Showing papers in "Journal of Polymer Science Part A in 2006"

Mechanism and kinetics of dithiobenzoate-mediated RAFT polymerization. I. The current situation

Abstract: Investigations into the kinetics and mechanism of dithiobenzoate-mediated Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerizations, which exhibit nonideal kinetic behavior, such as induction periods and rate retardation, are comprehensively reviewed. The appreciable uncertainty in the rate coefficients associated with the RAFT equilibrium is discussed and methods for obtaining RAFT-specific rate coefficients are detailed. In addition, mechanistic studies are presented, which target the elucidation of the fundamental cause of rate retarding effects. The experimental and theoretical data existing in the literature are critically evaluated and apparent discrepancies between the results of different studies into the kinetics of RAFT polymerizations are discussed. Finally, recommendations for further work are given. (c) 2006 Wiley Periodicals, Inc.

Formation of honeycomb-structured, porous films via breath figures with different polymer architectures

Abstract: Honeycomb-structured, porous films with pore sizes ranging from 200 nm to 7 mu m were prepared with breath figures. The regularity of the hexagonal array and the pore size was influenced by the polymer architecture and the casting conditions. A nanoscaled suborder next to the microarray was obtained with amphiphilic block copolymers. These films were shown to be suitable as surfaces for cell growth. (c) 2006 Wiley Periodicals, Inc.

Effects of end group polarity and molecular weight on the lower critical solution temperature of poly(N‐isopropylacrylamide)

Abstract: The lower critical solution temperatures (LCSTs) for mass fractionated samples of poly(N-isopropylacrylamide) (PNIPAM) were studied to determine the effect of polymer molecular weight on the LCST using a high throughput temperature gradient apparatus. PNIPAM fractions prepared by a conventional radical polymerization using azoisobutyronitrile (AIBN) as the initiator had LCSTs that were largely invariant with molecular weight or dispersity. Only slight deviations were noted with lower molecular weight samples. An 18-kDa sample had a 0.6 °C higher LCST. A 56-kDa sample had a 0.2 °C higher LCST. PNIPAM derivatives prepared with a triphenylmethyl (trityl) functionalized azo initiator were also prepared and mass fractionated. These samples' LCSTs were identical to those of PNIPAM samples prepared using AIBN initiation when higher molecular weight samples were compared. The trityl-containing PNIPAM fractions' LCSTs varied when the molecular weight decreased below 100 kDa. Acidolysis of the trityl end groups provided a third set of PNIPAM derivatives whose LCST differed only with samples with Mw values < 60 kDa. These results show there is no effect of molecular weight on LCST until the degree of polymerization is such that end group structure becomes significant. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1492–1501, 2006

Facile syntheses of surface‐functionalized micelles and shell cross‐linked nanoparticles

Abstract: Block copolymer micelles and shell cross-linked nanoparticles (SCKs) pre- senting Click-reactive functional groups on their surfaces were prepared using two sep- arate synthetic strategies, each employing functionalized initiators for the controlled radical polymerization of acrylate and styrenic monomers to afford amphiphilic block copolymers bearing an alkynyl or azido group at the a-terminus. The first route for the synthesis of the azide-functionalized nanostructures was achieved via sequential nitro- xide-mediated radical polymerization (NMP) of tert-butyl acrylate and styrene, originat- ing from a benzylic chloride-functionalized initiator, followed by deprotection of the acrylic acids, supramolecular assembly of the block copolymer in water and conversion of the benzylic chloride to a benzylic azide. In contrast, the second strategy utilized an alkynyl-functionalized reversible addition fragmentation transfer (RAFT) agent directly for the RAFT-based sequential polymerization of tetrahydropyran acrylate and styrene, followed by selective cleavage of the tetrahydropyran esters to give the a-alkynyl-func- tionalized block copolymers. These Click-functionalized polymers, with the functionality located at the hydrophilic polymer termini, were then self-assembled using a mixed-mi- celle methodology to afford surface-functionalized \Clickable" micelles in aqueous solu- tions. The optimum degree of incorporation of the Click-functionalized polymers was investigated and determined to be ca. 25%, which allowed for the synthesis of well- defined surface-functionalized nanoparticles after cross-linking selectively throughout the shell layer using established amidation chemistry. Functionalization of the chain ends was shown to be an efficient process under standard Click conditions and the resulting functional groups revealed a more \solution-like" environment when com- pared to the functional group randomly inserted into the hydrophilic shell layer. V

