Synthesis of amphiphilic polycyclooctene-graft–poly(ethylene glycol) copolymers by ring-opening metathesis polymerization

In this paper, a novel monomer of 4-methyl-3-(carbamate)–carbanilic acid-4-cyclooctene ester (MCCCE) was synthesized and characterized by FTIR, NMR and ESI-MS. Polycyclooctene-graft-blocked isocyanate copolymers were prepared by the copolymerization of MCCCE and cyclooctene via ring-opening metathesis polymerization (ROMP). Amphiphilic polycyclooctene-graft–PEG copolymers were prepared by melt mixing the polycyclooctene-graft-blocked isocyanate copolymers with poly(ethylene glycol) (PEG) at 200 °C. The blocked isocyanate group on MCCCE can be dissociated to produce free isocyanate group, which will react with the end hydroxyl groups on PEG molecules. The effects of monomer-to-catalyst, monomer-to-chain transfer agent ratios on molecular weight of the copolymer were detailedly studied. The water contact angle of polycyclooctene-graft–PEG copolymer is much smaller than that of polycyclooctene.     

Biological effects of poly(ethylene glycol) on the microbial poly(β-hydroxyalkanoates) produced by pseudomonads microorganisms

Poly(ethylene glycol) of M_n 200 g/mol (PEG-200) was added to cultivation media of Pseudomonas oleovorans and Pseudomonas putida during fermentation. The carbon source and the medium used were sodium octanoate and medium E*, respectively. It was discovered that PEG-200 can control product molecular weight as well as cell productivity for both microorganisms. However, PEG-200 had no significant effect on the polymer compositions. The introduction of PEG-200 in the second-stage culture for 24 hr did not result in any notable cellular toxicity-measured in terms of colony forming unit/mL. Increasing the PEG-200 concentration to 8%, however, caused a decrease in the total polymer yield, the cell productivity as the well as M_n values. Gas chromatography analysis of products indicated that the major repeat units were β-hydroxycaproate, β-hydroxyoctanoate, and β-hydroxydeca noate. Thus, this work initiates new research opportunities for the control of product molecular weight for in-vivo microbial polymer synthetic reactions.     

Mixed micelles from methoxy poly(ethylene glycol)–polylactide and methoxy poly(ethylene glycol)–poly(sebacic anhydride) copolymers as drug carriers

mPEG–PLLA (poly l-lactic acid) is synthesized by ring-opening polymerization of lactide and conjugation with mPEG. Sebacic acid is modified with acetic anhydride and condensed with mPEG to form mPEG–PSA (poly sebacic anhydride). The micelles formed by mPEG–PLLA are characterized by slow degradation and low drug encapsulation efficiency; on the contrary, mPEG–PSA micelles are characterized by rapid degradation but high encapsulation efficiency. They can merge into spherical micelles (Φ = 140 nm) by self-assembly in water. The mixed micelles can successfully encapsulate a typical hydrophobic drug (curcumin), and significantly improve its solubility. Experimental results show that the mixed micelles have the features of high encapsulation efficiency and slow degradation.     

Effects of liquid–liquid phase separation on crystallization of poly(ethylene glycol) in blends with isotactic poly(methyl methacrylate)

To analyze the interplay between crystallization and liquid–liquid phase separation (LLPS), isothermal crystallization behavior of poly(ethylene glycol) (PEG) in blends with isotactic poly(methyl methacrylate) (i-PMMA) was investigated by differential scanning calorimetry (DSC). The blend system had an upper critical solution temperature (UCST) type phase diagram. When the crystallization occurred simultaneously with LLPS, the overall crystallization rate was enhanced at high crystallization temperatures T_c, relatively compared with that of neat PEG. This behavior was interpreted by the combination of the effects of spinodal quench depth ?T_s and usual supercooling degree ?T_c, according to the theory of Mitra and Muthukumar, namely, the crystallization rate is enhanced by the concentration fluctuation-assisted nucleation at high T_c. In the crystallization after LLPS proceeded, on the other hand, the overall crystallization rate was slow and less dependent on the blend composition. In addition, it was revealed by small-angle X-ray scattering measurements that amorphous i-PMMA was excluded from the interlamellar region of PEG crystals in SQ as well as WQ.     

