Well-defined higher-molecular-weight polyacrylonitrile via RAFT technique in the presence of disulfide compounds as a source of chain transfer agent

Well-defined polyacrylonitrile with a higher number-average molecular weight (R.) up to 200,000 and a lower polydispersity index (PDI, 1.7-2.0) was firstly obtained via reversible addition-fragmentation chain transfer (RAFT) process. This was achieved by selecting a stable, easy way to prepare disulfide compound intermediates including bis(thiobenzoyl) disulfide (BTBDS) and bis(thiophenylacetoyl) disulfide (BTPADS) to react with azobis(isobutyronitrile) to directly synthesize RAFT agents in situ.

Toxicological effects of cinnabar in rats by NMR-based metabolic profiling of urine and serum

Cinnabar, an important traditional Chinese mineral medicine, has been widely used as a Chinese patent medicine ingredient for sedative therapy. However, the pharmaceutical and toxicological effects of cinnabar, especially in the whole organism, were subjected to few investigations. In this study, an NMR-based metabolomics approach has been applied to investigate the toxicological effects of cinnabar after intragastrical administration (dosed at 0.5, 2 and 5 g/kg body weight) on male Wistar rats.

Regio-regular structure high molecular weight poly(propylene carbonate) by rare earth ternary catalyst and Lewis base cocatalyst

Lewis base modification strategy on rare earth ternary catalyst was disclosed to enhance nucleophilic ability of active center during copolymerization of carbon dioxide and propylene oxide (PO), poly(propylene carbonate) (PPC) with H-T linkages over 83%, and number-average molecular weight (M-n) up to 100 kg/mol was synthesized at room temperature using Y(CCl3OO)(3)-ZnEt2-glycerine catalyst and 1,10-phenanthroline (PHEN) cocatalyst. Coordination of PHEN with active Zinc center enhanced the nucleophilic ability of the metal carbonate, which became more regio-specific in attacking carbon in PO, leading to PPC with improved H-T linkages.

Fixation of carbon dioxide into aliphatic polycarbonate, cobalt porphyrin catalyzed regio-specific poly(propylene carbonate) with high molecular weight

Cobalt porphyrin complex ((TPPCoX)-X-III) (TPP = 5, 10, 15, 20-Tetraphenylporphyrin; X = halide) in combination with ionic organic ammonium salt was used for the regio-specific copolymerization of propylene oxide and carbon dioxide. A turnover frequency of 188 h(-1) was achieved after 5 h, and the byproduct propylene carbonate was successfully controlled to below 1%, where the obtained poly(propylene carbonate) (PPC) showed number average molecular weight (M-n) of 48 kg/mol, head-to-tail content of 93%, and carbonate linkage of over 99%.

Cytotoxicity of liver targeted drug-loaded alginate nanoparticles

In this study, novel liver targeted doxorubicin (DOX) loaded alginate (ALG) nanoparticles were prepared by CaCl2 crosslinking method. Glycyrrhetinic acid (GA, a liver targeted molecule) modified alginate (GA-ALG) was synthesized in a heterogeneous system, and the structure of GA-ALG and the substitution degree of GA were analyzed by H-1 NMR, FT-IR and elemental analysis. The drug release profile under the simulated physiological condition and cytotoxicity experiments of drug-loaded GA-ALG nanoparticles were carried out in vitro. Transmission electron micrographs (TEM) and dynamic light scattering (DLS) analysis showed that drug-loaded GA-ALG nanoparticles have spherical shape structure with the mean hydrodynamic diameter around 214 +/- 11 nm.

Metabolic profiling studies on the toxicological effects of realgar in rats by H-1 NMR spectroscopy

The toxicological effects of realgar after intragastrical administration (1 g/kg body weight) were investigated over a 21 day period in male Wistar rats using metabonomic analysis of H-1 NMR spectra of urine, serum and liver tissue aqueous extracts. Liver and kidney histopathology examination and serum clinical chemistry analyses were also performed. H-1 NMR spectra and pattern recognition analyses from realgar treated animals showed increased excretion of urinary Kreb's cycle intermediates, increased levels of ketone bodies in urine and serum, and decreased levels of hepatic glucose and glycogen, as well as hypoglycemia and hyperlipoidemia, suggesting the Perturbation of energy metabolism. Elevated levels of choline containing metabolites and betaine in serum and liver tissue aqueous extracts and increased serum creatine indicated altered transmethylation. Decreased urinary levels of trimethylamine-N-oxide, phenylacetylglycine and hippurate suggested the effects on the gut microflora environment by realgar.

Feasibility of biodegradable PLGA common bile duct stents: An in vitro and in vivo study

The current study investigates the feasibility of using a biodegradable polymeric stent in common bile duct (CBD) repair and reconstruction. Here, poly(l-lactide-co-glycolide) (PLGA, molar ratio LA/GA = 80/20) was processed into a circular tube- and dumbbell-shaped specimens to determine the in vitro degradation behavior in bile. The morphology, weight loss, and molecular weight changes were then investigated in conjunction with evaluations of the mechanical properties of the specimen. Circular tube-shaped PLGA stents with X-ray opacity were subsequently used in common bile duct exploration (CBDE) and primary suturing in canine models. Next, X-ray images of CBD stents in vivo were compared and levels of serum liver enzymes and a histological analysis were conducted after stent transplantation. The results showed that the PLGA stents exhibited the required biomedical properties and spontaneously disappeared from CBDs in 4-5 weeks. The degradation period and function match the requirements in repair and reconstruction of CBDs to support the duct, guide bile drainage, and reduce T-tube-related complications.

