Biodegradable Interpolyelectrolyte Complexes Based on Methoxy Poly(ethylene glycol)-b-poly(alpha,L-glutamic acid) and Chitosan

We synthesized methoxy poly(ethylene glycol)-b-poly(alpha,L-glutamic acid) (mPEGGA) diblock copolymer by ring-opening polymerization of N-carboxy anhydride of gamma-benzyl-L-glutamate (NCA) using amino-terminated methoxy polyethylene glycol (mPEG) as macroinitiator. Polyelectrolyte complexation between mPEGGA as neutral-block-polyanion and chitosan (CS) as polycation has been scrutinized in aqueous solution as well as in the solid state.

Phase Behavior and self-assembly of poly[N-vinylformamide-co-(acrylic acid)] copolymers under highly acidic conditions

Copolymers of N-vinylformamide and acrylic acid were synthesized by conventional aqueous free-radical polymerization. The phase behavior of the copolymer solutions was investigated through the addition of hydrochloric acid and the variation of the temperature. With a moderate content of N-vinylformamide, the copolymers showed complex phase behaviors. Under low-acidity conditions, a suspending liquid was formed, whereas under high-acidity conditions, the random copolymers could assemble into round nanoparticles with a broad particle size distribution.

Novel aliphatic poly(ester-carhonate) with pendant allyl ester groups and its folic acid functionalization

A series of novel poly(ester-carbonate)s bearing pendant allyl ester groups P(LA-co-MAC)s were prepared by ring-opening copolymerization Of L-lactide (LA) and 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) with diethyl zinc (ZnEt2) as initiator. NMR analysis investigated the microstructure of the copolymer. DSC results indicated that the copolymers displayed a single glass-transition temperature (T-g), which was indicative of a random copolymer, and the Tg decreased with increasing carbonate content in the copolymer.

Novel temperature- and pH-responsive graft copolymers composed of poly(L-glutamic acid) and poly(N-isopropylacrylamide)

A series of novel temperature- and pH-responsive graft copolymers, poly(L-glutamic acid)-g-poly(N-isopropylacrylamide), were synthesized by coupling amino-semitelechelic poly(N-isopropylacrylamide) with N-hydroxysuccinimide-activated poly(L-glutamic acid). The graft copolymers and their precursors were characterized, by ESI-FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (H-1 NMR). The phase-transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering.

Synthesis and characterisation of novel functional polyolefin containing sulfonic acid groups

The strong polar group, sulfonic acid, has successfully been introduced into ethylene/allylbenzene copolymers without degradation or crosslinking via chlorosulfonation reaction with chlorosulfonic acid as a chlorosulforiating agent in 1, 1,2,2-tetrachloroethane followed by hydrolysis. The degree of sulforiation (DS) can be easily controlled by changing the ratio of chlorosulfonic acid to the pendant phenyls of the copolymer. The microstructure of sulfonated copolymers were unambiguously revealed by H-1 NMR and H-1-H-1 COSY spectral analyses, which indicates that all the sulforiation reactions exclusively took place at the para-position of the aromatic rings.

Lamella reorientation in thin films of a symmetric poly(L-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(L-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (T-g(PLLA)), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (T-c), the glass transition temperature of PS (T-g(PS)), the peak melting point of PLLA crystals (T-m(PLLA)), and the end melting point of PLLA crystals (T-m,end(PLLA)). When annealed at (T-c =) 80 degrees C (T-c < T-g(PS) < T-ODT, order-disorder transition temperature), 123 degrees C (T-g(PS) < T-c < T-m(PLLA) < T-ODT). 165 degrees C (T-g(PS) < T-m(PLLA) < T-c < T-m,end(PLLA) < T-ODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced.

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.

