Development of a Sustainable Resource Based Conducting Composite of Polyaniline‐Poly(esteramideurethane)

Polymers synthesized from coconut oil as a precursor find scarce applications. Polyesteramide urethane synthesized from coconut oil, a natural resource, is a dough‐like material, unusable in our study. Upon loading with polyaniline it becomes tough and flexible. Composites of ClO₄ ^? doped polyaniline with coconut oil based poly(esteramide urethane) (CPEAU) were prepared by a solution blending technique, using different ratios of polyaniline(2 wt%, 4 wt% and 8 wt%). The composites were further characterized by FT‐IR, DSC, TGA, XRD, and SEM. Conductivity was found to be in the range 2.5×10^?5?5.7×10^?4 S cm^?1. The composite was found to show weak hydrogen bonding interactions between PANI and CPEAU at 8 wt% loading.     

Immobilization of biotinylated biomolecules onto electropolymerized poly(pyrrole-nitrilotriacetic acid)–Cu2+ film

A novel and simple immobilization strategy for biotinylated biological macromolecules onto electropolymerized poly(pyrrole-nitrilotriacetic acid)(NTA)–Cu²⁺ films without avidin as connecting bridge is reported. After complexation of Cu²⁺ by the polymerized NTA chelator, biotinylated biomolecules were immobilized by coordination of the biotin groups on the NTA–Cu²⁺ complex. The anchoring of biotinylated glucose oxidase was demonstrated by fluorescent characterization via FITC-labeled avidin and amperometric measurement of glucose. The resulting calibration curve led to a sensitivity and maximum current density values of 0.6 mA mol^?1 L cm^? 2 and 13.2 μA cm^? 2, respectively. Thus, biotinylated polyphenol oxidase was fixed leading to a catechol sensor with a sensitivity of 656 mA mol^?1 L cm^? 2 and maximum current density of 25.4 μA cm^? 2. This system was also applied to the efficient immobilization of biotinylated DNA, illustrated by impedimetric detection of the formation of the DNA duplex.     

Disorder Effects in “Plastic” and Highly Conducting Compounds of Poly(aniline)

Numerical methods of molecular dynamics have been combined to measurements of X-ray and neutron scattering in order to obtain a realistic view of structural and dynamical disorder properties of conducting compounds of so called “plastdoped” poly(aniline)s. This combination allowed us to propose for the whole family of these compounds one generic model of a layered structure in which exist statistical fluctuations of the electronic density along the stacking direction of alternating molecular layers. The most part of the dynamics in the 10⁻¹³–10⁻⁹ s time range concerns the motions of protons borne by the flexible tails of doping counter-ions contained in the structure. We found that the molecular dynamics is characterized by both broad time and spatial distributions. These experimental facts coupled to those obtained with electrical conductivity measurements indicate that the high mobility of the counter-ion sublattice seems to be a prerequisite to promote a global metal like electronic behaviour of the polymer films.     

Enzymatic hydrolysis by Humicola lanuginosa lipase of poly(lactic acid)–poly(glycolic acid) monolayers

 The enzymatic hydrolysis by Humicola lanuginosa lipase (HLL) of spread insoluble monolayers of poly (α-hydroxy acid)s with various molecular weights and various lactic–glycolic molar ratios was studied using a barostat surface balance. The interfacial hydrolysis under enzyme action leads to the progressive fragmentation of the polymer molecules. The appearance at the interface of charged insoluble fragments was detected by measuring the surface potential, while the solubilization of the small soluble fragments was detected by measuring the decrease in the surface area. The data obtained were used to test the mode of fragmentation: either random or chain-end scission. The catalytic specific activity of HLL was estimated in the framework of the random scission model and compared with the activities obtained for the hydrolysis of simple molecules of di- and tri-glycerides organized as monolayers or emulsion. Received: 9 August 1999 Accepted: 4 January 2000     

Novel ultrasound contrast agents——Biodegradable poly(lactic acid) microcapsules

The different intensities of reflecting and scattering ultrasound signal at the tissue interface of the body can help to deliver the inner information and have proven their tremendous usefulness in medicine. Because it has a lot of advantages such as safety, wide application, good repetition, effi-cient detection, flexibility and economy, ultrasound diagnostics becomes the primary technology of modern medical imaging diagnostics and plays a key role in the modern diagnostic technol-ogy[1]. Alt…     