Crosslinked epoxy materials exhibiting thermal remendablility and removability from multifunctional maleimide and furan compounds

Abstract: Crosslinked polymeric materials, which exhibit thermal remendability and removability through Diels–Alder (DA) and retro-DA reactions, were obtained from using multifunctional maleimide and furan compounds as monomers. The synthesized monomers possess low melting points and good solubility in organo solvents to show excellent processing properties. The performance of DA and retro-DA reactions were demonstrated with DSC and FTIR measurements. High performance of thermal remendablility and removability of the crosslinked materials were observed with SEM and solvent tests. These materials were applicable in advanced encapsulants and structural materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 905–913, 2006

Synthesis of metal (Fe or Pd)/alloy (Fe–Pd)‐nanoparticles‐embedded multiwall carbon nanotube/sulfonated polyaniline composites by γ irradiation

Abstract: Composites of multiwall carbon nanotubes (MWCNTs) and sulfonated polyaniline (SPAN) were prepared through the oxidative polymerization of a mixture of aniline, 2,5-diaminobenzene sulfonic acid, and MWCNTs. Fe, Pd, or Fe–Pd alloy nanoparticles were embedded into the MWCNT–SPAN matrix by the reduction of Fe, Pd, or a mixture of Fe and Pd ions with γ radiation. Sulfonic acid groups and the emeraldine form of backbone units in SPAN served as the source for the reduction of the metal ions in the presence of γ radiation. The existence of metallic/alloy particles in the MWCNT–SPAN matrix was further ascertained through characterization by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, thermogravimetric analysis, and conductivity measurements. HRTEM pictures clearly revealed the existence of Fe, Pd, and Fe–Pd nanoparticles of various sizes in the MWCNT–SPAN matrices. There were changes in the electronic properties of the MWCNT–SPAN–M composites due to the interaction between the metal nanoparticles and MWCNT–SPAN. Metal-nanoparticle-loaded MWCNT–SPAN composites (MWCNT–SPAN–M; M = Fe, Pd, or Fe–Pd alloy) showed better thermal stability than the pristine polymers. The conductivity of the MWCNT–SPAN–M composites was approximately 1.5 S cm−1, which was much higher than that of SPAN (2.46 × 10−4 S cm−1). Metal/alloy-nanoparticle-embedded, MWCNT-based composite materials are expected to find applications in molecular electronics and other fields. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3355–3364, 2006

Oxygen inhibition in thiol–acrylate photopolymerizations

Abstract: The overall effects of oxygen on thiol–acrylate photopolymerizations were characterized. Specially, the choice of thiol monomer chemistry, functionality, and concentration on the extent of oxygen inhibition were considered. As thiol concentration was increased, the degree of oxygen inhibition was greatly reduced because of chain transfer from the peroxy radical to the thiol. When comparing the copolymerization of 1,6-hexanediol diacrylate with the alkane-based thiol (1,6-hexane dithiol) to the copolymerization with the propionate thiol (glycol dimercaptopropionate), it was found that the propionate system was much more reactive and polymerized to a greater extent in the presence of oxygen. In addition, the functionality was considered where the glycol dimercaptopropionate was compared to a tetrafunctional propionate of similar chemistry (pentaerythritol tetrakis(mercaptopropionate)). Given the same thiol concentration, the higher functionality thiol imparted a faster polymerization rate, due to the increased polymer system viscosity, which limited oxygen diffusion and decreased the extent of overall oxygen inhibition. Thus, preliminary insight is provided into how thiol monomer choice affects the extent of oxygen inhibition in thiol–acrylate photopolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2007–2014, 2006

Synthesis and characterization of polyurethanes from epoxidized methyl oleate based polyether polyols as renewable resources

Abstract: Oligomeric polyether polyols were obtained through the acid-catalyzed ring-opening polymerization of epoxidized methyl oleate and the subsequent partial reduction of ester groups to give primary alcohols. The oligomers were characterized with titration, spectroscopic techniques (Fourier transform infrared and nuclear magnetic resonance), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, size exclusion chromatography, and differential scanning calorimetry. Depending on the degree of reduction, polyols of different hydroxyl content values were obtained and were reacted with 4,4′-methylenebis(phenyl isocyanate) to yield polyurethanes. These materials, which were characterized by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis, could behave as hard rubbers or rigid plastics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 634–645, 2006

