Complexation of linear and poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride) with poly(ethylene oxide‐block‐sodium methacrylate)

The interactions between oppositely charged polyelectrolytes were studied in saline aqueous solutions as functions of the temperature and the salt and polymer concentrations. The polyanion was a diblock copolymer composed of a poly(ethylene oxide) block and a poly(sodium methacrylate) block. Two polycations were used, the homopolymer poly(methacryl oxyethyl trimethylammonium chloride) and its poly(ethylene oxide)‐grafted analogue. By dynamic light scattering and turbidity measurements, it was observed that the salt concentration, temperature, and counterion size had a significant effect on the formation of the polymer complexes in aqueous solutions. At a fixed salt concentration and a fixed temperature, it was possible to form completely soluble complexes of an ionic polymer in aqueous solutions between poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride)and the polyanion with a poly(ethylene oxide) block at a 1:1 anion/cation ratio. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1904–1914, 2003     

Morphological study on diffusion‐limited aggregates of poly(ethylene oxide) on alkali halides

When poly(ethylene oxide) was crystallized on a fresh cleavage surface of alkali halides from solution in isoamyl acetate, diffusion‐limited‐aggregate dendrites were formed. Their patterns varied, depending on the kind of substrate on which the poly(ethylene oxide) crystallized: On a KCl substrate, rather ordered dendrites grew with fibrillar crystallites aligning roughly in the 〈110〉_KCl direction, and coarse dendritic clusters formed on NaCl and KBr during the initial stage of their growth. The dendrites grew and matured to sheet the whole surface of alkali halides with a uniform thickness, and subsequently, tetragonal lamellae formed on it through the spiral growth mechanism or the primary nucleation process. Tetragonal lamellar crystals grew with their diagonals parallel to fibrillar crystallites of dendrites. Their orientation did not result from direct, epitaxial contact with the alkali halide substrate but depended on the fibrillar orientation of the underlying sheeted layer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2421–2430, 2002     

A novel route to poly(α-hydroxyacrylic acid) derivatives by the hydrolysis of polymers containing 1,3-dioxolan-4-one moiety

The alkali hydrolysis of poly(2,2-dimethyl-5-methylene-1,3-dioxolan-4-one) and poly(2,2-dimethyl-5-methylene-1,3-dioxolan-4-one-co-styrene) was carried out with a sodium hydroxide solution (40%) in tetrahydrofuran at room temperature to obtain poly(α-hydroxyacrylic acid) or poly(α-hydroxyacrylic acid-co-styrene) with number-average molecular weights of 39,000–73,000 in 41–86% yields. The styrene unit in the hydrolyzed copolymer hindered the formation of a lactone ring. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1629–1633, 2001     

Synthesis of branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐ [linear‐poly(ε‐caprolactone)] by combination of glaser coupling reaction with ring‐opening polymerization

A novel amphiphilic branch‐ring‐branch tadpole‐shaped [linear‐poly(ε‐caprolactone)]‐b‐[cyclic‐poly(ethylene oxide)]‐b‐[linear‐poly(ε‐caprolactone)] [(l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL)] was synthesized by combination of glaser coupling reaction with ring‐opening polymerization (ROP) mechanism. The self‐assembling behaviors of (l‐PCL)‐b‐(c‐PEO)‐b‐(l‐PCL) and their π‐shaped analogs of poly(ε‐caprolactone)/poly(ethylene oxide)]‐b‐poly(ethylene oxide)‐b‐[poly(ε‐caprolactone)/poly(ethylene oxide) with comparable molecular weight in water were preliminarily investigated. The results showed that the micelles formed from the former took a fiber look, however, that formed from the latter took a spherical look. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of ABA‐type amphiphilic tri‐block copolymers through anionic polymerization using end functionalized poly(ethylene oxide) oligomers

