Polydispersity of ethylene sequence length in metallocene ethylene/alpha-olefin copolymers. I. Characterized by thermal-fractionation technique

In this article, the polydispersity of the ethylene sequence length (ESL) in ethylene/alpha-olefin copolymers was studied by atomic force microscopy (AFM) and the thermal-fractionation technique. The crystal morphology observation by AFM showed that morphology changed gradually with decreasing average ESL from complete lamellae over shorter and more curved lamellae to a granular-like morphology, and the mixed morphology was observed after stepwise crystallization from phase-separated melt. This result indicated that the ethylene sequence with different lengths crystallized into a crystalline phase with a different size and stability at the copolymer systems. The thermal-fractionation technique was used to characterize the polydispersity of ESL. Three of the following statistical terms were introduced to describe the distribution of ESL and the lamellar thickness: the arithmetic mean (L) over bar (n), the weight mean (L) over bar (w), and the broadness index I = (L) over bar (w)/(L) over bar (n). It was concluded that the polydispersity of ESL could be quantitatively characterized by the thermal-fractionation technique. The effects of temperature range, temperature-dependent specific heat capacity C-p of copolymer, and the molecular weight on the results of thermal fractionation were discussed,

Construction of CdS nanostructures on DNA template by LB technique

Mixed monolayer films of octadecylamine (ODA) and oligo-DNA were prepared by Langmuir-Blodgett technique and the monolayer films were used as template to direct the formation of different CdS nanostructures. It was found that CdS nanowire was observed when the monolayer film prepared at low surface pressure was used as template, and aggregate of CdS spheres was obtained when the monolayer film deposited at high surface pressure was used as template.

Improved thermal fractionation technique for chain structure analysis of ethylene/alpha-olefin copolymers

In this report, we describe an improved thermal fractionation technique used to characterize the polydispersity of crystalline ethylene sequence length (CESL) of ethylene/alpha -olefin copolymers. After stepwise isothermal crystallization, the crystalline ethylene sequences are sorted into groups by their lengths. The CESLs are estimated using melting points of known hydrocarbons. The content of each group is determined using the calibrated peak area. The statistical terms: the arithmetic mean (L) over bar (n), the weighted mean (L) over bar (w) and the broadness index I = (L) over bar (w)/(L) over bar (n) are used to describe the distribution of CESL. Results show that improved thermal fractionation technique can quantitatively characterize the polydispersity of CESL with a high degree of accuracy.

The synthesis of phenyl-capped trianiline and teraaniline by a modified-pseudo-high dilution technique and their UV-Vis spectral studies

Phenyl-capped trianiline and tetraaniline in the leucoemeraldine oxidation state were synthesized through a modified-pseudo-high-dilution technique. The chemical oxidation process of these compounds were studied by UV-Vis spectra. It was found that phenyl-capped trianiline in the leucoemeraldine oxidation state was oxidized to its EB form and then decomposed, Phenyl-capped tetraaniline was oxidized to its EB form and then to the pernigraniline oxidation state.

Studies on electrostatic adsorption of proteins on modified surface by real-time surface plasmon resonance technique

The elucidation of key influence factors for electrostatic adsorption is very important to control protein nonspecific adsorption on modified surfaces. In this study, real-time surface plasmon resonance technique is used to characterize the electrostatic adsorption of two proteins (mouse IgG and protein A) on carboxymethyldextran-modified surface. The results show that protein solution pH and ionic strength are key influence factors for efficient electrostatic adsorption. The influence of protein, solution pH on the amount of electrostatic adsorption depends on the type of the charge and the charge density of both protein and modified matrix on the surface. The electrostatic adsorption process involves a competition between the positively charged protein and other positively charged species in the buffer solution. A decrease of ionic strength leads to an increasing electrostatic adsorption. The kinetic adsorption constants of protein A at different pH values were also calculated and compared.

Electrostatic layer-by-layer assembly of polycation and DNA multilayer films by real-time surface plasmon resonance technique

The assembly of alternating DNA and positively charged poly(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer-by-layer adsorption has been studied. Real time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. The results indicate that the uniform multilayer can be obtained on the poly(ethylenimine) (PEI) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by real-time BIAcore technique, and the observed rate constant was calculated using a Langmuir model (k(obs) = (1.28 +/- 0.08) x 10(-2) s(-1)).

Superlattice structure of gold nanoparticles film deposited by Langmuir-Blodgett technique

Dodecanethiol-capped gold nanoparticles could spread on water subphase and be transferred by LB technique. The superlattice structure of gold nanoparticles multilayer was discussed.