Effect of silicone dioxide and poly(ethylene glycol) on the conductivity and relaxation dynamics of poly(ethylene oxide)–silver triflate solid polymer electrolyte

The conducting and relaxation dynamics of Ag⁺ ions in poly(ethylene oxide) (PEO)–silver triflate (AgCF₃SO₃) solid polymer electrolytes (SPEs) containing nanosize SiO₂ filler and poly(ethylene glycol) (PEG) as a plasticizer were studied in the frequency range 10 Hz to 10 MHz and in the temperature range 303–328 K. The comparatively lower conductivity of the plasticized (PEG) PEO–AgCF₃SO₃–SiO₂ nanocomposite electrolyte system was examined by analysis of the Fourier transform infrared (FTIR) spectroscopy and conductivity data. The electric modulus (M″) properties of the SPE systems were investigated. A shift of the M″ peak spectra with frequency was found to depend on the translation ion dynamics and the conductivity relaxation of the mobile ions. The value of the conductivity relaxation time was observed to be lower for the PEO–AgCF₃SO₃ system only with nanofiller SiO₂. The scaling behavior of the M″ spectra showed that the dynamical relaxation processes was temperature-independent in the PEO–AgCF₃SO₃ and PEO–AgCF₃SO₃–SiO₂–PEG polymer systems, whereas they were temperature-dependent for the PEO–AgCF₃SO₃–SiO₂ system. However, the relaxation processes of all of theses systems were found to be dependent on their respective compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of a novel amphiphilic poly (ethylene glycol)–poly (ε-caprolactone) graft copolymers

A series of amphiphilic graft copolymers PEO-g-PCL with different poly (ε-caprolactone) (PCL) molecular weight were successfully synthesized by a combination of anionic ring-opening polymerization (AROP) and coordination-insertion ring-opening polymerization. The linear PEO was produced by AROP of ethylene oxide (EO) and ethoxyethyl glycidyl ether initiated by 2-(2-methoxyethoxy) ethoxide potassium, and the hydroxyl groups on the backbone were deprotected after hydrolysis. The ring-opening polymerization of CL was initiated using the linear poly (ethylene oxide) (PEO) with hydroxyl group on repeated monomer as macroinitiator and Sn(Oct)₂ as catalyst, then amphiphilic graft copolymers PEO-g-PCL were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO-g-PCL with well-defined structure, molecular weight control, and narrow molecular weight distribution were prepared. The expected intermediates and final products were confirmed by ¹H NMR and GPC analyzes. In addition, these amphiphilic graft copolymers could form spherical aggregates in aqueous solution by self-assemble, which were characterized by transmission electron microscopy, and the critical micelle concentration values of graft copolymers PEO-g-PCL were also examined in this article.     

Suprarmolecular hydrogels driven by the dual host–guest interactions between α-cyclodextrin and ferrocene-modified poly(ethylene glycol) with low-molecular-weight

In general, α-cyclodextrin (α-CD) and low-molecular weight poly(ethylene glycol) (low-MW PEG) (M_w = 400–10,000) cannot construct supramolecular hydrogels but easily form crystalline precipitates. In this study, low-MW PEG (M_n = 2000, PEG-2000) was functionalized by ferrocene as mono-end-group. The obtained ferrocene-modified PEG-2000 (FcPEG-2000) further self-assembled into supramolecular hydrogel with α-CD even at low concentration (C_FcPEG-2000 = 17 mg/ml), driven by dual host–guest interaction between α-CD and FcPEG-2000. Interestingly, the hydrogel was still observed even when hydrophobic Fc group was oxidized to hydrophilic ferrocenium (Fc⁺) or included into the cavity of β-CD. In the former case, the existence of Fc⁺ end groups is considered to decrease the probability of PEG de-penetration from α-CD cavity, so that α-CDs have more location and opportunities to aggregate into more channel-type crystalline domains as physical cross-linking points. While in the later case, the synergistic effect of host–guest interaction between β-CD and ferrocenyl groups and host–guest interaction between α-CD and PEG chains are considered to be the main reason. The resultant FcPEG-2000 based hydrogels showed the property of shear-thinning.     

Synthesis of poly(lactic acid)–poly(ethylene glycol) copolymers using multi-SO3H-functionalized ionic liquid as the efficient and reusable catalyst

Poly(lactic acid)–poly(ethylene glycol) copolymers were synthesized under the catalysis of multi-SO₃H-functionalized ionic liquid. Compared to the ordinary ionic liquids and the traditional Lewis acid catalysts, the ionic liquids with multi-sulfonic acid groups were more catalytically active, and the reaction conversion rate reached up to 97.8 %. The molecular weight of the resulting copolymer was 5.69 × 10⁴ g mol^?1 and the degree of crystallinity was 42.9 %. The copolymers were also of higher hydrophilicity and better mechanical properties. The reaction kinetics of copolymerization was analyzed. The intrinsically high catalytic activity of multi-SO₃H groups originated from the lower activation energy and the higher free acidity. The recovering catalytic activity of the multi-SO₃H ionic liquid catalyst was higher, suggesting that it is a recyclable, environmentally friendly catalyst.     

