Aggregation Behavior of Poly(ethylene glycol)-block-poly (γ-benzyl L-glutamate)-graft-poly(ethylene glycol) Copolymer and its Blends with Poly(γ-benzyl L-glutamate) Homopolymer in Mixed Solvents

Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with mPEG. The self-association behaviors of PEG-b-PBLG-g-PEG and its blends with PBLG homopolymer in the mixtures of ethanol and dimethylformamide (DMF) were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and viscometry. Effects of the introduction of PBLG homopolymer, the grafting ratio, and the DMF content on the self-association behaviors of PEG-b-PBLG-g-PEG copolymer in the mixtures of ethanol and DMF were mainly researched. It was revealed that PEG-b-PBLG-g-PEG copolymer could self-assemble to form polymeric micelles with a core-shell structure in various shapes from different preparation conditions. The critical micelle concentration (CMC) and the average particle diameter of the micelles formed by PEG-b-PBLG-g-PEG copolymer in the mixed solvents also changed with different preparation conditions.     

Factors of Influencing the Grafting Ratio of Poly(γ-benzyl-L-glutamate)-graft-Poly (ethylene glycol) Copolymer

Poly(γ-benzyl-L-glutamate)-graft-poly(ethylene glycol) (PBLG-graft-PEG) copolymer was synthesized by the ester exchange reaction of PBLG with PEG. Nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the structure of PBLG-graft-PEG copolymer. The effects of reaction temperature, reaction time, and the chain length of PEG on the grafting ratio of PBLG-graft-PEG copolymer were investigated.     

Microwave-Assisted Synthesis of Poly(ε-caprolactone)-block-poly(ethylene glycol) and Poly(lactide)-block-poly(ethylene glycol)

Summary: This study reported the preparation and characterization of PCL-b-mPEG (poly(ε-caprolactone)-block-poly(ethylene glycol)) and PLL-b-mPEG (poly(L-lactide)-block-poly(ethylene glycol)) diblock copolymers by microwave heating and comparison of resulted products the ones with prepared by conventional heating. Diblock copolymers were synthesized successfully by the microwave-assisted ROP in the presence of stannous octoate (SnOct₂) as catalyst under nitrogen atmosphere in different monomer ratios. Structural and functional characterization of copolymers were performed by FTIR, ¹H-NMR and DSC. Molecular weight values were determined by GPC and also calculated from ¹H-NMR. According to the results, microwave irradiation allowed to obtain polymers with very narrow size distribution in very short reaction time. Similar polymers prepared by conventional heating were also synthesized for comparison. Molecular weight and conversion of polymers were increased by irradiation time. This change was continued until a certain time point after which no more increase was observed. It was concluded that microwave irradiation is a succesful method to obtain these diblock copolymers in very short reaction time and with a similar conversion obtained by conventional method.     

Electrospun Aligned Poly(L-lactide)/Poly(ϵ-caprolactone) /Poly(ethylene glycol) Blend Fibrous Membranes

Aligned poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL)/poly(ethylene glycol)(PEG) fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and in vitro degradation behaviors were investigated. With increasing the content of PEG, the PLLA/PCL/PEG blend fibers become thinner due to the increment in solution conductivity and decrease in solution viscosity. The thermal stability, hydrophilic properties, the tensile strength and elongation-at-break of PLLA/PCL/PEG blend fibrous membranes were improved, but porosity were decreased with the content of PEG changing from 10 wt% to 30 wt%. Furthermore, the incorporation of PEG enhanced the degradation of the PLLA/PCL/PEG fibrous membranes due to the better hydrophilic properties. In addition, the PLLA/PCL/PEG fibrous membranes have no toxic effect on proliferation of adipose-derived stem cells.     

Acid-Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5

PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring-opening copolymerization of ethylene oxide with 3,4-epoxy-1-butene (EPB) and subsequent modification to introduce acid-degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross-linking. Copolymers with different molar ratios of EPB, molecular weights (M_n) up to 10 000 g mol⁻¹ and narrow dispersities (Đ<1.05) were prepared. Both the P(EG-co-isoEPB)MA copolymer and the hydrogels showed pH-dependent, rapid hydrolysis at pH 5–6 and long-term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA-Alexa488 can be tailored from a few hours to several days (hydrolysis half-life time t_1/2 at pH 5: 13 h to 51 h).     