Crystalline morphology of poly(L-lactic acid) thin films

Crystalline morphologies of spin-coated poly(L-lactic acid) (PLLA) thin films under different conditions are investigated mainly with atomic force microscopy (AFM) technique. When PLLA concentration in chloroform is varied from 0.01 to 1% gradually, disordered structure, rod-shape and larger spheres aggregates are observed in thin films subsequently. Under different annealing temperature, such as at 78, 102, 122 degrees C, respectively, we can find most rod-like crystalline aggregates. Interestingly, we observed that nucleation sites locate at the edge of the holes at the original crystalline stage. Then, these holes developed to form chrysanthemum-like and rods subsequently with annealing time meanwhile the size and the shape of crystalline aggregate are changed. In addition. effect of substrate and solvent on morphology is also discussed. On the other hand, the possible mechanism of crystalline morphology evolution is proposed.

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.

Preparation of poly(acrylamide-co-acrylic acid) aqueous latex dispersions using anionic polyelectrolyte as stabilizer

High-solids, low-viscosity, stable poly(acrylamide-co-acrylic acid) aqueous latex dispersions were prepared by the dispersion polymerization of acrylamide (AM) and acrylic acid (AA) in an aqueous solution of ammonium sulfate (AS) medium using anionic polyelectrolytes as stabilizers. The anionic polyelectrolytes employed include poly(2-acrylamido-2-methylpropanesulfonic acid sodium) (PAMPSNa) homopolymer and random copolymers of 2-acrylamido-2-methylpropanesulfonic acid sodium (AMPSNa) with methacrylic acid sodium (MAANa), acrylic acid sodium (AANa) or acrylamide (AM). The influences of stabilizer's structure, composition, molecular weight and concentration, AA/AM molar feed ratio, total monomer, initiator and aqueous solution of AS concentration, and stirring speed on the monomer conversion, the particle size and distribution, the bulk viscosity and stability of the dispersions, and the intrinsic viscosity of the resulting copolymer were systematically investigated. Polydisperse spherical as well as ellipsoidal particles were formed in the system. The broad particle size distributions indicated that coalescence of the particles takes place to a greater extent.

Synthesis of novel functional polyolefin containing carboxylic acid via Friedel-Crafts acylation reaction

The strong polar group, carboxylic acid, has triumphantly been introduced into ethylene and allylbenzene copolymers without obvious degradation or crosslinking via Friedel-Crafts (F-C) acylation reaction with glutaric anhydride (GA), succinic anhydride (SA) and phthalic anhydride (PA) in the presence of anhydrous aluminum chloride in carbon disulfide. Some important reaction parameters were examined in order to optimize the acylation process. In the optimum reaction conditions, almost all of the phenyls can be acylated with any anhydride. The microstructure of acylated copolymer was characterized by Fr-IR, H-1 NMR and H-1-H-1 COSY. All the peaks of acylated copolymers can be accurately attributed, which indicates that all the acylation reactions occur only at the para-positions of the substituent of the aromatic rings. The thermal behavior was studied by differential scanning calorimetry (DSC), showing that the melting temperatures (T(m)s) of acylated copolymers with GA firstly decrease slowly and then increase significantly with the increase of the amount of carboxyl acid groups.

Triblock poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid)/paclitaxel conjugates: Synthesis, micellization, and cytotoxicity

A triblock poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) (PLA-PEG-PLA)/paclitaxel (PTX) conjugate was synthesized by the reaction of carboxyl-terminated copolymer PLA-PEG-PLA with PTX in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine. Carboxyl-terminated copolymer PLA-PEG-PLA was prepared by the reaction of the hydroxyl end groups in copolymer PLA-PEG-PLA with succinic anhydride. Its structure was confirmed by NMR and gel permeation chromatography. The PLA-PEG-PLA/PTX conjugates could self-assemble into micelles in aqueous solutions with a low critical micelle concentration. Dynamic light scattering and environmental scanning electron microscopy analyses of the PLA-PEG-PLA/PTX micelles revealed their spherical structure and size of 220 nm. The antitumor activity of the conjugate against woman Hela cancer cells, evaluated by the 3-(4,5-dimethylthiazol2-yl)-2,5-diphenyl tetrazolium bromide method, showed that the conjugates had an antitumor activity similar to that of pure PTX. The obtained PLA-PEG-PLA/PTX conjugates are expected to be used in clinical practice.

