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.

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.

An effective etching technique for polycarbonate/core-shell poly(butyl acrylate) poly(methyl methacrylate) blend

Two etching techniques are used to reveal the morphology of PC/PBA-cs-PMMA blend. One is based on acetic acid (CH3COOH) solutions, whereas the other uses CCl4/ C2H5OH (3/1 v/v). The latter approach shows to be more appropriate and successful for revealing the morphology of PC/PBA-cs-PMMA blend.

Impedance spectrum measurement in liquid/liquid interface electrochemistry .2. Study on the ion transfer at L/L interface by impedance spectrum technique

In this paper we study the ion transfer across the liquid/liquid interface by impedance spectrum technique in the four - electrode system. We present a method of getting the real interfacial impedance curve from the apparent impedance curve obtained in the four - electrode system. A practical kinetics investigation on the transfer of tetramethylammonium ion at the water/nitrobenzene interface was done with the method to verify the validity of the method. The transfer of tetramethylammonium ion at the W/O interface is really a reversible transfer.

A novel in-situ spectroelectrochemical technique with probe beam deflection: For study of the ion exchange between films on electrode surface and solutions

A novel in-situ spectroelectrochemical technique, the combination of probe beam deflection (PBD) with cyclic voltammetry (CV), was used to study the ion exchange process of prussian blue(PB) modified film electrode in contact with various electrolyte solutions. The ion exchange mechanism was verified as following: (K2Fe2+FeII)(CN)(6) -e(-)-k(+)reversible arrow +e(-)+k(+) (KFe3+FeII)(CN)(6) -ke(-)-xk(+)reversible arrow +xe(-)+kk(+) [(Fe3+FeIII)(CN)(6)](x)[(KFe3+FeII)(CN)(6)](1-x) where on reduction PB film in contact with an acidic KCl electrolyte, it was confirmed that protons enter into the PB film before K+ cations.