New architectures of poly(ethylene glycol) and poly(methylthiirane) in block copolymers

Two synthetic ways were experimented to prepare new architectures of block copolymers made of poly(ethylene glycol) (PEG) and poly(methylthiirane). The coupling of both blocks conveniently end-capped as well as anionic polymerization of methylthiirane initiated by PEG-thiols gave readily the copolymers. Their characterization by ¹H NMR, SEC and IR confirmed the expected structures.     

Supercritical carbon dioxide assisted synthesis of amphiphilic graft copolymers based on poly(styrene-co-maleic anhydride) with methoxyl poly(ethylene glycol) side chains

Supercritical carbon dioxide (scCO2) was used as a reaction medium in synthesizing amphiphilic graft copolymers composed of poly(styrene-co-maleic anhydride) (SMA) backbones and methoxyl poly(ethylene glycol) (MPEG) side chains via esterification.The synthesized copolymers were characterized by Four     

Self-aggregated nanoparticles from methoxy poly(ethylene glycol)-modified chitosan: synthesis; characterization; aggregation and methotrexate release in vitro

Methoxy poly(ethylene glycol)-grafted-chitosan (mPEG-g-CS) conjugates were synthesized by formaldehyde linking method and characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (¹H-NMR). The degree of substitution (DS) of methoxy poly (ethylene glycol) (mPEG) in the mPEG-g-CS molecules determined by ¹H-NMR ranged from 19% to 42%. The critical aggregation concentration (CAC) was determined by fluorescence spectroscopy using pyrene as fluorescence probe and its value was 0.07 mg/mL in water. mPEG-g-CS formed monodisperse self-aggregated nanoparticles with a roughly spherical shape and a mean diameter of 261.9 nm were prepared by the dialysis method. mPEG-g-CS self-aggregated nanoparticles were used as carriers of poorly water-soluble anticancer drug methotrexate (MTX). MTX was physically entrapped inside mPEG-g-CS self-aggregated nanoparticles by dialysis method and the characteristics of MTX-loaded mPEG-g-CS self-aggregated nanoparticles were analyzed using dynamic laser light scattering (DLLS), transmission electron microscopy (TEM). Moreover, in vitro release behavior of MTX was also investigated and the results showed that MTX was continuously released more than 50% in 48 h.     

Effects of polymerization conditions on the in vitro hydrolytic degradation of plaques of poly(dl-lactic acid-block-ethylene glycol) diblock copolymers

In the case of poly(lactic acid) stereocopolymers, it has been shown that the hydrolytic degradation of derived devices depends very much on whether zinc lactate or tin octoate was used to polymerize lactides. In contrast, no effect was found in the case of nanoparticles derived from poly(dl-lactic acid)-block-poly(ethylene glycol) copolymers obtained by anionic polymerization of dl-lactide initiated by the sodium salt of monomethoxypoly(ethylene glycol) or by coordination-insertion polymerization of dl-lactide initiated by monomethoxypoly(ethylene glycol) in the presence of tin octoate as catalyst. To understand the difference of behaviour, in vitro hydrolytic degradation of thick plates made of the same copolymers but under different conditions was investigated. Changes were monitored by ¹H Nuclear Magnetic Resonance, Size Exclusion Chromatography, Electrospray Mass Spectrometry and Capillary Zone Electrophoresis. It is shown that chain cleavage occurred from the very beginning of degradation and that plates disintegrated after 13 weeks. In all cases, degradation proceeded faster inside than at the surface, in contrast to what was observed for nanoparticles. Tin-type copolymer plates degraded more slowly than sodium macroalcoholate-type ones and were sensitive to purification conditions, in contrast to the latter.     

Crystallization of photo-chain extended poly(ethylene glycol)

Coumarin-functionalized poly(ethylene glycol) (PEG) monols and diols were isothermally crystallized at temperatures between 20 and 35 °C before and after exposure to approximately 110 J cm⁻² of ultra-violet A (λ > 300 nm, UVA) irradiation. Irradiation dimerized the coumarin groups and chain-extended the coumarin-functionalized PEG oligomers. The higher molecular weights reduced the crystal growth rate by as much as 50% compared to the non-irradiated coumarin-functionalized PEG oligomers under ambient crystallization conditions. Hoffman’s kinetic nucleation theory was utilized to evaluate the types of nucleation that occurred for the coumarin-functionalized PEG diols (COU-PEG-COU). Crystallization regimes II and III were observed for the coumarin-modified PEG oligomers before and after exposure to UVA light.     