ABA‐type amphiphilic tri‐block copolymers were successfully synthesized from poly(ethylene oxide) derivatives through anionic polymerization. When poly(styrene) anions were reacted with telechelic bromine‐terminated poly(ethylene oxide) ( 1 ) in 2:1 mole ratio, poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers were formed. Similarly, stable telechelic carbanion‐terminated poly(ethylene oxide), prepared from 1,1‐diphenylethylene‐terminated poly (ethylene oxide) ( 2 ) and sec‐BuLi, was also used to polymerize styrene and methyl methacrylate separately, as a result, poly (styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) and poly (methyl methacrylate)‐b‐poly(ethylene oxide)‐b‐poly(methyl methacrylate) tri‐block copolymers were formed respectively. All these tri‐block copolymers and poly(ethylene oxide) derivatives, 1 and 2 , were characterized by spectroscopic, calorimetric, and chromatographic techniques. Theoretical molecular weights of the tri‐block copolymers were found to be similar to the experimental molecular weights, and narrow polydispersity index was observed for all the tri‐block copolymers. Differential scanning calorimetric studies confirmed the presence of glass transition temperatures of poly(ethylene oxide), poly(styrene), and poly(methyl methacrylate) blocks in the tri‐block copolymers. Poly(styrene)‐b‐poly(ethylene oxide)‐b‐poly(styrene) tri‐block copolymers, prepared from polystyryl anion and 1 , were successfully used to prepare micelles, and according to the transmission electron microscopy and dynamic light scattering results, the micelles were spherical in shape with mean average diameter of 106 ± 5 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Thermoreversible gelation of poly(ethylene oxide) biodegradable polyester block copolymers. II

Poly(ethylene oxide)-b-poly(L-lactic acid) (PEO-PLLA) diblock copolymers were synthesized via a ring opening polymerization from poly(ethylene oxide) and l -lactide. Stannous octoate was used as a catalyst in a solution polymerization with toluene as the solvent. Their physicochemical properties were investigated by using infrared spectroscopy, ¹H-NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry, as well as the observational data of gel-sol transitions in aqueous solutions. Aqueous solutions of PEO-PLLA diblock copolymers changed from a gel phase to a sol phase with increasing temperature when their polymer concentrations are above a critical gel concentration. As the PLLA block length increased, the gel-sol transition temperature increased. For comparison, diblock copolymers of poly(ethylene oxide)-b-poly(l -lactic acid-co-glycolic acid) [PEO-P(LLA/GA)] and poly(ethylene oxide)-b-poly(dl -lactic acid-co-glycolic acid) [PEO-P(DLLA/GA)] were synthesized by the same methods, and their gel-sol transition behaviors were also investigated. The gel-sol transition properties of these diblock copolymers are influenced by the hydrophilic/hydrophobic balance of the copolymer, block length, hydrophobicity, and stereoregularity of the hydrophobic block of the copolymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2207–2218, 1999     

Water‐soluble poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) copolymer: Synthesis and characterization

Water‐soluble and photoluminescent block copolymers [poly(ethylene oxide)‐block‐poly(p‐phenylene vinylene) (PEO‐b‐PPV)] were synthesized, in two steps, by the addition of α‐halo‐α′‐alkylsulfinyl‐p‐xylene from activated poly(ethylene oxide) (PEO) chains in tetrahydrofuran at 25 °C. This copolymerization, which was derived from the Vanderzande poly(p‐phenylene vinylene) (PPV) synthesis, led to partly converted PEO‐b‐PPV block copolymers mixed with unreacted PEO chains. The yield, length, and composition of these added sequences depended on the experimental conditions, namely, the order of reagent addition, the nature of the monomers, and the addition of an extra base. The addition of lithium tert‐butoxide increased the length of the PPV precursor sequence and reduced spontaneous conversion. The conversion into PPV could be achieved in a second step by a thermal treatment. A spectral analysis of the reactive medium and the composition of the resulting polymers revealed new evidence for an anionic mechanism of the copolymerization process under our experimental conditions. Moreover, the photoluminescence yields were strongly dependant on the conjugation length and on the solvent, with a maximum (70%) in tetrahydrofuran and a minimum (<1%) in water. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4337–4350, 2005     

Novel materials for bioanalytical and biomedical applications: Environmental response and binding/release capabilities of amphiphilic hydrogels with shape‐persistent dendritic junctions