ABC-type hetero-arm star terpolymers through click chemistry

Abstract: Hetero-arm star ABC-type terpolymers, poly(methyl methacrylate)-polystyrene-poly(tert-butyl acrylate) (PMMA-PS-PtBA) and PMMA-PS-poly(ethylene glycol) (PEG), were prepared by using “Click” chemistry strategy. For this, first, PMMA-b-PS with alkyne functional group at the junction point was obtained from successive atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMP) routes. Furthermore, PtBA obtained from ATRP of tBA and commercially available monohydroxyl PEG were efficiently converted to the azide end-functionalized polymers. As a second step, the alkyne and azide functional polymers were reacted to give the hetero-arm star polymers in the presence of CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) in DMF at room temperature for 24 h. The hetero-arm star polymers were characterized by 1H NMR, GPC, and DSC. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5699–5707, 2006

Synthesis and characterization of conducting polythiophene/carbon nanotubes composites

Abstract: Conducting polythiophene (PTh)/single-wall carbon nanotubes (SWNTs) composites were synthesized by the in situ chemical oxidative polymerization method. The resulting cablelike morphology of the composite (SWNT–PTh) structures was characterized with elemental analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared, ultraviolet–visible spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The standard four-point-probe method was used to measure the conductivity of the samples. Field emission scanning electron microscopy and transmission electron microscopy analysis revealed that the SWNT–PTh composites were core (SWNTs) and shell (PTh) hybrid structures. Spectroscopic analysis data for the composites were almost identical to those for PTh, supporting the idea that SWNTs served as templates in the formation of a coaxial nanostructure for the composites. The physical properties of the composites were measured and also showed that the SWNTs were modified by conducting PTh with an enhancement of various properties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5283–5290, 2006

Development of organotellurium‐mediated and organostibine‐mediated living radical polymerization reactions

Abstract: Organotellurium-mediated living radical polymerizations (TERPs) and organostibine-mediated living radical polymerizations (SBRPs) provide well-defined polymers with a variety of polar functional groups via degenerative chain-transfer polymerization. The high controllability of these polymerizations can be attributed to the rapid degenerative-transfer process between the polymer-end radicals and corresponding dormant species. The versatility of the methods allows the synthesis of AB diblock, ABA triblock, and ABC triblock copolymers by the successive addition of different monomers. This review summarizes the current status of TERP and SBRP.

Well‐defined thermosensitive, water‐soluble polyacrylates and polystyrenics with short pendant oligo(ethylene glycol) groups synthesized by nitroxide‐mediated radical polymerization

Abstract: We report the synthesis and thermosensitive properties of well-defined water-soluble polyacrylates and polystyrenics with short pendant oligo(ethylene glycol) groups. Four monomers, methoxydi(ethylene glycol) acrylate (DEGMA), methoxytri(ethylene glycol) acrylate (TEGMA), α-hydro-ω-(4-vinylbenzyl)tris(oxyethylene) (HTEGSt), and α-hydro-ω-(4-vinylbenzyl)tetrakis(oxyethylene) (HTrEGSt), were prepared and polymerized by nitroxide-mediated radical polymerization with 2,2,5-trimethyl-3-(1-phenylethoxy)-4-phenyl-3-azahexane as an initiator. Kinetics and gel permeation chromatography analysis showed that the polymerizations were controlled processes yielding polymers with controlled molecular weights and narrow polydispersities. All polymers could be dissolved in water, forming transparent solutions, and undergo phase transitions when the temperature was above a critical point. The thermosensitive properties were studied by turbidimetry and variable-temperature 1H NMR spectroscopy. The cloud points of the polymers of DEGMA, TEGMA, HTEGSt, and HTrEGSt were around 38, 58, 13, and 64 °C, respectively. For all four polymers, the cloud point increased with decreasing concentration and increasing molecular weight in the studied molecular weight range of 5000–30,000 g/mol. The removal of the nitroxide group from the polymer chain end resulted in a higher cloud point. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2454–2467, 2006

