Showing papers in "Journal of Polymer Science Part A in 2005"
TL;DR: A review of the progress made in reversible addition-fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerization can be found in this article.
Abstract: Among the living radical polymerization techniques, reversible addition–fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations appear to be the most versatile processes in terms of the reaction conditions, the variety of monomers for which polymerization can be controlled, tolerance to functionalities, and the range of polymeric architectures that can be produced. This review highlights the progress made in RAFT/MADIX polymerization since the first report in 1998. It addresses, in turn, the mechanism and kinetics of the process, examines the various components of the system, including the synthesis paths of the thiocarbonyl-thio compounds used as chain-transfer agents, and the conditions of polymerization, and gives an account of the wide range of monomers that have been successfully polymerized to date, as well as the various polymeric architectures that have been produced. In the last section, this review describes the future challenges that the process will face and shows its opening to a wider scientific community as a synthetic tool for the production of functional macromolecules and materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:5347–5393, 2005
1,098 citations
TL;DR: In this paper, the authors discuss various strategies for their synthesis and the unique properties arising from their regular multibranched structure and highlight some recent advances in the application of cylindrical polymer brushes.
Abstract: In recent years, research on cylindrical polymer brushes (or molecular bottlebrushes) has received significant attention. In this article, we discuss various strategies for their synthesis and the unique properties arising from their regular multibranched structure. Some recent advances in the application of cylindrical polymer brushes are highlighted. Amphiphilic core– shell cylindrical polymer brushes, for example, have been successfully used as single molecular templates for inorganic nanoparticle formation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3461–3481, 2005
554 citations
TL;DR: In this paper, the authors described fifteen years of research on hyperbranched polymers in the group of Brigitte Voit, with a focus first on hyper-correlated polyester synthesis and then on the addition and cycloaddition reactions used for the preparation of the hyper-branched structure.
Abstract: Fifteen years of research on hyperbranched polymers in the group of Brigitte Voit are described, with a focus first on hyperbranched polyester synthesis and then on the addition and cycloaddition reactions used for the preparation of the hyperbranched structure. The characterization of structural details and bulk, solution, and thin-film properties is highlighted, and steps toward the elucidation of a general property profile of hyperbranched polymers are discussed. Some effects of hyperbranched polymers in reactive formulations and blends and in thin films are addressed that can lead to applications in coatings, as additives, and in microelectronics or sensorics. The great progress possible in the last years is shown, but open questions and unsolved problems are also pointed out. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2679–2699, 2005
366 citations
TL;DR: In this paper, a set of magnetic polyglycidyl methacrylate (PGMA) particles with functional amino groups were prepared by a process involving: (1) preparation of parent monodisperse PGMA particles by dispersion polymerization method, (2) chemical modification of the PGMA particle with ethylenediamine (EDA) to yield amino groups, and (3) impregnation of iron ions (Fe2+ and Fe3+) inside the particles and subsequently precipitating them with ammonium hydroxide to form magnetite (
Abstract: Micron-sized monodisperse superparamagnetic polyglycidyl methacrylate (PGMA) particles with functional amino groups were prepared by a process involving: (1) preparation of parent monodisperse PGMA particles by the dispersion polymerization method, (2) chemical modification of the PGMA particles with ethylenediamine (EDA) to yield amino groups, and (3) impregnation of iron ions (Fe2+ and Fe3+) inside the particles and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe3O4) nanoparticles within the polymer particles. The resultant magnetic PGMA particles with amino groups were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and vibrating sample magnetometry (VSM). SEM showed that the magnetic particles had an average size of 2.6 mu m and were highly monodisperse. TEM demonstrated that the magnetite nanoparticles distributed evenly within the polymer particles. The existence of amino groups in the magnetic polymer particles was confirmed by FTIR. XRD indicated that the magnetic nanoparticles within the polymer were pure Fe3O4 with a spinel structure. VSM results showed that the magnetic polymer particles were superparamagnetic, and saturation magnetization was found to be 16.3 emu/g. The Fe3O4 content of the magnetic particles was 24.3% based on total weight. (c) 2005 Wiley Periodicals, Inc.
328 citations
TL;DR: In this paper, a chitosan-based polymeric network was synthesized by crosslinking with a naturally occurring cross-linking agent (genipin) and the results showed that the crosslink reactions were pH-dependent.