Self-diffusion in poly(N -vinyl pyrrolidone) – poly(ethylene glycol) systems

 We have applied the PFG NMR technique to investigate the translational mobility in the PVP-PEG system as a function of composition and temperature at the stages of PVP-PEG complex formation, its swelling, and dissolution in excess of liquid PEG. It has been found that the variations of the spin-echo attenuation with PEG content, water amount, and temperature reflect the different stages. The first two stages are characterized by a distribution of the self-diffusion coefficients of PEG involved in the network. The dissolution shows two diffusion coefficients; the fast one is attributed to PEG molecules, the slow one to the associates of PEG and PVP. The temperature dependencies can be described by an Arrhenius law with an activation energy depending on the composition of the blend. The concentration dependence of the PEG self-diffusion coefficients in the blend occurred to be independent of the molecular weight of PVP. The results are discussed in terms of the Mackie-Meares model. Received: 23 August 2000 Accepted: 19 October 2000     

Synthesis and Characterization of a Novel Biomaterial： Maleic Anhydride-modified Poly（dl-lactic acid）

A novel modified poly(dl-lactic acid) (PDLLA) was obtained by covalently grafting of maleic anhydride onto the backbone of PDLLA, attempting to improve PDLLA‘s hydrophilicity and cell affinity and to provide reactive groups for further chemical modification. FTIR, ^13 C NMR and DSC were used to characterize the maleic anhydride-modified PDLLA.     

Covalent Immobilization of Lipase on Poly（ acrylonitrile-co-maleic acid） Ultrafiltration Hollow Fiber Membrane

IntroductionLipases are biotechnologically important enzymes,which are able to catalyze the hydrolysis/synthesis of awide range of soluble or insoluble carboxylic acid estersand amides.In this way,the enzymes have been wide-ly used biotechnologically in dairy industry,oil pro-cessing,the production of surfactants,and the prepara-tion of enantiomerically pure pharmaceuticals[1,2].However,like mostenzymes for industrial applica-tions,lipases are unstable and easy to lose their cata-lytic activit…     

Solvation Behaviors of Poly(acrylic acid) in Mixed Solvents of 2-Butoxyethanol + Water

Poly(acrylic acid) (PAA) is a well known weak polyelectrolyte in water but little is known about the solvation behavior of PAA in the mixtures of alcohol?+?water. In this study, the solvation behavior of PAA in the mixed solvents composed of 2-butoxyethanol (2BE)?+?water were investigated by measurements of volumetric properties, electrical conductivity, resonance light scattering and dynamic light scattering. All the measured experimental properties showed extrema or abrupt changes at a 2BE mole fraction of about 0.017 in 2BE?+?water. This may be explained by the formation of aggregates of 2BE and water, which is a poor solvent for PAA and results in cononsolvency of PAA in the mixture of the two good solvents, 2BE and water. We found that the volumetric property is sensitive to the occurrence of the specific aggregate of 2BE and water and the interactions in the complex fluid mixtures.     

Phase state diagram of a poly(amic acid)–solvent–nonsolvent system

Phase behavior and structure formation was studied using optical interferometry, nephelometry, and refractometry in the polymer–solvent–nonsolvent system for DMF solutions of two poly(amic acids): based on 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride and meta-phenylenediamine (PAA-1) and pyromellitic acid dianhydride and 4,4′-oxydianiline (PAA-2). Distilled water and its mixtures with DMF were used as a nonsolvent. According to the results of the study, isothermal cross sections of the phase state diagram in the threecomponent system were plotted, the position of the critical point, the spinodal, and the conodes were determined, the movement of the figurative points in the system was traced depending on the nonsolvent composition.     