A3‐type star polymers via click chemistry

Abstract: We report a simple preparation of three-armed (A3-type) star polymers based on the arm-first technique, using a click-reaction strategy between a well-defined azide-end-functionalized polystyrene, poly(tert-butyl acrylate), or poly(ethylene glycol) precursor and a trisalkyne-functional initiator, 1,1,1-tris[4-(2-propynyloxy)phenyl]ethane. The click-reaction efficiency for A3-type star formation has been investigated with gel permeation chromatography measurements (refractive-index detector). The gel permeation chromatography curves have been split with the deconvolution method (Gaussian area), and the efficiency of A3-type star formation has been found to be 87%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6458–6465, 2006

Ultrasound in polymer chemistry: Revival of an established technique

Abstract: The history of ultrasound in polymer chemistry goes back a long way. Initially, its uses were limited to being an alternative method of initiating radical polymerizations through the decomposition of solvents to form radicals or through the breakage of polymers leading to macroradicals. Recently, the raw power of ultrasound has been focused through the use of weak linkages in polymer chains, which enables the production of well-defined macroradicals and coordinatively unsaturated metal complexes

Preparation of block copolymers via Diels Alder reaction of maleimide‐ and anthracene‐end functionalized polymers

Abstract: A number of diblock copolymers were successfully prepared by Diels–Alder reaction, between maleimide- and anthracene-end functionalized poly (methyl methacrylate) (PMMA), polystyrene (PS), poly(tert-butyl acrylate) (PtBA), and poly(ethylene glycol) (PEG) in toluene, at 110 °C. For this purpose, 2-bromo-2-methyl-propionic acid 2-(3,5-dioxo-10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-en-4-yl)-ethyl ester, 2, 9-anthyrylmethyl 2-bromo-2-methyl propanoate, 3, and 2-bromo-propionic acid 2-(3,5-dioxo-10-oxa-4-azatricyclo[5.2.1.02,6]dec-8-en-4-yl)-ethyl ester, 4, were used as initiators in atom transfer radical polymerization, in the presence of Cu(I) salt and pentamethyldiethylenetriamine (PMDETA), at various temperatures. On the other hand, PEG with maleimide- or anthracene-end functionality was achieved by esterification between monohydroxy PEG and succinic acid monoathracen-9-ylmethyl ester, 1, or 4-maleimido-benzoyl chloride. Thus-obtained PMMA-b-PS, PEG-b-PS, PtBA-b-PS, and PMMA-b-PEG block copolymers were characterized by 1H NMR, UV, and GPC. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1667–1675, 2006

Solubilizing single‐walled carbon nanotubes with pyrene‐functionalized block copolymers

Abstract: The effect of pyrene distribution within pyrene-functionalized random and block copolymers on noncovalent polymer/single-walled carbon nanotube (SWNT) interactions was investigated. The block copolymers served as superior solubilizing agents in comparison with the random copolymers. Also, increasing the pyrene content within a polymer, while a constant molecular weight was maintained, improved SWNT solubility and therefore had to result in stronger polymer–nanotube interactions. However, increasing the length of the pyrene-containing block diminished nanotube solubility, likely because of a lower number of polymer chains that were capable of binding to the nanotube surface. Atomic force microscopy and transmission electron microscopy indicated that the polymer–SWNT interactions were capable of partially debundling the nanotubes into individual solvated structures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1941–1951, 2006

Alternating copolymerization of propylene oxide and carbon dioxide with highly efficient and selective (salen)Co(III) catalysts: Effect of ligand and cocatalyst variation

Abstract: Synthetic routes to a series of new (salen)CoX (salen = N,N′-bis(salicylidene)-1,2-diaminoalkane; X = Br or pentafluorobenzoate (OBzF5)) species are described. Several of these complexes are active for the copolymerization of propylene oxide (PO) and CO2, yielding regioregular poly(propylene carbonate) (PPC) without the generation of propylene carbonate byproduct. Variation of the salen ligand, as well as the inclusion of organic-based ionic or Lewis basic cocatalysts, has dramatic effects on the resultant (salen) CoX catalytic activity. Highly active (R,R)-(salen-1)CoOBzF5 (salen-1 = N,N′-bis(3,5- di-tert-butylsalicylidene)-1,2-diaminocyclohexane) catalysts with [Ph4P]Cl or [PPN]Y ([PPN] = bis(triphenylphosphine)iminium; Y = Cl or OBzF5) cocatalysts exhibited turnover frequencies up to 720 h−1 for rac-PO/CO2 copolymerization, yielding PPC with greater than 90% head-to-tail connectivity. Additionally, the (R,R)-(salen-1)CoOBzF5/[PPN]Cl catalyst system demonstrated a krel of 9.7 for the enchainment of (S)- over (R)-PO when the copolymerization was carried out at low temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5182–5191, 2006

