Microwave dielectric relaxation and molecular dynamics in binary mixtures of poly(propylene glycol) 2000 and poly(ethylene glycol)s of varying molecular weight in dilute solution

Molecular dynamics of binary mixtures of poly(propylene glycol) (PPG) and poly(ethylene glycol)s (PEGs) of varying molecular weight due to molecular interactions, chain coiling and elongation in dilute solution under various conditions, ie varying number of monomer units of PEG, method of mixing of polymers and solvent environment, has been explored using microwave dielectric relaxation times. The average relaxation time τ_o, relaxation time corresponding to segmental motion τ₁ and group rotations τ₂, of a series of binary mixtures of poly(propylene glycol) 2000 and poly(ethylene glycol) of varying molecular weight (ie PPG 2000 + PEG 200, PPG 2000 + PEG 300, PPG 2000 + PEG 400, and PPG 2000 + PEG 600 mixed by equal volume in the pure liquid states, and PPG 2000 + PEG 1500, PPG 2000 + PEG 4000 and PPG 2000 + PEG 6000 mixed equal weights in solvent) have been determined in dilute solution in benzene and carbon tetrachloride at 10.10 GHz and 35 °C. A comparison of the results of these binary systems of highly associating molecules shows that the molecular dynamics corresponding to rotation of a molecule as a whole and segmental motion in dilute solutions are governed by the solvent density when the solutes are mixed in their pure liquid state. Furthermore, the molecular motion is independent of solvent environment when the polymers are added separately in the solvent for the preparation of binary mixtures. It has also been observed that there is a systematic elongation of the dynamic network of the species formed during mixing of pure liquid polymers in lighter environment of solvent with increasing PEG monomer units, while the elongation behaviour of the same species in the heavier environment of carbon tetrachloride solvent is in contrast to the elongation behaviour of the polymeric species formed in pure PEG. The role of rotating methyl side‐groups in the PPG molecular chain has been discussed in term of the breaking and reforming of hydrogen bonds in complex polymeric species for the segmental motion. In all these mixtures, the relaxation time corresponding to group rotations is independent of the solvent environment and constituents of the binary mixtures. The effect of chain flexibility and coiling in these binary mixtures is discussed by comparing the relaxation times of the mixtures with their individual relaxation times in dilute solutions measured earlier in this laboratory. © 2001 Society of Chemical Industry     

Pressure-volume-temperature properties for binary and ternary polymer solutions of poly(ethylene glycol), poly(propylene glycol), and poly(ethylene glycol methyl ether) with anisole

Pressure-volume-temperature properties were measured for polymer solutions of poly(propylene glycol) (PPG)+anisole, polymer blends of PPG+poly(ethylene glycol methyl ether) (PEGME), and the blends of PPG+PEGME and poly(ethylene glycol) (PEG)+PPG with anisole at temperatures from 298.15 to 348.15 K and pressures up to 50 MPa. The Tait equation represents accurately the pressure effect on the liquid densities over the entire pressure range. The excess volumes change from positive to negative as increasing the mole fraction of PPG in the binary systems of PPG+anisole and PPG+PEGME. The volumetric data of the related binary systems were correlated with the Flory-Orwoll-Vrij and the Schotte equations of state to determine the binary parameters. By using these determined binary parameters, both equations predicted the specific volumes of the polymer blends with anisole to average absolute deviations of better than 0.13%.     

Synthesis, characterization and properties of chitosan modified with poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers

Synthesis of poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers is discussed herein. Siloxane prepolymer was first prepared via acid-catalyzed ring-opening polymerization of octamethylcyclotetrasiloxane (D₄) to form polydimethylsiloxane (PDMS) prepolymers. It was subsequently functionalized with hydroxy functional groups at both terminals. The hydroxy-terminated PDMS can readily react with acid-terminated poly(ethylene glycol) (PEG diacid) to give PEG-PDMS block copolymers without using any solvent. The PEG diacid was prepared from hydroxy-terminated PEG through the ring-opening reaction of succinic anhydride. Their chemical structures and molecular weights were characterized using ¹H NMR, FTIR and GPC, and thermal properties were determined by DSC. The PEG-PDMS copolymer was incorporated into chitosan in order that PDMS provided surface modification and PEG provided good water swelling properties to chitosan. Critical surface energy and swelling behavior of the modified chitosan as a function of the copolymer compositions and contents were investigated.     