聚丙烯酰胺-聚乙二醇-水体系相图及丙烯酰胺单体在两相中的分配

聚丙烯酰胺(PAAm)和聚乙二醇(PEG)两种水溶液混合时能形成双水相体系,其中上层为PEG富集相,下层为PAAm和PEG的混合相.用凝胶渗透色谱(GPC)法和浊度滴定法研究了PAAm-PEG-H₂O双水相体系的相图,结果表明,随着PEG分子量的升高,体系的分相浓度下降.在PAAm-PEG20000-H₂O体系中,随着体系温度升高,分相浓度先下降后升高,55℃时分相浓度最低.丙烯酰胺(AAm)单体能在两相中发生相分配,分配系数随着PAAm浓度和平衡温度的增加而增大,随着PEG浓度的增加而下降.     

Polycaprolactone–poly(ethylene glycol) block copolymer,I: synthesis and degradability in vitro

A new type of biodegradable polymer material, poly(caprolactone)–poly(ethylene glycol) block copolymer (PCL-b-PEG), was synthesized by means of direct copolycondensation of ε-caprolactone with poly(ethylene glycol) in the presence of a Ti(OBu)₄ catalyst. The degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL-b-PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.     

Methoxy poly(ethylene glycol)-b-poly(valerolactone) diblock polymeric micelles for enhanced encapsulation and protection of camptothecin

Amphiphilic block copolymers, methoxy poly(ethylene glycol)-b-poly(valerolactone) (mPEG-b-PVL), were synthesized via ring opening polymerization of δ-valerolactone in the presence of methoxy poly(ethylene glycol) (mPEG). The copolymers form micelle-like nanoparticles by their amphiphilic characteristics and their structures were examined by Nuclear Magnetic Resonance (NMR). The sizes of nanoparticles ranged from 60 to 120 nm as measured by dynamic light scattering detection, and were larger with higher molecular weight of the copolymers. The Critical Micelle Concentration (CMC) of these nanoparticles in water decreased with increasing molecular weight of hydrophobic segment. Stability analysis showed that the micellar solutions maintain their sizes at 37 °C for six weeks without aggregation or dissociation. The lyophilization method was better than the evaporation method when camptothecin (CPT) was incorporated to the micelles. The former method yielded higher CPT loading efficiency and lower aggregation. The loading efficiency of CPT could be more than 96% and a steady release rate of CPT was kept for twenty six days. Moreover, the mPEG-b-PVL polymeric micelles offered good protection of CPT lactone form at 37 °C for sixteen days. The copolymers showed no cytotoxicity towards L929 mouse muscular cells when incubated for one day. Taken together, the mPEG-b-PVL copolymer has potential to be used for the delivery of CPT or other similar drugs.     

Determination of poly(ethylene glycol)s by both normal-phase and reversed-phase modes of high-performance liquid chromatography

A normal-phase HPLC system using an amino column has been developed to characterise oligomers of poly(ethylene glycol)s (PEGs) of average M_r 400 to 2000 with derivatisation by dinitrobenzoate. Normal-phase HPLC with gradient elution using ternary solvents of hexane, dichloromethane and methanol has produced a baseline resolution for oligomers of PEG 400, 600 and 1000, while PEG 1000 and 2000 were analysed by using binary solvents of acetonitrile and water. Mixtures of PEGs have been determined by these HPLC systems. PEG 400 in a textile finish has also been determined with satisfactory recovery. It has been found that the hydroxyl group of solvents in normal-phase HPLC plays an important role in resolution and retention of PEG oligomers. Derivatisation efficiency for PEGs by dinitrobenzoyl chloride and quantitative determination of derivatised PEGs by HPLC have been studied. A reversed-phase (RP) mode of HPLC was examined for determination of PEG 400 oligomers. The normal-phase system provided greater resolution for oligomers of PEGs.     

Preparation, characterization and biocompatibility of poly(ethylene glycol)-poly(n-butyl cyanoacrylate) nanocapsules with oil core via miniemulsion polymerization

A new type of nanocapsules with an oil core, coated by poly(ethylene glycol) (PEG) was designed. The loading efficiency and the biocompatibility of the polymeric nanocapsules were evaluated when it was used as a carrier for hydrophobic agent paclitaxel. The nanocapsules were synthesized through miniemulsion polymerization of butylcyanoacrylate (BCA) with PEG as initiator. The particle size and zeta potential of nanocapsules were influenced by the PEG content in the polymerization system. Fourier transform infrared (FTIR) spectra and ¹H NMR demonstrated the chemical coupling between PEG and poly(butylcyanoacrylate) (PBCA). Thermal characteristics of the copolymer were investigated by differential scanning calorimetry (DSC). The encapsulation efficiency increased concurrently with the increase of the PEG content in the system. The hemolytic assay and the cytotoxicity measurement showed that the PEG coating could significantly reduce the hemolytic potential and cytotoxicity of the nanocapsules. The results showed that the PEG-PBCA nanocapsules could be an effective carrier for hydrophobic agents.     