Preparation And Characterization of a New Blend of Poly(2-hydroxyethyl methacrylate) And Poly(ethylene glycol)

Poly(2-hydroxyethylmethacrylate)(PHEMA)isahydroge1widelyusedinthefieldsofcontactlenses,atificialcorneasandsofttissuesubstitutes.However,theuseofPHEMAhydrogelisrestrictedduetoitsinsufficientlypermeablecharacterandlimitedwaterintake.Therefore,modificationsofthePHEMAhydrogelp1ayakeyroleinitspracticalaPplications'.Poly(ethyleneglycol)(PEG)isanonionicwatersolublematerialthathascomplexsolubilityproperties'.Meanwhile,PEGisnontoxic.Water-swellable,water-insolublehydrogelsmaybemadefromPEGbym…     

Synthesis of Poly(ethylene glycol) Functionalized Star-shaped Tricationic Imidazolium Based Ionic Liquid

We report on the preparation of a well-defined star-shaped tricationic ionic liquid possessing three arms of poly(ethylene glycol) functionalized imidazolium rings. Remarkable solubility was found in most of the organic solvents we used. Thermogravimetric analysis(TGA) exhibited excellent thermal stability and two distinct decomposition temperatures were attributed to two kinds of chemical degradation. Differential scanning calorimetry(DSC) was further employed to investigate the thermal phase transitions, that three different signals(Tg, Tc, and Tm) were shown upon the second heating process. Moreover, CH2Cl2 solution of the ionic liquid expressed an excitation-wavelength dependent fluorescence response, leading to the facile modulation of photoluminescence behavior. This work represents an example of utilizing molecular design to construct novel ionic liquids and endow further potential to be used in the engineering materials.     

Poly（L—lactide）—Poly（ethylene glycol） Multiblock Copolymers：Synthesis and Properties

Poly (L-lactide)-poly (ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. These copolymers presented special properties, such as better miscibility between the two components, low crystallinity and better hydrophilicity, which can be modulated by adjusting the block lengths of the two components.     

Poly(ethylene glycol)-supported Piperazine——Synthesis and Application in Knoevenagel Condensation

A soluble,poly(ethylene glycol)-supported piperazine catalyst was prepared.This soluble catalyst efficiently catalyzes the Knoevenagel condensation of various aromatic aldehydes with diethyl malonate or ethyl acetoacetate in a homogeneous phase to afford the desired alkenes in good purity and yield with a facile work-up process.It was found that the polymer reagent could be repeatedly used at least four times without the too much loss of activity.The catalyst has shown a good activity,stability,and recyclin...     

Enhanced Gas Separation Performance by Embedding Submicron Poly(ethylene glycol) Capsules into Polyetherimide Membrane

Recently, hollow filler as an emerging concept is attracting more attention in preparation of mixed matrix membranes(MMMs). Herein,poly(ethylene glycol) microcapsules(PMC) are synthesized via distillation precipitation polymerization and embedded into the polyetherimide(Ultem■1000) matrix to fabricate MMMs for CO₂ capture. The PMC exhibits a preferential hollow structure within the Ultem matrix to furnish highways within membrane, and thus achieve high gas permeability. Meanwhile, the favorable affinity of poly(ethylene glycol)(PEG)microcapsule with ether oxygen group(EO) towards CO₂ enhances the CO₂ solubility selectivity. Such integration of physical and chemical microenvironments in the as-designed PEG microcapsule affords highly enhanced CO₂ separation performance. Compared to pristine Ultem■1000, the membrane with 2.5 wt% PMC loading exhibits 310% increment in CO₂ permeability and 22% increment in CO₂/N₂ selectivity,which shows the promising prospects of designing PEG-containing microcapsules as the filler of MMMs for CO₂ capture.     

