Distribution by Scientific Domains

Kinds of Polyester

  • aliphatic polyester
  • biodegradable polyester
  • hyperbranched polyester
  • unsaturated polyester

  • Terms modified by Polyester

  • polyester composite
  • polyester fabric
  • polyester fiber
  • polyester film
  • polyester matrix
  • polyester resin
  • polyester segment

  • Selected Abstracts

    A Novel Micellar PEGylated Hyperbranched Polyester as a Prospective Drug Delivery System for Paclitaxel

    Christina Kontoyianni
    Abstract A hyperbranched aliphatic polyester has been functionalized with PEG chains to afford a novel water-soluble BH40-PEG polymer which exhibits unimolecular micellar properties, and is therefore appropriate for application as a drug-delivery system. The solubility of the anticancer drug paclitaxel was enhanced by a factor of 35, 110, 230, and 355 in aqueous solutions of BH40-PEG of 10, 30, 60, and 90 mg,,mL,1, respectively. More than 50% of the drug is released at a steady rate and release is almost complete within 10 h. The toxicity of BH40-PEG was assessed in vitro with A549 human lung carcinoma cells and found to be nontoxic for 3 h incubation up to a 1.75 mg,,mL,1 concentration while LD50 was 3.5 mg,,mL,1. Finally, it was efficiently internalized in cells, primarily in the absence of foetal bovine serum, while confocal microscopy revealed the preferential localization of the compound in cell nuclei. [source]

    Encapsulation and Controlled Release of a Hydrophobic Drug Using a Novel Nanoparticle-Forming Hyperbranched Polyester,

    Jianhua Zou
    Abstract Summary: An amphiphilic, hyperbranched polymer suitable for use in controlled drug delivery is reported. This polymer was obtained by modification of the hyperbranched aliphatic polyester Boltorn H20 (H20) with succinic anhydride and then glycidyl methacrylate, and formed nanoparticles in aqueous solution. The critical association concentration was 7.4,,10,3 g,,L,1, as determined by fluorescence spectroscopy using pyrene as a molecular probe. A static/dynamic laser light scattering (LLS) study revealed that the average particle size was 39.4 nm with a low particle size distribution (PDI = 0.04), and that each particle was composed of about 350 amphiphilic molecules. Daidzein, a hydrophobic traditional Chinese medicine, was encapsulated during particle formation and the release properties were determined. The optimal feeding concentration of daidzein to hyperbranched polyester was 4.9,,10,5 g,,mL,1 to 5.0,,10,3 g,,mL,1 with a loading efficiency of 76.1%. In the presence of the enzyme Lipase PS, the drug loaded nanoparticles degraded in a random one-by-one manner and released the drug over a few days. This system is therefore a novel controlled drug release system based on nanoparticles formed of hyperbranched polyester. Encapsulation of daidzein by hyperbranched polyester particles. [source]

    Synthesis and Characterization of a Novel Degradable Aliphatic Polyester that Contains Monomeric Lactate Sequences

    Congming Xiao
    Abstract Summary: A novel degradable aliphatic polyester that contains monomeric lactate sequences is synthesized via melt-polycondensation of ethylene glycol lactate diol (EGLD) with succinic anhydride without the use of catalyst. The structure of the EGLD precursor and the polyester are verified with FT-IR and 1H NMR spectra. Gel permeation chromatography reveals that the weight-average molecular weight of the polyester is 5.5,,104 with a polydispersity index (PDI) of 1.7. Differential scanning calorimetry profiles reveal that the polyester is a semicrystalline polymer with a glass transition temperature of ,12,C and melting temperature of 101,C. The weight loss percentage of the polyester after immersing for 208 d in active sludge is 2.7%, which suggests degradation has occurred. The synthesis route of the polyester synthesized here (see inset for structure). [source]