Molecular weight effect on theta-gel formation in poly(vinyl alcohol)–poly(ethylene glycol) mixtures

Injectable hydrogel formulations that undergo in situ gelation at body temperature are promising for minimally invasive tissue repair. This work focuses on the investigation of injectable poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) mixtures. The injectable PVA–PEG aqueous solutions form a hydrogel as temperature is reduced to near body temperature, while filling a defect in the injection site. Gamma sterilization of these solutions compromises injectability presumably due to crosslinking of PVA. We hypothesized that by modifying the PEG molecular weight and its concentration, injectability of radiation sterilized PVA–PEG hydrogels can be optimized without compromising the mechanical properties of the resulting gel. The use of a bimodal mixture of higher and lower molecular weight PEG (600 and 200 g/mol) resulted in lower PVA/PEG solution viscosity, better injectability, and higher gel mechanical strength. The PVA/bimodal-PEG had a lower viscosity at 2733 ± 149 cP versus a viscosity of 5560 ± 278 cP for PVA/unimodal-PEG (400 g/mol). The gel formed with the bimodal PEG mixture had higher creep resistance (61% total creep strain under 0.5 MPa) than that formed with unimodal PEG (84%). These hydrogel formulations are promising candidates for minimally invasive tissue repair. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Biodegradable nanoparticles of methoxy poly(ethylene glycol)-b-poly( d, l-lactide)/methoxy poly(ethylene glycol)- b-poly(ϵ-caprolactone) blends for drug delivery

The effects of blend weight ratio and polyester block length of methoxy poly(ethylene glycol)-b-poly( d, l-lactide) (MPEG- b-PDLL)/methoxy poly(ethylene glycol)- b-poly(ϵ-caprolactone) (MPEG- b-PCL) blends on nanoparticle characteristics and drug release behaviors were evaluated. The blend nanoparticles were prepared by nanoprecipitation method for controlled release of a poorly water-soluble model drug, indomethacin. The drug-loaded nanoparticles were nearly spherical in shape. The particle size and drug loading efficiency slightly decreased with increasing MPEG- b-PCL blend weight ratio. Two distinct thermal decomposition steps from thermogravimetric analysis suggested different blend weight ratios. Thermal transition changes from differential scanning calorimetry revealed miscible blending between MPEG- b-PDLL and MPEG- b-PCL in an amorphous phase. An in vitro drug release study demonstrated that the drug release behaviors depended upon the PDLL block length and the blend weight ratios but not on PCL block length.     

Effects of Fe addition on the structure and catalytic performance of mesoporous Mn/Al–SBA-15 catalysts for the reduction of NO with ammonia

Mesoporous Al–SBA-15 has been synthesized by a hydrothermal method and used as a support for Mn/Al–SBA-15, Fe/Al–SBA-15, and Mn–Fe/Al–SBA-15 catalysts. XRD, N₂ sorption, XPS, H₂-TPR and activity tests have been used to assess the properties of catalysts. The Mn–Fe/Al–SBA-15 catalyst exhibited a higher SCR activity than Mn/Al–SBA-15 or Fe/Al–SBA-15 due to a synergistic effect between Mn and Fe. After the addition of Fe, the binding energy of Mn 2p_3/2 on Mn–Fe/Al–SBA-15(573) decreased by about 0.4 eV and the Mn^4 +/Mn^3 + ratio decreased to 1.10. The appropriate Mn^4 +/Mn^3 + ratio may have a great effect on the reduction of NO over Mn–Fe/Al–SBA-15(573) catalyst.     