Synthesis and characterization of complexes between poly(itaconic acid) and poly(ethylene glycol)

Summary Interpolymer complexes of poly(itaconic acid) and poly(ethylene glycol) (PIA/PEG) were prepared by two different procedures: simple mixing of preformed PIA and PEG and by polymerization of itaconic acid on poly(ethylene glycol) as a template. Complex formation was attributed to hydrogen bond formation between the carboxyl group of PIA and the ether group of PEG. The two types of complexes were characterized by viscometric measurements, thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy and adhesive force measurements. The results indicate that complexes prepared by template polymerization have a stronger hydrogen bonding and hence more ordered structure and better mucoadhesive properties.     

Intermolecular interaction in aqueous solution of binary blends of poly(acrylamide) and poly(ethylene glycol)

The interaction between poly(acrylamide) (PAM) and poly(ethylene glycol) (PEG) in their solid mixture was studied by Fourier transform infrared spectroscopy (FTIR); and their interaction in aqueous solution was investigated by nuclear magnetic resonance spectroscopy (NMR). For the solid PAM/PEG mixtures, an induced shift of the >C?O and >N? H in amide group was found by FTIR. These results could demonstrate the formation of intermolecular hydrogen bonding between the amide group of PAM and the ether group of PEG. In the aqueous PAM/PEG solution system, the PAM and PEG associating with each other in water, i.e., the amide group of PAM interacting with the ether group of PEG through hydrogen bonding was also found by ¹H NMR. Furthermore, the effects of different molecular weight of PAM on the strength of hydrogen bonding between PAM and PEG in water were investigated systemically. It was found that the hydrogen bonding interaction between PAM and PEG in water did not increase with the enlargement of the PAM molecular weight as expected. This finding together with the viscosity reduction of aqueous PAM/PEG solution with the PAM molecular weight increasing strongly indicated that PAM molecular chain, especially having high molecular weights preferred to form spherical clews in aqueous PEG solution. Therefore, fewer amide groups in PAM could interact with the ether groups in PEG. Based on these results, a mechanism sketch of the interaction between PAM and PEG in relatively concentrated aqueous solution was proposed. The fact that the phase separation of aqueous PAM/PEG solution occurs while raising the temperature indicates that this kind of hydrogen bonding between PAM and PEG in water is weak and could be broken by controlling the temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure–property relationships of poly(urethane‐urea)s with ultralow monol content poly(propylene glycol) soft segments. III. influence of mixed soft segments of ultralow monol poly(propylene glycol), poly(tetramethylene ether glycol), and tri(propylene glycol)

Recent advances in the catalyst technology associated with the production of poly(propylene glycol) (PPG) have allowed for the fabrication of ultralow monol content PPG macrodiols (Acclaim? polyols), which are highly bifunctional and can be produced in substantially higher molecular weights and with narrower molecular weight distributions than previously possible. These factors have enabled the preparation of higher value elastomers and may allow for the first manufacture of economically attractive PPG‐based poly(urethane‐urea) (PUU) fibers. In the past, many performance polyurethane and PUU elastomers used poly(tetramethylene ether glycol) (PTMEG) for the soft segments either alone or in combination with other macrodiols. The work presented here details the investigation of the morphological features of PUU systems with mixed soft segments of PPG, PTMEG, and a low molecular analog of PPG, tri(propylene glycol) (TPG) in an effort to ascertain the influence of structural features on the mechanical and thermal properties of the elastomers. Also of interest was whether the incorporation of PPG and TPG would either prohibit or greatly hinder the formation of strain‐induced PTMEG crystallites. It was found that, even when only 60 wt % of the soft segments consisted of PTMEG, those soft segments were still able to undergo recognizable strain‐induced crystallization as detected by wide‐angle X‐ray scattering. It was also seen that, as the ratio of PPG to PTMEG was varied, there were systematic changes in the soft segment glass transition and cold crystallization characteristics. Inclusion of PPG and TPG resulted in PTMEG's diminished ability to undergo cold and strain‐induced crystallization, as seen with differential scanning calorimetry and wide‐angle X‐ray scattering. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3520–3529, 2003     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Rheological studies of disulfonated poly(arylene ether sulfone) plasticized with poly(ethylene glycol) for membrane formation