The binding and release capabilities of a hydrogel series, constructed of hydrophilic poly(ethylene glycol) segments and hydrophobic dendritic junctions [poly (benzyl ether)s], are evaluated in aqueous media. The environmental response of the amphiphilic networks is also tested in water at three pH values: 1.5, 7.0, and 10.1. The highest swelling ratio is observed under acidic conditions and varies between 3.7 and 6.5, depending on the crosslinking density and dendrimer generation. Gel specimens with embedded indicators react within 3–6 s with a clear color switch to the change in the pH of the surrounding medium. The experiments with model anionic and cationic indicators and stains show that the hydrogels have basic interiors. The gel binding capabilities depend on the water solubility of the substrate and on the size of the incorporated dendritic fragments. Model release studies have been performed at 37 °C and pHs 1.5, 7.0, and 10.1. The observed phenomena are explained by the transformations in the structure and charge that both the networks and the model compounds undergo with the changes in the pH of the aqueous medium. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4017–4029, 2005     

Block copolymers of poly(ethylene oxide) and poly(vinyl alcohol) synthesized by the RAFT methodology

A methodology for the synthesis of well‐defined poly(ethylene oxide)‐block‐poly(vinyl alcohol) (PEO‐b‐PVA) and PVA‐b‐PEO‐b‐PVA polymers was reported. Novel xanthate end‐functionalized PEOs were synthesized by a series of end‐group transformations. They were then used to mediate the reversible addition–fragmentation chain transfer polymerization of vinyl acetate to obtain well‐defined poly(ethylene oxide)‐b‐poly(vinyl acetate) (PEO‐b‐PVAc) and PVAc‐b‐PEO‐b‐PVAc. When these block copolymers were directly hydrolyzed in methanol solution of sodium hydroxide, polymers with brown color were obtained, which was due to the formation of conjugated unsaturated aldehyde structures. To circumvent these side reactions, the xanthate groups were removed by adding a primary amine before hydrolysis and the products thus obtained were white powders. The polymers were characterized by gel permeation chromatography, ¹H NMR spectroscopy and FT‐IR. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1901–1910, 2009     

Observations of crystallization and melting in poly(ethylene oxide)/poly(methyl methacrylate) blends by hot-stage atomic-force microscopy

The binary blend of poly(ethylene oxide)/atactic poly(methyl methacrylate) is examined using hot-stage atomic-force microscopy (AFM) in conjunction with differential scanning calorimetry and optical microscopy. It was found possible to follow in real time the melting process, which reveals itself to be nonuniform. This effect is ascribed to the presence of lamellae having different thicknesses. The crystallization process of poly(ethylene oxide) from the miscible melt is also followed in real time by AFM, affording detailed images of the impingement of adjacent spherulites and direct observation of lamellar growth and subsequent polymer solidification in the interlamellar space.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2643–2651, 1998     

Multistimuli responsive grafted poly(ether tert‐amine) (gPEA): Synthesis,characterization and controlled morphology in aqueous solution

Multistimuli responsive grafted poly(ether tert‐amine) (gPEAs), which were comprised of poly(propylene oxide) (PPO) in backbone and poly(ethylene oxide) (PEO) as grafted chain, were successfully synthesized through nucleophilic addition/ring‐opening reaction of commercial poly(propylene glycol) diglycidyl ether and Jeffamine L100. These gPEAs exhibit very sharp response to temperature, pH and ionic strength with tunable cloud point (CP). The CP of gPEA aqueous solution increases with increasing the PEO content or decreasing pH value, varying from 27 to 77 °C. Compared with linear PEA101, gPEA110 of completely grafted structure in aqueous solution exhibits sharper response to temperature with ΔT around 1 °C. The results obtained from TEM and dynamic light scattering reveal that gPEAs are dispersed as uniform sized nano‐micelles in aqueous at room temperature, which can further aggregate into mesoglobules of complex structure at high temperature (>CP). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6353–6361, 2009     

Blends of organosilicon polymers with polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide)

Blends of organosilicon polymers with polystyrene, PS, and poly(2,6-dimethyl-1,4-phenylene oxide), PPE, were investigated by transmission electron microscopy and differencial scanning calorimetry. Blends with poly(tetramethylsilphenylenesiloxane), PTMPS, showed a morphology characterized by globular domains dispersed in the organic matrix. An apparent homogeneous system was observed when poly(dimethylsilphenylene), PDSP, was mixed with PPE. A crystalline phase was found in samples with a higher PDSP content. The morphology of PS/PDSP blends with low PDSP content showed a dendritic phase dispersed in the PS-rich matrix. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2609–2616, 1997     

From poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) triblock copolymer to poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) hydrogels: Synthesis and rapid deswelling and reswelling behavior of hydrogels

Poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide)‐block‐poly(N‐isopropylacrylamide) (PNIPAAm‐b‐PEO‐b‐PNIPAAm) triblock copolymer was synthesized via the reversible addition‐fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process with xanthate‐terminated poly(ethylene oxide) (PEO) as the macromolecular chain transfer agent. The successful synthesis of the ABA triblock copolymer inspired the preparation of poly(N‐isopropylacrylamide)‐block‐poly(ethylene oxide) (PNIPAAm‐b‐PEO) copolymer networks with N,N′‐methylenebisacrylamide as the crosslinking agent with the similar approach. With the RAFT/MADIX process, PEO chains were successfully blocked into poly(N‐isopropylacrylamide) (PNIPAAm) networks. The unique architecture of PNIPAAm‐b‐PEO networks allows investigating the effect of the blocked PEO chains on the deswelling and reswelling behavior of PNIPAAm hydrogels. It was found that with the inclusion of PEO chains into the PNIPAAm networks as midblocks, the swelling ratios of the hydrogels were significantly enhanced. Furthermore, the PNIPAAm‐b‐PEO hydrogels displayed faster response to the external temperature changes than the control PNIPAAm hydrogel. The accelerated deswelling and reswelling behaviors have been interpreted based on the formation of PEO microdomains in the PNIPAAm networks, which could act as the hydrophilic tunnels to facilitate the diffusion of water molecules in the PNIPAAm networks. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Rapid metal‐free macromolecular coupling via In Situ nitrile oxide‐activated alkene cycloaddition

Nitrile oxide 1,3 dipolar cycloaddition is a simple and powerful coupling methodology. However, the self‐dimerization of nitrile oxides has prevented the widespread use of this strategy for macromolecular coupling. By combining an in situ nitrile oxide generation with a highly reactive activated dipolarophile, we have overcome these obstacles and present a metal‐free macromolecular coupling strategy for the modular synthesis of several ABA triblock copolymers. Nitrile oxides were generated in situ from chloroxime terminated poly(dimethylsiloxane) B‐blocks and coupled with several distinct hydrophilic (poly(2‐methyloxazoline) and poly(ethylene glycol)), and poly(N‐isopropylacrylamide) or hydrophobic (poly(l ‐lactide) A‐blocks terminated in activated dipolarophiles in a rapid fashion with high yield. This methodology overcomes many drawbacks of previously reported metal‐free methods due to its rapid kinetics, versatility, scalability, and ease of introduction of necessary functionality. Nitrile oxide cycloaddition should find use as an attractive macromolecular coupling strategy for the synthesis of biocompatible polymeric nanostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3134–3141     

Graft copolymers prepared by ethoxylation of polyamide 12 and poly(ethylene-co-vinyl alcohol)

Graft copolymers consisting of polyamide 12 or poly(ethylene-co-vinyl alcohol) as backbone polymers and side chains of poly(ethylene oxide) have been synthesized. The amide and hydroxyl groups of the backbone polymers were used as initiation sites for the polymerization of ethylene oxide (EO). Potassium tert-butoxide was used for ionization of the active groups, and the polymerization of EO was carried out in dimethyl sulfoxide. The graft copolymers were characterized with respect to molecular weight and composition using elemental analysis, ¹H-NMR, gel permeation chromatography, and FTIR. The size of the side chains varied between 300 and 1000 g/mol. Thermal properties were examined by DSC. The graft copolymers showed increasing crystallinity and increasing melt temperature with increasing molecular weight of the side chains. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 803–811, 1998     

Synthesis and characterization of new alternating,amphiphilic, comblike copolymers of poly(ethylene oxide) macromonomer and N‐phenylmaleimide