Abstract: In this study, a novel chitosan-based polymeric network was synthesized by crosslinking with a naturally occurring crosslinking agent—genipin. The results showed that the crosslinking reactions were pH-dependent. Under basic conditions, genipin underwent a ring-opening polymerization prior to crosslinking with chitosan. The crosslink bridges consisted of polymerized genipin macromers or oligomers (7 ∼ 88 monomer units). This ring-opening polymerization of genipin was initiated by extracting proton from the hydroxyl groups at C-1 of deoxyloganin aglycone, followed by opening the dihydropyran ring to conduct an aldol condensation. At neutral and acidic conditions, genipin reacted with primary amino groups on chitosan to form heterocyclic amines. The heterocyclic amines were further associated to form crosslinked networks with short chains of dimmer, trimer, and tetramer bridges. An accompanied reaction of nucleophilic substitution of the ester group on genipin by the primary amine group on chitosan would occur in the presence of an acid catalysis. The extent in which chitosan gels crosslinked with genipin was significantly dependent on the crosslinking pH values: 39.9 ± 3.8% at pH 5.0, 96.0 ± 1.9% at pH 7.4, 45.4 ± 1.8% at pH 9.0, and 1.4 ± 1.0% at pH 13.6 (n = 5, p < 0.05). Owing to the different crosslinking extents and different chain lengths of crosslink bridges, the genipin-crosslinked chitosan gels showed significant difference in their swelling capability and their resistance against enzymatic hydrolysis, depending on the pH conditions for crosslinking. These results indicated a direct relationship between the mode of crosslinking reaction, and the swelling and enzymatic hydrolysis properties of the genipin-crosslinked chitosan gels. The ring-opening polymerization of genipin and the pH-dependent crosslinking reactions may provide a novel way for the preparation and exploitation of chitosan-based gels for biomedical applications. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1985–2000, 2005
266 citations
TL;DR: Experimental methods used in high-vacuum anionic polymerization are described in detail, with extensive illustrations to demonstrate proper procedures and techniques as mentioned in this paper, and a primary emphasis is placed on safety.
Abstract: Experimental methods used in high-vacuum anionic polymerization are described in detail, with extensive illustrations to demonstrate proper procedures and techniques. These descriptions include construction and operation of the vacuum line, handling purification chemicals, ampulization techniques, short-path distillations, initiator synthesis, polymerization procedures, and linking reactions using chlorosilanes. A primary emphasis is placed on safety. We believe that this review of these methods will be useful to scientists working in the field of anionic polymerization and may also benefit other researchers in performing tasks requiring ultra-high-purity reaction conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6179–6222, 2005
262 citations
TL;DR: This article focuses on a special class of biologi cal-synthetic hybrids that are obtained by site-selective conjugation of a protein or peptide and a synthetic polymer, and the properties and potential applications of these materials are discussed.
Abstract: Although biopolymers and synthetic polymers share many common features, each of these two classes of materials is also characterized by a distinct and very specific set of advantages and disadvantages. Combining biopolymer elements with synthetic polymers into a single macromolecular conjugate is an interesting strategy for synergetically merging the properties of the individual components and overcoming some of their limitations. This article focuses on a special class of biologi cal-synthetic hybrids that are obtained by site-selective conjugation of a protein or peptide and a synthetic polymer. The first part of the article gives an overview of the different liquid-phase and solid-phase techniques that have been developed for the synthesis of well-defined, that is, site-selectively conjugated, synthetic polymer-protein hybrids. In the second part, the properties and potential applications of these materials are discussed. The conjugation of biological and synthetic macromole cules allows the modulation of protein binding and recognition properties and is a powerful strategy for mediating the self-assembly of synthetic polymers. Synthetic polymer-protein hybrids are already used as medicines and show significant promise for bio-analytical applications and bio-separations. © 2004 Wiley Periodicals, Inc.
253 citations
TL;DR: An appropriate definition of metallosupramolecular coordination polymer is offered, and the relationship between the polymer length, binding constant, and concentration is clarified in this article, where the possibility of influencing the binding constant with chelating ligands is discussed on the basis of examples of different Zn 2+ complexes and their respective binding constants.
