Synthesis and characterization of PCL/PEG/PCL triblock copolymers by using calcium catalyst

Triblock copolymer PCL-PEG-PCL was prepared by ring-opening polymerization of epsilon-caprolactone (CL) in the presence of poly(ethylene glycol) catalyzed by calcium ammoniate at 60 degreesC in xylene solution. The copolymer composition and triblock structure were confirmed by H-1 NMR and C-13 WR measurements. The differential scanning calorimetry and wide-angle X-ray diffraction analyses revealed the micro-domain structure in the copolymer. The melting temperature T-c and crystallization temperature T-c of the PEG domain were influenced by the relative length of the PCL blocks. This was caused by the strong covalent interconnection between the two domains. Aqueous micelles were prepared from the triblock copolymer. The critical micelle concentration was determined to be 0.4-1.2 mg/l by fluorescence technique using pyrene as probe, depending on the length of PCL blocks, and lower than that of corresponding PCL-PEG diblock copolymers. The H-1 NMR spectrum of the micelles in D2O demonstrated only the -CH2CH2O- signal and thus confirmed. the PCL-core/PEG-shell structure of the micelles.

Synthesis of poly(epsilon-caprolactone)-b-poly(gamma-benzyl-L-glutamic acid) block copolymer using amino organic calcium catalyst

A biodegradable two block copolymer, poly(epsilon-caprolactone)-b- poly(gamma-benzyl-L-glutamic acid) (PCL-PBLG) was synthesized successfully by ring-opening polymerization of N-carboxyanhydride of gamma-benzyl-L-glutamate (BLG-NCA) with aminophenyl-terminated PCL as a macroinitiator. The aminophenethoxyl-terminated PCL was prepared via hydrogenation of a 4-nitrophenethoxyl-teminated PCL, which was novelly obtained from the polymerization of c-caprolactone (CL) initiated by amino calcium 4-nitrobenzoxide. The structures of the block copolymer and its precursors from the initial step of PCL were confirmed and investigated by H-1 NMR, FT-IR, GPC, and FT-ICRMS analyses and DSC measurements.

Strontium-based initiator system for ring-opening polymerization of cyclic esters

An amino isopropoxyl strontium (Sr-PO) initiator, which was prepared by the reaction of propylene oxide with liquid strontium ammoniate solution, was used to carry out the ring-opening polymerization (ROP) of cyclic esters to obtain aliphatic polyesters, such as poly(epsilon-caprolactone) (PCL) and poly(L-lactide) (PLLA). The Sr-PO initiator demonstrated an effective initiating activity for the ROP of epsilon-caprolactone (epsilon-CL) and L-lactide (LLA) under mild conditions and adjusted the molecular weight by the ratio of monomer to Sr-PO initiator. Block copolymer PCL-b-PLLA was prepared by sequential polymerization of epsilon-CL and LLA, which was demonstrated by H-1 NMR, C-13 NMR, and gel permeation chromatography. The chemical structure of Sr-PO initiator was confirmed by elemental analysis of Sr and N, H-1 NMR analysis of the end groups in epsilon-CL oligomer, and Fourier transform infrared (FTIR) spectroscopy. The end groups of PCL were hydroxyl and isopropoxycarbonyl, and FTIR spectroscopy showed the coordination between Sr-PO initiator and model monomer gamma-butyrolactone. These experimental facts indicated that the ROP of cyclic esters followed a coordination-insertion mechanism, and cyclic esters exclusively inserted into the Sr-O bond.

Synthesis and structural characterization of organolanthanide complexes with 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolate ligands

