Ultrasound enhances lipase-catalyzed synthesis of poly (ethylene glutarate)

The present work explores the best conditions for the enzymatic synthesis of poly (ethylene glutarate) for the first time. The start-up materials are the liquids; diethyl glutarate and ethylene glycol diacetate, without the need of addition of extra solvent. The reactions are catalyzed by lipase B from Candida antarctica immobilized on glycidyl methacrylate-ter-divinylbenzene-ter-ethylene glycol dimethacrylate at 40 °C during 18 h in water bath with mechanical stirring or 1 h in ultrasonic bath followed by 6 h in vacuum in both the cases for evaporation of ethyl acetate. The application of ultrasound significantly intensified the polyesterification reaction with reduction of the processing time from 24 h to 7 h. The same degree of polymerization was obtained for the same enzyme loading in less time of reaction when using the ultrasound treatment. The degree of polymerization for long-term polyesterification was improved approximately 8-fold due to the presence of sonication during the reaction. The highest degree of polymerization achieved was 31, with a monomer conversion of 96.77%. The ultrasound treatment demonstrated to be an effective green approach to intensify the polyesterification reaction with enhanced initial kinetics and high degree of polymerization.     

Crystallization Behavior of Modified Polyester with Varied Macromolecular Architecture

Several modified polyesters with varied macromolecular architecture, such as branched poly(ethylene terephthalate) (PET) based on glycerol (GL) from 0.004 to 0.05 mol ratio as a branching agent, blocked and branched poly(butylene terephthalate)‐polyether containing poly(tetramethylene oxide) (PTMO) as soft segment and GL as a branching unit, as well as segmented poly(ethylene terephthalate)‐polyether,were prepared. Their crystallization behavior was studied by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized optical microscopy (POM). It was found that a small extent of branching may enhance the crystallization of poly(ethylene terephthalate), while high degrees of branching (0.035–0.05) could block the development of crystallization. On the other hand, for even a small extent of incorporation of GL in the more flexible poly(butylene terephthalate)‐polyether chains, no enhanced crystallization was observed; blocking of crystallization from a branching defect may play the main role. The introduction of PTMO in poly(ethylene terephthalate) chains to a small degree facilitated the nucleation and speeded crystallization, but decreased the melting points of the polymers. A small number of nuclei and the greater induction time were found for branched PETs. The spherulities developed in branched PETs were larger and more perfect than those in PET due to less truncation of spherulites resulting from fewer nuclei, whereas the size of spherulities in poly(ethylene terephthalate)‐polyether became smaller with the increase of PTMO.     

Enzymatic synthesis of multi-component copolymers and their structural characterization

The use of enzymes in synthetic applications has increased dramatically in the recent years and the field of polymer science is part of this trend. Synthesis of a variety of polymers using lipase catalyzed (Candida antarctica) polymerization reactions has led to a variety of new materials with interesting properties in our laboratories. This paper describes the synthesis of multi-component polyesters and mixed polymers having polyester and polyamide linkages under solvent-less conditions using Candida antarctica lipase B. The effect of a third component, i.e. a series of 1,omega-alkanediols (1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol and 1,16-hexadecanediol) on the copolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol 600) has been studied and the mechanism for the incorporation of the third component is proposed. We have also studied the effect of different functional groups during terpolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol) by adding a third component having different functionalities (1,6-hexanediol, 1,6-hexanediamine or 1,6-hexanedithiol) and compared the effect of hydroxyl, amine and thiol groups on the polymerization reactions.     

Underwater excimer laser ablation of polymers

In this paper, we study the photoablation kinetic of poly (ethylene terephthalate) (PET), polycarbonate (PC), polyimide (PI) and polystyrene (PS) in both air and water. Compared to the results obtained in air, we highlight the decrease of the ablation threshold (AT) of polyesters in contact with water as a function of polymer chemical structure. In order to check the expected hydrolytic reaction of polyesters near the ablation threshold, the chemical modification of the polymer surfaces, as well the composition of the ablation products, were investigated after irradiation near the fluence of ablation threshold in air (air-F _t ) by X-ray photoelectron spectroscopy (XPS) and confocal Raman microspectroscopy. The morphology of polymers obtained by underwater irradiation and near the air-F _t was also examined using scanning electron microscopy (SEM). To understand the process and its dynamics in contact with water, we consider the model of temperature at the polymer-water interface based on the semi-analytical solution of the transit heat-diffusion equation.     