Metabolic profiling of serum from gadolinium chloride-treated rats by H-1 NMR spectroscopy

Metabolic profiling of serum from gadolinium chloride (GdCl3, 10 and 50 mg/kg body weight, intraperitoneal [i.p.])-treated rats was investigated by the NMR spectroscopic-based metabonomic strategy. Serum samples were collected at 48, 96, and 168 h postdose (p.d.) after exposure to GdCl3. H-1 NMR spectra of serum were analyzed by pattern recognition using principal components analysis. The studies showed that there was a dose-related biochemical effect of GdCl3 treatment on the levels of a range of low-molecular weight compounds in serum. The liver damage induced by GdCl3 was characterized by the elevation of lactate, pyruvate, and creatine as well as the decrease of branched-chain amino acids (valine and isoleucine), alanine, glucose, and trimethylamine-N-oxide concentration in serum samples. The biochemical effects of GdCl3 in rats could be consulted when evaluating the biochemical profile of gadolinium-containing compounds that are being developed for nuclear magnetic resonance imaging.

2-cyanoprop-2-yl dithiobenzoate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2-cyanoprop-2-yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANS were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. H-1 NMR analysis confirmed the high chain-end functionality of the resultant polymers.

The critical lowest molecular weight for PEG to crystallize in cross-linked networks

Poly(ethylene glycol) (PEG) networks were synthesized by gamma-irradiation. The crystalline behavior of PEG was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). It was shown that the crystallinity of PEG is dramatically lower in the cross-linked, networks than in pure PEG. When the molecular weight of PEG in the networks decreased to 1000, it could not crystallize at all. Moreover, we also found that the melting temperature of PEG is greatly affected by the presence of a cross-linked network.

Effects of molecular weight, solvent and substrate on the dewetting morphology of polystyrene films

Surface morphology of polystyrene (PS) films on different substrates by spin-coating before and after annealing was observed using atomic force microscopy (AFM). The effects of polymer molecular weight, substrates, solvents, and annealing conditions on the morphology of the films were investigated. Before annealing, the grain height decreases, and simultaneously the grain diameter increases with molecular weight (M-w) within the measured molecular weight. After annealing. the situation is opposite, i.e., the grain height increases while the grain diameter decreases with M-w. Furthermore, after annealing the smaller surface roughness (Ra) was obtained. It was also found that film surface roughness (Ra) depends on the vapor pressure and dipole moment of different used solvents as well as the substrates. The experimental results show that when the used solvents have similar dipole moment but different vapor pressure, the Ra of PS film decreased with the decreasing vapor pressure of solvents whether on silicon or on mica. And when the used solvents have close vapor pressure but different dipole moment, the Ra decreased with the increasing of solvent dipole moments on both substrates.

Microwave-assisted synthesis of high-molecular-weight poly(ether imide)s by phase-transfer catalysis

A facile and rapid polycondensation reaction of disodium bisphenol A with bis(chlorophthalimide)s was preformed with a domestic microwave oven in o-dichlorobenzene by phase-transfer catalysis. The polymerization reactions, in comparison with conventional heating polycondensation, proceeded rapidly and were completed within 25 min. The polymerizations gave the corresponding poly(ether imide)s with inherent viscosities of 0.55-0.92 dL g(-1). The effects of various factors on the polymerization, such as the amount of the catalyst, the reaction time, and the microwave power were studied. The properties of the polymers were briefly characterized.

Molecular weight effects on the phase morphology of PS/P4VP blend films on homogeneous SAM and heterogeneous SAM/Au substrates

The effects of the molecular weight of polystyrene (PS) component on the phase separation of PS/poly(4-vinylpyridine) (PS/P4VP) blend films on homogeneous alkanethiol self-assembled monolayer (SAM) and heterogeneous SAM/Au substrates have been investigated by means of atomic force microscopy (AFM). For the PS (22.4k)/P4VP (60k) system, owing to the molecular weight of PS component is relatively small, the well-aligned PS and P4VP stripes with good thermal stability are directed by the patterned SAM/Au surfaces. With the increase of the molecular weight of PS component (for the PS (582k)/P4VP (60k) system), the diffusion of P4VP is hindered by the high viscosity of PS during the fast spin-coating process. The phase separation behavior of PS/P4VP on the SAM/Au patterned substrates is similar to that on the homoueneous SAM and cannot be easily directed by the patterned SAM surfaces even though the characteristic length of the lateral domain morphology is commensurate with the stripe width.

A modified Wittig polycondensation - to high-trans- and high-molecular weight PPVs

A modified Wittig polycondensation was developed by replacing the bulky -PPh3 with -PBu3 ylide. Our studies suggested that the modified polymerization dramatically enhances trans-selectivity due to the decreased 1.3-steric interaction between butyl chain and triphenylamine group, together with the 1,2-steric interaction between the phenyl ring of the ylide and the triphenylamine group of the aldehyde. Moreover, the method also enhances high-molecular weight products by increasing the activity and solubility of the ylide.

Preparation of linear alpha-olefins to high-molecular weight polyethylenes using cationic alpha-diimine nickel(II) complexes containing chloro-substituted ligands

A series of alpha-diimine nickel(II) complexes containing chloro-substituted ligands, [(Ar)N=C(C10H6)C=N(Ar)]NiBr2 (4a, Ar = 2,3-C6H3Cl2; 4b, Ar = 2,4-C6H3Cl2; 4c, Ar = 2,5-C6H3Cl2; 4d, Ar = 2,6-C6H3Cl2; 4e, Ar = 2,4,6-C6H2Cl3) and [(Ar)N=C(C10H6)C=N(Ar)](2)NiBr2 (5a, Ar = 2,3-C6H3Cl2; 5b, Ar = 2,4-C6H3Cl2; 5c, Ar = 2,5-C6H3Cl2), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl-substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear alpha-olefins to high-molecular weight polyethylenes.