Adhesion properties of physically crosslinked elastic gels of poly(sodium acrylate)–poly(acrylic acid) mixtures evaluated by a point contact method

Adhesion properties of physically crosslinked hydrogels consisting of partially hydrated poly(sodium acrylate) (PSA) and poly(acrylic acid) (PAA) were investigated. The adhesion force and separation energy between the gels in swollen states were measured using a simple tack-evaluation technique by a point contact. As a result, the adhesion properties were significantly affected by the PSA/PAA ratio, which resulted from the fact that the physical and chemical properties of gels were changed through the replacement of PSA by PAA at gelation. The measurements of attenuated total reflectance Fourier transform infrared spectroscopy and the dynamic shear viscoelasticity suggested that the number of nonionized carboxyl groups increased and the stiffness increased with increasing the PAA ratio, respectively. In order to understand the adhesion properties further, the apparent contact area was evaluated by a stamp experiment using vermilion ink. The relationships between the adhesion properties and the physical and chemical features of gels are discussed in terms of the surface molecular interaction, the elastic and viscous properties of the bulk, and the apparent and true contact areas of the present system. From these results, the factors that determine the adhesion curve and the uniqueness and advantages of the present evaluation method are clarified.     

Compatibilization of immiscible poly(lactic acid)/poly(ε-caprolactone) blend through electron-beam irradiation with the addition of a compatibilizing agent

The aim of this study was to compatibilize immiscible poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blend by using electron-beam radiation method with the addition of a compatibilizing agent. Glycidyl methacrylate (GMA) was chosen as the compatibilizing agent, in the expectation that the GMA plays a role as a monomeric compatibilizer and a reactive agent at the interface between the PLA and the PCL phases. Compatibilization process has been investigated through the melt mixing of the PLA/PCL and the GMA by using a twin-screw extruder and the exposure of the PLA/PCL/GMA mixture to electron-beam radiation at room temperature. The melt mixing process was performed to locate the GMA at the interface, thereby expecting a finer morphology due to the GMA as the monomeric plasticizer. The exposure process was carried out to induce definite interfacial adhesion at the interface through electron-beam initiated cross-copolymerization by the medium of the GMA as the reactive agent. To investigate the results of this compatibilization strategy, the morphological, mechanical, and rheological properties of the blend were analyzed. The morphological study clearly showed the reduced particle size of dispersed PCL domains and significantly improved interfacial adhesion by the electron-beam irradiation with the addition of the GMA. The stress–strain curves of the blends irradiated at less than 20 kGy showed the typical characteristics of ductile materials. The tensile properties of the blend were strongly affected by the dose of irradiation.     

Thermal degradation of two classes of block copolymers based on poly(lactic-glycolic acid) and poly(ϵ-caprolactone) or poly(ethylene glycol)

Thermodegradative investigations of two classes of multi-block copolymers containing poly(D,L-lactic-glycolic acid) (PLGA) and either poly(ethylene glycol) (PEG) or poly(ϵ-caprolactone) diol-terminated (PCDT) segments were performed. In particular, the influence of the type and length of the segments as well as of the molar ratio between the D,L-lactic acid (LA) and glycolic acid (GA) residues was investigated at 180°C in air by viscometry, FT-IR analysis and isothermal thermogravimetry. The thermal oxidative degradation of these materials is largely affected by the LA/GA ratio, a higher LA content generally imparting higher stability. The FT-IR analysis suggests that, depending on the composition of the PLGA segments, degradative processes are triggered which can lead to a preferential degradation of the blocks.     

Why does poly(acrylic acid) addition improve the quality of holograms recorded in dichromated poly(vinyl alcohol)?

Holographic measurements have shown that the addition of 0.5% of poly(acrylic acid) (PAA) can improve the quality of holograms recorded in poly(vinyl alcohol) (PVA) doped with ammonium dichromate (ADC). The purpose of this paper is to explain this improvement. First, an analytical approach investigated the structural and architectural modification of the polymeric matrix and the fate of the various chromium species within PVA/PAA/ADC films. The addition of PAA in dichromated PVA led to a pre-reticulation of the polymeric matrix. This process increased with the amount of PAA.Second, an analytical approach focused on the evolution of PVA/PAA/ADC films upon irradiation at 365 nm, which is representative of hologram formation. The improvement brought by the presence of 0.5% of PAA in PVA/ADC was assigned to an additional source of crosslinking through the formation of covalent bonds. This process paralleled the crosslinking through coordination bonds involving Cr(V) and PVA units. At 0.5% of PAA, the mobility of the medium before exposure was sufficient to allow the migration of the species involved in the reticulation process during hologram formation, whereas higher concentrations of PAA inhibited this migration.     