    Polymers with benzofuro-benzofuran structures,

    Behzad Pourabas
    Abstract Several kinds of molecules and also polymers are going to be discussed in the present article. Common feature in these molecules and polymers is the possessing of a specific structural part, namely benzofuro,benzofuran. This structure will appear in several molecules and kinds of polymers in the text. A condensation reaction between glyoxal and phenols is the reaction needed to produce the mentioned structural part, ie benzofuro,benzofuran. Because of the importance of this reaction, a brief historical background in the initial section of the article, and some discussion on the structural assignment of the reaction product and the reaction mechanism is also given in sections later on. Types of polymers, which are discussed in this article, are mainly heat stable polymers including polyamide, poly(ether ketone sulfone), polybenzimidazole, poly(amide-benzimidazole) and polyarylates. Polyester, polyhaydrezide and polymers with NLO property are the other kinds of the discussed polymers in the text with the benzofuro,benzofuran structure in their main chain. There is not any detailed procedure provided in the text about the synthesis of the molecules or even the polymers and the general procedures provided follow only the methodological purposes of the authors. Thermal properties of the polymers are discussed in the final section of the article with an attempt to provide a comparative argument in order to reach a relationship between structure and thermal properties. 2001 Society of Chemical Industry. [source]

    Antibacterial Nitric Oxide-Releasing Polyester for the Coating of Blood-Contacting Artificial Materials

    ARTIFICIAL ORGANS, Issue 7 2010
    Amedea B. Seabra
    Abstract The emergence of multidrug-resistant bacteria associated with blood-contacting artificial materials is a growing health problem, which demands new approaches in the field of biomaterials research. In this study, a poly(sulfhydrylated polyester) (PSPE) was synthesized by the polyesterification reaction of mercaptosuccinic acid with 3-mercapto-1,2-propanediol and blended with poly(methyl methacrylate) (PMMA) from solution, leading to solid PSPE/PMMA films, with three different PSPE : PMMMA mass ratios. These films were subsequently S-nitrosated through the immersion in acidified nitrite solution, yielding poly(nitrosated)polyester/PMMA (PNPE/PMMA) films. A polyurethane intravascular catheter coated with PNPE/PMMA was shown to release nitric oxide (NO) in phosphate buffered saline solution (pH 7.4) at 37C at rates of 4.6 nmol/cm2/h in the first 6 h and 0.8 nmol/cm2/h in the next 12 h. When used to coat the bottom of culture plates, NO released from these films exerted a potent dose- and time-dependent antimicrobial activity against Staphylococcus aureus and a multidrug-resistant Pseudomonas aeruginosa strains. This antibacterial effect of PSPE/PMMA films opens a new perspective for the coating of blood-contacting artificial materials, for avoiding their colonization with highly resistant bacteria. [source]

    Biofilm Growth and Bed Fluidization in a Fluidized Bed Reactor Packed with Support Materials of Low Density,

    R.A. Saucedo-Tern
    Abstract Support materials of low-density for fluidized bed reactors provide several operational advantages, including lower energy requirements and proper biofilm growth balance. The aim of this investigation was to study the extent of biofilm growth and bed fluidization in an experimental reactor, using polyester resin (,pr,=,1220,kg/m3) and vitrified expanded perlite (,vep,=,1710,kg/m3) as alternative support materials to conventional silica sand. A noteworthy amount of biofilm was observed to be attached to both support materials from the very beginning of the bioreactor operation. Nevertheless, there were significant variations in biofilm growth and activity over the course of the experimental trials. For both perlite and polyester beds, the highest biofilm mass and the highest total number of mesophilic bacteria were observed between the 7th and the 10th day, showing a steady state trend at the end of the experimental runs. The chemical oxygen demand (COD) removal levels were concomitant with biofilm mass and total mesophilic bacteria changes, although the polyester bed efficiency was slightly higher than that for the perlite bed. As expected, the polyester bed was fluidized at a lower re-circulation flow compared to the perlite bed. Reactor back-washing was not required for these support materials since biomass excess was adequately separated by means of a special internal device. The efficiencies of removal of organic matter achieved were acceptable (up to 78,%) despite the low volume of the support material (25,%) and the low hydraulic retention time (30,min). [source]

    Biodegradation of poly(tetramethylene succinate-cotetramethylene abdicate) and poly(tetramethylene succinate) through water-soluble products