Preparation of SnO2 thin films with extremely preferred orientation along (101) plane by LB deposition technique

SnO2 thin films with extremely preferred orientation along (101) plane were made by LB technique and characterized by FTIR,, UV-visible, X-ray diffraction, X-ray photoelectron spectroscopy and SEM.

Technique for determination of gold electrode area and its application of characterization in self-assembling process

Underpotential deposition(UPD) of copper at polycrystal gold surface under different concentrations has been studied, and its reversibility and stability in high concentration (0.2M CuSO4+0.IM H2SO4) have been demonstrated by cyclic voltermmetry and EQCM. A Valid approach to determine the gold electrode area in presence of adsorbed species has been provided by using Cu UPD method. Further, the growth kinetics of decane thiol on gold has also been investigated based on such a Cu UPD technique.

Facile synthesis of phenyl-capped oligoanilines using pseudo-high dilution technique

Monodispersed phenyl-capped trianiline and tetraaniline were successfully synthesized by the reactions of diphenylamine with acetaldehyde-based Sckiff's bases of N-phenyl-1,4-phenylenediamine and 1,4-phenylenediamine, respectively, in the presence of ammonium persulfate and hydrochloric acid, subsequent deprotonation and reduction with phenylhydrazine. The reaction mechanism probably involves the slow hydrolysis of the Sckiff's bases and subsequent oxidative coupling reactions of the formed ammonium salts with diphenylamine at pseudo-high dilution condition of the salts.

A study of the effect of shell content on the mechanical properties of polycarbonate/poly(butyl acrylate)-cs-poly(methyl methacrylate) blends

The toughening effect of the shell content of a core-shell latex polymer poly(butyl acrylate) (PBA)-cs-poly(methyl methacrylate) (PMMA) on its blends with polycarbonate (PC) was studied. The changes of mechanical properties, morphology, and compatibility of the blends of PC/PBA-cs-PMMA with the change of the shell thickness of PBA-cs-PMMA were investigated. It is interesting to notice that mechanical properties of the blends are very sensitive to the shell thickness (i.e., shell content), and that there is a possibility to adjust the impact and tensile properties of the blend by selecting a PBA-cs-PMMA with a proper core/shell ratio. Hence, a modified PC material with balanced mechanical properties may be prepared.

Effect of the core-shell latex polymer content on the compatibility, morphology and mechanical properties of PC/PBA-cs-PMMA blends

The toughening effect of the content of a core-shell poly(butyl acrylate)/poly(methyl methacrylate) latex polymer (PBA-cs-PMMA) on the mechanical properties, morphology and compatibility of its blends with polycarbonate(PC), i.e., PC/PBA-cs-PMMa, was studied. The mechanical properties of the blends are strongly affected by varying the content of PBA-cs-PMMA in the blend. When the PBA-cs-PMMA content is only 5 wt.-%, the impact strength of PC/PBA-cs-PMMA is almost 19 times as high as that of pure PC, indicating that PBA-cs-PMMA is a very good impact modifier for PC. With increasing interphacial layer thickness and decreasing interphacial tension, the interphacial activity becomes more and more effective and, at the same time, miscibility increases too.

Structure of [C8H7](+) and intramolecular proton transfer reactions in 3-phenyl-1-butyn-3-ol by MS/MS technique

The electron impact mass spectrum (EIMS) of 3-phenyl-1-butyn-3-ol was reported in this paper. Collision-induced dissociation (CID) was used to study the gas phase ion structure of [C8H7](+) formed by the fragmentation of ionized 3-phenyl-1-butyn-3-ol, and that it has the same structure as m/z 103 ions generated by cinnamic acid and alpha-methylstyrene. Deuterium labelling, metastable ion (MI) and CID experimental results indicate the formation of m/z 103 ion resulting from molecular ion of 3-phenyl-1-butyn-3-ol, which is a stepwise procedure via twice proton transfers, rather than concerted process during the successive elimination of methyl radical and neutral carbon monoxide accompanying hydrogen transfer. Moreover, in order to rationalized these fragmentation processes, the bimolecular proton bound complex between benzyne and acetylene intermediate has been proposed.

Single crystal growth and spectroscopic properties of KZnF3:Eu3+

Single crystal of KZnF3 : Eu3+ has been grown by means of Bridgman-Stockbarger technique in Ar atmosphere, The emission and excitation spectra of europium ion were measured, The results show that a small amount of Eu2+ exists in the crystal, The existence of Eu2+ ions was also confirmed by ESR data, The valence change of Eu ions during the crystal growth is due to unequivalent substitution of Eu3+ ions for the lattice ions. The sites possibly occupied by Eu ions in this crystal were also discussed.