Poly(oxyalkylene) synthesis in Brønsted acid ionic liquids

The polyetherification of diols with 4-12 methylene units was studied in Br?nsted Acid Ionic Liquids (BAILs). High molar mass poly(oxyalkylene)s were obtained at relatively low temperatures (130 °C), except in the cases of 1,4-butanediol and 1,6-hexanediol where cyclic ether formation was observed.     

Enhanced photodegradation of TiO2-containing poly(ε-caprolactone)/poly(lactic acid) blends

The calamitous accumulation of plastic waste in the environment, especially single-use disposables, calls for new approaches to materials design. One method to address the persistence of plastics beyond their intended use is to impart them with functionalities that will either allow for their recyclability or their degradation to basic natural components. This work focuses on the fabrication of photodegradable polyester blends and investigates the impact of compatibilization on photodegradation rates. Specifically, we blended poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) polymers by (reactive) extrusion in the presence or absence of dicumyl peroxide (DCP), a radical generator, and titanium dioxide (TiO₂), an inorganic photocatalyst. We examined the effects of DCP and TiO₂ loadings as well as copolymer composition on the thermomechanical properties, photodegradability, and morphology. We found that the inclusion of TiO₂ dramatically increased flexural moduli and photodegradation rates in both dry and wet conditions, while reactive compatibilization had little effect of the tested properties. This simple and scalable approach is promising to fabricate materials that can readily photodegrade.     

Raman Spectroscopic Study of the Conformation and Melting of Poly(dG) · Poly(dC) and Poly(dG-dC) · Poly(dG-dC) in Aqueous Solution

Raman spectroscopic measurements on aqueous solutions of poly(dG) · poly(dC)indicate that the conformation of the polynucleotides in this double helicalcomplex are distributed between the A and B types at room temperature, the Aform being predominant at –15°C and decreasing progressively upon raising thetemperature to 65°C. A reversible pretransition has been found in this complexnear 70°C. Modifications in the spectra at this temperature indicate no majorconformational changes, but rather suggest altered base pairing and hydration ofthe carbonyl groups, accompanied by a slight distortion of the double helix,resulting in a slightly reduced stacking of the cytosine bases. Measurements inself-pressurized solutions of the complex at high temperature show that it meltsat 103°C in 0.1M NaCl solution (107°C in 0.5M NaCl). These values are somewhatlower than those we have determined in the same manner for the complexpoly(dG-dC) · poly(dG-dC): 117°C in 0.1M MgCl₂ and 113°C or higher in 0.1MNaCl solution.     

Thermoreversible Gelation of Poly(vinylidene fluoride) – Camphor System

Poly (vinylidene fluoride) (PVF₂) produces thermoreversible gel in camphor when quenched to 25°C from the melt under sealed condition. The SEM micrograph of dried PVF₂/camphor gel (Wequation/tex2gif-inf-3.gif= 0.25) indicates presence of fibrillar network structure and the gels at different composition shows reversible first order phase transition. The phase diagram of the gel suggest the formation of a polymer- solvent complex. The melting enthalpy gives a stoichiometric composition of the complex at Wequation/tex2gif-inf-5.gif= 0.25. This corresponds to a molar ratio of PVF₂ monomer/camphor ≈ 4/5. Temperature-dependent synchroton experiments further support the conclusions derived from the phase diagram.     

Effect of Physical Aging on Heterogeneity of Poly(ε-caprolactone) Toughening Poly(lactic acid) Probed by Nanomechanical Mapping

Poly(lactic acid)(PLA) is a promising bio-based environmentally-friendly plastic. Nevertheless, the physical aging-induced brittleness of PLA limits its widespread applications. Blending with immiscible ductile polymer is an effective way to toughen PLA. However, the underlying details of the toughening mechanism and, in particular, the effect of physical aging are not well understood. Herein, atomic force microscopy(AFM) based nanomechanical mapping technology was utilized to visualize the diff...