The Surface Modification of Hydroxyapatite Nanoparticles by the Ring Opening Polymerization of gamma-Benzyl-L-glutamate N-carboxyanhydride

The surface modification of hydroxyapatite (HA) nanoparticles by the ring opening polymerization (ROP) of gamma-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) was proposed to prepare the poly(gamma-benzyl-L-glutamate) (PBLG)-grafted HA nanoparticles (PBLG-g-HA) for the first time. HA nanoparticles were firstly treated by 3-aminopropylthriethoxysilane (APS) and then the terminal amino groups of the modified HA particles initiated the ROP of BLG-NCA to obtain PBLG-g-HA. The process was monitored by XPS and FT-IR. The surface grafting amounts of PBLG on HA ranging from 12.1 to 43.1% were characterized by thermal gravimetric analysis (TGA). The powder X-ray diffraction (XRD) analysis confirmed that the ROP only underwent on the surface of HA nanoparticles without changing its bulk properties. The SEM measurement showed that the PBLG-g-HA hybrid could form an interpenetrating net structure in the self-assembly process.

Organic-inorganic hybrid material for the cells immobilization: Long-term viability mechanism and application in BOD sensors

In this paper, organic-inorganic hybrid material, which is composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)), was employed to immobilize Trichosporon cutaneum strain 2.570 cells. Cells entrapped into the hybrid material were found to keep a long-term viability. The mechanism of such a long-term viability was investigated by using confocal laser scanning microscopy (CLSM). Our studies revealed that arthroconidia produced in the extracellular material might play an important role in keeping the long-term viability of the immobilized microorganism. After the arthroconidia were activated, an electrochemical biochemical oxygen demand (BOD) sensor based on cell/hybrid material-modified supporting membrane was constructed for verifying the proposed mechanism.

Reactive compatibilization of LLDPE/PS blends with a new type of Lewis acid as catalyst

The reactive compatibilization of LLDPE/PS (50/50 wt%) was achieved by Friedel-Crafts alkylation reaction with a combined Lewis acids (Me3SiCl and InCl3 center dot 4H(2)O) as catalyst. The graft copolymer at the interface was characterized by Fourier transform infrared spectroscopy and the morphology of the blends was analysized by scanning electron microscopy. It was found that the combined Lewis acids had catalytic effect on Friedel-Crafts alkylation reaction between LLDPE and PS, and the catalytic effect was maximal when the molar ratio of InCl3 center dot 4H(2)O to Me3SiCl was 1:5. The graft copolymer LLDPE-g-PS was formed via the F-C reaction and worked as a tailor-made compatibilizer to reduce the interfacial tension. The mechanical properties of reactive blend with combined Lewis acids as catalyst was notably improved compared to that of physical LLDPE/PS blend and serious degradation had been decreased compared to the reactive blend system with AlCl3 as catalyst; we interpreted the above results in term of acidity of combined Lewis acids.

Preparation and Physical Properties of LLDPE Grafted with Novel Nonionic Surfactants

Copolymers of linear low-density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATW-EEN80), containing hydrophilic and hydrophobic groups and 1-olefin double bond were prepared by using a plasticorder at 190 degrees C. To evaluate the grafting degree, two different approaches based on H-1-NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small-amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (T-C) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films.

Synthesis and self-assembly of poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate)

Poly(ethylene oxide)-b-poly(2-hydroxyethyl methacrylate) (PEO-b-PHEMA) was synthesized by successive atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate(HEMA) monomer using PEO-Br macroinitiator as initiator, CuBr/CuBr2 and 2,2.-bipyridyl (bpy) as catalyst and ligand. IR, H-1 NMR, and GPC analysis indicate that PEO-b-PHEMA block copolymer with low polydispersity index (M-w/M-n approximate to 1.1) has been formed. Self-assembly of this double hydrophilic block copolymer in the selective solvent and water was also studied. Owing to the high hydrophilic nature of the PEO and PHEMA blocks, this double hydrophilic block copolymer cannot disperse well in water. So block copolymer was modified by part esterification of PEO-b-PHEMA with acetic anhydride, which increased the hydrophobic group of the PHEMA block. The TEM results show that this block copolymer spontaneously form well-defined micelles in water.

Synthesis and Characterization of Hyperbranched Poly(ether amide)s with Thermoresponsive Property and Unexpected Strong Blue Photoluminescence

A facile and efficient strategy for the syntheses of novel hyperbranched poly(ether amide)s (HPEA) from multihydroxyl primary amines and (meth)acryloyl chloride has been developed. The chemical structures of the HPEAs were confirmed by IR and NMR spectra. Analyses of SEC (size exclusion chromatography) and viscosity characterizations revealed the highly branched structures of the polymers obtained. The resultant hyperbranched polymers contain abundant hydroxyl groups. The thermoresponsive property was obtained from in situ surface modification of abundant OH end groups with N-isopropylacrylamide (NIPAAm). The study oil temperature-dependent characteristics has revealed that NIPAAm-g-HPEA exhibits an adjustable lower critical solution temperature (LCST) of about 34-42 degrees C depending on the grafting degree. More interestingly, the work provided an interesting phenomenon where the HPEA backbones exhibited strong blue photoluminescence.

