Chitosan/poly (vinyl alcohol) films containing ZnO nanoparticles and plasticizers

In this study ZnO nanoparticles were prepared by the Pechini method from a polyester by reacting citric acid with ethylene glycol in which the metal ions are dissolved, and incorporated into blend films of chitosan (CS) and poly (vinyl alcohol) (PVA) with different concentrations of polyoxyethylene sorbitan monooleate, Tween 80 (T80). These films were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling degree, degradation of films in Hank's solution and the mechanical properties. Besides these characterizations, the antibacterial activity of the films was tested, and the films containing ZnO nanoparticles showed antibacterial activity toward the bacterial species Staphylococcus aureus. The observed antibacterial activity in the composite films prepared in this work suggests that they may be used as hydrophilic wound and burn dressings.     

Synthesis and characterization of fluorescent poly(oxadiazole)s containing 3,4-dialkoxythiophenes

We report the synthesis, optical and electrochemical details, and properties of three conjugated copolymers (P1–P3) consisting of alternate hole-transporting thiophene derivative and electron-transporting 1,3,4-oxadiazole units. The polymers are prepared using the precursor polyhydrazide route. The polymers have well defined structure and exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 °C. All the polymers are soluble in organic solvents such as DMF, DMSO, NMP and in strong organic acids like trifluoroacetic acid. The optical and charge-transporting properties of the polymers are investigated by UV–visible spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The UV–visible absorption spectra of polymers in solution showed a maximum at around 400 nm. The polymers depicted green fluorescence both in solution and as thin films. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from −3.28 to −3.36 eV and high-lying HOMO energy levels ranging from −5.5 to −5.56 eV, which indicated that they may be promising candidates for electron-transporting or hole-blocking materials in light-emitting diodes.     

Highly ordered poly(thiophene)s prepared in mesoporous silica nanoparticles

Nanostructured PEDOT was synthesized using mesoporous silica as a nano-template. The polymerization of thiophene monomers was performed with an oxidant and mesoporous silica nanoparticles. The silica particles took essential role in absorbing monomers and oxidant molecules, and growth of polymers inside their pores. As prepared polymer/silica composite was treated with HF solution to remove silica template to result in 1D wire structure and mesh type porous 3D structures from SBA-15 and KIT-6 template, respectively. The average size of the poly(thiophene) wires was 10 15 nm, which was matched well to the pores size of the silica templates, as determined from an electron microscopy. At optimized condition, the room temperature electrical conductivities of the PEDOT grown from SBA-15 and KIT-6 template were similar as 1.1 and 1.0 S/cm, respectively. However, the evolution of the PEDOT conductivity versus temperature was different depending on the templates. These results gave a unique chance to tailor made 3 dimensional structure as well as properties of conductive polymer.     

Poly(etherimide)s and poly(esterimide)s containing azobenzene units: Characterization and study of photoinduced optical anisotropy

In this paper novel processable, photoresponsible aromatic polymers with imide rings and covalently boned azobenzene units are presented. Prepolymerization strategy based on polycondensation of two diamines with azobenzene group, that is, 2,4-diamino-4′-cyanoazobenzne and 2,4-diamino-4′-nitroazobenzene and two dianhydrides, was utilized for preparation of the new photochromic polyimides. The obtained polymers differ in the chemical structure of polymer backbone and the kind of substituents on azobenzene moieties. Polymers were characterized and evaluated by FT-IR, ¹H NMR, X-ray, UV-vis, DSC, and TGA methods. The synthesized azopolymers exhibited glass transition temperatures in the range of 140-170 °C, thermal stability with initial decomposition temperatures (T_d) in the range of 266-290 °C, and excellent solubilities in common organic solvents, providing optical-quality films. The light-induced optical anisotropy was studied in obtained polymers by photoinduced birefringence measurements. The birefringence was generated by the femtosecond pulses at 400 nm via a linear absorption of the trans-azobenzene. A large light-induced birefringence (Δn = 0.02) was achieved in poly(esterimide)s contrary to poly(etherimide)s. The birefringence exhibited a very stable behavior after switching off the writing light indicating a permanent storage capacity.     

