Fabrication of conductive metallized nanostructures from self-assembled amphiphilic triblock copolymer templates: Nanospheres, nanowires, nanorings

Various metallized nanostructures (such as rings, wires with controllable lengths, spheres) have been successfully fabricated by coating metallic nanolayers onto soft nanotemplates through simple electroless methods. In particular, bimetallic nanostructures have been obtained by using simple methods. The multiple functional polymeric nanostructures, were obtained through the self-assembly of polystyrene/poly(4-vinyl pyridine) triblock copolymer (P4VP-b-PS-b-P4VP) in selective media by changing the common solvent properties. By combining field emission scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization, it was confirmed that polymer/metal and bimetallic (Au@Ag) core-shell nanostructures could be achieved by chemical metal deposition method.

RGD peptide grafted biodegradable amphiphilic triblock copolymer poly(glutamic acid)-b-poly(L-lactide)-b-poly(glutamic acid): Synthesis and self-assembly

A novel amphiphilic biodegradable triblock copolymer (PGL-PLA-PGL) with polylactide (PLA) as hydrophobic middle block and poly(glutamic acid) (PGL) as hydrophilic lateral blocks was successfully synthesized by ring-opening polymerization (ROP) Of L-lactide (LA) and N-carboxy anhydride (NCA) consecutively and by subsequent catalytic hydrogenation. The results of cell experiment of PGL-PLA-PGL suggested that PGL could improve biocompatibility of polyester obviously. The copolymer could form micelles of spindly shape easily in aqueous solution. The pendant carboxyl groups of the triblock copolymer were further activated with N-hydroxysuccinimide and combined with a cell-adhesive peptide GRGI)SY Incorporation of the oligopeptide further enhanced the hydrophilicity and led to formation of spherical micelles. PGL-PLAPGL showed better cell adhesion and spreading ability than pure PLA and the GRGDSY-containing copolymer exhibited even further improvement in cell adhesion and spreading ability, indicating that the copolymer could find a promising application in drug delivery or tissue engineering.

Biodegradable amphiphilic triblock copolymer bearing pendant glucose residues: Preparation and specific interaction with Concanavalin A molecules

A novel biodegradable amphiphilic block copolymer PLGG-PEG-PLGG bearing pendant glucose residues is successfully prepared by the coupling reaction of 3-(2-aminoethylthio) propyl-R-D-glucopyranoside with the pendant carboxyl groups of PLGG-PEG-PLGG in the presence of N,N'-carbonyldiimidazole. The polymer PLGG-PEG-PLGG, i.e., poly {(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}-block-poly(ethylene glycol)-block-poly{( lactic acid)-co-[( glycolic acid)-alt-(L-glutamic acid)]}, is prepared by ring-opening copolymerization of L-lactide (LLA) with (3s)-benzoxylcarbonylethylmorpholine-2,5-dione (BEMD) in the presence of dihydroxyl PEG with molecular weight of 2000 as macroinitiator and Sn(Oct)(2) as catalyst, and then by catalytic hydrogenation. The glucose-grafted copolymer shows a lower degree of cytotoxicity to ECV-304 cells and improved specific recognition and binding with Concanavalin A (Con A). Therefore, this kind of glucose-grafted copolymer may find biomedical applications.

Well-organized structures of ZnS semiconductor nanocrystals using amphiphilic triblock copolymer aggregates as templates

Ring- and rod-shaped P4VP-b-PS-b-P4VP ( PS, polystyrene; P4VP, poly( 4-vinylpyridine)) triblock copolymer aggregates are used as templates to synthesize ZnS nanocrystals. Herein, PVP serves as both a stabilizing agent and a structure- directing agent. The resulting ZnS nanocrystals could be aligned along the corona of the copolymer aggregates in near-perfect structures through control of both the molar ratio of Zn2+ to P4VP and the reaction time. The diameter of the as-synthesized ZnS layer on the surface of polymer template is approximate 2 - 3 nm. High-resolution transmission electron microscopy images reveal that the ZnS particles are single crystal in a zinc blende structure. This method provides a simple, reproducible route at room temperature to prepare assembled hybrid polymer - semiconductor nanocrystal nanocomposites.

Synthesis and characterization of the biodegradable polycaprolactone-graft-chitosan amphiphilic copolymers

A novel synthetic approach to biodegradable amphiphilic copolymers based on poly (epsilon-caprolactone) (PCL) and chitosan was presented, and the prepared copolymers were used to prepare nanoparticles successfully. The PCL-graft-chitosan copolymers were synthesized by coupling the hydroxyl end-groups on preformed PCL chains and the amino groups present on 6-O-triphenylmethyl chitosan and by removing the protective 6-O-triphenylmethyl groups in acidic aqueous solution. The PCL content in the copolymers can be controlled in the range of 10-90 wt %. The graft copolymers were thoroughly characterized by H-1 NAM, C-13 NMR, FT-IR and DSC. The nanoparticles made from the graft copolymers were investigated by H-1 NMR, DLS, AFM and SEM measurements. It was found that the copolymers could form spherical or elliptic nanoparticles it? water. The amount of available primary amines on the surface of the prepared nanoparticles was evaluated by ninhydrin assail, and it can be controlled by the grafting degree of PCL.

