Aggregation behavior and catalytic properties of systems based on aminomethylated calix[4]resorcinarenes and poly(ethylene) imines

Self-assembling in systems poly(ethylene) imine-aminomethylated calix[4]resorcinarene-water-DMF (30 vol%) and catalytic properties of these compositions in hydrolysis of 4-nitrophenylbis (chloromethyl)phosphinate are studied. Critical concentrations of association, aggregates radii, and kinetic parameters of the reaction are established.     

Etching of crystalline poly(ethylene terephthalate) by hydrolysis

Conditions have been found for the etching of poly(ethylene terephthalate) with water so that the crystalline portions alone remain. Initial sample and hydrolysis products are analyzed by extraction of low molecular weight products; density, viscosity molecular weight, and endgroup determination; heating-rate-dependent thermal analysis; low-angle and wide-angle x-ray analysis; and electron microscopy. On hydrolysis of a 67% crystalline polymer at 180°C for about 300 min, almost fully crystalline extended-chain oligomers can be obtained with about 65% yield. The morphology of melt-crystallized poly(ethylene terephthalate) and the melting behavior of oligomer lamellae are discussed.     

Systems based on the hydrophobically modified poly(ethylene imines) and surfactants: Aggregation and catalysis

The aggregation in aqueous systems of hydrophobically modified poly(ethylene imines) and their mixtures with cationic surfactants, as well as the catalytic activity of these compositions in the hydrolysis of O-4-nitrophenyl-O-ethylchloromethylphosphonate, are studied by conductometry, tensiometry, light-scattering, and viscometry methods. Critical association concentration, hydrodynamic radii of polymer and polymer-colloid aggregates formed in such systems, as well as kinetic parameters of hydrolysis are determined.     

Synthesis of double hydrophilic graft copolymer containing poly(ethylene glycol) and poly(methacrylic acid) side chains via successive ATRP

A well‐defined double hydrophilic graft copolymer, with polyacrylate as backbone, hydrophilic poly(ethylene glycol) and poly(methacrylic acid) as side chains, was synthesized via successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl methacrylate) side chains. The grafting‐through strategy was first used to prepare poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer. The obtained comb copolymer was transformed into macroinitiator by reacting with lithium diisopropylamine and 2‐bromopropionyl chloride. Afterwards, grafting‐from route was employed for the synthesis of poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methoxymethyl methacrylate) amphiphilic graft copolymer. The molecular weight distribution of this amphiphilic graft copolymer was narrow. Poly(methoxymethyl methacrylate) side chains were connected to polyacrylate backbone through stable C? C bonds instead of ester connections. The final product, poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methacrylate acid), was obtained by selective hydrolysis of poly(methoxymethyl methacrylate) side chains under mild conditions without affecting the polyacrylate backbone. This double hydrophilic graft copolymer was found be stimuli‐responsive to pH and ionic strength. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4056–4069, 2008     

Effect of Polymer and Surfactant‐Polymer Couples on the Acid-Catalyzed Hydrolysis of Phenyl Urea

The mechanism of the hydrolysis decomposition of phenyl urea in acid, polymer, and surfactant‐polymer media was investigated, the addition‐elimination mechanism with rate determining attack of water at N‐protonated substrate having already been studied. This study has introduced the polymer PEG (MW‐400) and (surfactant‐polymer) (ceteyl trimethyl ammonium bromide‐poly ethylene glycol) (CTAB‐PEG), (cetyl pyridinium bromide‐polyethylene glycol) (CPC‐PEG) (sodium dodecyl sulphate‐poly ethylene glycol) (SDS‐PEG), (Triton X‐100‐poly ethylene glycol) (TX‐100‐PEG), and (Brij35‐poly ethylene glycol) (Brij35‐PEG) in acid media. The results indicate that the presence of polymer and surfactant‐polymer enhances the rate of reaction at 80°C in the presence of 0.9 M H₂SO₄. Kinetic studies show that the reaction obeyed first‐order kinetics. The reaction kinetics can be well explained by micellar catalysis models like the PPIE.     

聚己内酯-聚醚嵌段共聚物的光降解特性与机理

聚己内酯-聚醚嵌段共聚物(PCE)是一种可生物降解的高聚物[1].我们已经报道了PCE在体内及体外的降解特性,发现PCE的降解速度随着共聚物中聚醚含量的增加,温度升高,介质的酸碱性和酶的存在而加快.当PCE植入于动物体内,它的降解速度大大加快,因此PCE是一种极具应用前景的生物医用材料[2,3].     

Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers

A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.     

Hydrogels of β-cyclodextrin crosslinked by acylated poly(ethylene glycol): Synthesis and properties

Networks of β-cyclodextrin have been prepared by reaction with acylated poly(ethylene glycol) with a molar mass of 600 g/mol. Samples with different β-cyclodextrin/poly(ethylene glycol) ratios: 1/4, 1/6, 1/8 and 1/10 have been prepared. Both components are bonded by ester groups, resulting in a network that can be degraded by hydrolysis in basic and acidic media. The maximum stability of the hydrogels is reached at pH 4. The hydrogel percentage water content depends on β-cyclodextrin content ranging from 82 to 98, and the swelling data obtained for these hydrogels fit well with a second order kinetics. The sorption behavior of these hydrogels has been tested by employing 1-naphthol as model molecule. The sorption capacity is close to other cyclodextrin networks previously reported and depends on the hydrogel composition and the concentration of 1-naphthol.     

A new water‐soluble branched poly(ethylene imine) derivative having hydrolyzable imidazolidine moieties and its application to long‐lasting release of aldehyde

A new water‐soluble poly(ethylene imine)‐derivative having imidazolidine moieties was developed. With using branched poly(ethylene imine) (BPEI) as a precursor, it was modified by Michael addition reaction of its primary amino group to an acrylate having poly(ethylene glycol) (PEG) chain. The modified BPEI was reacted with octanal to give the corresponding BPEI derivative having octanal‐derived imidazolidine moieties. The obtained polymer inherited the high hydrophilicity of the attached PEG chains to allow hydrolysis of the imidazolidine moieties under homogeneous conditions in aqueous media, leading to long‐lasting release of octanal. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Ultrafast dynamics of liquid poly(ethylene glycol)s and crown ethers studied by femtosecond Raman-induced Kerr effect spectroscopy

Ultrafast molecular dynamics of liquid poly(ethylene glycol)s, tetra(ethylene glycol), penta(ethylene glycol), and poly(ethylene glycol) with the molecular weight of 600, and crown ethers, 12-crown-4 and 15-crown-5, have been investigated by means of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. Picosecond Kerr transients of poly(ethylene glycol)s and crown ethers are characterized by a biexponential function with the time constants of about 2 and 20 ps. Both the faster and slower time constants do not vary much among the five oligo(ethylene oxide)s. Femtosecond dynamics is discussed based on the Kerr (depolarized Raman) spectra obtained by Fourier transform deconvolution analysis of the high time resolution Kerr transients. The broad low-frequency band (0-200 cm(-1)) in the Kerr spectrum is analyzed by two Brownian oscillators. The spectral shapes of linear poly(ethylene glycol) and cyclic crown ether are very different. Both the low- and high-frequency Brownian oscillators for crown ethers show lower frequency and broader spectral features than those for poly(ethylene glycol)s. The comparison of the low-frequency spectra of poly(ethylene glycol)s and crown ethers shows that the low-frequency spectrum of 15-crown-5 is closer to that of poly(ethylene glycol)s than that of 12-crown-4 is. The difference of the low-frequency spectra between poly(ethylene glycol) and crown ether is discussed with the concepts of molecular conformation and liquid density. The features of the observed intramolecular vibrational bands are also correlated with the molecular conformations.     

Synthesis of polyrotaxanes from acetyl-β-cyclodextrin

Polyrotaxanes are intermediary products in the synthesis of topological gels. They are created by inclusion complex formation of hydrophobic linear macromolecules with cyclodextrins or their derivatives. Then, pairs of cyclodextrin molecules with covalently linkage were practically forming the nodes of the semi-flexible polymer network. Such gels are called topological gels and they can absorb huge quantities of water due to the net flexibility allowing the poly(ethylene oxide) chains to slide through the cyclodextrin cavities, without being pulled out altogether. For polyrotaxane formation poly(ethylene oxide) was used like linear macromolecules. There are hydroxyl groups at poly(ethylene oxide) chains, whereby the linking of the voluminous molecules should be made. To avoid the reaction of cyclodextrin OH groups with stoppers, they should be protected by, e.g., acetylation. In this work, the acetylation of the OH groups of β-cyclodextrin was performed by acetic acid anhydride with iodine as the catalyst. The acetylation reaction was assessed by the FTIR and HPLC method. By the HPLC analysis was found that the acetylation was completed in 20 minutes. Inserting of poly(ethylene oxide) with 4000 g/mol molecule mass into acetyl-β-cyclodextrin with 2:1 poly(ethylene oxide) monomer unit to acetyl-β-cyclodextrin ratio was also monitored by FTIR, and it was found that the process was completed in 12 h at the temperature of 10°C. If the process is performed at temperatures above 10°C, or for periods longer than 12 hours, the process of uncontrolled hydrolysis of acetate groups was initiated.     

