyamides, being soluble in aprotic polar solvents. All polymers could be processed to tough, creasable amorphous ®lms with good mechanical properties, the values of tensile strength ranging from 92 to 113 MPa with moduli above 2 GPa. The glass transition temperatures were above 3008C, whilst the onset of thermal degradation ranged from 455 to 5158C. A theoretical study was also done, by means of computational chemistry methods, to relate the orientation of the benzoxazole ring in both series with monomer reactivity and polymer properties. q

This paper aims to provide an exhaustive and comprehensive overview on flame treatment as a valuable technique for improving the surface properties of polymers, especially polyolefins. It starts with a brief historical excursus on the origin of flame treatment, and the second section deals with the major fundamentals of flame chemistry, with a special focus on the combustion process and mechanism of surface activation. The most important parameters influencing the extent of the oxidation reaction along with relevant practical notes are discussed in the third section. The concluding section outlines how the most significant features of flame treatment can be profitably used to improve the wettability and adhesion properties of polyolefin surfaces, especially from the perspective of developing novel composite solutions such as polyolefins/bio-based coating pairs intended for many different applications.

The photosensitization mechanism for cationic polymerizations initiated by diaryliodonium salts photosensitized by anthracene was investigated using fluorescence and phosphorescence spectroscopy. In situ photosensitizer fluorescence measurements confirmed that the photosensitization reaction proceeds by an electron transfer process. Transient phosphorescence studies demonstrated that electron transfer occurred from the triplet excited state of anthracene to the initiator, with an intrinsic kinetic rate constant of 2 X 1 0 ' L/mol s. Further evidence for the role of the triplet state was provided by an observed seven-fold decrease in the polymerization rate upon addition of a triplet state quencher. Finally, numerical solution of the photophysical kinetic equations indicated that the triplet state concentration was approximately three orders of magnitude higher than that of the singlet state, and that 94-96% of the active cationic centers are produced by reaction of the initiator with the triplet state. These results indicate that the electron transfer occurs primarily from the triplet state of anthracene, with the singlet state providing only a minor contribution to the photosensitization reaction. 0 1995 John Wiley & Sons, Inc.

The quantitative investigation of the radical scavenging properties of polyaniline (PANI) upon reaction with excess of the stable DPPH radical (a 4:1 ratio of DPPH to aniline units in the polymer) was carried out using 15 N and 13 C solid state NMR spectroscopy. During the ...

Boron doped and undoped Poly(vinyl) alcohol/Zirconium-yttrium acetate (PVA/Zr-Y) nanofibers were prepared by electrospinning using PVA as a precursor. The effect of boron doping was investigated in terms of solution properties, morphological changes and thermal properties. The effect of boron doping on calcined yttria stabilized zirconia (YSZ) fibers were evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy analysis. XRD
analysis revealed varying amounts of monoclinic and tetragonal zirconia present in the undoped fibers calcined at 800oC. The average crystallite sizes of the undoped YSZ were increased from 9.28 to 22.79 nm with calcining temperature increasing from 250 to 800 °C. The crystallite size was enhanced with boron doping. The systematic evolution of morphological features in the spun and the processed fibers were employed by scanning electron microscopy.

Allantoin, a crystalline compound was isolated from the methanolic extract of Cleome viscosa and it was reported for first time from this plant. The structure of Allantoin was elucidated by single crystal XRD and it was further confirmed through FTIR and ESI-MS spectroscopy techniques. It was crystallized in monoclinic crystal system with the space group P2i/c. Electronic structure characterization of the isolated Allantoin was done through density functional theory calculation. The atomic charges, dipole moment, frontier molecular orbital and the electrostatic potential map of the molecule in the gaseous phase and in the active site have also been analyzed. The optimized geometry was used for molecular docking to identify the possible binding mode. Furthermore, the in vitro antibacterial activity of the isolated Allantoin against Gram-positive and Gram-negative bacteria was evaluated. Maximum Inhibitory Concentrations (MIC) of isolated Allantoin results showed 4 µg/mL for B. subtilis and 8 µg/mL for S. aureus, E. coli and K. pneumoniae.