Polymer chemistry in flow: New polymers, beads, capsules, and fibers

Abstract: The union between polymer science and microfluidics is reviewed. Fluids in microreactors allow the synthesis of a wide range of polymeric materials with unique properties. We begin by discussing the important fluid dynamics that dominate the behavior of fluids on the micrometer scale. We then progress through a comprehensive analysis of the polymeric materials synthesized to date. This highlight concludes with an overview of the methods used to make microreactors. We enthusiastically endorse microreactors as a powerful approach to making materials with controlled properties, although we have tried to provide a critical eye to help the nonexpert enter the field. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6505–6533, 2006

Synthesis and properties of flame‐retardant benzoxazines by three approaches

Abstract: We propose three approaches to obtain flame-retardant benzoxazines. In the first approach, we synthesize a novel benzoxazine (dopot-m) from a phosphorus-containing triphenol (dopotriol), formaldehyde, and methyl amine. Dopot-m is copolymerized with a commercial benzoxazine [6′,6-bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazineyl)methane (F-a)] or diglycidyl ether of bisphenol A (DGEBA). The thermal properties and flame retardancy of the F-a/dopot-m copolymers increase with the content of dopot-m. As for the dopot-m/DGEBA curing system, the glass-transition temperature of the dopot-m/DGEBA copolymer is 252 °C, which is higher than that of poly(dopot-m). The 5% decomposition temperature of the dopot-m/DGEBA copolymer increases from 323 to 351 °C because of the higher crosslinking density caused by the reaction of phenolic OH and epoxy. In the second approach, we incorporate the element phosphorus into benzoxazine via the curing reaction of dopotriol and F-a. After the curing, the thermal properties of the F-a/dopotriol copolymers are almost the same as those of neat poly(F-a), and this implies that we can incorporate the flame-retardant element phosphorus into the polybenzoxazine without sacrificing any thermal properties. In the third approach, we react dopo with electron-deficient benzoxazine to incorporate the element phosphorus. After the curing, the glass-transition temperatures of polybenzoxazines decrease slightly with the content of dopo, mainly because of the smaller crosslinking density of the resultant polybenzoxazines. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3454–3468, 2006

Inorganic–organic nanocomposites of polybenzoxazine with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane

Abstract: Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used to prepare the polybenzoxazine (PBA-a) nanocomposites containing polyhedral oligomeric silsesquioxane (POSS). The crosslinking reactions involved with the formation of the organic-inorganic networks can be divided into the two types: (1) the ring-opening polymerization of benzoxazine and (2) the subsequent reaction between the in situ formed phenolic hydroxyls of PBA-a and the epoxide groups of OpePOSS. The morphology of the nanocomposites was investigated by means of scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Differential scanning calorimetry and dynamic mechanical analysis showed that the nanocomposites displayed higher glass-transition temperatures than the control PBA-a. In the glassy state, the nanocomposites containing less than 30 wt % POSS displayed an enhanced storage modulus, whereas the storage moduli of the nanocomposites containing more than 30 wt % POSS were lower than that of the control PBA-a. The dynamic mechanical analysis results showed that all the nanocomposites exhibited enhanced storage moduli in the rubbery states, which was ascribed to the two major factors, that is, the nanoreinforcement effect of POSS cages and the additional crosslinking degree resulting from the intercomponent reactions between PBA-a and OpePOSS. Thermogravimetric analysis indicated that the nanocomposites displayed improved thermal stability.

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

Abstract: The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface-initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft-functionalized PVDF surfaces were characterized by X-ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2-(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) with the reaction time, indicating that the chain growth from the surface was consistent with a controlled or living process. The living chain ends were used as macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA-grafted PVDF films and PDMAEMA-grafted PVDF films in comparison with the pristine PVDF surface.