Abstract: An appropriate definition of metallosupramolecular coordination polymer is offered, and the relationship between the polymer length, binding constant, and concentration is clarified. The possibility of influencing the binding constant with chelating ligands is discussed on the basis of examples of different Zn 2+ complexes and their respective binding constants. In the main part, coordination polymers constructed by a supramolecular approach from different metal ions and pyridine-ligand systems are highlighted, and their applications as functional materials for artificial membrane and enzyme models, responsive gels, light-harvesting systems, and organic light-emitting diodes are discussed on the basis of individual examples.
251 citations
TL;DR: In this paper, 3-furfuryl-3,4-dihydro-2H-1,3-benzoxazine (P-FBz) and bis(3-furmuryl)-3, 4-Dihydron (2H)-1, 3-Benzoxazinylisopropane (BPA-FBZ) are derived using furfurylamine as a raw material.
Abstract: Furan-containing benzoxazine monomers, 3-furfuryl-3,4-dihydro-2H-1,3-benzoxazine (P-FBz) and bis(3-furfuryl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (BPA-FBz), were prepared using furfurylamine as a raw material. The chemical structures of P-FBz and BPA-FBz were characterized with FTIR, 1 H NMR, elemental analysis, and mass spectrometry. Formation of furfurylamine Mannich bridge networks in the polymerizations of P-FBz and BPA-FBz increased the cross-linking densities and thermal stability of the resulting polybenzoxazines. P-FBz- and BPA-FBz-based polymers also exhibited high glass transition temperatures above 300 °C, high char yields, and low flammability with limited oxygen index values of 31. The dielectric (D k = 3.21-3.39) and mechanical properties (high storage modulus of 3.0-3.9 GPa and low coefficient of thermal expansion of 37.7-45.4 ppm) of the P-FBz-and BPA-FBz-based polymers were superior or comparable to other polybenzoxazines.
238 citations
TL;DR: In this paper, a thermally induced shape-memory effect was found in polymeric networks under photocuring with or without an initiator, and shape memory properties such as the strain fixity and strain recovery rate were quantified with cyclic thermomechanical tensile experiments for different maximum elongations.
Abstract: Polymer networks showing a thermally induced shape-memory effect were prepared through the crosslinking of oligo(ϵ-caprolactone)dimethacrylates under photocuring with or without an initiator. The influence of the molecular weight of the oligo(ϵ-caprolactone)dimethacrylates and the initiator concentration on the macroscopic properties of the polymer networks was investigated. The isothermal and nonisothermal crystallization behavior of the polymer networks was evaluated as a basic principle of the functionalization process. Shape-memory properties such as the strain fixity and strain recovery rate were quantified with cyclic thermomechanical tensile experiments for different maximum elongations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1369–1381, 2005
210 citations
TL;DR: In this paper, a series of imidazolium-based ionic liquid monomers and their corresponding polymers (poly(ionic liquid)s) were synthesized, and their CO2 sorption was studied.
Abstract: A series of imidazolium-based ionic liquid monomers and their corresponding polymers (poly(ionic liquid)s) were synthesized, and their CO2 sorption was studied. The poly(ionic liquid)s had enhanced CO2 sorption capacities and fast sorption/desorption rates compared with room temperature ionic liquids. The effects of the chemical structures, including the types of anion, cation, and backbone of the poly(ionic liquid)s on their CO2 sorption have been discussed. In contrast to room temperature ionic liquids, the polymer with PF anions had the highest CO2-sorption capacity, while those with BF or Tf2N− anions had the same capacities. The CO2 sorption and desorption of the polymers were fast and reversible, and the sorption was selective over H2, N2, and O2. The measured Henry's constants of P[VBBI][BF4] and P[MABI][BF4] were 26.0 bar and 37.7 bar, which were lower than those of similar room temperature ionic liquids. The preliminary study of the mechanism indicated that the CO2 sorption of the polymer particles was more absorption (the bulk) but less adsorption (the surface). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5477–5489, 2005
TL;DR: In this article, a multiple aromatic ether linked phthalonitrile was synthesized and characterized, which exhibited good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long-term oxidative stability.
Abstract: A multiple aromatic ether linked phthalonitrile was synthesized and characterized. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A with 4,4'-difluorobenzophenone in the presence of K 2 CO 3 as the base in an N,N-dimethylformamide/toluene solvent mixture, followed by end capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. The monomer properties were compared to those of the known resin 2,2-bis[4-(3,4-dicyanophenoxylphenyl]propane after being cured in the presence of bis[4-(4-aminophenoxy)-phenyllsulfone. Rheometric measurements and thermogravimetric analysis showed that the oligomeric phthalonitrile resin maintained good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long-term oxidative stability. The ether-linked phthalonitrile resin absorbed less than 2.5% water by weight after exposure to an aqueous environment for extended periods.