Enzymatic Synthesis and Characterization of Novel Amphiphilic Triblock Copolymer Poly（p-dioxanoneco-5-benzyloxytrimethylene carbonate）-block-poly（ethylene glycol）

In recent years, amphiphilic block copolymers consisting of hydrophilic and hydrophobic segments have attracted much attention, because of their unique phase behavior in aqueous media and potential applications as drug delivery systems1. Poly(ethylene gly…     

Solubility of naphthalene in aqueous solutions of poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) triblock copolymers and (2-hydroxypropyl)cyclodextrins

The solubility of naphthalene was investigated in aqueous solutions of triblock copolymers poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) (PEG–PPG–PEG) and (2-hydroxypropyl)cyclodextrins. The results with solutions of the individual solubilizers were as expected: the solubility enhancement was much higher with a micelle-forming copolymer than with the non-micellizing one and with (2-hydroxypropyl)--cyclodextrin (HPBCD) than with (2-hydroxypropyl)--cyclodextrin (HPACD). Although the formation of inclusion complexes between HPACD and PEG and between HPBCD and PPG is well established, the naphthalene solubility in mixed solutions does not significantly deviate from that predicted for a mixture of independent solubilizers. Thus the interactions between HPCD and PEG–PPG–PEG copolymers are not strong enough to disrupt micelles and aggregates formed by those copolymers. In fact, slight synergetic deviations were observed with the micellizing copolymer, indicating the existence of ternary naphthalene/HPCD/copolymer interactions. For pharmaceutical applications, it is important that the solubilization efficacy of PEG–PPG–PEG copolymers and that of cyclodextrins modified by the 2-hydroxypropyl group would not be compromised if these two types of solubilizers were co-administered.     

The Synthesis of Poly(ethylene oxide)-Block-Polybutylacrylate

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How Low Can You Go? Low Densities of Poly(ethylene glycol) Surfactants Attract Stealth Proteins

It is now well‐established that the surface chemistry and “stealth” surface functionalities such as poly(ethylene glycol) (PEG) chains of nanocarriers play an important role to decrease unspecific protein adsorption of opsonizing proteins, to increase the enrichment of specific stealth proteins, and to prolong the circulation times of the nanocarriers. At the same time, PEG chains are used to provide colloidal stability for the nanoparticles. However, it is not clear how the chain length and density influence the unspecific and specific protein adsorption keeping at the same time the stability of the nanoparticles in a biological environment. Therefore, this study aims at characterizing the protein adsorption patterns depending on PEG chain length and density to define limits for the amount of PEG needed for a stealth effect by selective protein adsorption as well as colloidal stability during cell experiments. PEG chains are introduced using the PEGylated Lutensol AT surfactants, which allow easy modification of the nanoparticle surface. These findings indicate that a specific enrichment of stealth proteins already occurs at low PEG concentrations; for the decrease of unspecific protein adsorption and finally the colloidal stability a full surface coverage is advised.     

Crystallization of Poly(ethylene adipate) within γ-Phase Poly(vinylidene fluoride) Matrix

The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF.     

The Synthesis of Soluble Copolymer of Poly(p-Phenylene Vinylene)

Poly(p-phenylenevinylene)rePV)anditsderivahveshavearousedgreatinterest,'sinceBurroughes:discoveredthatPPVshowedexcellentelectrolulninescent(EL)propenies.However,PPVanditsderivativessynfllesizedbyconventionalpolylnerizationreachons3areusuallyinsolubleandidesible,whichshowsinferiormechanicalpropelles.AlthoughtheprecursorpolymerroutecancircmnventfileinsolubilityofPPV,thestrategyneedsamuhStCpreachonandlhghtemperaturewlticllaffordslowyieldandoillerdisadvantages.'So,theSynthesisofsolublePPVd…     

Thermal characterization of biodegradable methoxy poly(ethylene glycol)-b-poly(d,l-lactide)/methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) blend nanoparticles