Synthesis and properties of a new fluorine‐containing polybenzimidazole for high‐temperature fuel‐cell applications

Abstract: An amorphous, organosoluble, fluorine-containing polybenzimidazole (PBI) was synthesized from 3,3′-diaminobenzidine and 2,2-bis(4-carboxyphenyl)hexafluoropropane. The polymer was soluble in N-methylpyrrolidinone and dimethylacetamide and had an inherent viscosity of 2.5 dL/g measured in dimethylacetamide at a concentration of 0.5 g/dL. The 5% weight loss temperature of the polymer was 520 °C. Proton-conducting PBI membranes were prepared via solution casting and doped with different amounts of phosphoric acid. In the methanol permeability measurement, the PBI membranes showed much better methanol barrier ability than a Nafion membrane. The proton conductivity of the acid-doped PBI membranes increased with increasing temperatures and concentrations of phosphoric acid in the polymer. The PBI membranes showed higher proton conductivity than a Nafion 117 membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4508–4513, 2006

Synthesis and characterization of new polymeric ionic liquid microgels

Abstract: A new two-step route toward the synthesis of polymeric ionic liquid microgel particles is presented In the first step, hydrophilic microparticles were prepared by the concentrated emulsion polymerization of the ionic liquid 1-vinyl-3-ethylimidazolium bromide in the presence of small amounts of N,N-dimethylenebisacrylamide as a crosslinking agent In the second step, the bromide anion was exchanged in water with different anions such as BF, CF3SO, (CF3SO2)2N−, (CF3CF2SO2)2N−, and dodecylbenzenesulfonate, and this resulted in the coagulation of the microparticles, which were easily recovered by filtration The obtained polymeric ionic liquid microparticles could be swollen in a very broad range of organic solvents, including apolar organic solvents As an application, glucose oxidase was encapsulated inside polymeric ionic liquid microparticles, which were used in an amperometric biosensor The response of the biosensor showed excellent values that strongly depended on the nature of the polymeric ionic liquid counteranion in the order of Br− > BF > (CF3SO2)2N− © 2006 Wiley Periodicals, Inc J Polym Sci Part A: Polym Chem 44: 3958–3965, 2006

Highly magnetic latexes from submicrometer oil in water ferrofluid emulsions

Abstract: The synthesis of functionalized submicrometer magnetic latex particles is described as obtained from a preformed magnetic emulsion composed of organic ferrofluid droplets dispersed in water. Composite (polystyrene/y-Fe 2 O 3 ) particles were prepared according to a two-step procedure including the swelling of ferrofluid droplets with styrene and a crosslinking agent (divinyl benzene) followed by seeded emulsion polymerization with either an oil-soluble [2,2'-azobis(2-isobutyronitrile)] or water-soluble (potassium persulfate) initiator. Depending on the polymerization conditions, various particle morphologies were obtained, ranging from asymmetric structures, for which the polymer phase was separated from the inorganic magnetic phase, to regular core-shell morphologies showing a homogeneous encapsulation of the magnetic pigment by a crosslinked polymeric shell. The magnetic latexes were extensively characterized to determine their colloidal and magnetic properties. The desired core-shell structure was efficiently achieved with a given styrene/divinyl benzene ratio, potassium persulfate as the initiator, and an amphiphilic functional copolymer as the ferrofluid droplet stabilizer. Under these conditions, ferrofluid droplets were successfully turned into superparamagnetic polystyrene latex particles, about 200 nm in size, containing a large amount of iron oxide (60 wt %) and bearing carboxylic surface charges.

Synthesis and thermoresponsive property of end‐functionalized poly(N‐isopropylacrylamide) with pyrenyl group