One-pot synthesis and characterization of poly(alkoxysilane)s promoted by silver colloidal nanoparticles

Si-Si/Si-O dehydrocoupling of hydrosilanes with alcohols (1:1.5 mole ratio), catalyzed by AgNO3 which converted to Ag(0) colloidal nanoparticles, gave poly(alkoxysilane)s in one-pot in moderate to high yield. The hydrosilanes include p-X-C6H4SiH3 (X = H, CH3, OCH3, F), PhCH2SiH3, and (PhSiH2)2. The alcohols include MeOH, EtOH, (i)PrOH, PhOH, and CF3(CF2)2CH2OH. The weight average molecular weight and polydispersity of the poly(alkoxysilane)s were in the range of 1,600 approximately 8,000 Dalton and 1.4 approximately 3.5. The dehydrocoupling reactions of phenylsilane with ethanol (1:3 mole ratio) in the presence of the silver nanocolloid catalyst produced only triethoxyphenylsilane as product.     

Holographic grating studies in pendant xanthene dyes containing poly(alkyloxymethacrylate)s

A series of xanthene dyes based poly(alkyloxymethacrylate)s were synthesized with even number of side-chain methylene spacers by free radical addition polymerization method for holographic grating studies. Chemical structure of monomers and polymers were confirmed by FTIR and ¹H-NMR spectroscopy. Thermal property was investigated by TGA and DSC. Lengthy spacers favor improved optical quality film formation than shorter spacer length containing polymers; however, thermal stability and Tm decreased. Absorption and emission spectra have been studied in different polar solvents. UV–vis absorption maxima were broad and red-shifted with increasing spacer length. Life-time decay analysis exhibited double exponential decay. Polymer films were tested for holographic grating formation and their diffraction efficiency compared. Photo bleaching mechanism of polymer films was disclosed by measuring electrochemical potential value.     

新型含杂萘联苯聚醚砜类嵌段共聚物的合成与性能研究

采用连续缩聚法合成氯端基聚醚砜齐聚物,然后与杂萘联苯构成的类双酚合成的羟端基齐聚物进行缩聚反应,合成了新型PPES-PES嵌段共聚物.用IR、DSC、TGA、X-WAXD等方法对聚合物进行了表征,并研究了聚合物的溶解性能.结果表明该嵌段共聚物具有较高的玻璃化转变温度,较好的热稳定性和良好的溶解性能,为非结晶型聚合物,并可浇铸得到透明、韧性高的薄膜.实验还发现聚醚砜组分含量变化对共聚物的热性能影响很大,对杂萘联苯聚醚砜改性效果明显.     

Synthesis and properties of diblock copolymers containing poly(3-hexylthiophene) and poly(fluorooctyl methacrylate)

This study reports the synthesis of regioregular poly(3-hexylthiophene)-b-poly(1H,1H-dihydro perfluorooctyl methacrylate) (P3HT-b-PFOMA) block copolymers by atom transfer radical polymerization of FOMA using P3HT macroinitiators. The P3HT macroinitiator was previously prepared by chemical modification of hydroxy terminated P3HT The block copolymers were characterized by 1H-NMR, 13C-NMR, GPC, DSC, TGA and TEM. The block copolymers are able to self-assemble into phase separated micellar thin film morphology from chloroform.     

Solution properties of poly(decylmethacrylate)s

Samples of poly(decylmethacrylate)s (PDMA) of a narrow molecular weight distribution were characterized by means of light-scattering, osmotic pressure, intrinsic viscosity and gelpermeation chromatography. The Kuhn-Mark-Houwink equation for molecularly uniform PDMA in THF at 25°C was calculated to be log [η] (ml/g) = ?2.67 + 0.80 logM (g/mol). The following Θ-solvents were found: 2-propanol, 2-propylacetate, 1-butanol and 1-pentanol. The molecular weight dependence of the demixing behaviour yields a Θ-temperature of 9.6°C for 1-pentanol and of 37.4°C for 1-butanol. Flow curves were measured in various solvents of different thermodynamic quality. A first valuation of the observed non-Newtonian behaviour is given.     

Electrospinning of novel biodegradable poly(ester urethane)s and poly(ester urethane urea)s for soft tissue-engineering applications

The development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Segmented poly(ester urethane)s and poly(ester urethane urea)s have been infrequently used for the fabrication of electrospun nanofibrous tissues, which is surprising because these polymers represent a very large variety of materials with tailored properties. This study reports the preparation of new electrospun elastomeric polyurethane scaffolds. Two novel segmented polyurethanes (SPU), synthesized from poly(ε-caprolactone) diol, 1,6-hexamethylene diisocyanate, and diester-diphenol or diurea-diol chain extenders, were used (Caracciolo et al. in J Mater Sci Mater Med 20:145–155, 2009). The spinnability and the morphology of the electrospun SPU scaffolds were investigated and discussed. The electrospinning parameters such as solution properties (polymer concentration and solvent) and processing parameters (applied electric field, needle to collector distance and solution flow rate) were optimized to achieve smooth, uniform bead-free fibers with diameter (~700 nm) mimicking the protein fibers of native extracellular matrix (ECM). The obtained elastomeric polyurethane scaffolds could be appropriate for soft tissue-engineering applications.     