    Eiichi Kitakuni
    Abstract Poly(tetramethylene succinate-co-tetramethylene adipate) (PBSA) and poly(tetramethylenesuccinate) (PBS) were hydrolyzed experimentally into water-soluble oligomers and monomers by Chromobacterium extracellular lipase. The oligomers were identified by high-performance liquid chromatography,mass spectrometry and 1H-nuclear magnetic resonance, which indicated that a total of 28 oligomer species were liberated from PBSA, and that 13 of them were identical to the hydrolysates from PBS. Moreover, 20 of the species were polyester-based compounds of monomer units, and the other 8 species were small amounts of diurethane compounds. Bis(hydroxybutyl) succinate (BSB) and bis(hydroxybutyl) hexamethylene dicarbamate (BHB) were the typical oligomers and were chemically synthesized. Biodegradability of BSB and BHB was examined for 28 d in the activated sludge, and analysis of the results of this study indicated that the final conversion rate of constituent carbon to carbon dioxide was estimated at 80 mol% for BSB and 10 mol% for BHB. The remaining amount of carbon in the undegraded BHB was 20 mol%. In the presence of BSB, the biodegradability of BHB was increased by about 1.5 times. The suggestion was made that BSB induced a growth of microorganisms and helped BHB degradation. This is consistent with the observation that the biodegradation of BHB in native soil for 60 d reached > 60%. [source]

    The use of fire-retardant intumescent mats for fire and heat protection of glass fibre-reinforced polyester composites: Thermal barrier properties

    FIRE AND MATERIALS, Issue 1 2010
    Everson Kandare
    Abstract This study investigates the use of integral, hybrid intumescent thermal barriers (mats) to provide surface protection to the core fibre-reinforced polyester composite structural integrity when exposed to a fire or heat source. Glass fibre-reinforced composites protected by intumescent mats/fabrics containing silicate fibres, expandable graphite and in some cases borosilicate glass bounded together by an organic matrix have been evaluated for fire performance under a constant heat flux of 50kW/m2. The effect of insulative fabric thickness as well as chemical composition on the flammability of the resultant hybrid composites is evaluated. Glass fibre-reinforced polyester (GRP) composites without any surface protection have a relatively higher time-to-ignition and peak heat release rate values when compared with core composites protected by insulative fabrics. Thermograms representing the variation of temperature on the reverse side of the hybrid composites with time when exposed to a constant heat flux show that the inclusion of intumescent surface barriers results in retarded temperature increments within the core GRP composites. Copyright 2009 John Wiley & Sons, Ltd. [source]

    An analysis of the burning of polyester and vinylester fibre glass composites

    FIRE AND MATERIALS, Issue 4 2005
    P. J. Burchill
    Abstract An analysis of mass loss and damage depth produced by the combustion of styrenic resins and their fibre glass composites has been undertaken. Mass loss rates at a selected heat flux were found to be linearly related to those at a different heat flux. Given the scatter in the experimental data, these relative rates obeyed the same Arrhenius relationship for both resins and their fibre glass composites. Damage depth in composites was also found to be linearly related to mass loss, and thus may be predicted. It is therefore shown that mass loss and damage depth can be predicted as a function of time at any desired heat flux given that mass loss-time data are available at a specific heat flux. The predictions are limited to consumption of the matrix of about 30% by weight, at which stage the mechanical properties are greatly reduced. Copyright Commonwealth of Australia 2004. Published by John Wiley & Sons, Ltd. [source]

    Polyurethane/clay and polyurethane/POSS nanocomposites as flame retarded coating for polyester and cotton fabrics

    FIRE AND MATERIALS, Issue 4-5 2002
    Eric Devaux
    Polyurethane resins (PU) are widely used as coatings for textile fabrics in order to improve some properties (for example mechanical behaviour, water repellency and air impermeability). Two kinds of additives have been added to the polyurethane in order to provide flame retardancy to the coated textile structure: montmorillonite clay and polyhedral oligomeric silsesquioxanes (POSS) have been used to process PU nanocomposites. The paper presents some results obtained with PU/clay and PU/POSS coated polyester or cotton fabrics, using cone calorimetry and thermogravimetric analysis. The efficiency of the additive chosen is clearly demonstrated and discussed. In particular, the great potential of using POSS for fire retardant applications is highlighted. Copyright 2002 John Wiley & Sons, Ltd. [source]