Disulfonated poly(arylene ether sulfone) (BPS) random copolymers, prepared from a sulfonated monomer, have been considered for use as membrane materials for various applications in water purification and power generation. These membranes can be melt-processed to avoid the use of hazardous solvent-based processes with the aid of a plasticizer, a low molecular weight poly(ethylene glycol) (PEG). PEG was used to modify the glass transition temperature and melt rheology of BPS to enable coextrusion with polypropylene (PP). Our previous paper discussed the miscibility of BPS with PEG and the influence of PEG on the glass transition of BPS. In this study, the rheological properties of disulfonated poly(arylene ether sulfone)s plasticized with poly(ethylene glycol) (PEG) are investigated to identify coextrusion processing conditions with candidate PPs. The effects of various factors including PEG molecular weight, PEG concentration, temperature and BPS molecular weight on blend viscosity were studied. The rheological data effectively lie on the same master curve developed by Bueche and Harding for non-associating polymers such as poly(methyl methacrylate) (PMMA) and polystyrene (PS). Although sulfonated polysulfone contains ionic groups, the form of its viscosity versus shear rate (or frequency) behavior appears to be dominated by the relaxation of polymer entanglements.     

Inhibition of bovine serum albumin adsorption by poly(ethylene glycol) soft segment in biodegradable poly(ethylene glycol)/poly(L-lactide) copolymers

The objective of this study was to investigate the effects of the incorporation of ether linkages into polylactide (PLLA) chains and the time of biodegradation on the behavior of protein adsorption. The content of poly(ethylene glycol) (PEG) in PLLA/PEG copolymers is from 4.4 to 18.3 wt %, and the length of the PEG soft segment is 1000, 2000, and 6000 daltons. The bovine serum albumin (BSA) adsorption onto the biodegradable PLLA/PEG copolymers was carried out using ultraviolet spectroscopy. The surface tension of PLLA and PLLA/PEG was measured using a contact angle. The data show that the incorporation of PEG segments makes the copolymer more polar and, therefore, leads to a reduction of protein adsorption. As the hydrolysis of polymers proceeds, both PLLA and PLLA/PEG turn out to be more polar. However, the initial compositions of degraded PLLA/PEG have a weak influence on the protein adsorption onto its hydrolyzed surface with a substantially long duration of hydrolysis. This phenomenon is attributed to the hydrophobic interaction between polar PLLA/PEG and BSA. © 1993 John Wiley & Sons, Inc.     

Synthesis,characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

BACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation. RESULTS: The copolyesters were characterized using ¹H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters. CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry     

Thermo-oxidative degradation of poly(ethylene glycol)/poly( -lactic acid) blends

The thermo-oxidative degradation of poly(ethylene glycol)/poly( -lactic acid) (PEG/PLLA) blends was studied by infra-red spectroscopy (IR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and thermogravimetry (TGA). The thermo-oxidative degradation of PEG occurred after a period time of aging in air at 80 °C. The mechanism of thermo-oxidative degradation of PEG was found to be the random chain scission of the main chain. As PEG blending with PLLA, the existence of PLLA appeared to enhance the thermo-oxidative degradation of PEG. The enhancement of thermo-oxidative degradation increased first and then decreased with the increase of PLLA. The results could be attributed to the ease of abstraction of the carboxylic hydrogen (–COOH) of PLLA, which enhanced the thermo-oxidative degradation of PEG. Also, the dilution effect of PLLA on the concentration of free radicals was an important factor of the thermo-oxidative degradation.     

Hydrophilicity,crystallinity and electrostatic dissipating properties of poly(oxyethylene)-segmented polyurethanes

Plaques of poly(oxyethylene)-segmented polyurethanes prepared from isophorone diisocyanate (IPDI) and polyethylene glycol (PEG) were used to probe the structure/property relationships with regard to hydrophilicity, crystallinity and electrostatic dissipating (ESD) ability. The prepared urethane polymers or oligomers consistently exhibited lower surface resistivities than their corresponding PEG-1000, 2000 and 8000 starting materials. The magnitude of the decrease in surface resistivity (ohm/sq) was correlated with heat of crystallinity, measured by differential scanning calorimetry. Surface resistivity as low as 10^7.5 ohm/sq for PEG-1000/IPDI polyurethane, a decrease by 2.5 orders of magnitude from pure PEG-1000, was observed and attributed to the differences in crystallinity. Polyurethanes containing PEG, polypropylene glycol (PPG) and mixed PEG/PPG were also prepared for comparison. The mixed PEG/MDEA (N -methyl diethanolamine) polyurethanes further demonstrated the importance of the nature and mobility of the hydrophilic groups for lowering the polymer surface resistivity. To account for these observations, an electron conducting mechanism via association and mobility of the hydrogen-bonded water molecules with hydrophilic poly(oxyethylene) groups is suggested. © 1999 Society of Chemical Industry     