具柔性链段磺化聚芳醚酮质子交换膜的制备与性能研究

以二氟二苯甲酮(DFBP),磺化二氟二苯甲酮(SDFBP),4,4’-二羟基二苯醚(DOPE)和双酚芴(BHF)为单体,通过亲核缩聚反应合成了分子链磺酸含量不同具柔性链段的磺化聚芳醚酮.研究结果表明:所合成的聚合物具有较高的分子量,可通过流延成膜的方法制备出柔韧、透明的膜.所制备的膜具有较高的吸水率与尺寸稳定性及抗氧化性,在同等测试条件下,具有与Nafion 117膜相当的质子传导率,且甲醇透过率比Nafion 117膜低1、2个数量级.     

Synthesis and characterization of a novel multiblock copolyester containing poly(ethylene succinate) and poly(butylene succinate)

Multiblock copolyester (PBS-b-PES) containing poly(butylene succinate) (PBS) and poly(ethylene succinate) (PES) was successfully synthesized by chain-extension of dihydroxyl terminated PBS (HO-PBS-OH) and PES (HO-PES-OH) using 1,6-hexmethylene diisocyanate (HDI) as a chain extender. The chemical structures, molecular weights, crystallization behaviors, thermal and mechanical properties of the copolyesters were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), wide-angle X-ray diffraction (WAXD), tensile testing and hydrolytic degradation. High-molecular-weight copolyesters with M_w more than 2.0 × 10⁵ g mol⁻¹ were easily obtained through chain-extension. The copolyesters showed a single glass transition temperature (T_g) which increased with PES content. The melting point temperature (T_m) and relative degree of crystallinity (X_c) of the copolyesters decreased first and then increased with PES content. The copolyesters manifested excellent mechanical properties, for example, PBS₅-b-PES₅ had fracture stress of 61.8 MPa and fracture strain of 1173%. The chain-extension reaction provided a very effective way to produce high molecular weight multiblock copolyesters.     

Synthesis and characterization of poly(silphenylenesiloxane)s containing functional side groups,a study to high-temperature elastomer

Poly(silphenylenesiloxane)s containing hydride or vinyl functional side groups were successfully synthesized by deaminative polycondensation of bis(aminosilane)s having the functional groups with monomeric or polymeric bis(silanol). The bis(silanol) prepolymer was prepared by palladium-catalyzed dehydrocoupling polymerization of 1,4-bis(dimethylsilyl)benzene with water. ¹H, ¹³C, and ²⁹Si NMR revealed that the polymers have exactly alternating structure of the starting component units. The poly(silphenylenesiloxane)s containing functional side groups have low T_gs ranging from −23 to −40 °C, and exhibit good thermal stability in both nitrogen and air atmosphere. For example, the most thermally stable polymer 3b-alt, having vinyl side groups on half silicon atoms, has T_g at –33°C which is 11°C lower than that of the all-methyl substituted PTMPS, and shows the highest degradation temperature at 498°C in nitrogen and 521°C in air. The TGA residues at 800°C are 67% in nitrogen and 54% in air. Isothermal studies revealed 3b-alt only lost 2.5% weight after 5h at 400°C in nitrogen.     

Preparation and characterization of mucoadhesive nanoparticles of poly (methyl vinyl ether-co-maleic anhydride) containing glycyrrhizic acid intended for vaginal administration

Traditional vaginal preparations reside in the vaginal cavity for relatively a short period of time, requiring multiple doses in order to attain the desired therapeutic effect. Therefore, mucoadhesive systems appear to be appropriate to prolong the residence time in the vaginal cavity. In the current study, mucoadhesive nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) intended for vaginal delivery of glycyrrhizic acid (GA) (a drug with well-known antiviral properties) were prepared and characterized. Nanoparticles were generated by a solvent displacement method. Incorporation of GA was performed during nanoprecipitation, followed by adsorption of drug once nanoparticles were formed. The prepared nanoparticles were characterized in terms of size, Z-potential, morphology, drug loading, interaction of GA with PVM/MA (by differential scanning calorimetry) and the in vitro interaction of nanoparticles with pig mucin (at two pH values, 3.6 and 5; with and without GA adsorbed). The preparation method led to nanoparticles of a mean diameter of 198.5?±?24.3?nm, zeta potential of ?44.8?±?2.8?mV and drug loading of 15.07?±?0.86?µg/mg polymer. The highest mucin interaction resulted at pH 3.6 for nanoparticles without GA adsorbed. The data obtained suggest the promise of using mucoadhesive nanoparticles of PVM/MA for intravaginal delivery of GA.     