Abstract: N-Isopropylacrylamide (NIPAM) was polymerized using 1-pyrenyl 2-chloropropionate (PyCP) as the initiator and CuCl/tris[2-(dimethylamino)ethyl]-amine (Me 6 TREN) as the catalyst system. The polymerizations were performed using the feed ratio of [NIPAM] 0 /[PyCP] 0 /[CuCl] 0 /[Me 6 TREN] 0 = 50/1/1/1 in DMF/water of 13/2 at 20 °C to afford an end-functionalized poly(N-isopropylacrylamide) with the pyrenyl group (Py-PNIPAM). The characterization of the Py-PNIPAM using matrix-assisted laser desorption ionization time-of-flight mass spectrometry provided the number-average molecular weight (M n,MS ). The lower critical solution temperature (LCST) for the liquid-solid phase transition was 21.7, 24.8, 26.5, and 29.3 °C for the Py-PNIPAMs with the M n,MS 's of 3000, 3400, 4200, and 5000, respectively; hence, the LCST was dramatically lowered with the decreasing M n,MS . The aqueous Py-PNIPAM solution below the LCST was characterized using a static laser light scattering (SLS) measurement to determine its molar mass, M w,SLS . The aqueous solutions of the Py-PNIPAMs with the M n,MS 's of 3000, 3400, 4200, and 5000 showed the M w,SLS of 586,000, 386,000, 223,000, and 170,000, respectively. Thus, lowering the LCST for Py-PNIPAM should be attributable to the formation of the PNIPAM aggregates. The LCST of 21.7 °C for Py-PNIPAM with the M n,MS of 3000 was effectively raised by adding β-cyclodextrin (β-CD) and reached the constant value of ∼26 °C above the molar ratio of [β-CD]/[Py-PNIPAM] = 2/1, suggesting that β-CD formed an inclusion complex with pyrene in the chain-end to disturb the formation of PNIPAM aggregates, thus raising the LCST.

Preparation and characterization of MPEG-PCL diblock copolymers with thermo-responsive sol-gel-sol phase transition

Abstract: MPEG–PCL diblock copolymers consisting of methoxy polyethylene glycol (MPEG, 750 g/mol) and poly(ϵ-caprolactone) (PCL) were synthesized by ring-opening polymerization. Aqueous solutions of the synthesized diblock copolymers were prepared by dissolving the MPEG–PCL diblock copolymers at concentrations in the range of 0–20 wt %. When the PCL molecular weight was 3000 or greater, the polymer was only partially soluble in water. As the temperature was increased from room temperature, the diblock copolymer solutions showed two phase transitions: a sol-to-gel transition and a gel-to-sol transition. The sol-to-gel phase transition temperature decreased substantially with increasing PCL length. The sol–gel–sol transition with the increase in temperature was confirmed by monitoring the viscosity as a function of temperature. The temperature ranges of the phase transitions measured by the tilting method were in full agreement with those determined from the viscosity measurements. The maximum viscosity of the copolymer solution increased with increasing hydrophobicity of the diblock copolymer and with increasing copolymer concentration. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses revealed that the diblock copolymers exhibited crystalline domains that favored the formation of an aggregated gel because of the tight aggregation and strong packing interactions between PCL blocks. Scanning electron micrographs of the diblock copolymer solutions in the sol state showed interconnected polyhedral pore structures, whereas those of the gel state revealed a fibrillar-like morphology. Atomic force microscope (AFM) studies of the sol and gel surfaces showed that the sol surface was covered with fine globular particles, whereas the gel surface was covered with particles in micron-scale irregular islets. These findings are consistent with uniform mixing of the diblock copolymer and water in the sol state, and aggregation of PCL blocks in the gel state. In conclusion, we confirm that the MPEG–PCL diblock copolymer solution exhibited a sol–gel–sol transition as a function of temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5413–5423, 2006

Preparation of ABC miktoarm star terpolymer containing poly(ethylene glycol), polystyrene, and poly(tert‐butylacrylate) arms by combining diels–alder reaction, atom transfer radical, and stable free radical polymerization routes

Abstract: The ABC type miktoarm star terpolymer was prepared utilizing “core-in” and “core-out” methods via combination of Diels–Alder reaction (DA), stable free radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, in DA reaction, poly(ethylene glycol)-maleimide (PEG-maleimide) precursor was reacted with succinic acid anthracen-9-ylmethyl ester 3-(2-bromo-2-methyl-propionyloxy)-2-methyl-2-[2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethoxy-carbonyl]-propyl ester, 8, to give DA adduct, 9, which has appropriate functional groups for SFRP and ATRP. Second, a previously obtained 9 was used as a macroinitiator for SFRP of styrene at 125 °C. As a third step, this PEG-polystyrene (PEG-PSt) precursor with a bromine functionality in the core was employed as a macroinitiator for ATRP of tert-butylacrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C to give ABC type miktoarm star terpolymer (PEG-PSt-PtBA) with controlled molecular weight and low polydispersity (Mw/Mn < 1.27). The obtained polymers were characterized by gel permeation chromatography and 1H NMR. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 499–509, 2006