Nanocomposite polymer electrolytes containing silica nanoparticles: Comparison between poly(ethylene glycol) and poly(ethylene oxide) dimethyl ether

Nanocomposite polymer electrolytes consisting of low molecular weight poly(ethylene oxide) (PEO), iodine salt MI (M = K⁺, imidazolium⁺), and fumed silica nanoparticles have been prepared and characterized. The effect of terminal group in PEO, i.e., hydroxyl (? OH) and methyl (CH₃) using poly(ethylene glycol) (PEG) and PEO dimethyl ether (PEODME), respectively, was investigated on the interactions, structures, and ionic conductivities of polymer electrolytes. Wide angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and complex viscositymeasurements clearly showed that the gelation of PEG electrolytes occurred more effectively than that of PEODME electrolytes. It was attributed to the fact that the hydroxyl groups of PEG participated in the hydrogen‐bonding interaction between silica nanoparticles, and consequently helped to accelerate the gelation reaction, as confirmed by FTIR spectroscopy. Because of its interaction, the ionic conductivities of PEG electrolytes (maximum value ～ 6.9 × 10^?4 S/cm) were lower than that of PEODME electrolytes (2.3 × 10^?3 S/cm). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Plasticization of semicrystalline poly(l-lactide) with poly(propylene glycol)

Plasticization of semicrystalline poly(l-lactide) (PLA) with a new plasticizer - poly(propylene glycol) (PPG) is described. PLA was plasticized with PPG with nominal M_w of 425 g/mol (PPG4) and 1000 g/mol (PPG1) and crystallized. The plasticization decreased T_g, which was reflected in a lower yield stress and improved elongation at break. The crystallization in the blends was accompanied by a phase separation facilitated by an increase of plasticizer concentration in the amorphous phase and by annealing of blends at crystallization temperature. The ultimate properties of the blends with high plasticizer contents correlated with the acceleration of spherulite growth rate that reflected accumulation of plasticizer in front of growing spherulites causing weakness of interspherulitic boundaries. In PLA/PPG1 blends the phase separation was the most intense leading to the formation of PPG1 droplets, which facilitated plastic deformation of the blends that enabled to achieve the elongation at break of about 90-100% for 10 and 12.5 wt% PPG1 content in spite of relatively high T_g of PLA rich phase of the respective blends, 46.1-47.6 °C. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal M_w of 600 g/mol, was also used to plasticize PLA for comparison.     

Layer-by-layer assembly of myoglobin and nonionic poly(ethylene glycol) through ion-dipole interaction: An electrochemical study

Nonionic poly(ethylene glycol) (PEG) and myoglobin (Mb) were successfully assembled into {PEG/Mb}_n layer-by-layer films on various solid surfaces. Quartz crystal microbalance (QCM), UV-vis spectroscopy and cyclic voltammetry (CV) were used to monitor and confirm the film growth and characterize the films. The Mb in stable {PEG/Mb}_n films showed a quasi-reversible CV response for its heme Fe(III)/Fe(II) redox couple, and was used to electrocatalyze the reduction of various substrates. The interaction between PEG and Mb in the assembly was investigated in detail. A series of comparative experiments showed that the ion-dipole interaction between positively charged groups on the Mb surface and electronegative ether oxygen groups of PEG would be the main driving force for the assembly of {PEG/Mb}_n films, while other interactions such as hydrogen bonding and/or hydrophobic interaction may also play an important role in stabilizing the films in blank buffers.     