Efficient water‐soluble drag reducing star polymers with improved mechanical stability

We describe here the first example of the synthesis of 4‐arm star poly(acrylic acid) for use as a water‐soluble drag reducing agent, by applying Cu(0)‐mediated polymerization technique. High molecular weight 4‐arm star poly(tert‐butyl acrylate) (M_n = 3.0–9.0 × 10⁵ g mol^?1) was first synthesized using 4,4′‐oxybis(3,3‐bis(2‐bromopropionate)butane as an initiator and a simple Cu(0)/TREN catalyst system. Then, 4‐arm star poly(tert‐butyl acrylate) were subjected to hydrolysis using trifluoroacetic acid resulting in water‐soluble 4‐arm star poly(acrylic acid). Drag reduction test rig analysis showed 4‐arm star poly(acrylic acid) to be effective as a drag reducing agent with drag reduction of 24.3%. Moreover, 4‐arm star poly(acrylic acid) exhibited superior mechanical stability when compared with a linear poly(acrylic acid) and commercially available drag reducing polymers; Praestol and poly(ethylene oxide). The linear poly(acrylic acid), Praestol, and poly(ethylene oxide) all showed a large decrease in drag reduction of 8–12% when cycled 30 times through the drag reduction test rig while, in contrast, 4‐arm star poly(acrylic acid) demonstrated much higher mechanical stability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 335–344     

Core-shell-corona au-micelle composites with a tunable smart hybrid shell

Micelles having a core of polystyrene and a mixed shell of poly(ethylene glycol) and poly(4-vinylpyridine) were formed through self-assembly of a triblock copolymer poly(ethylene glycol)- block-polystyrene- block-poly(4-vinylpyridine) in acidic water (pH 2). Reducing the HAuCl(4)-treated micelle solution leads to the formation of the Au-micelle composites with a core of polystyrene, a hybrid shell of poly(4-vinylpyridine)/Au/poly(ethylene glycol), and a corona of poly(ethylene glycol). The gold nanoparticles with controlled sizes were anchored to poly(4-vinylpyridine) to form the physically cross-linked hybrid shell. In aqueous solution, the hybrid shell is swollen and the swollen degree is sensitive to the pH condition. Under basic conditions, the channel in the hybrid shells of the composite is produced, which renders the composites a good catalytic activity. In addition, the composites also show good stability, unchanged hydrodynamic diameter, and surface plasmon absorption under different pH conditions.     

废旧聚酯（PET）的化学循环利用

废旧PET 聚酯可通过化学解聚来实现其循环利用。本文总结了废旧PET 聚酯化学循环利用领域的研究现状, 介绍了目前国内外开发的主要化学解聚工艺方法, 包括水解法、甲醇解聚法、乙二醇解聚法等, 同时对各种工艺过程的优缺点进行了综合比较。     

Gas Permeation Properties of Organic-Inorganic Hybrid Membranes Prepared from Hydroxyl-Terminated Polyether and 3-isocyanatopropyltriethoxysilane

Organic-inorganic hybrid materials were prepared by reacting 3-isocyanatopropyltriethoxysilane (IPTS) with hydroxyl terminated poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PEPG), followed by hydrolysis and condensation with acid catalysis. Composite membranes have been obtained by casting hybrid sol on the microporous polysulfone substrate. The membranes were characterized by Fourier transform infrared (FT-IR), ¹³C NMR and ²⁹Si NMR. The permeability coefficients of N₂, O₂, CH₄ and CO₂ were measured by variable volume method. The gas permeability coefficients increase with increasing molecular weight of the polyethers. For the membranes containing PEG and PEPG, the higher values of CO₂ permeability coefficients and CO₂/N₂ separation factors are due to the presence of ethylene oxide segments. In case of PEPG membranes, molecular weight has more influence on CO₂ permeability than the effect of facilitation by ethylene oxide. The addition of TEOS into hybrid sol results in the decrease of all the gas permeability and does not affect the gas selectivity. PEG2000 membrane display the most performance among the hybrid membranes investigated here. The best values observed are CO₂ permeability of 94.2 Barrer with selectivity of 38.3 for CO₂/N₂ and 15.6 for CO₂/CH₄.     