TL;DR: Ionic liquids are organic salts that are liquid at ambient temperatures, preferably at room temperature, and they are nonvolatile, thermally and chemically stable, highly polar liquids that dissolve many organic, inorganic, and metallo-organic compounds as mentioned in this paper.
Abstract: Ionic liquids are organic salts that are liquid at ambient temperatures, preferably at room temperature. They are nonvolatile, thermally and chemically stable, highly polar liquids that dissolve many organic, inorganic, and metallo-organic compounds. Many combinations of organic cations with different counterions are already known, and the properties of ionic liquids may be adjusted by the proper selection of the cation and counterion. In the last decade, there has been increasing interest in using ionic liquids as solvents for chemical reactions. The interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction. In recent years, ionic liquids have also attracted the attention of polymer chemists. Although the research on using ionic liquids in polymer systems is still in its infancy, several interesting possibilities have already emerged. Ionic liquids are used as solvents for polymerization processes, and in several systems they indeed show some advantages. In radical polymerization, the kp/kt ratio (where kp is the rate constant of propagation and kt is the rate constant of termination) is higher than in organic media, and thus better control of the process can be achieved. Ionic liquids, as electrolytes, have also attracted the attention of researchers in the fields of electrochemical polymerization and the synthesis of conducting polymers. Finally, the blending of ionic liquids with polymers may lead to the development of new materials (ionic liquids may act as plasticizers, electrolytes dispersed in polymer matrices, or even porogens). In this article, the new developments in these fields are briefly discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4675–4683, 2005
TL;DR: The reversible addition-fragmentation chain transfer (RAFT) polymerization technique has been employed to synthesize linear α,ω -telechelic polymers with either hydroxyl or carboxyl end groups as mentioned in this paper.
Abstract: The reversible addition–fragmentation chain transfer (RAFT) polymerization technique has been employed to synthesize linear α,ω -telechelic polymers with either hydroxyl or carboxyl end groups. Methyl methacrylate, butyl methacrylate, and butyl acrylate were polymerized with RAFT polymerization. The polymerizations exhibited the usual characteristics of living processes. Telechelic polymethacrylates were obtained from a hydroxyl monofunctional RAFT polymer with a two-step chain-end modification procedure of the dithioester end group. The procedure consisted of an aminolysis followed by a Michael addition on the resulting thiol. The different steps of the procedure were followed by detailed analysis. It was found that this route was always accompanied by side reactions, resulting in disulfides and hydrogen-terminated polymer chains as side products next to the hydroxyl-terminated telechelic polymers. Telechelic poly(butyl acrylates) with carboxyl end groups were produced in a single step procedure with difunctional trithiocarbonates as RAFT agents. The high yield in terms of end group functionality was confirmed by a new critical-liquid-chromatography method, in which the polymers were separated based on acid-functionality and by mass spectrometry analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 959–973, 2005
TL;DR: In this article, the use of functional block copolymers for the localization of metal species, especially nanoparticles, on the nanometer scale through blockcopolymer phase segregation is discussed.
Abstract: The combination of metals and polymers in hybrid materials is a research area of great current interest. A number of methods for controlling the positioning of metallic species within polymer matrices on the nanometer scale have been developed. This highlight focuses on the use of functional block copolymers for the localization of metal species, especially nanoparticles, on the nanometer scale through block copolymer phase segregation. Research from the author's group on the use of alkyne-functional block copolymers for the preparation of cobalt-containing materials is discussed in this context.
TL;DR: In this article, the photocuring kinetics of UV-initiated free-radical photopolymerizations of acrylate systems with and without silica nanoparticles were determined for hybrid organic-inorganic nanocomposite systems.
