Changzheng Yang

Synthesis and characterization of chitosan-poly(acrylic acid) nanoparticles.

Chitosan (CS)-poly(acrylic acid) (PAA) complex nanoparticles, which are well dispersed and stable in aqueous solution, have been prepared by template polymerization of acrylic acid (AA) in chitosan solution. The physicochemical properties of nanoparticles were investigated by using size exclusion chromatography, FT-IR, dynamic light scattering, transmission electron microscope and zeta potential. It was found that the molecular weight of PAA in nanoparticles increased with the increase of molecular weight of CS, indicating that the polymerization of acrylic acid in the chitosan solution was a template polymerization. It was also found that the prepared nanoparticles carried a positive charge and showed the size in the range from 50 to 400 nm. The surface structure and zeta potential of nanoparticles can be controlled by different preparation processes. The experiment of in vitro silk peptide (SP) release showed that these nanoparticles provided a continuous release of the entrapped SP for 10 days, and the release behavior was influenced by the pH value of the medium.

Preparation and drug release behaviors of nimodipine-loaded poly(caprolactone) poly(ethylene oxide) polylactide amphiphilic copolymer nanoparticles

Amphiphilic block copolymers, poly(caprolactone)-poly(ethylene glycol)-poly(lactide) (PCELA), were synthesized by ring opening polymerization of caprolactone and lactide initiated with the hydroxyl groups of poly(ethylene glycol) (PEG). These copolymers could form micelle-like nanoparticles due to their amphiphilic characteristic. From the observation of transmission electron microscopy (TEM), the nanoparticles exhibited a regular spherical shape with core-shell structure. The critical micelle concentrations (CMC) of these nanoparticles in water were decreased as molecular weight of PEG decreased. The particle sizes obtained by dynamic light scattering of these nanoparticles were in the range of 100-200 nm, and increased as the hydrophobic property of the nanoparticles increased. Nimodipine as a model drug was loaded in these nanoparticles to investigate the drug release behavior. It was found that the chemical composition of the nanoparticles was a key factor in controlling nanoparticle size, nanoparticle yields, drug-entrapment efficiency, and drug release behavior. When the PEG content is about 2% (wt), the release profile of PCELA nanoparticles appeared to follow zero-order kinetics.

Preparation, characterization, and drug release behaviors of drug-loaded ε-caprolactone/L-lactide copolymer nanoparticles

Copolymers of e-caprolactone and L-lactide (PCLLA) with different monomer ratio were synthesized by ring opening polymerization, and drug-loaded nanoparticles of poly-e-caprolactone (PCL), poly-L-lactide (PLLA), and their copolymers were prepared by precipitation method, respectively. The results of differential scanning calorimetry and X-ray diffraction indicated that the copolymerization of PCLLA decreased the crystallinity of the polymers, and the results of transmission electron micrograph and laser light scattering (LLS) revealed that the prepared nanoparticles had a spherical shape, and the size of PCLLA nanoparticles (∼ 85 nm) was smaller than that of the PCL and PLLA nanoparticles. The experiment of in vitro drug release showed that the drug release rate from PCLLA nanoparticles was slower than that from PCL and PLLA nanoparticles, and the release profile of PCL6/LA4 nanoparticles appeared to follow zero order kinetics. These results suggested that the polymer composition made a great influence on the nanoparticle size and drug release behavior.

Anomalous magnetic properties in Co3O4 nanoparticles covered with polymer decomposition residues

Co3O4 nanoparticles with and without covering of residues from the decomposed polymer at the surface have been fabricated, respectively. It has been revealed that anomalous magnetic properties of the nanoparticles covered with the residues deviate greatly from those of the ones without residues. In comparison with the “naked” Co3O4 nanoparticles, for the “covered” sample, the saturation field, coercivity, loop shift and average permanent magnetic moments per Co3O4 particle are enhanced remarkably. It is believed that the anomalous magnetic properties and their significant difference are caused by the presence of residues at the surface, consistent to the reported results in literature.