Magnetite nanoparticles stabilized with polymeric bilayer of poly(ethylene glycol) methyl ether-poly(?-caprolactone) copolymers

In this work, we report a synthetic method of water dispersible magnetite nanoparticles having oleic acid and poly(ethylene glycol) methyl ether-poly(?-caprolactone) (mPEG-PCL) amphiphilic block copolymer as polymeric stabilizers. The particles were prepared by coprecipitation of Fe(II) and Fe(III) in NH₄OH and had bilayer surface with hydrophobic inner layer and hydrophilic corona. mPEG-PCL copolymer was synthesized by a ring-opening polymerization of ?-caprolactone using mPEG as a macroinitiator in the presence of stannous octoate catalyst. FTIR and thermogravimetric analysis (TGA) indicated the presence of the copolymer on the particle surface. Roles of reaction parameters, such as stabilizer concentrations and time of ultrasonicating treatment, on percent of magnetite in the complex and its magnetic properties were investigated. Transmission electron microscopy (TEM) showed the average particle size about 9.0 ± 1.1 nm in diameter. Vibrating sample magnetometry (VSM) measurement indicated that the magnetite nanoparticles were superparamagnetic at room temperature. Approximately 6.8 ± 0.5% of indomethacin model drug (68 μg/mg of magnetite) was effectively entrapped on the particles.     

The crystallization behavior of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers with asymmetric block compositions

Crystallization behavior, structural development and morphology evolution of a series of poly (ethylene glycol)-poly(ε-caprolactone) diblock copolymers (PEG-b-PCL) were investigated via differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). In these copolymers, both blocks were crystallizable and biocompatible. The mutual effects between the PEG and PCL blocks were significant, leading to the obvious block composition dependence of the crystallization behavior and morphology of the PEG-b-PCL copolymers. The relative block length determined which block crystallized first. The temperature-dependent XRD measurements confirmed which block crystallized first from the copolymer during the cooling procedure. Single crystals of the PCL and PEG homopolymers and the PEG-b-PCL copolymers were obtained and observed by AFM. The block (PCL or PEG) crystallized first would determine the crystal morphology. The block crystallized later acted as a solvent, which was advantageous to forming perfect single crystals of the whole block copolymers.     

Preparation and characterization of poly (ethylene glycol) grafted Ca-alginate fibers by γ-irradiation for biomedical applications

Radiation processing, being a physical process, is an environmentally friendly alternative to chemical modifications. It is economically viable, safe, and possesses several advantages over other conventional methods employed for modification and grafting. To improve the physico-mechanical properties of Ca-alginate fiber (CaAF), poly (ethylene glycol) (PEG) was grafted by applying γ-radiation of different intensities. The effect of γ-irradiation on the physico-mechanical, thermal, morphological, thermal and water aging, water, and simulated body fluid (SBF) uptake were evaluated. FT-IR results confirmed that PEG was successfully grafted onto Ca-alginate fibers by γ-irradiation. From the detailed experimental results, irradiation doses and PEG concentration were optimized for grafting processes. The results showed that 50% PEG and 2.5?kGy irradiation dose yielded the highest tensile strength. Differential scanning calorimetric (DSC) analysis showed that with increasing γ-intensity a decrease of dehydration temperature of the fibers had occurred. On the other hand, the glass transition temperature (T _g) increased with increasing irradiation dose. The tensile cracked surfaces of the grafted alginate fibers were analyzed by scanning electron microscope (SEM) in order to monitor their surface morphologies. The SEM images of the cracked surfaces demonstrated that spherical shape rods were present for irradiated fiber sample while no such rods were observed for non-irradiated fibers. The characteristic data obtained from SBF and water uptake, and water and thermal aging experiments indicated that CaAF grafted with 50% PEG by applying 2.5?kGy γ-irradiation can be potentially employed for biomedical purposes, such as surgical suture.     

Ultrasonic assisted organo-modification of mesoporous SBA-15 with N-trimellitylimido-l-methionine and preparation of the poly(amide–imide)/SBA nanocomposites

Mesoporous SBA-15 materials were functionalized with N-trimellitylimido-l-methionine through ultrasonic irradiation, and the resulting functionalized materials were investigated as reinforcing agent for the preparation of the polymer based nanocomposites (NCs). An optically active and organo-soluble l-methionine containing poly(amide–imide) (PAI) was synthesized by the direct step-growth polymerization reaction of the above chiral diacid and 3,5-diamino-N-(pyridin-3-yl) benzamide in molten tetrabutylammonium bromide as a green solvent. A simple solution blending process was used to efficiently disperse modified-SBA into the chiral PAI to obtain PAI/modified-SBA NCs. The obtained NCs were characterized by Fourier transform-infrared spectroscopy, thermogravimetry analysis (TGA), X-ray diffraction, field emission-scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TGA data indicated an increasing in thermal stability of the NCs when compared to the pure polymer. TEM images show well-ordered hexagonal arrays of mesopores SBA and the average distances between neighboring pores is around 3–5 nm.     

