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1.
Highly water soluble polymer (DD) was prepared and evaluated for its fluorescence response towards various amino acids. The polymer consists of dansyl hydrazine unit conjugated into dextran template. The conjugation enhances higher water solubility of dansyl hydrazine moiety. Of screened amino acids, DD exhibited selective fluorescence quenching in the presence of aspartic acid (Asp) and glutamic acid (Glu). A plot of fluorescence intensity change of DD against the concentration of corresponding amino acids gave a good linear relationship in the range of 1?×?10?4 M to 25?×?10?3 M. This establishes DD as a potential polymeric sensor for selective sensing of Asp and Glu.
Figure 1
Fluorescence quenching of dansyl hydrazine dextran conjugate (DD) in the presence of L-aspartic or L-glutamic acids  相似文献   
2.
Epoxidised natural rubber (ENR) latex, having 25% of epoxide content, was prepared by in situ epoxidation reaction using performic acid. The ENR latex film surface was modified by immersing into methyl methacrylate (MMA) emulsion and then alkaline aqueous solution of ferrous ion/fructose for redox-initiated polymerisation. Increasing polymerisation time caused an increase in percent conversion of MMA swelled in ENR sheet. The presence of poly(methyl methacrylate) on the ENR surface was examined by attenuated total reflection-Fourier transform infrared spectroscopy. The nano-scale indentation experiment performed on the cross-section of the modified ENR sheet indicated that MMA polymerisation occurred mainly near the rubber’s surface. The surface morphology observed under scanning electron microscopy and atomic force microscopy revealed a pronounced roughness which, consequently, decreased the friction coefficient of ENR surface.  相似文献   
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4.
The prevulcanisation of skim latex, a by-product of field natural rubber (NR) latex concentrated by centrifugation, using sulphur and peroxide systems was investigated. Compared to the peroxide prevulcanisation, the lower swelling ratio of film casted from sulphur-prevulcanised skim (SPVS) latex was observed. The latter was then employed for preparation of NR/SPVS core–shell particles by using heterocoagulation technique whose driving force was an interpolymer complex between poly(ethylene oxide) (PEO) moieties of a non-ionic surfactant (Nonidet) adsorbed on small SPVS particles and the indigenous surfactant (protein–lipid) on a large NR particle. The value of zeta potential of heterocoagulated particle and the better oil resistance of films casted from the composite latex when compared to that of the NR film revealed the NR/SPVS core–shell structure.  相似文献   
5.
Octadecane (OD), a heat storage material, was encapsulated into poly(divinylbenzene-co-methyl methacrylate) or P(DVB-co-MMA) matrix via the microsuspension polymerization. The oil droplets were first generated by using the phase inversion emulsification, i.e., adding a sodium dodecyl sulphate (SDS) aqueous solution into an oil phase (monomers:OD = 1:1) containing various concentrations of poly(vinyl alcohol) (PVA). Results showed that 0.1 wt% of SDS in aqueous medium with the additional rate of 2 mL/min and 3 wt% of PVA in oil phase were the optimal conditions for the formation of nonspherical microcapsules. The smallest number- (dn) and weight- (dw) average diameters of P(DVB-co-MMA)/OD were, respectively, 3.1 and 3.2 µm with a narrow particle size distribution (dw/dn) of 1.02. The latent heats of the encapsulated OD increased with increasing MMA content of microcapsules. The heat of melting (ΔHm; 223 J/g-OD) and crystallization (ΔHc; 230 J/g-OD) of the OD encapsulated in microcapsules using DVB:MMA of 30:70 were higher than those using only PDVB (189 and 193 J g-OD for ΔHm and ΔHc, respectively) and comparable to those of bulk OD (233 and 234 J/g-OD for ΔHm and ΔHc, respectively). The obtained P(DVB-co-MMA)/OD microcapsules would be useful as high performance heat storage material.  相似文献   
6.
The nanoparticle with simultaneous combination of magnetic and fluorescent properties was prepared by immobilization of fluorescein isothiocyanate (FITC) onto magnetic polymeric nanoparticle (MPNP). The MPNP with 41% magnetic content was obtained from incorporating Fe(3)O(4) magnetic nanoparticles (MNPs) into poly(styrene/divinyl benzene/acrylic acid) via the miniemulsion polymerization. Before labeling with FITC, the carboxylated MPNP was coated with chitosan (CS) having low, medium, or high molecular weight (MW) in order to avoid quenching of the fluorescent by iron oxide. Data obtained from TEM, size and zeta potential measurements clearly indicated the presence of CS as a shell surrounding the superparamagnetic MPNP core. The zeta potential, FTIR, and fluorescent spectroscopies confirmed the attachment of FITC to the MPNP-CS via covalent bonding. The higher MW or longer chains of CS (300kDa) offered the larger spacer with multiple sites for the FITC binding and, thus, provided the higher fluorescent emission intensity. The MPNP-CS immobilized with FITC would be useful for cell-labeling application.  相似文献   
7.
This paper examines the relation between debt and corporate governance in emerging market economies. We use firm-level panel data of listed companies from Thailand and Indonesia to analyze the firm’s corporate financing behaviors in connection with its corporate governance arrangements. Our results show that the debt structure is linked to the corporate governance. We find that weaker corporate governance firms, in particular measured by the entrenchment effects, tend to have a higher debt level. The evidence is relatively stronger during the crisis period. Our results also shed lights on the importance of the country-specific institutional settings that would affect the empirical results.  相似文献   
8.
The first observation of bulk phase separation in immiscible natural rubber (NR)/poly(methyl methacrylate) (PMMA) film using atomic force microscopy (AFM) is reported. Three different forms of AFM measurements: topographic, friction force imaging, and nanoindentation have been effectively used to investigate combined morphological and compositional mapping of the NR/PMMA system. The fracture temperature during sample microtoming and material physical properties could be responsible for the observed topographic contrast. The stronger contrast of friction imaging, relative to topographic imaging, is ascribed to local variations in mechanical properties of the phase-separated domains. Friction force imaging associated with nanoindentation response, performed under AFM force mode, highlights the AFM's ability for probing local friction, adhesion, and elastic properties, and for compositional mapping of heterogeneous polymer film. The resulting friction force imaging along with the response of the nanoindentation are in good agreement, indicating that PMMA exists mainly near the modified NR surface.  相似文献   
9.
Transmission electron microscopy provided direct evidence of the morphology of sulphur- and peroxide-prevulcanised natural rubber latex particles. A mesh structure of all cross-linked rubber particles containing polystyrene, prepared using the phase-transfer/bulk polymerisation process, was found. Each peroxide-prevulcanised particle had a nonuniform network structure, whereas the rubber network in sulphur-prevulcanised particles was homogeneous, irrespective of size. The effects of maturation and sodium dodecyl sulphate on the swelling ratio of the sulphur-prevulcanised latex film were investigated.  相似文献   
10.
A novel tool for the detection of BCR/ABL fusion gene in chronic myelogenous leukemia (CML) was developed by a magneto-polymerase chain reaction (PCR)-enzyme linked gene technique. The forward primers covalently bound to the surface of magnetic nanoparticles allowed a convenient separation of PCR products with high sensitivity (0.5 pg ml(-1)) and high specificity using K562 cell line and CML patients. The results were obtained when the biotinylated-reverse primer bound to streptavidin-horseradish peroxidase (HRP) and hydrolysed the substrate. This novel readout system was approximately 1000-fold more sensitive than the conventional agarose gel electrophoresis. The present technique is practical and useful for following up CML patients and for providing appropriate treatment, particularly to patients in remote areas.  相似文献   
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