    Thermal processing of prawn ,kuruma' in retortable pouches and aluminium cans

    Chitradurga O. Mohan
    Summary Prawn ,kuruma' was prepared from Indian white shrimp (Fenneropenaeus indicus), packed in conventional 301 206 and 401 411 aluminium cans and in thin profile retort pouches having a three-layer configuration of 12.5 , polyester, 12.5 , aluminium foil and 85 , cast polypropylene of size 16 20 cm and 17 30 cm. The physico-chemical tests conducted on these containers showed their suitability for thermal processing. Prawn to kuruma ratio of 65:35 was maintained in all the containers and heat processed to equal lethality in an over pressure autoclave with the facility to record the time,temperature data, F0 value and cook value. The process time was calculated by using formula method. The processing in 16 20 cm and 17 30 cm retortable pouch resulted in 35.67% and 56.56% reduction in process time compared with 301 206 and 401 411 cans, respectively, with equal pack weight. The amino acid content did not vary considerably in both containers. In the canned samples the reduction of sulfhydryl content was 50.54% more when compared with the pouched product. Products packed in pouches were found to be superior to canned products with regard to sensory and textural attributes such as colour, firmness, hardness, chewiness, and overall acceptability. [source]

    Changes in carotenoid, physicochemical and sensory values of deep-fried carrot chips during storage

    Ahmad Sulaeman
    Summary Deep-fried carrot chips were packaged in layered film (metallized polyester and linear low-density polyethylene) pouches under a partial vacuum of <1% O2 concentration. Packages containing chips were stored in dark chambers at three conditions: 0,1 C, 94,98% relative humidity (r.h.) (A); 22,23 C, 31,45% r.h. (B); and 29,31 C, 89,93% r.h. (C) for 0,5 months. Retention of , - and , -carotene content and vitamin A activity were >82% over 5 months for all conditions. Colour values (L, a, b) were unchanged over 5 months for A and B, but decreased gradually (P < 0.05) for C. No changes in moisture content, fat content, water activity, texture values and sensory values were observed over time for A and B, but changed (P < 0.05) for C. No sensory differences were observed by condition or time in colour. Carrot chips, packaged in partially vacuumed opaque pouches, can be stored for at least 5 months at 0,1 C, 94,98% r.h. or 22,23 C, 31,45% r.h. [source]

    Processing, mechanical properties, and interfacial bonding of a thermoplastic core-foam/composite-skin sandwich panel,

    S. Pappad
    Abstract In this work, a thermoplastic sandwich panel was designed, produced, and tested for use in insulating walls of containers for food transportation. A sandwich construction comprising a poly(ethylene terephthalate) core and polypropylene/glass fiber skins was evaluated as possible replacement of systems consisting of polyurethane foam in combination with unsaturated polyester glass-reinforced skins that are currently used for the manufacture of these structures. Factors were taken into account to satisfy the simultaneous need of thermal insulation and adequate mechanical properties that are required for the production of large flat panels 100-mm thick. The influences of different manufacturing processes and skin-core adhesion on the mechanical properties of this thermoplastic sandwich were investigated and are discussed in the text. 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:137,145, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20186 [source]

    Recycling of the solid residue obtained from the pyrolysis of fiberglass polyester sheet molding compound

    A. Torres
    Abstract This paper is part of a project devoted to study the pyrolysis process as an alternative for recycling sheet molding compound (SMC), a thermoset composite of polyester and fiberglass. A standard SMC was pyrolyzed under nitrogen, at 300, 400, 500, 600, and 700C, for 30 min in a 3.5-dm3 autoclave. This paper focuses on the possibilities of reusing the fibers and fillers contained in the solid residue obtained from SMC pyrolysis. The solid pyrolysis residue was recycled in another thermoset composite, bulk molding compound (BMC), of polyester and fiberglass. The mechanical properties of BMCs prepared with different proportions of the solid residue (fiber + CaCO3 filler) from SMC pyrolysis were compared with those of BMCs prepared with the same proportions of virgin fiber and CaCO3. In summary, pyrolysis can be an appropriate technique for recycling SMC, with 500C, the most suitable temperature for the process. Solid residues of 75 wt%, composed of 65 wt% of powdery material (mainly CaCO3) and 35 wt% of fiberglass, were obtained. Such solids can be recycled in a proportion of 6 wt% in BMC to replace virgin filler and fiberglass, with no detrimental effect on the BMC mechanical properties. 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:141,149, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20150 [source]