Grafting of poly(ethylene oxide) with Schiff's base end group onto chloromethylated polystyrene via Decker-Forster reaction

Amphiphilic graft copolymer of polystyrene (PS) as backbone and poly(ethylene oxide) (PEO) as branch chain was prepared by Decker-Forster reaction. PEO with Schiff's base end group (PEO_s) was obtained by ring-opening polymerization of ethylene oxide (EO) initiated with protected potassium aminoethoxide, and then alkylated with chloromethylated polystyrene (c-PS). A graft copolymer with high grafting efficiency was derived by hydrolysis of the above-mentioned product.     

Poly(ethylene glycol)-supported copper(II) triazacyclononane: an efficient, recoverable, and recyclable catalyst for the cleavage of a phosphodiester

The triazacyclononane macrocycle has been linked to the soluble polymer monomethoxy poly(ethylene) glycol and its copper(II) complex efficiently catalyzes the hydrolysis of a model phosphodiester. The catalyst, easily recovered from the water solution, shows no appreciable loss of activity when recycled three times.     

Synthesis and characterization of copolymers containing biphenylyl rings linked to the main chain through spacers of various lengths

Copolymers between 1-(4-biphenylyloxy carbonyl)ethylene (I), 1-[2-(4-biphenylyloxy)ethyloxy carbonyl]ethylene (II) and 1-[6-(4-biphenylyloxy carbonyl)]ethylene (III) were synthesized by radical polymerization. They were characterized by DSC, TOA, RX and viscosity techniques. The smectic order of poly(I) and the crystalline order of poly(III) depend on the amounts of comonomers incorporated. The obtained data demonstrate that the presence of quantities of comonomers exceeding 10% leads to complete destruction of smectic and crystalline order in poly(I) and poly(III) respectively.     

Excess molar enthalpies of binary mixtures containing ethylene glycols or poly(ethylene glycols) + ethyl alcohol at 308.15 K and atmospheric pressure

Excess molar enthalpies, , of binary mixtures containing ethylene glycols and poly(glycols) + ethyl alcohol were measured by a flow microcalorimeter at 308.15 K and at atmospheric pressure over the whole composition range. Binary mixtures contain ethyl alcohol + ethylene glycol, + di(ethylene glycol), + tri(ethylene glycol), + tetra(ethylene glycol), + poly(ethylene glycol)-200, + poly(ethylene glycol)-300, + poly(ethylene glycol)-400, + poly(ethylene glycol)-600. Effects of the molecular weight distribution (MWD), of the polymer were investigated too, by preparing three additional samples of poly(ethylene glycol) with the same number average molecular weight (M_n ≈ 300), but different MWD. For all mixtures, results were fitted to the Redlich–Kister polynomial. curves are asymmetrical, showing positive values which vary from 280 J mol⁻¹ (diethylene glycol + ethyl alcohol) to 1034 J mol⁻¹ (mixture containing PEGs (200 + 400) + ethyl alcohol). Effects of changes in the glycols chain length and in MWD on the molecular interactions among the mixture components are discussed.     

Enzyme-mediated enantioselective hydrolysis of poly(ethylene glycol)-supported carbonates

Kinetic resolution of poly(ethylene glycol)(PEG)-supported carbonates by enzymatic hydrolysis is discussed. Water-soluble carbonates are prepared by immobilization of racemic secondary alcohols onto low-molecular weight monomethoxy PEG (MPEG) through a carbonate linker. Porcine pancreas lipase (PPL) enantioselectively catalyzes the hydrolysis of the substrates to give optically active compounds. In this system, the separation of the resulting alcohols and the remaining substrates is achieved by an extraction process without laborious column chromatography. The carbonates are easily hydrolyzed with K₂CO₃ to afford the corresponding alcohols.