Reactions of anhydrous LnCl(3) (Ln = Nd, Gd, Dy, Er, Yb) with 2 equiv of LiCp' in THF afford the lanthanocene complexes Of CP'(2)Ln(mu-Cl)(2)Li(THF)(2) (CP' = eta(5)-t-BuC5H4, Ln = Nd (1), Gd (2), Dy (3), Er (4), Yb (5); Cp'= 1,3-eta(5)-t-Bu2C5H3, Ln = Nd (6), Gd (7), Dy (8), Er (9), Yb (10)). The molecular structures of 7 and 8 were characterized by X-ray crystallographic analysis. In these complexes, two Cp' ring centroids and two it-bridging chloride atoms around the lanthanide atoms form a distorted tetrahedron. The insertion of elemental chalcogen E (E = S, Se) into Li-C bonds of dilithium o-carborane in THF solution afforded dimers of dilithium. dichalcogenolate carboranes, [(THF)(3)LiE2C2B10H10Li(THF)](2) (E = S (12a), Se (12b)), which were confirmed by a crystal structure analysis. Reactions Of Cp'(2)Ln(mu-Cl)(2)Li(THF)(2) (1-10) with 12a or 12b gave dinuclear complexes of the formula [Li(THF)(4)](2)[Cp'(2)LnE(2)C(2)B(10)H(10)](2) (Cp'= eta(5)-t-BuC5H4, E = S, Ln = Nd (13a), Gd (14a), Dy (15a), Er (16a), Yb (17a); E = Se, Ln = Nd (13b), Gd (14b), Dy (15b), Er (16b), Yb (17b); Cp'= 1,3-eta(5)-t-Bu2C5H3 E = S, Ln = Nd (18a), Gd (19a), Dy (20a), Er (21a), Yb (22a); E = Se, Ln = Nd (18b), Gd (19b), Dy (20b), Er (21b), Yb (22b)). According to the X-ray structure analyses, the dianions of 13a and 13b contain two o-carborane dichalcogenolate bridges, and each CP'2Ln fragment is attached to one terminal and two bridging chalcogen ligands. The central Ln(2)E(2) four-membered ring is not planar, and the direct metal-metal interaction is absent.

Infrared spectrum of 2-octadecyl-7,7,8,8-tetracyanoquinodimethane

Infrared spectrum of 2-octadecyl-7,7,8,8-tetracyanoquinodimethane was dealt with 2nd-derivative and deconvolution methods. It was first discovered that the band near 2849 cm(-1) assigned to the CH2 Symmetric stretching mode splited into two bands and this splitting might result from the coexistence of two kinds of conformations of CH2 in the hydrocarbon chain.

Synthesis and characterization of novel lanthanocene complexes with dichalcogenolate o-carboranyl ligands

Reactions of [ Cp(2)Ln(mu-Cl)](2) (Cp = eta(5)-C5H5, Ln = Nd, Yb, Dy, Gd, Er) with an equivalent of [ (THF)(3)LiE2C2B10H10Li. (TT-IF) (THF)](2) (E = S, Se) in THF afforded the dinuclear sandwich complexes of formula[Cp(2)LnE(2)C(2)B(10)H(10)](2)[Li(THF)(4)](2) [E = S, Ln = Nd (1a), Yb (2a), Dy (3a), Gd (4a), Er (5a); E = Se, Ln = Nd (1b), Yb (2b), Dy (3b), Gd (4b), Er (5b)]. The molecular structures of complexes la, 2a and 2b were determined by the single crystal X-ray structure analyses. Two lanthanide atoms are connected by a pair chalcogen (eta(1), eta(2)-E2C2B10H10) bridging ligands and the central Ln(2)E(2) four membered ring is not planar.

Synthesis and characterization of a time-resolved fluorescence analysis chelate reagent-BCPDA

In this paper, we report on a solid phase time-resolved fluorescence immunoassay chelate reagent-4,7-bis(chlorosulfophenyl)1, 10-phenanthroline-2,9-dicarboxylic acid (BCPDA), which is suitable as a fluorescent labeling agent. The five step synthesis product of BCPDA was presented for improving the purity of the product based on the three step synthesis product. The approach involves chlorization, hydrolyzing the ester, preparing disodium, carboxylate to diacid, sulfonation. The yield of five step product is 99 %, 45 %, 94 %, 95 %, 80 % respectively. The structure and purity of product was characterized by the melting point, IR,H-1 NMR, UV spectrum, element analysis, and proved to be consistent with the structure predictal.