Improvement of biocompatibility and biodegradability of poly(ethylene succinate) by incorporation of poly(ethylene glycol) segments

Poly(ethylene glycol) (PEG) segments were incorporated into poly(ethylene succinate) (PES) by chain-extension reaction of PEG with PES using 1,6-hexamethylene diisocyanate as a chain-extender, forming a poly(ester ether urethane) (PEEU). The chemical structures and molecular weights of the PEEUs were determined by ¹H NMR and GPC, respectively. The composition dependence of thermal transitions, crystallization, hydrophilicity, in vitro biocompatibility, in vitro biodegradation and tensile properties of the PEEUs were systematically investigated. The glass transition temperature and degree of crystallinity of PEEU decreased with increase of PEG content. The hydrophilicity increased with PEG content as proved by the decreased water contact angle and increased water absorption. The results of cell culturing suggested that the in vitro biocompatibility increased with PEG content. Hydrolytic degradation demonstrated that degradation rate of PEEU increased with PEG content, which was caused by the increased hydrophilicity and decreased degree of crystallinity with increase of PEG content. The tensile results proved that the tensile strength and modulus decreased while elongation at break increased with PEG content.     

Lithium ionic conductivity in poly(ether urethanes) derived from poly(ethylene glycol) and lysine ethyl ester

Poly(ether urethanes) obtained by the copolymerization of poly(ethylene glycol) (PEG) and lysine ethyl ester (LysOEt) are elastomeric materials that can be processed readily to form flexible, soft films. In view of these desirable physicomechanical properties, the potential use of these new materials as solid polymer electrolytes was explored. Solid polymer electrolytes were prepared with copolymers containing PEG blocks of different lengths and with different concentrations of lithium triflate (LiCF₃SO₃). Correlations between the length of the PEG block, the concentration of lithium triflate in the formulation, and the observed Li⁺ ion conductivity were investigated. Solid electrolyte formulations were characterized by differential scanning calorimetry for glass transition temperatures (T_g), melting points (T_m), and crystallinity. Ionic conductivity measurements were carried out on thin films of the polymer electrolytes that had been cast on a microelectrode assembly using conventional ac-impedance spectroscopy. These polymer electrolytes showed inherently high ionic conductivity at room temperature. The optimum concentration of lithium triflate was about 25–30% (w/w), resulting at room temperature in an ionic conductivity of about 10⁻⁵ S cm⁻¹. For poly(PEG₂₀₀₀-LysOEt) containing 30% of LiCF₃SO₃, the activation energy was ∼ 1.1 eV. Our results indicate that block copolymers of PEG and lysine ethyl ester are promising candidates for the development of polymeric, solvent-free electrolytes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1449–1456, 1997     

Autoxidation of poly(alkylene glycols) in solution

Data reported for the autoxidation of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) in solution at relatively long reaction times were analyzed. A relatively simple and a more general kinetic scheme with corresponding rate expressions were used. It was found that the more general scheme gave somewhat more satisfactory agreement between calculated and observed values of several reaction variables. Limitations in the applications of both schemes to PEG and PPG autoxidations are mentioned.     

Thermal characteristics of IPNs composed of poly(propylene glycol) and poly(acrylic acid)

Interpenetrating polymer networks (IPNs) based on poly(propylene glycol) (PPG) and poly(acrylic acid) (PAAc) were prepared by UV irradiation and characterized using fourier transform infrared (FTIR), differential scanning calorimetry (DSC), dielectric analysis (DEA), and thermogaravimetry (TGA). The glass transition temperatures (T_gs) of these IPNs exhibited a relatively higher temperature with an increased PAAc content. The decomposition temperature of PAAc is lower than that of PPG. PAAc affects the thermal stability of IPN more than PPG. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2570–2574, 2003     

Modification of unsaturated polyesters by poly(ethylene glycol) end groups

This article reports on the modification of unsaturated polyesters by poly(ethylene glycol) end groups in order to influence the solution behavior in styrene and to modify mechanical properties of the cured resin. The synthesis was done by the reaction of a carboxyl-terminated unsaturated polyester with various poly(ethylene glycol) mono-methyl ethers of molecular weights from 350 to 2000 g/mol. The characterization and curing properties of the synthesized block copolymers are presented. The glass transition temperatures decrease with increasing length of the poly(ethylene glycol) end groups. The introduction of long poly(ethylene glycol) end groups (2000 g/mol) leads to a phase separated and partly crystalline block copolymer with a melting point of 48°C. The block copolymers can be easily diluted in styrene to create the curable resins. The mixtures containing the block copolymers with the short poly(ethylene glycol) end groups (350 and 550 g/mol) could be cured in a reasonably short time. Compared to commercial unsaturated polyesters the mechanical testing revealed that the tensile strength is decreasing while the elongation is increasing. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 527–537, 1997