Lithium ionic conduction in poly (methacrylic acid)-poly (ethylene oxide) complex containing lithium perchlorate

Polymeric solid electrolytes were prepared by dispersing homogeneously lithium perchlorate in a hydrogen-bonding type intermacromolecular complex of poly(methacrylic acid)-poly(ethylene oxide). They showed ionic conductivity of more than 10^-6 (S/cm) at room temperature. The conductivity depended on the molecular weight of the poly(ethylene oxide), the proportion of poly(ethylene oxide) and lithium perchlorate, and so on. Poly(ethylene oxide) with average molecular weights ranging from 400 to 2 × 10⁴ were used to clarify the effect of chain length on the conductivity. The conductivity increased and the flexibility of the films improved with increasing the content of poly(ethylene oxide) with average molecular weight of 400. The maximum conductivity of 1.3 × 10^-5 (S/cm) at 60°C was obtained for the flexible film when the composition of poly(methacrylic acid)/poly(ethylene oxide)/lithium perchlorate was in the ratio of 17.0/ 68.0/15.0 in unit mol%.     

Investigations on PMMA-PVdF polymer blend electrolyte with esters of dibenzoic acids as plasticizers

Plasticizers can be used to change the electrical and mechanical properties of polymer electrolytes by reducing the degree of crystallinity and lowering the glass transition temperature. The transport properties of gel type ionic conducting membranes consisting of poly (methyl methacrylate) (PMMA), poly (vinylidene fluriode) (PVdF), Lithium perchlorate (LiClO₄) and dioctyl phthalate (DOP), dibutyl phthalate (DBP), dimethyl phthalate (DMP) or diethyl phthalate (DEP) were studied. The polymer films were characterized by X-ray diffraction, Thermal, Fourier transform infrared and impedance spectroscopic studies. It is found that the addition of DMP as the plasticizer in the PMMA / PVdF-LiClO₄ polymer complex favours an enhancement in ionic conductivity. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and the results are discussed.     

On crystallization and phase separation phenomena in PEN/PHBA copolyesters

Two different etching techniques that reveal the semicrystalline morphology of polyesters have been developed and applied to an analysis of the phase structure of copolyesters made by reacting poly(hydroxybenzoic acid) (PHBA), and poly(ethylene naphtha-lene-dicarboxylate) (PEN). One technique is based on oxidation with acidic permanganate solutions and is used to study the macroscopic distribution of different phases. The other is based on sa-ponification with alkaline reagents and reveals more detailed structure within the various phases. Etching and electron microscopic examinations have been carried out for three different PEN-co-PHBA compositions. Three different types of solid phase are revealed: (1) a phase rich in PEN; (2) a phase containing roughly equal proportions of the two components, liquid crystalline at high temperatures; (3) a solid phase of crystalline HBA-rich molecules, which segregate into laminar regions. These observations are consistent with the previously published thermal, x-ray, and dynamic mechanical analyses of these materials.     

High-Pressure Analysis of the Multiple Melting Endotherms of Poly(ethylene succinate) and Poly(butylene succinate)

The origin of the multiple melting peaks in two linear polyesters, poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS), of isothermally crystallized samples was investigated by differential scanning calorimetry (DSC) at atmospheric pressure and high-pressure differential thermal analysis (HP-DTA) at elevated pressures. In PES, the DSC melting curves showed three endothermic peaks at slow heating rates, which decreased to two with increasing heating rates. The HP-DTA curves showed that the area (qualitative) and peak height of the high-temperature peak decreased with increasing pressure and merged with the low-temperature peak at pressures above 450 MPa. This behavior supported the melting, recrystallization, and remelting model for the observed multiple melting endotherms. In PBS, the DSC melting curves were similar to those seen in PES. The HP-DTA curves were also similar to PES up to 400 MPa, but above this pressure the area and the peak height of the high-temperature peak and the temperature difference between the high- and low-temperature peaks remained unchanged. This observation suggested that the two peaks in PBS were due to the melting of two populations of crystals with different lamellar thickness originally present in the sample. The multiple melting behavior in isothermally crystallized PBS is proposed to incorporate both the melting of two populations of crystals and melting, recrystallization, and remelting.     

