Synthesis and properties of segmented polyurethane using phenolphthalein as chain extenders

Three series of novel polyurethane elastomers containing phenolphthalein as chain extenders were synthesized. The structure of the polyurethane was analyzed using IR and wide-angle X-ray diffraction studies. Tensile strength and percentage of elongation of all the series of polymers were studied. Thermal decomposition was studied using differential scanning calorimetry. © 1993 John Wiley & Sons, Inc.     

The effect of a non-Newtonian lubricant on piston ring lubrication

The effect of a non-Newtonian oil (shear thinning) on the lubrication of a piston ring is theoretically investigated. A variation of shear strain rate with shear stress that is cubic in form is used to obtain a modified form of the Reynolds equation (dynamic) applicable to a run-in ring profile which is considered to be a double parabola with a central straight portion. Numerical solutions are obtained for the film thickness, pressure and frictional force over a complete stroke for the case of a constant load. Results presented in non-dimensional form show that the effect of pseudo plasticity is to reduce slightly the minimum film thickness, peak pressure ratio and friction coefficient.     

Size-dependent antimicrobial properties of sugar-encapsulated gold nanoparticles synthesized by a green method

The antimicrobial properties of dextrose-encapsulated gold nanoparticles (dGNPs) with average diameters of 25, 60, and 120 nm (± 5) and synthesized by green chemistry principles were investigated against both Gram-negative and Gram-positive bacteria. Studies were performed involving the effect of dGNPs on the growth, morphology, and ultrastructural properties of bacteria. dGNPs were found to have significant dose-dependent antibacterial activity which was also proportional to their size. Experiments revealed the dGNPs to be bacteriostatic as well as bactericidal. The dGNPs exhibited their bactericidal action by disrupting the bacterial cell membrane which leads to the leakage of cytoplasmic content. The overall outcome of this study suggests that green-synthesized dGNPs hold promise as a potent antibacterial agent against a wide range of disease-causing bacteria by preventing and controlling possible infections or diseases.     

Synthesis and photovoltaic properties of donor–acceptor polymers incorporating a structurally-novel pyrrole-based imide-functionalized electron acceptor moiety

A structurally-novel pyrrole-based imide-functionalized electron accepting monomer unit, 4,6-dibromo-2,5-dioctylpyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (DPPD), was prepared. The new DPPD unit was copolymerized with pyrrole-based electron rich monomers, such as thiophene-(N-alkyl)pyrrole-thiophene (TPT) and fused thiophene-(N-alkyl)pyrrole-thiophene (DTP) derivatives, to afford two new polymers, namely P(TPT-DPPD) and P(DTP-DPPD), respectively. The two polymers showed a strong absorption band at 300–600 nm and 300–650 nm, respectively, and their calculated optical band gaps were 2.09 eV and 1.89 eV, respectively. The electrochemical analysis reveals that the highest occupied molecular orbital (HOMO) energy levels of P(TPT-DPPD) and P(DTP-DPPD) were positioned at −5.55 eV and −5.24 eV, respectively, whereas their lowest unoccupied molecular orbital (LUMO) energy levels were positioned at −3.46 eV and −3.35 eV, respectively. The preliminary photovoltaic properties of the polymers, P(TPT-DPPD) and P(DTP-DPPD), were examined by fabricating polymer solar cells (PSCs) with each polymer as an electron donor and PC₇₁BM as an electron acceptor. The PSCs fabricated with the configuration of ITO/PEDOT:PSS/P(TPT-DPPD) or P(DTP-DPPD):PC₇₁BM/LiF/Al showed maximum power conversion efficiency (PCE) of 0.73% and 1.64%, respectively.     

Solvent Detection and Water Monitoring With a Macroporous Silicon Field-Effect Sensor

Integration of electrical and fluidic systems for the design and fabrication of a system-on-chip (SOC) capable of sensing various liquid phase solvents is reported. A monolithic integration strategy makes use of macroporous silicon (MPS) as a gateway to interface the electrical and fluidic domains. In this application, the MPS material, acting as a sensing membrane, is used in a flow-through structure to transport an analyte from fluidic channels on one side of the chip to sensing electrodes on the other. A fluid-oxide-semiconductor interface results in the modulation of a space charge region in the semiconductor where real-time measurements are used to detect and distinguish between the presences of various solvents. The fluidic system has delivered sample volumes as small as 2 mul. Selected test solvents (i.e. acetone, ethanol, isopropyl alcohol, methanol, and toluene) have generated a measured change in capacitance up to 11%. A practical application of this sensor was demonstrated by monitoring various concentrations of isopropyl alcohol in a water supply. Undiluted samples provide characteristic responses that can be used for signature identification. The sensing device has a high degree of reusability and does not require heating or other solvent removal methods often necessitated in other sensing devices     