Thermogelation properties of poly(N-isopropylacrylamide) – block – poly(ethylene glycol) – block – poly(N-isopropylacrylamide) triblock copolymer aqueous solutions

Low polydispersity PNIPAM–PEG–PNIPAM triblock copolymers with PEG blocks of 1–6 kDa and PNIPAM chains of 5–30 kDa were synthesized and their thermogelation behavior in aqueous solution as a function of their composition and block length was investigated for the first time. DSC, dynamic rheometry and the tube inverting method were employed to characterize the gelation process at various polymer concentrations, and their results were compared. The thermogelation process depended mainly on the length of both PNIPAM and PEG blocks. Both association and aggregation temperatures of the PNIPAM chains decreased with the MW of PNIPAM and increased with the length of the PEG block. The amplitude of these effects depended on the molecular weights of the blocks forming the copolymer as a consequence of the partial mixing of PNIPAM and PEG chains during the association/aggregation process, while the overall hydrophilicity of the entire copolymer played only a minor role. The length of the PEG block proved also to be the most important factor for the preparation of a stable gel in 20 wt.% solutions, while the hydrophilic groups/hydrophobic groups ratio had no importance.     

Synthesis and characterization of polymers from β-propiolactone and poly(ethylene glycol)s

Uncatalysed polymerizations of β-propiolactone with low-molecular-weight poly(ethylene glycol)s were carried out in bulk, at temperatures in the range of 70 to 120°C. ¹H nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) measurements on the resulting products indicated a block copolymer structure. Gel permeation chromatography (g.p.c.) and d.s.c. analyses showed that in some cases the copolymerization is accompanied by homopolymerization of β-propiolactone, probably due to the presence of residual water in the poly(ethylene glycol). N.m.r. and infra-red (i.r.) spectra of copolymers revealed the presence of hydroxyl and carboxyl end groups. The copolymerization reaction may be visualized as a two-step process, in which the ring opening of β-propiolactone takes place on both the hydroxyl groups of poly(ethylene glycol), followed by repetitive monomer addition forming an ester-ether-ester triblock copolymer.     

Chlorinating cleavage of silicon–naphthyl bonds of polycarbosilane,and introduction of poly(ethylene glycol) graft copolymer micelles

A new series of polycarbosilanes [(PhCH₂)SiCH₃Cl, Poly B] was designed by chlorinating cleavage reaction of silicon–naphthyl in polycarbosilane. The ¹H spectra of poly B revealed that the SiCH₂ and the SiCH₃ protons peak were up-field shifted compared with the type [(PhCH₂)SiCH₃Np, Poly A] polycarbosilane. Grafted polycarbosilane was synthesized with poly ethylene glycol (PEG) by nucleophilic substitution of the chloride substituents on the polycarbosilane. The aggregation behaviors of graft copolymers were investigated by dynamic light scattering and fluorescence at 25 °C in aqueous solutions of different polyethylene glycol (PEG) substituent.     

Properties influenced by addition of copoly (ethylene/octene) in BR–NBR blends

Abstract

The effects of copoly (ethylene/octene) (EOM) on rheological, mechanical, and cure properties and on carbon black distribution in each phase of butadiene rubber–nitrile/butadiene rubber (BR–NBR) blends have been investigated. It was found that EOM added to the blends is able to function as a plasticising agent for BR and NBR, and the plasticising efficiency of EOM is more significant in NBR than BR. With increasing EOM content, the deviation of Mooney viscosity from the additive line (interpolated values) reduces markedly. In pure components (i.e. 100 : 0 and 0 : 100), cure rate reduces and cure time increases with addition of EOM. In contrast in the blend systems, cure rate increases and cure time decreases when EOM is added. The distribution of carbon black in each phase of the blends is strongly controlled by the viscosity of each phase in the blend. The lower the phase viscosity, the greater the residual carbon black. Accordingly, dynamic mechanical thermal analysis reveals a slight shift in the glass transition temperature of the BR phase to higher temperature, compared with the NBR phase, as EOM is added. From the results obtained, it is proposed that EOM exists in the interfacial area between the two phases. However, at higher amounts of EOM, saturation of EOM at the interfacial area occurs and the excess EOM starts to migrate to the BR phase. Further increase in EOM concentration leads to saturation of EOM in the BR phase and EOM then migrates to the NBR phase.