    Adaptive control for edge alignment in polyester film processing

    Chang-Chiun Huang
    Abstract Edge alignment of polyester (PET) films is important for achieving product quality and processing speed in winding, coating, drying, and other processes. The edge alignment can be achieved by lateral deflection control, provided that the film tension and transport speed are even at desired values. This article aims to correct the lateral deflection of films by designing robust controllers to swivel the guiding rollers and to maintain even tension and speed at target levels. The self-tuning neuro-proportional integral derivative controller and adaptive high-gain output feedback controller are adopted to guide the lateral deflection so that the film aligns at the desired position. A control scheme, neuron controller by associative learning, is used for maintaining tension and speed control. These strategies are applied to a simplified PET film processing system. The experimental results demonstrate that in our setup, the control schemes can effectively alleviate not only the lateral deflection but also the tension and speed fluctuation at target levels. 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:153,162, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20096 [source]

    Application of hydrophilic finished of synthetic fabrics coated with CMC/acrylic acid cured by electron beam irradiation in the removal of metal cations from aqueous solutions

    Sayeda M. Ibrahim
    Abstract Modified textile fabrics were used to remove Cu+2 and Cr+3 ions from aqueous solutions. For this purpose, modified Nylon-6, polyester woven and knitted fabrics were prepared by coating the surface with a thin layer of aqueous solution of carboxymethyl cellulose (CMC) and acrylic acid (AAc) of thickness 25 ,m. Radiation crosslinking of the coated layer was carried out by electron beam irradiation with a constant dose of 30 kGy. Morphology of the coated fabrics was examined by scanning electron microscope (SEM) which indicated the compatibility between the coated layer and fabrics. Properties attributed to the hydrophilicity, especially water uptake and weight loss before and after several washing cycles were followed up. The effect of AAc concentration on the hydrophilic properties of the coated fabrics was studied. A considerable enhancement in water uptake has been attained on increasing AAc content in solution in case of nylon-6 followed by polyester woven followed by polyester knitted fabrics. The performances of the modified textile fabrics were evaluated for the recovery of Cu+2 and Cr+3 from aqueous solution. The metal ion absorption efficiency of the modified textile fabrics was measured using UV Spectrophotometer analysis and EDX. Parameters affecting the efficiency of these textile fabrics in the removal of metal ions from aqueous solution namely, concentration of AAc and the immersion time were studied. It was found that there was a marked increase in the recovery of metal ions on increasing both immersion time and concentration of AAc. This study evidences that the modified textile fabrics can be used for the purpose of removal of some heavy metals such as Cu and Cr. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agent

    Luigi Torre
    Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Broadband dielectric spectroscopy on the molecular dynamics in different generations of hyperbranched polyester

    Gamal Turky
    Abstract Dielectric spectroscopy (10,2 Hz to 106 Hz) was employed to investigate the molecular dynamics of hyperbranched polyesters where the number of the generation is systematically varied from 2 to 5. As a first result, the dielectric properties depends strongly on the generation of the hyperbranched polymers. For higher generations (3 to 5) at temperatures below Tg two relaxation processes are observed, a ,-process at lower temperatures and a ,-process at higher ones. The apparent activation energies are around 100 kJ/mol which seems to be too high for truly localized processes. For the Generation 2, only the ,-process is observed. For all investigated polymers the dielectric ,-relaxation could not be observed because of strong conductivity effects. Therefore, the conductivity is systematically analyzed which obeys the peculiarities found to be characteristic for semiconducting disordered materials. Especially, the Barton/Nakajima/Namikawa relationship is found to be valid. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Dyeability improvement of polyester pretreated with some alkoxides

    A. Bendak
    Abstract The influence of some alkoxides in alcoholic media, having various dielectric constants, on the physical and mechanical properties was thoroughly studied in a previous work to attain silk-like polyester fibers. In this investigation, the dyeability behavior of this silk-like polyester is tried. Both immersion and padding techniques are applied in the treatment. The dyeability of the pretreated polyester fabric with disperse dyes shows some progressive improvements with lowering the dyeing temperature and/or decreasing the time of dyeing attained. Ethoxide is found to be more effective in enhancing the dyeability of polyester fabric than either methoxide or propoxide. Dyeing of the pretreated polyester fabric at the boil without using carriers or conducting high temperature/high pressure dyeing is also possible. Washing and crocking fastness are relatively enhanced. Physicochemical investigations of the dyeing process and a mathematical analysis for evenness are given. A decrease in the half dyeing time and an increase in the rate of dyeing of the pretreated polyester as compared with the untreated one are noticed. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Thermal energy transport within porous polymer materials: Effects of fiber characteristics