Objective: Six different mushroom species (Termitomyces, Ganoderma, Amauroderma, Mycena, Marasmus and an unknown) were studied to ascertain their phytochemical and antioxidant properties and determine their TLC analysis of methanolic extracts. Materials and Methods:The DPPH (1,1-diphenyl-2-picrylhydrazyl) model was employed to determine free radical scavenging activity of the methanolic extracts of the mushrooms, aluminum chloride calorimetric method for flavonoid, Thin layer chromatography (TLC) for retention factor and atomic absorption spectrophotometric (AAS) for macro and micronutrients. Results: Phytochemical analyses of the methanolic extract revealed the presence of antioxidants, phenols and flavonoids. The antioxidant values (IC 50 (µg/ml)) ranged from 1.56 x 10-4 to 21.07 x10-4 .Total phenol content ranged between 2.54 and 17.53 mg/g GAE with a mean of about 11.27 mg/g GAE. Total flavonoid content also ranged from 5.46 to 23.75 mg/g RUE with a mean of 13.41 mg/g RUE. Micronutrients such as cadmium, iron, lead, manganese and zinc were determined. Also macronutrients determined included, calcium, potassium, magnesium and sodium. Sodium ranged the highest with values ranging 6966.67 mg/L to 9600.00 mg/L followed by iron ranging from 1613.67 to 3040.00 mg/L. Percentage crude protein ranged between 11.09 % and 28.24 %. Alkaloid was present in only Mycena sp and Ganoderma sp with a band each of R f value of 0.49. A total of 18 different bands were recorded for flavonoid with R f values that ranged between 0.20 and 0.97, respectively. Conclusion: The antioxidant potential of the methanolic extracts of the mushroom samples in this study recorded higher values. This indicates that mushrooms have high antioxidant properties and rationalizes further investigation in the potential discovery of new natural bioactive principles from these mushrooms.

Dynamic mechanical spectroscopy and transmission electron microscopy were utilized to investigate the properties of composites resulting from the formation of a cross-linked inorganic network via the polymerization of tetraethoxysilane (TEOS) in situ in a poly(methyl methacrylate) (PMMA) binder. The results show that the morphology and physical properties obtained are governed by sample preparation and by the catalyst used to polymerize the TEOS ; major differences are obtained when the polymerization of TEOS is performed in different pH regimes. The morphologies which develop are consistent with the known differences in gel structures obtained during the polymerization of TEOS in acidic or basic media. When TEOS is reacted under acidic conditions at elevated temperatures, small (< 100/k) SiO 2 domains which are well dispersed in the PMMA matrix result, producing a composite material with a high plateau modulus above the Tg of PMMA which extends to at least 250°C. The time-temperaturetransformation concept, proposed by Gillham for thermosetting organic polymers, is employed to explain some of these results.

A new class of ionic copolymers containing amine and phosphonate functionalities has been prepared for the first time. N,N-Diallyl-3-(Diethylphosphonato)-methylammonium chloride underwent cyclocopolymerization with SO 2 to give a cationic polyelectrolyte (CPE) in very good yields. Likewise, ethyl 3-(N,N-diallylammonio)methanephosphonate/SO 2 cyclopolymerization afforded the corresponding polyzwitterion-ester (PZE), which on neutralization with NaOH gave the anionic polyelectrolyte (APE). Both CPE and PZE on hydrolysis of the phosphonate ester functionalities gave the same polyzwitterionic acid (PZA). The pH-responsive PZA on treatment with excess NaOH was converted to dianionic polyelectrolyte (DAPE) which on treatment with 1 equivalent HCl afforded the zwitterionic-anionic polyelectrolyte (ZAPE). Solution properties of the CPE, PZE, DAPE, APE and ZAPE having similar degree of polymerization have been studied in some detail. The apparent basicity constants of the amine group in APE have been determined. An aqueous two-phase system of polyethylene glycol-DAPE-H 2 O (0.4 N NaCl) has been constructed for its potential application in selective separation of toxic metal ions since polyphosphonates are expected to be effective chelators.

Starting from the natural amino-acid L-tyrosine, a diphenolic monomeric molecule was developed using carbodiimide mediated solidphase synthesis techniques. This monomeric molecule was polymerized by reacting it in equimolar proportions with suitable dihalophosphates to yield novel biodegradable polyphosphates containing peptide linkages and phosphoester linkages alternating in the polymer backbone. The biodegradability of such a polymer is expected to arise from the hydrolytic degradability of the phosphoester linkages and the enzymatic degradability of the peptide linkages in the polymer backbone. Design of such a polymer is expected to make a significant contribution to biomaterials research, regarding drug delivery device and tissue engineering scaffold applications. The monomer was obtained by a novel solid phase carbodiimide-mediated amide coupling process. The subsequent polymers were obtained by solutionphase dehydrochlorination polycondensation reactions in the presence of a suitable acid acceptor. The synthesized polymers were characterized by 13 C NMR, 31 P NMR and FTIR for their chemical structure, by GPC for their molecular weight distribution, and by DSC and TGA for their thermal transition characteristics.

Macromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by theactivated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DP, -15 for propylene oxide and DP, -20 for epichlorohydrin, polymerization proceeds as a living process,

Star polymer chains with 12 arms in a good solvent have been investigated using a dynamic Monte Carlo algorithm with the bond fluctuation model in the dilute, semidilute and concentrated regimes. We have characterized the self-diffusion coefficient and different relaxation modes of individual chains. We discuss the variation of the results with the arm length (or number of beads) and concentration. The ratio of diffusion coefficient of a star to that of a homologous linear chain is shown to increase progressively with concentration for overlapped non-entangled chains. It is also observed that diffusion and elastic relaxation of individual arms are more sensitive to the chains overlapping than global rotation or disentanglement between arms. q

In preparation for studying the hydrolytic degradation of Estane® 5703 and related poly(ester urethane) elastomers, the absorption (solubility) and diffusion of water in these polymers have been examined experimentally and modeled theoretically. Weight gain and loss experiments have been carried out. The amount of water absorbed per gram of sample was linear at low relative humidities (RHs) but curved upward at higher RHs. This curvature was not fit by Henry's law or the Flory–Huggins equation but was easily fit by a water-cluster model. Diffusion coefficients were determined by fitting the time dependence of the sample weights, and the diffusion appeared Fickian to within experimental uncertainty. The similarity of related polymers was used to determine the approximate temperature dependence of the absorption. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 181–191, 2002

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long multimode polymer waveguide.

The crystallinity degree of thin polyamide ®lms (PA66, 610 and 612) spin coated on four types of substrates are estimated. Two original methods based on the analysis of infrared spectra are proposed. The high sensitivity of polarization modulation re¯ection-absorption spectroscopy for the study of thin polymer ®lms leads to quantitative results. These two methods offer the possibility to estimate the degree of crystallinity by using infrared spectroscopy, independently of any other technique, if the crystallinity degree in the isotropic bulk state is known. Polyamides are spin coated, on the one hand, on inert and highly re¯ecting gold substrates, and on the other hand, on the same gold substrates grafted with different chemical functionality. Our calculations show a lower crystallinity degree for inert substrate and higher values for functionalized systems with respect to the bulk. These results suggest that the surface chemical grafts not only play the role of nucleation seeds, but also affect the crystalline morphology as seen by atomic force microscopy. q

Hydrogel networks based on N-isopropylacrylamide (NIPAM) and sodium acrylate (SA) were prepared by redox-polymerization in the presence of N,N 0 -methylenebisacrylamide (MBA). Highly stable and uniformly distributed silver nanoparticles have been prepared using these hydrogel networks as a carrier via in situ reduction of silver nitrate in the presence of sodium borohydride as a reducing agent. It has been demonstrated that the hydrogel hybrid with different sizes of silver nanoparticles can be effectively employed as antibacterial material.

In this paper, series of polyimide films with different aggregation structures were prepared through a partially pre-imidization process, and the properties were investigated in detail. The pre-imidization degree (pre-ID) was successfully controlled by adjusting the amount of dehydrating reagents, which was confirmed by FT-IR spectra measurement. PI films exhibited a quite different degree of crystallinity, which increased with pre-ID increasing. DSC curves showed obvious melt endothermic peaks at about 450 C. The tensile strength, tensile moduli and elongation at break of the PI films increased obviously with pre-ID increasing. The corresponding values of PI-100 increased by 37.9%, 11.7% and 336%, respectively, compared with those of PI-0. TMA measurement showed that the coefficient of thermal expansion of PI films decreased with pre-ID increasing, indicating that the PI molecular chains were restricted by the crystalline structure. Meanwhile, those PI films obtained by the pre-imidization process still possess excellent thermal stability. The present work provided the theoretic indicators for controllable preparing of high-performance polyimide films.

Sulfur dioxide, N,N-diallyl-N-carboethoxymethylammonium chloride and the hydrophobic monomers N,N-diallyl-N-dodecylammonium chloride or N,N-diallyl-N-octadecylammonium chloride were cyclocopolymerized in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator to afford water-soluble cationic polyelectrolyte (CPE) having five-membered cyclic structure on the polymeric backbone. The CPE on acidic (HCl) hydrolysis of the pendent ester groups gave the corresponding cationic acid salt (CAS) which was converted to the anionic polyelectrolyte (APE) by treatment with sodium hydroxide. The solution properties of the CPE and APE containing varying amount of the hydrophobic monomers in the range 0 -10 mol% were investigated by viscometric techniques. The polymers showed that concentration (C p HA ) of less than 1 wt% was required for the manifestation of hydrophobic association, and displayed significant hydrophobic association in salt (NaCl)-free as well as salt-added solutions. q

A novel sulfonated diamine monomer, 1,4-bis(4-aminophenoxy)-naphthyl-2,7-disulfonic acid (BAPNDS), was synthesized. A series of sulfonated polyimide copolymers were prepared from BAPNDS, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and nonsulfonated diamine 4,4′-diaminodiphenyl ether (ODA). Flexible, transparent, and mechanically strong membranes were obtained. The membranes displayed slightly anisotropic membrane swelling. The dimensional change in thickness direction was larger than that in planar. The novel SPI membranes showed higher conductivity, which was comparable or even higher than Nafion 117. Membranes exhibited methanol permeability from 0.24 × 10−6 to 0.80 × 10−6 cm2/s at room temperature, which was much lower than that of Nafion (2 × 10−6 cm2/s). The copolymers were thermally stable up to 340 °C. These preliminary results have proved its potential availability as proton-exchange membrane for PEMFCs or DMFCs.