Electrolytic conduction in amorphous salt complexed polyethers

Phosphate ester extended and crosslinked poly(ethylene glycol)s were prepared from reaction of the glycols with chlorophosphates. Fully amorphous electrolytes formed with lithium trifluoromethanesulphonate showed enhanced conductivity over comparable poly(ethylene oxide) electrolytes in the temperature range 293–373 K. With O/Li=27.6, α=5.2×10⁻⁶S cm⁻¹ at 293 K. A conductivity maximum was detected at ca. 1 mol dm⁻³ concentration consistent with the increase in charge carrier density opposed by medium viscosity. For all complexes the temperature dependence of conductivity obeyed the Vogel-Tamman-Fulcher and Williams-Landel-Ferry equations, with T_g(onset) for the parent polymer as the ideal glass transition temperature. Activation energy parameters from use of the VTF equation and Adam-Gibbs configurational entropy model showed a linear dependence on salt concentration.     

Immobilization of poly(?-caprolactone)-poly(ethylene oxide)-poly(?-caprolactone) triblock copolymer on poly(lactide-co-glycolide) surface and dual biofunctional effects

Poly(?-caprolactone)-poly(ethylene oxide)-poly(?-caprolactone) (PCL-PEG-PCL) triblock copolymer was covalently immobilized onto poly(lactide-co-glycolide) (PLGA) surface with the precursor of photopolymerizable and biodegradable PCL-PEG-PCL diacrylates. Argon plasma technique was exploited to obtain hydrophilic PLGA surface (HPLGA). The surface properties were characterized by Water contact angle and X-ray photoelectron spectroscopy (XPS) techniques. PCL-PEG-PCL surface modified hydrophobic PLGA and hydrophilic PLGA results in different surface physicochemical properties. PCL-PEG-PCL modified hydrophobic PLGA surface (PLGA-PCL-PEG-PCL) demonstrates excellent inhibition of platelet adhesion and activation; while PCL-PEG-PCL modified hydrophilic PLGA surface (HPLGA-PCL-PEG-PCL) results in good cytocompatibility. The possible mechanism was discussed and the driven force was ascribed to the different assembly behavior of PCL-PEG-PCL on PLGA surface dependant on the hydrophilic/hydrophobic property of PLGA. This simple and effective surface engineering method is also suitable for the other biomaterials such as polyurethane (PU), silicon rubber and poly(ethylene terephthalate) (PET) to obtain the enhanced biocompatibility.     

Characteristics of Rubber/Sodium Montmorillonite Nanocomposites Prepared by a Novel Method

In order to enhance the fine dispersion of hydrophilic sodium montmorillonite (Na‐MMT) in the matrix of hydrophobic rubber, the hydrophobic modification of Na‐MMT was carried out via an in situ method in the melt compounding process using the modifiers poly(ethylene glycol) monooleate or poly(ethylene glycol) diacrylate, both of which have a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic hydrocarbon segment. The X‐ray diffraction patterns showed that the interlayer distance of Na‐MMT was expanded by the intercalation of these modifiers. The morphology observed by scanning electron microscopy as well as the cure characteristics and tensile modulus showed that this organic modification effectively enhanced the fine dispersion of Na‐MMT in the rubber matrix.     

The physical and electrochemical properties of poly(vinylidene chloride-co-acrylonitrile)-based polymer electrolytes prepared with different plasticizers