Abstract: We used photodifferential scanning calorimetry to investigate the photocuring kinetics of UV-initiated free-radical photopolymerizations of acrylate systems with and without silica nanoparticles. Two kinetics parameters-the rate constant (k) and the order of the initiation reaction (m)-were determined for hybrid organic-inorganic nanocomposite systems containing different amounts of added silica nanoparticles (0-20 wt %) and at different isothermal temperatures (30-100 °C) using an autocatalytic kinetics model. The kinetic analysis revealed that the silica nanoparticles apparently accelerate the cure reaction and cure rate of the UV-curable acrylate system, most probably due to the synergistic effect of silica nanoparticles during the photopolymerization process. However, a slight decrease in polymerization reactivity that occurred when the silica content increased beyond 15 wt % was attributed to aggregation between silica nanoparticles. We also observed that the addition of silica nanoparticles lowered the activation energy for the UV-curable acrylate system, and that the collision factor for the system with silica nanoparticles was higher than that obtained for the system without silica nanoparticles, indicating that the reactivity of the former was greater than that of the latter.
TL;DR: In this paper, the evolution of the bromine end functionality during the bulk atom transfer radical polymerization (ATRP) of styrene [in the presence of the catalyst CuBr/4,4'-di-(5-nonyl)-2,2'-bipyridine] was monitored with 600MHz 1 H NMR.
Abstract: The evolution of the bromine end functionality during the bulk atom transfer radical polymerization (ATRP) of styrene [in the presence of the catalyst CuBr/4,4'-di-(5-nonyl)-2,2'-bipyridine] was monitored with 600-MHz 1 H NMR. A decrease in the functionality versus the conversion was observed. The loss of functionality was especially significant at very high conversions (>90%). The experimental data were compared with a kinetic model of styrene ATRP. The latter indicated that the loss of chain-end functionality was partly due to bimolecular terminations but was mainly due to β-H elimination reactions induced by the copper(II) deactivator. These elimination reactions, which occurred later in the reaction, did not significantly affect the polymer molecular weights and the polydispersity. Therefore, a linear evolution of the molecular weights and low-polydispersity polymers were still observed, despite a loss of functionality. Understanding these side reactions helped in the selection of the proper conditions for reducing the contribution of the elimination process and for preparing well-defined polystyrene (number-average molecular weight ∼10,000 g mol -1 ; weight-average molecular weight/number-average molecular weight ∼1.1) with a high functionality (92%).
TL;DR: In this paper, a series of waterborne polyurethane (WBPU)/multiwalled carbon nanotube (CNT) and WBPU/nitric acid treated multi-walled CNT composites were compared.
Abstract: A series of waterborne polyurethane (WBPU)/multiwalled carbon nanotube (CNT) and WBPU/nitric acid treated multiwalled carbon nanotube (A-CNT) composites were prepared by in situ polymerization in an aqueous medium. The optimum nitric acid treatment time was about 0.5 h. The effects of the CNT and A-CNT contents on the dynamic mechanical thermal properties, mechanical properties, hardness, electrical conductivity, and antistatic properties of the two kinds of composites were compared. The tensile strength and modulus, the glass-transition temperatures of the soft and hard segments (Tgs and Tgh, respectively), and ΔTg (Tgh − Tgs) of WBPU for both composites increased with increasing CNT and A-CNT contents. However, these properties of the WBPU/A-CNT composites were higher than those of the WBPU/CNT composites with the same CNT content. The electrical conductivities of the WBPU/CNT1.5 and WBPU/A-CNT1.5 composites containing 1.5 wt % CNTs (8.0 × 10−4 and 1.1 × 10−3 S/cm) were nearly 8 and 9 orders of magnitude higher than that of WBPU (2.5 × 10−12 S/cm), respectively. The half-life of the electrostatic charge (τ1/2) values of the WBPU/CNT0.1 and WBPU/A-CNT0.1 composites containing 0.1 wt % CNTs were below 10 s, and the composites had good antistatic properties. From these results, A-CNT was found to be a better reinforcer than CNT. These results suggest that WBPU/A-CNT composites prepared by in situ polymerization have high potential as new materials for waterborne coatings with good physical, antistatic, and conductive properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3973–3985, 2005
TL;DR: In this paper, the alternating copolymerization of CO2 and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated.
Abstract: The alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe (1a)–tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a–Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain-transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005
TL;DR: Curcumin, a naturally occurring, intensely yellow dye extracted from the spice turmeric, is an efficient photosensitizer for diaryliodonium salt photoinitiators at wavelengths ranging from 340 to 535 nm.