Helix-sense-selective polymerization of N,N-diphenyl (meth)acrylamide by anionic catalysts

In this paper, the helix-sense-selective polymerization of N,N-diphenyl acrylamide (DPAA) and N,N-diplienyl methacrylamide(DPMAA) were studied with living helix prepolymer as anionic initiator, and the chiral optical properties of the obtained polymers were investigated too. It was shown that optically active polymers of DPAA and DPMAA could be obtained under the experimental condition, and exhibited the same screw sense as that of the prepolymer.

Aggregation behavior of amphiphilic D-pi-A molecules bearing recognition group

Aggregation behavior of two amphiphilic D-pi -A molecules bearing barbituric acid as both recogniton group and electron-drawing substituent, 5-(4-dodecyl oxybenzylidene)-(1H, 3H)-2,4,6-pyrimidine trione (PB12) and 5-(4-N,N-didodecyl aminobenzylidene)-(1H,3H)-2,4,6-pyrimidine trione (AB(12)) was studied by UV-visible, fluorescence, and surface voltaic spectroscopies (SPS). The experimental results indicate that PB12 tends to form J-aggregate and AB(12) tends to form H-aggregate under increasing concentration. An intramolecular twisted charge transfer (TICT) emission around 500 nm is observed when J-aggregate is formed between PB12 molecules, and an excimer emission around 600 nm is observed when H-aggregate is formed between AB(12) molecules.

Electric field-induced conformational transition of bovine serum albumin from alpha-helix to beta-sheet

The irreversible conformational transition of bovine serum albumin (BSA) from alpha-helix to beta-sheet, induced by electric field near the electrode surface, was monitored by circular dichroism (CD) with a long optical path thin layer cell (LOPTLC).

Chlorohydrin water swellable rubber compatibilized by an amphiphilic craft copolymer. I. Synthesis and characterization of compatibilizer PVA-g-PBA

The graft copolymerization of butyl acrylate onto poly(vinyl alcohol) with eerie ammonium nitrate as redox initiator in a aqueous medium has been investigated. The formation of graft copolymer was confirmed by means of IR, scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD). The percentage of mononer conversion and percentage of grafting varied with concentrations of initiator, nitric acid, monomer, macromolecular backbone (X-n = 1750, M = 80 000), reaction temperature and reaction time. Some inorganic salts and organic solvents have a great influence upon grafting. The reaction mechanism has been explored, and rate equations for the reaction are established. (C) 2000 John Wiley & Sons, Inc.

Synthesis, luminescence, energy transfer and Langmuir-Blodgett films of amphiphilic complexes of rare earths with monooctadecyl phthalate

Three new amphiphilic rare earth complexes with only two organic long chains Ln (MOP)(2)Cl (MOP=monooctadecyl phthalate, Ln=Eu, Tb, Gd) were synthesized and characterized by elemental analysis. The complexes (Eu, Tb) showed good luminescence property with long fluorescence lifetime, whereas the intensity and lifetime of Tb complex are greater than those of Eu complex, By measuring the triplet energy levels of ligand based on energy transfer mechanism, above phenomena have been well explained. The Langmuir films of the complexes on the air/water interface were also studied and the results show that all of them have good film-forming property.

Studies on water-swellable elastomers .2. Thermal properties and crystalline behavior of amphiphilic graft copolymers with poly(ethylene glycol) side chains

The thermal properties and crystalline structure of the amphiphilic graft copolymers CR-g-PEG600, CR-g-PEG2000, and CR-g-PEG6000 using chloroprene rubber (CR) as the hydrophobic backbone and poly(ethylene glycol) (PEG) with different molecular weights as the hydrophilic side chains were studied by DSC and WAXD. The results showed that a distinct phase-separated structure existed in CR-g-PEGs because of the incompatibility between the backbone segments and the side-chain segments. For all the polymers studied, T-m2, which is the melting point of PEG crystalline domains in CR-g-PEG, decreased compared to that of the corresponding pure PEG and varied little with PEG content. For CR-g-PEG600 and CR-g-PEG2000, T-m1, which is the melting point of the CR crystalline domains, increased with increasing PEG content when the PEG content was not high enough, and at constant PEG content, the longer were the PEG side chains the higher was the T-m1. The crystallite size L-011 of CR in CR-g-PEGs increased compared to that of the pure CR and decreased with increasing PEG content. (C) 1997 John Wiley & Sons, Inc.

Studies on water-swellable elastomer .1. Synthesis and characterization of amphiphilic polymer

A new amphiphilic polymer i.e., polyethylene glycol (PEG) grafted crystalline neoprene, which was used as compatibilizer to improve the compatibility of elastomer and water-absorbent resin, has been investigated. The synthesis was based on the reaction between chlorine in neoprene and sodium salts of PEG. PEGs with molecular weights of 600 and 2000 were used. The grafting percent and the PEG content were calculated through elemental analysis of chlorine in the resulted copolymers. The maximum grafting percent of copolymers was ca. 24.80%. The molecular parameters such as number-average molecular weight and the average number of grafting chains on one CR backbone were also calculated and discussed. (C) 1996 John Wiley & Sons, Inc.