Lithium ion-conducting membranes with poly(ethylene oxide) (PEO)/poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN)/lithium perchlorate (LiClO₄) were prepared by solution casting method. Different plasticizers ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (gBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dibutyl phthalate (DBP) were complexed with the fixed ratio of PEO/PVdC-co-AN/LiClO₄. The preparation and physical and electrochemical properties of the gel polymer electrolytes have been briefly elucidated in this paper. The maximum ionic conductivity value computed from the ac impedance spectroscopy is found to be 3?×?10^?4 S cm^?1 for the EC-based system. From DBP-based system down to EC-based system, a decrease of crystallinity and an increase of amorphousity are depicted by X-ray diffraction technique, the decrease of band gap energy is picturized through UV–visible analysis, the decrease of glass transition temperature is perceived from differential scanning calorimetry plots, and the reduction of photoluminescence intensity is described through photoluminescence spectroscopy study at an excitation wavelength of 280 nm. Atomic force microscopic images of EC-based polymer electrolyte film show the escalation of micropores. Fourier transform infrared spectroscopy study supports the complex formation and the interaction between the polymers, salt, and plasticizer. The maximum thermal stability is obtained from thermogravimetry/differential thermal analysis, which is found to be 222 °C for the sample complexed with EC. The cyclic voltagram of the sample having a maximum ionic conductivity shows a small redox current at the anode, and cathode and the chemical stability is confirmed by linear sweep voltammetry.     

Mechanism of nanocapsules of Matricaria recutita L. extract formation by the emulsion–diffusion process

Nanocapsules coated by medicinal plants have many applications in drug manufacturing. Medicinal plants can be loaded on nanocapsules with polyesteric triblock copolymer poly ethylene glycol–poly butylene adipate–poly ethylene glycol (PEG–PBA–PEG) as shell and olive oil can be introduced as a core of nanocapsules by a method known as polymer deposition solvent evaporation method. In this research, first, certain amount of polymer, Matricaria recutita extract and olive oil were mixed with acetone and then, water was added to the solution using magnetic stirrer. After which the acetone was removed by vacuuming and finally nanocapsules were found by freezing-drier. The study showed the size of nanocapsules depends on variety of factors such as the ratio of polymer to oil and concentration of polymers and plant extract. The nanocapsules were identified by scanning electron microscopy (SEM) and zeta potential sizer (ZPS), Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR).     

Nanostructured Thermosetting Blends of Phenolic Thermosets and Poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) Triblock Copolymer

The amphiphilic triblock copolymer, poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐b‐PPO‐b‐PEO) was incorporated into novolac resin to prepare thermosetting blends. The morphology of the thermosetting blends was investigated by means of atomic force microscopy (AFM) and small‐angle x‐ray scattering (SAXS) and the nanostructures were obtained. It was identified that the reaction‐induced phase separation occurred in the blends of phenolic thermosets with the model poly(propylene oxide) (PPO), whereas poly(ethylene oxide) (PEO) was miscible with novolac resin after and before the curing reaction. In terms of miscibility and phase behavior of the subchains of the triblock copolymer with novolac resin, it was demonstrated that the formation of nanostructures in the thermosets followed a mechanism of reaction‐induced microphase separation.     

A Comparison of the Effects of Calcium Glutarate and Pimelate on the Formation of β Crystalline Form in Isotactic Poly(propylene)

The effect of calcium glutarate (Cagt) and calcium pimelate (Capt) on the formation of β crystalline form in isotactic poly(propylene) in the crystallization temperature range of 110–130°C has been investigated. The content of β phase crystals increase with the addition of calcium glutarate. K (relative content of β crystalline form in the iPP sample) attains its maximum value for iPP doped with 0.3 wt.% Cagt isothermally crystallized at 110°C (26.71%) or 120°C (30.27%), and for iPP doped with 0.2 wt.% Cagt isothermally crystallized at 130°C (31.97%), respectively. Compared with the K values of iPP doped with 0.1 wt.% Capt (78.33–94.76%), the β nucleation ability of Cagt is inferior to that of Capt. The spherulite size of iPP doped with Capt is smaller than that of iPP doped with Cagt. The difference in the β nucleation ability between Cagt and Capt is explained by the difference between their crystal structure parameters and those of β‐iPP.     

Synthesis and characterization of polymeric nanospheres loaded with the anticancer drug paclitaxel and magnetic particles

We describe the preparation (by nanoprecipitation) and characterization of nanospheres (NPs) for magnetic drug targeting made of a magnetic fluid with poly(ethylene glycol), poly(d,l-lactic-co-glycolic acid) (PLGA), and the anticancer drug paclitaxel (Taxol^®). Infrared spectroscopy confirmed the incorporation of the drug in the PLGA NPs, which were also characterized in terms of morphology, size (typical diameter 200-250 nm) and colloidal stability in aqueous solutions of NaCl. Drug release and in vivo toxicity experiments of the prepared samples were performed. Their stability, magnetic properties (superparamagnetism), and lethal dose were found to be acceptable for the proposed application in cancer therapy.     