Abstract: Curcumin, a naturally occurring, intensely yellow dye extracted from the spice turmeric, is an efficient photosensitizer for diaryliodonium salt photoinitiators at wavelengths ranging from 340 to 535 nm. With curcumin as a photosensitizer, it is possible to carry out the cationic photopolymerization of a wide variety of epoxide, oxetane, and vinyl monomers with long-wavelength UV and visible light. An example of the photopolymerization of an epoxide monomer with ambient solar irradiation is provided. Several other curcumin analogues were synthesized, and their use as photosensitizers is examined. With such photosensitizers, the range of spectral sensitivity can be extended well into the visible region of the electromagnetic spectrum. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5217–5231, 2005
TL;DR: In this article, two ionic liquid monomers, 1-(4-vinylbenzyl)-3-butyl imidazolium tetrafluoroborate (VBIT) and 1-(1.5-3)-butyl ionic hexafluorophosphate (VBIH), were synthesized through the quaternization of N-butylimidazole with 4-vineldazole and a subsequent anion-exchange reaction with sodium tetraflamide or potassium hexafloorophosphates.
Abstract: Polymeric forms of ionic liquids have many potential applications because of their high thermal stability and ionic nature. Two ionic liquid monomers, 1-(4-vinylbenzyl)-3-butyl imidazolium tetrafluoroborate (VBIT) and 1-(4-vinylbenzyl)-3- butyl imidazolium hexafluorophosphate (VBIH), were synthesized through the quaternization of N-butylimidazole with 4-vinylbenzylchloride and a subsequent anion- exchange reaction with sodium tetrafluoroborate or potassium hexafluorophosphate. Copper-mediated atom transfer radical polymerization was used to polymerize VBIT and VBIH. The effects of various initiator/catalyst systems, monomer concentrations, solvent polarities, and reaction temperatures on the polymerization were examined. The polymerization was well controlled and exhibited living characteristics when CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine or CuBr/2,2′-bipyridine was used as the catalyst and ethyl 2-bromoisobutyrate was used as the initiator. Characterizations by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction showed that the resulting VBIT polymer, poly[1-(4-vinylbenzyl)-3-butyl imidazolium tetrafluoroborate] (PVBIT), was amorphous and had excellent thermal stability, with a glass-transition temperature of 84 °C. The polymerized ionic liquids could absorb CO2 as ionic liquids: PVBIT absorbed 0.30% (w/w) CO2 at room temperature and 0.78 atm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1432–1443, 2005
TL;DR: In this article, the authors provide useful insights into the important kinetic parameters that control the rate of polymerization and the evolution of the molecular weight distribution (MWD) with conversion.
Abstract: Living radical polymerization has allowed complex polymer architectures to be synthesized in bulk, solution, and water. The most versatile of these techniques is reversible addition-fragmentation chain transfer (RAFT), which allows a wide range of functional and nonfunctional polymers to be made with predictable molecular weight distributions (MWDs), ranging from very narrow to quite broad. The great complexity of the RAFT mechanism and how the kinetic parameters affect the rate of polymerization and MWD are not obvious. Therefore, the aim of this article is to provide useful insights into the important kinetic parameters that control the rate of polymerization and the evolution of the MWD with conversion. We discuss how a change in the chain-transfer constant can affect the evolution of the MWD. It is shown how we can, in principle, use only one RAFT agent to obtain a poly-mer with any MWD. Retardation and inhibition are discussed in terms of (1) the leaving R group reactivity and (2) the intermediate radical termination model versus the slow fragmentation model. (c) 2005 Wiley Periodicals, Inc.
TL;DR: In this article, a novel poly(amidoamine) (PAAs) containing disulfide linkages regularly arranged along their backbones were synthesized by the stepwise polyaddition of 2-methylpiperazine to N,N-bis(acryloyl)cystamine (BACy1) or N, N-bis (acry loyl)-(L)- cystine (bACy2), and the products were characterized with 1 H and 13 C NMR spectroscopy.