An analysis of the complexation between poly(aspartic acid) and poly(ethylene glycol)

The compatibility between poly(aspartic acid) and poly(ethylene glycol) for the formation of an interpolymer complex (IPC) was investigated by dynamic rheology and evaluation of zeta potential values. The homogeneity of the realized IPC was observed by near infrared chemical imagistic (NIR-CI) technique. The data were sustained and underlined by the assessment of the compatibility between the polymeric compounds.     

Synthesis and micellization of amphiphilic poly(sebacic anhydride)–poly(ethylene glycol)–poly(sebacic anhydride) block copolymers

Amphiphilic biodegradable block copolymers [poly(sebacic anhydride)–poly(ethylene glycol)–poly(sebacic anhydride)] were synthesized by the melt polycondensation of poly(ethylene glycol) and sebacic anhydride prepolymers. The chemical structure, crystalline nature, and phase behavior of the resulting copolymers were characterized with ¹H NMR, Fourier transform infrared, gel permeation chromatography, and differential scanning calorimetry. Microphase separation of the copolymers occurred, and the crystallinity of the poly(sebacic anhydride) (PSA) blocks diminished when the sebacic anhydride unit content in the copolymer was only 21.6%. ¹H NMR spectra carried out in CDCl₃ and D₂O were used to demonstrate the existence of hydrophobic PSA domains as the core of the micelle. In aqueous media, the copolymers formed micelles after precipitation from water‐miscible solvents. The effects on the micelle sizes due to the micelle preparation conditions, such as the organic phase, dropping rate of the polymer organic solution into the aqueous phase, and copolymer concentrations in the organic phase, were studied. There was an increase in the micelle size as the molecular weight of the PSA block was increased. The diameters of the copolymer micelles were also found to increase as the concentration of the copolymer dissolved in the organic phase was increased, and the dependence of the micelle diameters on the concentration of the copolymer varied with the copolymer composition. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1271–1278, 2006     

Formation of nanoporous poly(aryl amide ether) (PAAE) films by selective removal of poly(ethylene glycol) (PEG) from PEG/PAAE composite films

Poly(aryl amide ether) (PAAE) thin films with nanometer-sized pores have been prepared in two steps: (1) solution casting of partially miscible poly(ethylene glycol) (PEG)/PAAE blends from one of their common solvents, dimethyl sulfoxide (DMSO), results in formation of PEG/PAAE nanocomposite films; (2) selective removal of PEG component by water washing yields nanosized, porous PAAE films. The pores have been found to have a small size variation and cover the whole surface homogeneously. With an increase in PEG contents, the sizes of the pores increase but the size distributions do not have much changes. This has been ascribed to formation of small PEG domains in PEG/PAAE composite films, which is facilitated by the strong interactions, mostly hydrogen bonds, between PEG and PAAE macromolecular chains.     

Synthesis and properties of polymer brushes composed of poly(diphenylacetylene) main chain and poly(ethylene glycol) side chains

Novel cylindrical polymer brushes consisting of poly(diphenylacetylene) main chain and poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) side chains were synthesized by the diphenylacetylene macromonomer or side chain initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether monomethacrylate (PEGMA) from an bromo isobutyryl-bearing poly(diphenylacetylene) (poly(BrDPA)) method. The diphenylacetylene macromonomer, namely, DPA-PPEGMA, were prepared by the ATRP of PEGMA from bromo isobutyryl-bearing diphenylacetylene. DPA-PPEGMA was polymerized successfully with WCl₆-Ph₄Sn catalyst to give high molecular weight polymer brushes poly(DPA-PPEGMA). Meanwhile, polymer brushes (PDPA-g-PPEGMA) were obtained by ATRP of PEGMA from poly(BrDPA). The molecular weight of the side chains of PPEGMA could be controlled simply by modulating the ATRP time. The macromonomer and polymer brushes are soluble in nonpolar solvents such as toluene and chloroform. The polymers of poly(BrDPA) and poly(DPA-PPEGMA) absorb in the longer wavelength region, with two peaks at around 370 and 414 nm. The polymers are thermally stable and exhibit double crystallization and melting peaks during the cooling and heating scans.     