A surface‐active p‐vinyl benzyloxy‐ω‐hydroxy‐poly(ethylene oxide) macromonomer containing 22 pendant structural units of ethylene oxide (St–PEO₂₂) was synthesized with an initiation method. Because of its solubility in a large variety of solvents, the free‐radical copolymerization with electron‐acceptor N‐phenylmaleimide (NPMI) was performed at 60 °C in benzene and tetrahydrofuran (THF) as isotropic media and in a water–THF mixture or water as a heterogeneous medium. Oil‐soluble 2,2′‐azobisisobutyronitrile and water‐soluble 4,4′‐azobis(4‐cyanovaleric acid) were used as the initiators at fixed concentrations. Two different St–PEO₂₂/NPMI comonomer ratios (1/1 and 3/7) at a fixed total comonomer concentration in the polymerization system were used. The structures, compositions, and microstructure peculiarities of the obtained alternating, amphiphilic, comblike copolymers were determined by NMR analysis. For the copolymers synthesized in hydrophilic media, differential scanning calorimetry showed, near the endothermic peak attributed to the melting of the poly(ethylene oxide) side chains, the presence of a second peak due to the partially ordered phase that could exist between the crystalline state and the isotropic melt. Also, the thermal stability of the obtained copolymers was studied with thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 479–492, 2005     

Synthesis and characterization of novel degradable photocrosslinked poly(ether‐anhydride) networks

New degradable poly(ether‐anhydride) networks were synthesized by UV photopolymerization. Dicarboxylated poly(ethylene glycol) (PEG) or poly(tetramethylene glycol) (PTMG) was reacted with an excess of methacrylic anhydride to form dimethacrylated macromers containing anhydride linkages. The percent of conversion for the macromer formation was more than 80% at 60 °C after 24 h. ¹H NMR and IR spectroscopies show the presence of anhydride linkages in the macromer. In vitro degradation studies were carried out at 37 °C in PBS with crosslinked polymer networks formed by UV irradiation. All PEG‐based polymers degraded within 2 days, while PTMG‐based polymers degraded by 50% of the initial weight after 14 days. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1277–1282, 2000     

Synthesis of new amphiphilic diblock copolymers containing poly(ethylene oxide) and poly(α‐olefin)

This article discusses an effective route to prepare amphiphilic diblock copolymers containing a poly(ethylene oxide) block and a polyolefin block that includes semicrystalline thermoplastics, such as polyethylene and syndiotactic polystyrene (s‐PS), and elastomers, such as poly(ethylene‐co‐1‐octene) and poly(ethylene‐co‐styrene) random copolymers. The broad choice of polyolefin blocks provides the amphiphilic copolymers with a wide range of thermal properties from high melting temperature ～270 °C to low glass‐transition temperature ～?60 °C. The chemistry involves two reaction steps, including the preparation of a borane group‐terminated polyolefin by the combination of a metallocene catalyst and a borane chain‐transfer agent as well as the interconversion of a borane terminal group to an anionic (? O^?K⁺) terminal group for the subsequent ring‐opening polymerization of ethylene oxide. The overall reaction process resembles a transformation from the metallocene polymerization of α‐olefins to the ring‐opening polymerization of ethylene oxide. The well‐defined reaction mechanisms in both steps provide the diblock copolymer with controlled molecular structure in terms of composition, molecular weight, moderate molecular weight distribution (M_w/M_n < 2.5), and absence of homopolymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3416–3425, 2002     

Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)

Multiwall carbon nanotube (MWNT) was grafted with polyacrylate‐g‐poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid‐treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880–6887, 2006     

Molecular composites of poly(p‐phenylene terephthalamide) anion and poly(ethylene oxide): Thermal behavior and morphology

Molecular composites, in which a small concentration of ionically modified poly(p‐phenylene terephthalamide) (PPTA) is dispersed in a poly(ethylene oxide) matrix, have been prepared. With the content of PPTA anion increasing to about 5 wt %, the glass‐transition temperature rises and the melting temperature decreases. From the equilibrium‐melting‐temperature depression data that were obtained from Hoffman–Weeks plots, the Flory–Huggins interaction parameter was determined to be negative (−1.10). These indications of enhanced miscibility between the components are attributed to intermolecular ion–dipole interactions. The presence of rigid PPTA‐anion reinforcement alters the morphology; for example, the spherulite size is reduced, and the degree of crystallinity is lowered. Possible models of how the reinforcement is incorporated into the composite are presented. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1369–1376, 2000