Synthesis of conjugated polymers for application in light-emitting diodes (PLEDs)

In the field of electroluminescent organic materials, conjugated polymers have attracted much attention over recent years owing to their versatile synthesis, their relative ease of processing and the possibility of establishing predictive structure–function relationships between chemical structures and optical properties. This review article highlights the advances made in the synthesis of conjugated polymers for use in light-emitting devices (LEDs) covering the last two years. Research efforts were largely directed towards the improvement of the synthesis of monomers and polymers involving classical polymer structures such as poly( p -phenylene vinylene)s (PPVs), poly( p -phenylene)s (PPPs), poly(2,7-fluorene)s (PFs), or poly(2,5-thienylene)s (PTs). Control of the color of emission by modulation of the effective conjugation length, improving balanced charge injection and transport properties by introduction of electron-donating or -withdrawing moieties directly into the polymer backbone or enhancement of the emission efficiency by attempts to influence film morphology are some examples of recent research directions. All these investigations contributed to a significantly better understanding of the chemical and physical processes spanning topics from the manufacturing process to the operation of LEDs and leading to the announcement of the first commercial products. In addition to the classical π -conjugated polymers a few examples of rather unusual structures have also emerged.     

Sequential Structure,Crystallization, and Properties of Biodegradable Poly(ethylene Terephthalate-Co-Ethylene Oxide-Co-Lactide) Copolyester

The sequential structure, isothermal crystallization, tensile property, and degradation behavior of poly(ethylene terephthalate-co-ethylene oxide-co-lactide) (ETOLA) copolyester based on melt transesterification of poly(ethylene terephthalate) with poly(ethylene oxide) and oligo(lactic acid) was investigated. The degree of randomness was calculated to be 0.38, showing the incorporation of poly(ethylene oxide) (PEO) blocks into the homogeneous sequences of ethylene terephthalate (ET) and lactide (LA) units. The isothermal crystallization kinetics results revealed that the crystallization activation energy of the copolyester calculated using the Arrhenius’ equation was lower than that reported for poly(ethylene terephthalate) (PET), indicating that the addition of PEO and LA units into PET retarded the crystallization of PET. The copolyester exhibited the same crystal structure at different crystallization temperatures, similar to that of PET homopolymer, based on wide angle X-ray diffraction results. The size of the spherulites of ETOLA increased with crystallization temperature. The increase of crystallization temperature reduced the elongation at break of the copolyesters, as well as the enzymatic degradation.     

Grafting onto poly(ethylene terephthalate) driven by 172 nm UV light

The reactivity of the surface of poly(ethylene terephthalate) (PET) film under 172 nm UV irradiation (xenon excimer lamp) towards nitrogen-borne 1-octene, n-nonane and heptafluorodecene vapor was investigated. Materials receiving from 0 to 24 J/cm² of UV were examined by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF/SIMS), water and mineral oil contact angle measurement and atomic force microscopy (AFM). A uniform nanoscale layer developed on PET surface attributed to the grafting reaction between photolytically-produced polymer radicals and vapor phase molecules.     

Investigation of dibutyl phthalate as plasticizer on poly(methyl methacrylate)–lithium tetraborate based polymer electrolytes

Polymer electrolyte membranes, comprising of poly(methyl methacrylate) (PMMA), lithium tetraborate (Li₂B₄O₇) as salt and dibutyl phthalate (DBP) as plasticizer were prepared using a solution casting method. The incorporation of DBP enhanced the ionic conductivity of the polymer electrolyte. The polymer electrolyte containing 70 wt.% of poly(methyl methacrylate)–lithium tetraborate and 30 wt.% of DBP presents the highest ionic conductivity of 1.58 × 10⁻⁷ S/cm. The temperature dependence of ionic conductivity study showed that these polymer electrolytes obey Vogel–Tamman–Fulcher (VTF) type behaviour. Thermogravimetric analysis (TGA) was employed to analyse the thermal stability of the polymer electrolytes. Fourier transform infrared (FTIR) studies confirmed the complexation between poly(methyl methacrylate), lithium tetraborate and DBP.