    Huijun Wu
    Abstract A theoretical model integrating the radiative and conductive heat transfer is presented and applied to evaluate the thermal energy transport within porous polymer materials. The model was first validated by comparing the computed thermal energy flux with the experimental measurements of two porous polymer materials made of wool and polyester. The model was then used to predict the effects of the polymer fiber characteristics (viz. fiber fractional volume, fiber emissivity, fiber radius, and fiber thermal conductivity) on the thermal energy flux within the porous polymer materials. It was found that decreasing fiber radius would significantly reduce the total thermal energy flux through the porous polymer materials, whereas increasing fibre emissivity or decreasing the thermal conductivity would cause a just slight reduction of the total thermal energy flux. The fiber fractional volume had a significant influence on the thermal energy flux, and thereby the fiber fractional volume can be optimized in view of improving the thermal insulating performance of the porous polymer materials. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    Biodegradable poly(vinyl alcohol)- graft - poly(,-caprolactone) comb-like polyester: Microwave synthesis and its characterization

    Zhaoju Yu
    Abstract Poly(vinyl alcohol)-initiated microwave-assisted ring opening polymerization of ,-caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)- graft -poly(,-caprolactone) (PVA- g -PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3,24 and 0.35,0.89, respectively. The resultant comb-like PVA- g -PCL copolymers were confirmed by means of FTIR, 1H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA- g -PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973,3979, 2007 [source]

    Cation exchange finishing of nonwoven polyester with polycarboxylic acids and cyclodextrins

    L. Ducoroy
    Abstract We describe a chemical method for the finishing of polyester nonwoven fabrics that aimed to obtain ion exchange textiles. This approach was based on the use of polycarboxylic acids (PCA) and cyclodextrins as carbohydrate compounds and finishing agents, respectively. It was observed that the reaction between these reactants yielded a crosslinked polymer that was physically anchored onto the fibers. This polymer can be considered as a resin issued from the esterification between the COOH groups of the PCA with the OH groups of the carbohydrate. As the esterification reaction was not complete, many free carboxylic groups remained on the surface of the coating polymer. This feature offered the ion exchange properties to the textile support. In this article, we described the pad-dry-cure process and showed the influence of the curing parameters (time and temperature), the nature, and the concentration of the components and the pH of the impregnating bath. The grafting rate (in wt %) and the ion exchange capacity (IEC) were observed in parallel. First, it was observed that the best IEC capacity (that could reach 1 mmol/g) was obtained when an ideal compromise was applied between time and temperature of curing. We also evidenced that IEC depended on the nature and on the concentration of the PCA (chosen among citric acid, 1,2,3,4-butanetetracarboxylic acid, and polyacrylic acid) and on the pH of the impregnating bath. Finally, it was observed that cyclodextrins were more appropriate than starch as finishing coreactants. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3730,3738, 2007 [source]

    Artificial polymerases and molecular chaperones

    Akira Harada
    Abstract Cyclodextrins (CDs) were found to initiate polymerization of lactone to give polyesters with a CD ring at the end of the polymer chain in high yields only by mixing and heating with monomer without cocatalysts or solvents. CD-tethered polyester propagates with the formation of poly-pseudorotaxane, which is necessary to initiate further polymerization. CDs threaded onto the polymer chain are also essential for maintaining the propagating state of the polyester. By polymerizing with CD, switching the activity of the polymerization by photoisomerization was demonstrated. This polymerization system showed specific substrate recognition, releasing the products from the active site. By using the above polymerization system, ,-CD nanospheres which initiates the oligomerization of lactone were constructed. It was found that the formation of poly-pseudorotaxane on the nanosphere enabled further polymerization activity for lactone. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4469,4481, 2009 [source]

    Mapping the characteristics of the radical ring-opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyester

    Peter Plikk
    Abstract Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4587,4601, 2009 [source]

    Degradable star polymers with high "click" functionality

    James T. Wiltshire
    Abstract Degradable polyester-based star polymers with a high level of functionality in the arms were synthesized via the "arms first" approach using an acetylene-functional block copolymer macroinitiator. This was achieved by using 2-hydroxyethyl 2,-methyl-2,-bromopropionate to initiate the ring-opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end-group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4,-bioxepanyl-7,7,-dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl-protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide-functionalized linear polystyrene via a copper (I)-catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with "brush-like" arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485,1498, 2009 [source]