Preparation and Bioactivity of the Composite of PLGA and Hydroxyapatite Nanocrystals Surface-grafted with L-lactic Acid Oligomer

The hydroxyapatite (HA) nanocrystals of 100-200 nm in length and 20-30 nm in width were hydrothermally synthesized by the reaction of phosphoric acid and calcium hydroxide. Lactic acid oligomer surface grafted HA(op-HA) nanoparticles were obtained by oligomeric lactic acid with a certain molecular weight grafting onto the HA surface to form a Ca carboxylate bond in the absence of any catalyst. The op-HA was further blended with poly(lactide-co-glycolide) (PLGA) to prepare the nanocomposite of op-HA/PLGA. FTIR, TGA, ESEM and EDX were used to analyze grafting reaction, the graft ratio of op-HA, surface topography and calcium deposition of the composites, respectively. The rabbit osteoblasts were seeded and cultured on the surface of composites in vitro. The cell morphology, adhesion, proliferation and gene expression were evaluated with FITC staining, NIH image J software and the analysis of real-time PCR, respectively. The results show that the graft ratio of op-HA is 8.3% (mass fraction). The op-HA/PLGA nanocomposite possessed more suitable surface properties, including roughness and plenty of calcium and phosphor. It exhibited better cell adhesion, spreading and proliferation of rabbit osteoblasts, compared to pure PLGA.

SYNTHESIS AND CHARACTERIZATION OF A CROSSLINKING POLYETHYLENIMINE AS SMART GENE CARRIER AND EFFECTS OF PEGYLATION DEGREE

A smart biodegradable cationic polymer (CBA-PEI) based on the disulfide bond-containing cross-linker cystamine bisacrylamide (CBA) and low molecular weight branched polyethylenimine (1800-Da, PEI1800) was successfully synthesized by Michael addition reaction in our recent study. Furthermore, a series of copolymers (CBA-PEI-PEG) with different PEGylation degree were obtained by the mPEG-SPA (5000-Da) reacting with CBA-PEI at various weight ratios directly. The molecular structures of the resulting polymers CBA-PEI and CBA-PEI-PEG were evaluated by nuclear magnetic resonance spectroscopy (H-1-NMR) and capillary viscosity measurements, all of which had successfully verified formation of the copolymers. The polymer/DNA complexes based on CBA-PEI and CBA-PEI-PEG were measured by dynamic light scattering and gel retardation assay. The results showed that the particle size and zeta potential of complexes were reduced with increasing amount of PEG grafting, even no particle formation. The particle size of CBA-PEI/DNA complexes was in range of 103.1 to 129.1 nm, and the zeta potential was in range of 14.2 to 24.3 mV above the 2:1 weight ratio. In the same measure condition, the particle size of CBA-PEI-PEG complexes was reduced to a range of 32.2 to 55 nm, and the zeta potential was in range of 9.3 to 13.8 mV at the 2:1 weight ratio.

Synthesis, self-assembly in water, and cytotoxicity of MPEG-block-PLLA/DX conjugates

Docetaxel (DX) is one of the most effective antineoplastic drugs. Its current clinical administration is limited because of its hydrophobicity and Serious side effects. A polymer/DX conjugate is designed and successfully prepared to solve these problems. It is monomethoxy-poly(ethylene glycol)-block-poly(L-lactide)/DX (MPEG-PLLA/DX) It was synthesized by reacting DX with carboxyl-terminated copolymer MPEG-PLLA, which was prepared by reacting succinic anhydride with hydroxyl-terminated copolymer monomethoxy-poly(ethylene glycol)-block-poly (L-lactide) (MPEG-PLLA). Its structure and molecular weight was confirmed by H-1 NMR and GPC. The MPEG-PLLA/DX micelles in aqueous solution were prepared Using a SO]vent displacement method and characterized by dynamic light scattering for size and size distribution, and by transmission electron microscopy for surface morphology. Its antitumor activity against HeLa cancer cells evaluated by MTT assay showed that it had a similar antitumor activity to Pure D at the same drug content.

Multi-armed poly(L-glutamic acid)-graft-oligoethylenimine copolymers as efficient nonviral gene delivery vectors

Background The application of polyethylenimine (PEI) in gene delivery has been severely limited by significant cytotoxicity that results from a nondegradable methylene backbone and high cationic charge density. It is therefore necessary to develop novel biodegradable PEI derivates for low-toxic, highly efficient gene delivery.Methods A series of novel cationic copolymers with various charge density were designed and synthesized by grafting different kinds of oligoethylenimine (OEI) onto a determinate multi-armed poly(L-glutamic acid) backbone. The molecular structures of multi-armed poly(L-glutamic acid)-graft-OEI (MP-g-OEI) copolymers were characterized using nuclear magnetic resonance, viscosimetry and gel permeation chromatography. Moreover, the MP-g-OEI/DNA complexes were measured by a gel retardation assay, dynamic light scattering and atomic force microscopy to determine DNA binding ability, particle size, zeta potential, complex formation and shape, respectively. MP-g-OEI copolymers were also evaluated in Chinese hamster ovary and human embryonic kidney-293 cells for their cytotoxicity and transfection efficiency.