Kinetics of the iodine transfer polymerization of vinylidene fluoride

Abstract: The kinetics of the iodine transfer polymerization (ITP) of vinylidene fluoride (VDF) was achieved in the presence of three different chain-transfer agents (CTAs): 1-iodoperfluorohexane (C6F13I), 1-iodo-2H,2H-perfluorooctane (C6F13H2CF2I), and 1,1,2,2-tetrafluoro-3-iodopropane (HCF2CF2CH2I). ITPs of VDF carried out in the presence of C6F13I and C6F13CH2CF2I showed the following: (1) a linear increase in DPn versus alpha(VDF), which evidenced the controlled character of ITP, although the polydispersity indices were slightly high (ca 1.5), and (2) theoretical DPn values close to the targeted ones. In contrast, neither of these statements was observed for the ITP of VDF in the presence of HCF2CF2CH2I achieved under the same conditions, even if the synthesized oligomers could be reactivated. Although the C-Tr values of C6F13I and C6F13CH2CF2I were close (i.e., 7.7 at 75 degrees C), that of HCF2CF2CH2I was lower (0.3 at 75 degrees C). The percentages of -CF2I and -CH2I functionalities were also assessed, and in the course of the reaction, a reduction of -CF2I end groups was noted. Then, the mechanism of the ITP of VDF was proposed. (c) 2006 Wiley Periodicals, Inc.

Novel aromatic polyamides and polyimides functionalized with 4‐tert‐butyltriphenylamine groups

Abstract: A new triphenylamine-containing diamine monomer, 4,4 0 -diamino-4@-tert- butyltriphenylamine, was successfully synthesized by the cesium fluoride-mediated N,N-diarylation of 4-tert-butylaniline with 4-fluoronitrobenzene, followed by the reduc- tion of the nitro group. The obtained diamine monomer was reacted with various aro- matic dicarboxylic acids and tetracarboxylic dianhydrides to produce two series of novel triphenylamine-based polyamides and polyimides with pendent tert-butyl substituents. Most of the polymers were readily soluble in polar organic solvents, such as N-methyl- 2-pyrrolidone and N,N-dimethylacetamide (DMAc), and could be solution cast into tough and flexible polymer films. These polymers showed high glass transition tempera- tures between 282 and 320 8C, and they were fairly stable up to a temperature above 450 8C (for polyamides) or 500 8C (for polyimides). These polymers exhibited UV absorp- tion maxima around 308 to 361 nm. The photoluminescence spectra of the polyamides in DMAc exhibited a peak emission wavelength in the blue at 421-433 nm. Cyclic vol- tammograms of polyamides and polyimides showed an oxidation wave at 1.0-1.1 V ver- sus Ag/AgCl in an acetonitrile solution. All the polyamides and polyimides exhibited excellent reversibility of electrochromic characteristics by continuous several cyclic scans between 0.0 and 1.1-1.3 V, with a color change from the original pale yellowish neutral form to the green or blue oxidized forms. V C 2006 Wiley Periodicals, Inc. J Polym Sci

Preparation and characterization of magnetic polymeric composite particles by miniemulsion polymerization

Abstract: A water-based magnetite ferrofluid, with an average size of about 10 nm, was prepared in a first step by the chemical coprecipitation of ferrous and ferric salts. Oil-based styrene (St) magnetite ferrofluid was obtained by the acidification of the water-based magnetite ferrofluid and the dispersion of the acidified magnetite in St. Magnetic polymeric composite particles (MPCPs) were prepared by miniemulsion polymerization in the presence of the oil-based St magnetite ferrofluid with hexadecane as a hydrophobe, 2,2′-azobisisobutyronitrile as an initiator, and sodium dodecyl sulfate as an emulsifier. Methacrylic acid was used as a comonomer, and hydroxyethyl cellulose and polyvinylpyrrolidone were used as aid stabilizers subsequently. With the aim of improving the encapsulation degree of magnetite, avoiding pure polymer particles and exposed magnetite particles, and obtaining the narrowest particle size distributions, the encapsulation conditions of magnetite were investigated in detail. The results show that miniemulsion polymerization is an effective method for encapsulating magnetite into a hydrophobic polymer successfully. Exposed magnetite particles and pure polymer particles can be avoided completely by the selection of the appropriate preparation conditions. All the resulting MPCPs exhibited superparamagnetism and possessed some magnetic response. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4187–4203, 2006