Abstract: Novel poly(amidoamine)s (PAAs) containing disulfide linkages regularly arranged along their backbones were synthesized by the stepwise polyaddition of 2-methylpiperazine to N,N-bis(acryloyl)cystamine (BACy1) or N,N-bis(acryloyl)-(L)- cystine (BACy2). Both bisacrylamides had, in turn, been obtained by the reaction of acryloyl chloride with the corresponding amines. All the products were characterized with 1 H and 13 C NMR spectroscopy, and the average molecular weights of the polymers were determined by size exclusion chromatography. Both PAAs showed different sol- ubility properties. In particular, PAA-Cy1, derived from BACy1, was sparingly soluble in water, whereas PAA-Cy2, derived from BACy2, was very soluble in aqueous media. The polymerization rates were investigated with 1 H NMR spectroscopy. In both cases, the experimental data were consistent with pseudo-second-order kinetics. The calcu- lated kinetic constants were 5.96 10 3 and 5.90 10 2 min 1 L mol 1 for the polyaddition of BACy1 and BACy2, respectively. The observed hydrolytic degradation rate of PAA-Cy2 in a pH 7.4 tris(hydroxymethyl)aminomethane (TRIS) buffer was comparable to that of conventional amphoteric PAAs, that is, PAAs containing carboxyl groups in their repeating unit. Degradation experiments carried out in the presence of 2-mercaptoethanol with both PAAs demonstrated that the disulfide groups contained in its repeating units were susceptible to reductive cleavage in the presence of thiols.
TL;DR: Differences in the hydrogel properties were correlated to the chemical structures of the UPEA precursors; that is, the different locations of the >CC< double bonds in individual U PEA segments resulted in their different reactivities toward PEG-DA to form hydrogels.
Abstract: A series of novel biodegradable hydrogels were designed and synthesized from four types of unsaturated poly(ester amide) (UPEA) and poly(ethylene glycol) diacrylate (PEG-DA) precursors by UV photocrosslinking. These newly synthesized biodegradable UPEA/PEG-DA hydrogels were characterized by their gel fraction (Gf), equilibrium swelling ratio (Qeq), compressive modulus, and interior morphology. The effect of the precursor feed ratio (UPEAs to PEG-DA) on the properties of the hydrogels was also studied. The incorporation of UPEA polymers into the PEG-DA hydrogels increased their hydrophobicity, crosslinking density (denser network), and mechanical strength (higher compressive modulus) but reduced Qeq. When different types of UPEA precursors were coupled with PEG-DA at the same feed ratio (20 wt %), the resulting hydrogels had similar Qeq values and porous three-dimensional interior morphologies but different Gf and compressive modulus values. These differences in the hydrogel properties were correlated to the chemical structures of the UPEA precursors; that is, the different locations of the >CC< double bonds in individual UPEA segments resulted in their different reactivities toward PEG-DA to form hydrogels. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3932–3944, 2005
TL;DR: The use of Fusarium solani pisi cutinase to modify the surface of textile synthetic fibers like polyester, polyamide 6.6, and acrylics is described.
Abstract: Synthetic fibers represent almost 50% of the worldwide market of textile fibers. Major characteristics of synthetic fibers are their hydrophobicity and low reactivity with most common chemical agents. The low hydrophobicity makes those fibers less suitable to be in contact with the human skin, and the low reactivity makes the fiber unsuitable to act as carrier to other chemical finishing agents. Strong alkaline treatments can improve hydrophilicity and chemical reactivity of synthetic fibers but the treatment extension is hard to control, leading to unacceptable levels of strength loss. Various attempts to overcome these difficulties were done before, using esterase enzymes to modify poly(ethyleneterephthalate), and nitrilases to modify polyacrilonitrile fibers. Cutinase was chosen for the modification of synthetic fibers because it is described as esterase that degrades cutin, a structural polyester of plants. Cutinase is a serine hydrolase with low specificity that is known to hydrolyze p-nitrophenyl esters and soluble and insoluble triglycerides. In this article, we describe the use of Fusarium solani pisi cutinase to modify the surface of textile synthetic fibers like polyester, polyamide 6.6, and acrylics. In polyester, the cutinase hydrolysis yields terephthalic acid and etylenoglicol. In polyamide, the cutinase hydrolysis yields hexamethylenediamine and adipic acid. The cutinase hydrolysis of acrylics (constituted by polyacrylonitrile and 7% of vinyl acetate as comonomer) yields acetic acid, leaving vinyl alcohol at the fiber surface.
TL;DR: In this paper, spontaneous gradient copolymers were obtained with an array of gradient compositions ranging from a subtle to strong variation in monomer distribution along the polymer backbones, depending on the ratio of comonomers initially added to the copolymerization system.