Study of self-assembly of symmetric coil-rod-coil ABA-type triblock copolymers by self-consistent field lattice method

The self-assembly of symmetric coil-rod-coil ABA-type triblock copolymer melts is studied by applying self-consistent field lattice techniques in a three-dimensional space. The self-assembled ordered structures differ significantly with the variation of the volume fraction of the rod component, which include lamellar, wave lamellar, gyroid, perforated lamellar, cylindrical, and spherical-like phases. To understand the physical essence of these phases and the regimes of occurrence, we construct the phase diagram, which matches qualitatively with the existing experimental results. Compared with the coil-rod AB diblock copolymer, our results revealed that the interfacial grafting density of the separating rod and coil segments shows important influence on the self-assembly behaviors of symmetric coil-rod-coil ABA triblock copolymer melts. We found that the order-disorder transition point changes from f(rod)=0.5 for AB diblock copolymers to f(rod)=0.6 for ABA triblock copolymers. Our results also show that the spherical-like and cylindrical phases occupy most of the region in the phase diagram, and the lamellar phase is found stable only at the high volume fraction of the rod.

Order-disorder transition in eicosylated polyethyleneimine comblike polymers

Order-disorder transition (ODT) behavior in eicosylated polyethyleneimine (PEI20C) comblike polymer obtained by grafting n-eicosyl group on polyethyleneimine backbone was systematically investigated by the combination of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR) spectroscopy as well as solid-state high resolution nuclear magnetic resonance (NMR) spectroscopy. DSC investigations showed two obvious transitions, assigned to the transitions (1) from orthorhombic to hexagonal and (2) from hexagonal to amorphous phase, respectively. These transitions are induced by the variations of alkyl side chain conformation and packing structure with temperature changing, which consequently lead to the destruction of original phase equilibrium. The ODT behavior can also be confirmed by spectroscopic methods like WAXD, FTIR and NMR. The ordered structure and the transition behavior of the alkyl side chains confined by the PEI backbone are obviously different from those of pristine normal alkanes. The transition mechanism of ODT and the origin of the phase transition behavior in PEI20C comblike polymer were discussed in detail in this paper.

Synthesis and properties of novel soluble polyimides having a spirobisindane-linked dianhydride unit

A new synthetic procedure was elaborated allowing the preparation of semiaromatic dianhydride. N-Methyl protected 4-chlorophthalic anhydride was nitrated with HNO3 to produce N-methyl-4-chloro-5-nitrophthalimide (1). The aromatic nucleophilic substitution reaction between 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1-spirobisindane and 1 afforded spirobisindane-linked bis(N-methylphthalimide) (2), which was hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). The latter was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The properties of polyimides such as inherent viscosity, solubility, UV transparency and thermal stability were investigated to illustrate the contribution of the introduction of spirobisindane groups into the polyimide backbone. The resulting polyimides were readily soluble in polar solvents such as chloroform, THF and N-methyl-2-pyrrolidone. The glass-transition temperatures of these polyimides were in the range of 254-292 degrees C. The tensile strength, elongation at break, and Young's modulus of the polyimide film were 68.8-106.6 MPa, 5.9-9.8%, 1.7-2.0 GPa, respectively. The polymer films were colorless and transparent with the absorption cutoff wavelength at 286-308 nm.

Synthesis and characterization of soluble poly(amideimide)s bearing triethylamine sulfonate groups as gas dehumidification membrane material

A series of soluble poly(amide-imide)s (PAIs) bearing triethylammonium sulfonate groups were synthesized directly using trimellitic anhydride chloride (TMAC) polycondensation with sulfonated diamine such as 2,2'-benzidinedisulfonic acid (BDSA), 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS), and nonsulfonated diamine 4,4-diaminodiphenyl methane in the presence of triethylamine. The resulting copolymers exhibited high molecular weights (high inherent viscosity), and a combination of desirable properties such as good solubility in dipolar aprotic solvents, film-forming capability, and good mechanical properties. Wide-angle X-ray diffraction revealed that the polymers were amorphous. These copolymers showed high permeability coefficients of water vapor because of the presence of the hydrophilic triethylammonium sulfonate groups. The water vapor permeability coefficients (P-w) and permselectivity coefficients of water vapor to nitrogen and methane [alpha(H2O/N-2) and (alpha(H2O/CH4)] Of the films increased with increasing the amount of the triethylammonium sulfonated groups.