Gene transfection of hyperbranched PEI grafted by hydrophobic amino acid segment PBLG

The complex copolymer of hyperbranched polyethylenimine (PEI) with hydrophobic poly(gamma-benzyl L-glutamate) segment (PBLG) at their chain ends was synthesized. This water-soluble copolymer PEI-PBLG (PP) was characterized for DNA complexation (gel retardation assay, particle size, DNA release and DNase I protection), cell viability and in vitro transfection efficiency. The experiments showed that PP can effectively condense pDNA into particles. Size measurement of the complexes particles indicated that PP/DNA tended to form smaller nanoparticles than those of PEI/DNA, which was caused by the hydrophobic PBLG segments compressing the PP/DNA complex particles in aqueous solution. The representative average size of PP/DNA complex prepared using plasmid DNA (pEGFP-N1, pDNA) was about 96 nm. The condensed pDNA in the PP/pDNA complexes was significantly protected from enzymatic degradation by DNase1. Cytotoxicity studies by MTT colorimetric assays suggested that the PP had much lower toxicity than PEI. The in vitro transfection efficiency of PP/pDNA complexes improved a lot in HeLa cells, Vero cells and 293T cells as compared to that of PEI25K by the expression of Green Fluorescent Protein (GFP) as determined by flow cytometry. Thus, the water-soluble PP copolymer showed considerable potential as carriers for gene delivery.

Fabrication and characterization of self-doped poly (aniline-co-anthranilic acid) nanorods in bundles

Poly (aniline-co-anthranilic acid) (PANANA) nanorods in bundles was prepared successfully in an alcohol/aqueous media without assistance of an), other kinds of acids. Anthranilic acid played all roles of monomer, acid-media provider, and dopant in the reaction system, and ammonium persulfate (APS) served as the oxidant. The morphologies of PANANA nanorods in bundles were investigated by scanning electron microscopy (SEM). Influences of the monomer molar ratio on the resulting morphology were investigated. Moreover the formation mechanism of the nanostructured copolymer was proposed. FT-IR. UV-vis and X-ray diffraction (XRD) measurements were used to confirm the molecular and electrical structure of the self-doped PANANA. The intrinsic properties, such as conductivity, electrochemical redox activity and room-temperature solubility of the resulting copolymer were explored.

Electrically conductive, melt-processed ternary blends of polyaniline/dodecylbenzene sulfonic acid, ethylene/vinyl acetate, and low-density polyethylene

Although polyaniline (PANI) has high conductivity and relatively good environmental and thermal stability and is easily synthesized, the intractability of this intrinsically conducting polymer with a melting procedure prevents extensive applications. This work was designed to process PANI with a melting blend method with current thermoplastic polymers. PANI in an emeraldine base form was plasticized and doped with dodecylbenzene sulfonic acid (DBSA) to prepare a conductive complex (PANI-DBSA). PANI-DBSA, low-density polyethylene (LDPE), and an ethylene/vinyl acetate copolymer (EVA) were blended in a twin-rotor mixer. The blending procedure was monitored, including the changes in the temperature, torque moment, and work. As expected, the conductivity of ternary PANI-DBSA/LDPE/EVA was higher by one order of magnitude than that of binary PANI-DBSA/LDPE, and this was attributed to the PANI-DBSA phase being preferentially located in the EVA phase. An investigation of the morphology of the polymer blends with high-resolution optical microscopy indicated that PANI-DBSA formed a conducting network at a high concentration of PANI-DBSA. The thermal and crystalline properties of the polymer blends were measured with differential scanning calorimetry. The mechanical properties were also measured.