Fractal aggregation and optical absorption of copper nanoparticles prepared by in situ chemical reduction within a Cu2+-polymer complex

A polymer-matrix nanocomposite containing copper particles has been prepared by in situ chemical reduction within a Cu2+-poly(itaconic acid-co-acrylic acid) complex solid film. The copper particle size in the order of 10 nm is controlled by the initial content of the metal ions in the complex. Their fractal pattern and the value of the fractal dimension indicate that there exists a cluster-cluster aggregation process in the present system. Optical absorption spectra of copper-polymer nanocomposites show distinct plasma absorption bands and quantum size effect in the samples. The calculated blueshift of the resonance peak based on a quantum-sphere model gives remarkable agreement with the experimental data as the size of copper particles embedded in the polymer becomes smaller.

A type of poly(vinylidene fluoride-trifluoroethylene) copolymer exhibiting ferroelectric relaxor behavior at high temperature (∼100°C)

We report a class of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers synthesized via reductive dechlorination from P(VDF-CTFE) [termed as the reduced P(VDF-TrFE) copolymer], which exhibit ferroelectric relaxor behavior at high temperature (∼100°C). It was found that the reduced P(VDF-TrFE) 66∕34mol% copolymer has very high content of head-to-head and tail-to-tail defects, which may act as random defects, leading to the observed ferroelectric relaxor at high temperature. Furthermore, the reduced copolymer also exhibits a high melting point (∼200°C), which also makes it attractive for high-temperature dielectric applications.

Optical emission from nano-poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] arrays

Using an anodic alumina membrane with an ordered nanopore array as a template, we have fabricated a two-dimensional light-emitting nanopolymer array by embedding the luminescence polymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) into the nanopores. It is revealed experimentally that the conformation of the MEH-PPV chains in the nanopores is in the form of a bunch of polymer chains. The number of the polymer chains in a bunch depends on the concentration of the polymer solution and the diameters of nanopores in the template. Investigation on the photoluminescence spectra of the nano-MEH-PPV array annealed under different temperatures shows that the nanopores can effectively hinder the relaxation of MEH-PPV, which leads to its high thermal stability.

Synthesis of cobalt disulfide nanoparticles in polymer matrix

Abstract Amorphous rod-like and needle-like nanoparticles of cobalt disulfide were prepared by the reaction of CoCl2·6H2O with thiourea in the presence of some hydrazine in aqueous solution. The reaction was undertaken in an open reflux system at a relatively low temperature. Polycrystalline cobalt disulfide nanorods were obtained by a similar reaction in an alcohol/water mixed solution. The products were characterized by Fourier transform infrared spectrometer (FTIR), X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The effects of solvent, temperature and time of the reaction on the formation of cobalt disulfide nanocrystalline were discussed. It was found that hydrazine played an important role in shaping rod- or needle-like nanoparticles, and the reflux temperature and time mainly influenced the crystallization of nanoparticles. In addition, the microwave (wavelength λ=3 cm) absorption property of this nanocomposite at room temperature was also investigated.

The Study of Metal–Schiff Base Coordinated Polyurethane

A series of coordination polyurethanes based on novel diols bis[N-[[2-hydroxyphenyl]methylene]hydroxylethyleneamino]–copper(II), cobalt(II) and nickel (II) was synthesized successfully. The geometric structures of the metal–Schiff base, which plays an important role on the properties of these materials, were studied by extended X-ray absorption fine structure and wide angle X-ray diffraction techniques.

Optical and electrical properties of single-ion transport light-emitting electrochemical cells

We present electrical and optical characteristics of single-ion transport light-emitting electrochemical cells (SLECs) based on a blend film of poly(p-phenylene vinylene) derivative with ion-conducting side groups and ionized polyurethane-poly(ethylene glycol). The turn-on voltage of the SLECs is lower than 4V. The response time of the SLECs is less than 10ms, which is approximately two orders of magnitude faster than that of conventional bi-ionic transport light-emitting electrochemical cells. The quick response can be explained on the basis of both good compatibility between the two polymers and weak scattering behavior of the counter ions. In addition, according to the transient current and electroluminescence characteristics, we reveal that the electrical field is close to zero in the inner of the SLEC under the condition of steady state.