Chain-extended polyurethanes—Synthesis and characterization

Thermoset polyurethane (PU) elastomers were prepared using hydroxyl-terminated polybutadiene (HTPB), toluene diisocyanate (TDI) and hexamethylene diisocyanate (HMDI). The effects of various diamines and diols on the mechanical and thermal properties of polyurethanes are discussed. The average molecular weight between crosslinks (M?/_c) was determined by swelling studies. The properties imparted by the extenders are explained on the basis of the groups present in the diamines and the number of methylene carbons in the diols.     

Crosslinked latex blends based on gelatin: Synthesis,morphology, thermal,and mechanical properties

Latex blends of different compositions of poly(methyl methacrylate-co-n-butylacrylate) and gelatin have been synthesised in latex form with crosslinking agents. These latex blends were characterized by thermal and mechanical properties. The morphology of cross-linked latex blends were studied by scanning electron microscopy (SEM).     

Polymer–filler interactions in hydroxy-terminated polybutadiene–ammonium perchlorate system in the presence of a bonding agent

Bonding between ammonium perchlorate (AP) and hydroxy-terminated polybutadiene (HTPB), constituting a nonreinforcing filler system, has been studied in the presence of a unique bonding agent (BA)–a switter ion molecule, 2,4-dinitrophenylhydrazone derivative of 1,1′-bisacetylferrocene (DNPHD AF). Extensive conjugation and a permanent ionic character makes the DNPHD AF to bond strongly with the ionic oxidizer AP. Through its terminal ? OH group, HTPH bonds with the NO₂ groups of DNPHD AF. Bonding sites in the molecules have been located from IR studies and from the first-order rate constant measurements of the bonding of DNPHD AF and other model BAs with HTPB and AP. The bonding ability of DNPHD AF is further evidenced from SEM micrographs.     

HLA association and occurrence of autoantibodies in Asian-Indian patients with ulcerative colitis

OBJECTIVES: The purpose of the present study was to determine the profile of HLA class I antigens, antinuclear antibodies (ANA), and antineutrophil cytoplasmic antibodies (ANCA) in ulcerative colitis (UC) patients from Northern India. METHODS: The study consisted of 100 UC patients with or without extraintestinal manifestations. Data on HLA, ANA, and ANCA were analyzed with respect to age at onset, sex, duration of disease, and occurrence of extraintestinal manifestations, and data were correlated with those of healthy controls from the same population. RESULTS: The most common extraintestinal manifestations in order of occurrence were arthralgia (53.8%), ocular lesions (18%), sacroiliitis (12.7%), hepatobiliary (7.7%), cutaneous (5%), and vascular (2.6%). ANA and ANCA were positive in only 3% of cases. Of the HLA class I antigens, HLA-A19 was significantly increased in UC patients compared with controls (63.4% vs. 33.5%, p < 0.001, RR = 3.4), particularly its subtype HLA-A33 (20.7% vs. 4%, p < 0.001, RR = 6.3). There was no deviation in the frequency of HLA-B locus antigens, whereas HLA-Cw6 was increased significantly in patients compared with controls (14.6% vs. 3.5%, p < 0.001, RR = 4.4). CONCLUSIONS: The occurrence of extraintestinal manifestations in Indian patients with UC is similar to that reported elsewhere, although ANA and ANCA positivity is lower. HLA studies revealed that A19(33) and Cw6 are associated with UC.     

Grafting of glycidyl methacrylate onto gelatin

Gelatin was graft copolymerized with poly(glycidyl methacrylate) using potassium peroxydisulfate in aqueous medium. Effect of temperature, time, initiator, monomer, and backbone concentrations were studied. The percent grafting was found to increase initially and then decrease in all the cases except with variation of monomer concentration. The rate of grafting, grafting efficiency, and percent of grafting were calculated. The grafting results have been discussed in the light of the rate of grafting. Mechanical properties, FT IR spectra, percent swelling, and percent dye uptake were carried out on the graft copolymerization and the results discussed.