    Anionic alternating copolymerization of 3,4-dihydrocoumarin and glycidyl ethers: A new approach to polyester synthesis

    Kazuya Uenishi
    Abstract Anionic copolymerizations of 3,4-dihydrocoumarin (DHCM) and a series of glycidyl ethers (n -butyl glycidyl ether, tert -butyl glycidyl ether, and allyl glycidyl ether) with 2-ethyl-4-methylimidazole as an initiator proceeded in a 1:1 alternating manner to give the corresponding polyesters, whose structures were confirmed by spectroscopic analyses and reductive scission of the ester bonds in the main chain with lithium aluminum hydride, followed by detailed analyses of the resulting fragments. The polyester obtained by the copolymerization of DHCM and allyl glycidyl ether inherited the allyl groups in the side chain, whose applicability to chemical modifications of the polyester was successfully demonstrated by a platinum-catalyzed hydrosilylation reaction. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4092,4102, 2008 [source]

    Dendrimer-star polymer and block copolymer prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization with dendritic chain transfer agent

    Chun-Yan Hong
    Abstract A new reversible addition-fragmentation chain transfer (RAFT) agent, dendritic polyester with 16 dithiobenzoate terminal groups, was prepared and used in the RAFT polymerization of styrene (St) to produce star polystyrene (PSt) with a dendrimer core. It was found that this polymerization was of living characters, the molecular weight of the dendrimer-star polymers could be controlled and the polydispersities were narrow. The dendrimer-star block copolymers of St and methyl acrylate (MA) were also prepared by the successive RAFT polymerization using the dendrimer-star PSt as macro chain transfer agent. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6379,6393, 2005 [source]

    Stereocontrolled anionic alternating copolymerization of ethylphenylketene with benzaldehyde by a bisoxazoline ligand

    Daisuke Nagai
    Abstract Anionic copolymerization of ethylphenylketene with benzaldehyde with butyllithium or diethylzinc as the initiator proceeded in a perfect 1:1 alternating manner to produce the corresponding polyester, whose repeating unit had two adjacent chiral centers. The relative stereochemistry between these two chiral centers was successfully controlled by the addition of (S,S)-(-)-2,2,-isopropylidenebis(4- tert -butyl-2-oxazoline), producing the corresponding polyester that had excellent diastereoselectivity (erythro -configuration : threo -configuration = 4:96). The diastereomeric ratio was determined by high-performance liquid chromatography analysis of the diol, which was obtained by reductive degradation of the polyester while maintaining the configuration of the repeating unit. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5384,5388, 2004 [source]

    Synthesis and characterization of multiblock copolymers based on L -lactic acid, citric acid, and poly(ethylene glycol)

    Fanglian Yao
    Abstract Because poly(L -lactic acid) (PLLA) is a biodegradable polyester with low immunogenicity and good biocompatibility, it is used as a biomaterial. However, hydrophobic PLLA does not have any reactive groups. Thus, its application is limited. To increase the hydrophilicity of PLLA and accelerate its degradation rate, functionalized pendant groups and blocks were introduced through copolymerization with citric acid and poly(ethylene glycol) (PEG), respectively. This article describes the synthesis and characterization of poly(L -lactic- co -citric acid) (PLCA)-PLLA and PLCA-PEG multiblock copolymers. The results indicated that the hydrolysis rate was enhanced, and the hydrophilicity was improved because of the incorporation of carboxyl groups in PLCA-PLLA. The joining of the PEG block led to improved hydrophilicity of PLCA, and the degradation rate of PLCA-PEG accelerated as compared with that of PLCA-PLLA. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2073,2081, 2003 [source]

    Alternating copolymerization of propylene oxide with carbon monoxide catalyzed by Co complex and Co/Ru complexes

    Daisuke Takeuchi
    Abstract Co2(CO)8 catalyzes the ring-opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8,3-hydroxypyridine catalyst, show the following structure [CH2CH(CH3)OCO]n. The Co2(CO)8,phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring-opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N,,N,-tetramethylethylenediamine, enhance the Co complex-catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl,cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl,cobalt bond. Co2(CO)8Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the RuCo mixed-metal cluster formed in the reaction mixture. 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530,4537, 2002 [source]