Determination of poly(ethylene glycol) 300 in long chain free fatty acid mixtures by reversed-phase high-performance liquid chromatography

A rapid sensitive method has been developed for the detection and quantitation of poly(ethylene glycol) 300 (PEG 300) in long-chain free fatty acid mixtures that requires minimal sample preparation. The PEG 300 was separated from the free fatty acids by RP-HPLC using a water–tetrahydrofuran gradient. PEG and the free fatty acids were detected using evaporative light scattering detection. The minimum detectable level of PEG in a free fatty acid mixture was 0.0125%.     

The influence of UV light on collagen/poly(ethylene glycol) blends

The photodegradation behaviour of the collagen and poly(ethylene glycol) PEG blends has been studied by Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and viscometry. Surface properties before and after UV irradiation were observed using optical microscope.Collagen and PEG were immiscible and the films obtained from the mixture were fragile with poor mechanical properties. The photochemical stability of the collagen and PEG blend was different from that of the single components. In general collagen/PEG blends are less stable under UV irradiation than pure collagen. The influence of PEG on the photochemical stability of collagen depends on its concentration in the blend. Microscope photographs showed that the surface characteristics of collagen and collagen/PEG blends in film form are not drastically altered after UV irradiation.     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions

In this work the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions were measured at 283.1–313.1 K. The expansion factor of polymer chain was calculated by use of the intrinsic viscosities data. The thermodynamic parameters of polymer solution (the entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were evaluated by temperature dependence of polymer chain expansion factor. The obtained thermodynamic parameters indicate that quality of water was decreased for solutions of poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(ethylene oxide)/poly(vinyl pyrrolidone) blends by increasing temperature. Compatibility of poly(ethylene oxide)/poly(vinyl pyrrolidone) blends were explained in terms of difference between experimental and ideal intrinsic viscosity and solvent–polymer interaction parameter. The results indicate that the poly(ethylene glycol)/poly(vinyl pyrrolidone) blends were incompatible.     

Rheology of an aqueous solution of an end-capped poly(ethylene glycol) polymer at high concentration

Generally it is observed that the viscosity of an aqueous solution of a hydrophobically modified polymer increases with concentration; however, here it is shown that the viscosity profile of an end-capped poly(ethylene glycol) polymer passes through a maximum. Thus, a substantial decrease in viscosity is observed at high concentrations (≥50 wt%). The observation is suggested to be due to a gradual change, on the molecular level, from a structure containing micellelike structures that are interconnected via polymer bridges to a more meltlike state, where micro segregation in hydrophilic and hydrophobic regions is less pronounced. Received: 23 October 1998 Accepted in revised form: 10 March 1999     

New approach on the development of plasticized polylactide (PLA): Grafting of poly(ethylene glycol) (PEG) via reactive extrusion

In this work, new ways of plasticizing polylactide (PLA) with low molecular poly(ethylene glycol) (PEG) were developed to improve the ductility of PLA while maintaining the plasticizer content at maximum 20 wt.% PLA. To this end, a reactive blending of anhydride-grafted PLA (MAG-PLA) copolymer with PEG, with chains terminated with hydroxyl groups, was performed. During the melt-processing, a fraction of PEG was grafted into the anhydride-functionalized PLA chains. The role of the grafted fraction was to improve the compatibility between PLA and PEG. Reactive extrusion and melt-blending of neat and modified PLA with PEG did not induce any dramatic drop of PLA molecular weight. The in situ reactive grafting of PEG into the modified PLA in PLA/PEG blends showed a clear effect on the thermal properties of PLA. It was demonstrated by DSC that the mobility gained by PLA chains in the plasticized blends yielded crystallization. The grafting of a fraction of PEG into PLA did not affect this process. However, DSC results obtained after the second heating showed an interesting effect on the T_g when 20 wt.% PEG were melt blended with neat PLA or 10 wt.% MAG-PLA. In the latter case, the T_g displayed by the reactive blend was shifted to even lower temperatures at around 14 °C, while the T_g of neat PLA and PLA blended with 20 wt.% PEG was around 60 and 23 °C, respectively. Regarding viscoelastic and viscoplastic properties, the presence of MAG-PLA does not significantly influence the behavior of plasticized PLA. Indeed, with or without MAG-PLA, elastic modulus and yield stress decrease, while ultimate strain increases with the addition of PEG into PLA.