A relocated technique of atomic force microscopy (AFM) samples and its application in molecular biology

A kind of simple atomic force microscopy (AFM) relocated technique, which takes advantage of homemade sample locator system, is used for investigating repeatedly imaging of some specific species on the whole substrate (over 1 x 1 cm(2)) with resolution about 400 nm. As applications of this sample locator system, single extended DNA molecules and plasmid DNA network are shown in different AFM operational modes: tapping mode and contact mode with different tips after the substrates have been moved.

Measurement of the single-color three-photon resonant ionization spectrum of atomic uranium under the "equivalent wavelength effect laser" interaction

Using Nd: YAG laser (532 nm) pumped mixed-dye laser. we obtained the output of this dye enhanced at the wavelength interval equivalent to that given by the copper vapor laser pumped dye laser. This measure favored is with the measurement of single-color three-photon resonant ionization spectrum of atomic uranium in the range of 562-586 nm,which is otherwise not efficiently covered by Nd: YAG laser pumped dye laser with any single dye. Thus 140 U I energy levels were obtained and the peaks of interest 575.814 nm and 575.836 rim were well resolved and their relative intensity determined.

Preparation and characterization of ordered yttrium arachidate multilayer

The behavior of arachidic acid on the surface of YCI3 aqueous subphase was studied by LB and Brewster angle microscopy techniques. The results showed that the pre-compressing time and the pH of the subphase played an important role in the forming of the monolayer. The monolayer on the subphase surface was irreversible. If the monolayer was compressed into wrinkles, the monolayer could not become uniform again. The optimum transferring conditions were selected and the ordered yttrium arachidate multilayer with a long spacing of 4.96 nm and a tilt angle of 28.5degrees of the three alkyl chains from the surface normal was fabricated and characterized.

Preparation of Pt nanoparticles assembled in multilayer films

PtCl62- anions were assembled on a glassy carbon electrode with [tetrakis(N-methylpyridyl)porphyrinato]cobalt cations through layer-by-layer method. then electrochemically reduced to yield zero valent Pt nanoparticles. Regular growth and surface morphology of the multilayer films were characterized by UV/vis. XPS and AFM.

Synthesis of tetra-iron substituted sandwich-type pentadecatungstodiarsenate and its multilayers on glassy carbon electrode by self-assembly with electrocatalytic properties

A novel sandwich-type compound, Na-12 [Fe-4 (H2O)(2) (As2W15O56)(2)] . 38H(2)O (denoted as Fe(4)AS(4)W(30)) was synthesized. The compound was well characterized by means of IR, UV-Vis, W-138 NMR and elemental analyses. Redox electrochemistry of the compound has been studied in acid buffer solutions using cyclic voltammetry(CV). The compound containing multilayer films has been fabricated on the 4-aminobenzoic acid(4-ABA) modified glassy carbon electrode(GCE) surface by alternate deposition with a quaternized poly (4-vinylpyridine) partially completed with [Os(bpy)(2)Cl](2+/-) (denoted as QPVP-Os). CV, X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy were used to characterize the asprepared multilayer films. It is proved that the multilayer films are uniform and stable. The electrocatalytic activities of the multilayer films were investigated on the reduction of two substrates of important analytical interest, NO2- and H2O2.

Preparation and gas sensitivity of octa-n-butoxy-2,3-naphthalocyanine copper(II) Langmuir-Blodgett film

The formation process of monolayer of octa-n-butoxy-2,3-naphthalocyanine copper ( I), [CuNc(OBu)(8)], on water subphase was studied. Its multilayers were successifully deposited on the hydrophilic substrates by Z-type deposition mode using LB technique. Stable solid film with a limiting molecular area of 0.74 nm(2) and a collapse pressure of 55 mN/m were formed. The LB film structure was characterized by IR and electronic absorption spectra. Macrocycle of CuNc (OBu)(8) molecules have a face-to-face arrangement in the multilayers. These films have good sensitivities to vapor of alcohols, with the following sequence of sensitivities: i-PrOH>EtOH>MeOH. The response time and recovery time of the LB films to vapor of MeOH, EtOH and i-PrOH[volume fraction (1-5) X 10(-5)] were within 2 and 5 seconds respectively, while those of the LB films to ammonia(1 X 10(-4)) were 30-60 seconds and 4-5 minutes respectively.