Abstract: Spontaneous gradient copolymers were prepared in both bulk and miniemulsion systems via Atom Transfer Radical Polymerization (ATRP) utilizing a Simultaneous Reverse and Normal Initiation (SR & NI) process. Both instantaneous and cumulative compositions were used to characterize the gradient copolymers. The gradient copolymers were obtained with an array of gradient compositions ranging from a subtle to strong variation in monomer distribution along the polymer backbones, depending on the ratio of comonomers initially added to the copolymerization system. The compositions of the gradient copolymer produced in miniemulsion systems were similar to those generated in bulk. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3616–3622, 2005
TL;DR: In this article, an initiator with dual functionality for ATRP/anionic ring-opening polymerization, 2-hydroxyethyl 2-bromoisobyrate, was used.
Abstract: Atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP) were combined to synthesize poly(ϵ-caprolactone-co-octadecyl methacrylate-co-dimethylaminoethyl methacrylate) copolymers possessing a triblock or random block structure. Various synthetic pathways (sequential or simultaneous approaches) were investigated for the synthesis of both copolymers. For the preparation of these copolymers, an initiator with dual functionality for ATRP/anionic ring-opening polymerization, 2-hydroxyethyl 2-bromoisobutyrate, was used. Copolymers were prepared with good structural control and low polydispersities (weight-average molecular weight/number-average molecular weight < 1.2), but one limitation was identified: the dimethylaminoethyl methacrylate (DMAEMA) block had to be synthesized after the ϵ-caprolactone block. ROP could not proceed in the presence of DMAEMA because the complexation of the amine groups in poly(dimethylaminoethyl methacrylate) deactivated tin(II) hexanoate, which was used as a catalyst for ROP. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1498–1510, 2005
TL;DR: In this paper, direct aromatic nucleophilic substitution polycondensations of disodium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone (SDFDPS), 4,4'difluminous diflussonate and 4, 4'thiobisbenzenethiol in the presence of potassium carbonate were investigated.
Abstract: Direct aromatic nucleophilic substitution polycondensations of disodium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone (SDFDPS), 4,4'-difluorodiphenylsulfone (DFDPS) (or their chlorinated analogs), and 4,4'-thiobisbenzenethiol in the presence of potassium carbonate were investigated. Electrophilic aromatic substitution was employed to synthesize the SDFDPS comonomer in high yields and purity. High molecular weight disulfonated copolymers were easily obtained using the SDFDPS monomers, but in general, slower rates and a lower molecular weight copolymer were obtained using the analogous chlorinated monomers. Tough and ductile membranes were solution cast from N,N-dimethylacetamide for both series of copolymers. The degrees of disulfonation (20-50%) were controlled by varying the ratio of disulfonated to unsulfonated comonomers. Precise control of the ionic concentration, well-defined ionic locations, and enhanced stability due to the deactivated position of the -SO 3 H group are some of the suggested advantages of direct copolymerization of sulfonated monomers. Further publications will discuss additional characteristics of these copolymers that have the same repeat unit, but different molecular weights, using methanol permeability, water uptake, protonic conductivity, and dynamic mechanical analysis.
TL;DR: In this paper, a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core-shell nanowires by in situ inverse microemulsion was demonstrated.
Abstract: We demonstrate here a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core-shell nanowires by in situ inverse microemulsion. Transmission electron microscopy and scanning electron microscopy showed that the carbon nanotubes were uniformly coated with a PPy layer with a thickness of several to several tens of nanometers, depending on the MWNT content. Fourier transform infrared spectra suggested that there was strong interaction between the π-bonded surface of the carbon nanotubes and the conjugated structure of the PPy shell layer. The thermal stability and electrical conductivity of the MWNT/PPy composites were examined with thermogravimetric analysis and a conventional four-probe method. In comparison with pure PPy, the decomposition temperature of the MWNT/PPy (1 wt % MWNT) composites increased from 305 to 335 °C, and the electrical conductivity of the MWNT/PPy (1 wt % MWNT) composites increased by 1 order of magnitude. The current-voltage curves of the MWNT/PPy nanocomposites followed Ohm's law, reflecting the metallic character of the MWNT/ PPy nanocomposites. The cyclic voltammetry measurements revealed that PPy/ MWNT composites showed an enhancement ii the specific charge capacity with respect to that of pure PPy.