Biodegradable methoxy poly(ethylene glycol)-b-poly(d,l-lactide) (MPEG-b-PDLL) and methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-b-PCL) diblock copolymers were synthesized by ring-opening polymerization of DLL and CL monomers in bulk using stannous octoate, and MPEG as the initiating system. Surfactant-free MPEG-b-PDLL/MPEG-b-PCL blend nanoparticles were prepared by the nanoprecipitation method. The influences of block length and blend ratio on morphology, average size, and thermal properties of the blend nanoparticles were determined. The blend nanoparticles were spherical in shape. The average particle sizes slightly decreased as the MPEG-b-PCL blend ratio increased. ¹H-NMR and thermogravimetry revealed the different MPEG-b-PDLL/MPEG-b-PCL blend ratios of the nanoparticles. Differential scanning calorimetry showed that the MPEG-b-PCL crystallinity steadily decreased as the MPEG-b-PDLL blend ratio increased, suggesting miscible blending between the MPEG-b-PDLL and MPEG-b-PCL in the amorphous phase of the nanoparticle matrix.     

Novel crosslinked thermoresponsive hydrogels with controlled poly(ethylene glycol)—poly(propylene glycol) multiblock copolymer structure

New thermoresponsive crosslinked hydrogels with controlled multiblock copolymer structure were prepared from equimolar amounts of α,ω-diamino poly(propylene glycol)s with molecular weights (MW) 230, 400, and 2,000 g mol^?1 and diepoxy-terminated poly(ethylene glycol)s of approximate MW 1,000; 2,000; and 4,000 g mol^?1. Their thermoresponsive character was investigated on the 10–70 °C interval, while the swelling behavior was tested at 21, 37, and 50 °C. All hydrogels displayed temperature sensitivity, but a volume phase transition was noticed only in the case of poly(propylene glycol) (PPG)₂₀₀₀-containing hydrogels. The volume phase transition temperature (T _VPT ) depended on the MW of the hydrophilic poly(ethylene glycol) (PEG) chains attached to the PPG₂₀₀₀ block, as well as on the added salts. Longer PEG blocks determined a shift of T _VPT towards higher values, while the influence of the salt added was in agreement with the Hofmeister series, except for NaH₂PO₄ which determined the destruction of the hydrogel network. The equilibrium swelling degree depended on the MW of both PEG and PPG blocks, as well as on temperature. The analysis of the swelling process indicated a modification of the gel characteristics with temperature and second-order kinetics for the water penetration into the hydrogel.     

Self-diffusion in poly(N -vinyl pyrrolidone) – poly(ethylene glycol) systems

 We have applied the PFG NMR technique to investigate the translational mobility in the PVP-PEG system as a function of composition and temperature at the stages of PVP-PEG complex formation, its swelling, and dissolution in excess of liquid PEG. It has been found that the variations of the spin-echo attenuation with PEG content, water amount, and temperature reflect the different stages. The first two stages are characterized by a distribution of the self-diffusion coefficients of PEG involved in the network. The dissolution shows two diffusion coefficients; the fast one is attributed to PEG molecules, the slow one to the associates of PEG and PVP. The temperature dependencies can be described by an Arrhenius law with an activation energy depending on the composition of the blend. The concentration dependence of the PEG self-diffusion coefficients in the blend occurred to be independent of the molecular weight of PVP. The results are discussed in terms of the Mackie-Meares model. Received: 23 August 2000 Accepted: 19 October 2000     

Studies on the Miscibility of Poly(2‐hydroxyethyl methacrylate) and Poly(ethylene oxide) Blends

Miscibility characteristics of poly[2‐hydroxyethylmethacrylate] (PHEMA) and poly[ethylene oxide] (PEO) have been investigated by solution viscometry, ultrasonic and differential scanning calorimetric (DSC) methods. The interaction parameters were obtained using the viscosity data. Ultrasonic velocity and adiabatic compressibility vs. blend composition have been plotted and are found to be linear. A single glass transition temperature was observed by differential scanning calorimetry. Variation of glass transition temperature (T_g) with composition follows Garden‐Taylor equation. T_g values have also been calculated from the Fox equation. The results obtained reveal that PHEMA forms a miscible blend with PEO in the entire composition range.