Novel poly(aryl ether)s containing benzimidazole pendants derived from 1,4-bis(2-benzimidazolyl)-2,5-difluorobenzene

A new difluoride monomer bilaterally substituted with rigid benzimidazole groups was synthesized efficiently. A series of new poly(aryl ether)s (PAEs) containing benzimidazole pendants were prepared from the novel difluoride monomer with various commercially available aromatic bisphenols using nucleophilic aromatic substitution reaction. All the PAEs show high glass transition temperatures (T _g > 205 °C), excellent thermal stability (T _d > 420 °C), and good solubility in common organic solvents. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

聚四氟乙烯的改性及应用

本文从聚四氟乙烯的组成、结构及物理化学特性、成型加工技术等方面说明了聚四氟乙烯改性的必要性 ,并对其表面改性、填充改性及共混改性作了较详细的介绍。认为聚四氟乙烯薄膜复合技术及改性技术将是未来聚四氟乙烯的主要发展方向 ,最后对聚四氟乙烯及其改性制品的应用作了介绍。     

Light emitting diodes containing Langmuir-Blodgett films of copolymer of a poly(p-phenylene-vinylene) derivative and poly(octaneoxide)

The properties of Langmuir and Langmuir-Blodgett (LB) films from a block copolymer with polyethylene oxide and phenylene-vinylene moieties are reported. The LB films were successfully transferred onto several types of substrates, with sufficient quality to allow for evaporation of a metallic electrode on top of the LB films to produce polymer light emitting diodes (PLEDs). The photoluminescence and electroluminescence spectra of the LB film and device were similar, featuring an emission at ca. 475 nm, from which we could infer that the emission mechanisms are essentially the same as in poly(p-phenylene) derivatives. Analogously to other PLEDs the current versus voltage characteristics of the LB-based device could be explained with the Arkhipov model according to which charge transport occurs among localized sites. The implications for nanotechnology of the level of control that may be achieved with LB devices will also be discussed.     

Surface modification of YAG:Ce3+ nanoparticles by poly(acrylic acid) and their biological application

Yttrium aluminum garnet Y₃Al₅O₁₂ (YAG):Ce³⁺ nanoparticles prepared by glycothermal method are modified with poly(acrylic acid) (PAA). This surface modification enables YAG:Ce³⁺ nanoparticles to be well dispersed in phosphate-buffered saline (PBS) without any serious aggregation. YAG:Ce³⁺ nanoparticles emit yellowish green light under the excitation of blue light. This fluorescent property does not change after the modification of PAA. Streptavidin (SA) is immobilized on the surface of PAA-modified YAG:Ce³⁺ nanoparticles by using carboxyl groups of PAA as cross-linking sites. We demonstrate the quantitative analysis of bovine serum albumin in PBS by SA-immobilized YAG:Ce³⁺ nanoparticles.     

Enhanced dispersity of gold nanoparticles modified by omega-carboxyl alkanethiols under the impact of poly(ethylene glycol)s

The physisorption of nonionic surfactant poly(ethylene glycol) (PEG) series and the chemisorption of carboxyl-terminated alkanethiols on surface of gold nanoparticles (AuNPs) were investigated. The physical adsorption of oligo(ethylene glycol) moieties introduced a tiny red shift of surface plasmon resonance (SPR) of AuNPs, indicating the formation of a protective layer of PEG molecules around gold surface. The subsequent chemisorption of omega-carboxyl alkanethiols was performed under the protection of PEG molecules, and the aggregation of metal nanoparticles did not appear by TEM observation. The successful adsorption of omega-carboxyl alkanethiol on gold surface was demonstrated according to FT-IR spectrum and the prior adsorbed PEG molecules could be washed out by centrifugation. Furthermore, the presence of nonionic surfactant even displayed a protective role in centrifugal process. The dispersity of modified AuNPs with peripheral functional groups was enhanced under the protection of PEG molecules as an important advantage in further biological applications.