Increasing PEG Content Research Articles

Effect of PEG additive and coagulation bath temperature on the morphology, permeability and thermal/chemical stability of asymmetric CA membranes

In this study, asymmetric cellulose acetate (CA) membranes were prepared from polymeric blend of CA–PEG/1-methyl-2-pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath. Effects of PEG concentration (0 wt.%, 5 wt.% and 10 wt.%) and coagulation bath temperature (CBT = 0 °C and 25 °C) on morphology, pure water permeation flux (PWF) and thermal/chemical stability of the prepared membranes were studied and discussed. Rejection of the developed CA membranes was quantified using human serum albumin (HSA) solution. Increasing PEG concentration in the cast solution film along with higher CBT results in increasing the membrane thickness, pure water flux (PWF) and HSA transmission, also these changes facilitate macrovoids formation (even with the size of more than 50 µm) in the membrane sublayer. On the other hand, increasing PEG concentration along with reduction of CBT results in increasing the thermal/chemical stability of the prepared membranes. Presence of low molecular weight PEG additive in the cast solution film increases porosity/permeability and simultaneously thermal/chemical stability of the prepared membranes. On the other hand, using cold coagulation bath despite of increasing the thermal/chemical stability of the prepared membranes results in reduction of membranes porosity/permeability.

Effect of polyethylene glycol on the performance of ultrahigh‐molecular‐weight polyethylene membranes

AbstractPorous, flat membranes of ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared by thermally induced phase separation, with mineral oil as a diluent and poly(ethylene glycol) with a weight‐average molecular weight of 20,000 (PEG20000) as an additive. Through the control of the rheological behavior, crystallite size, and pore structure, the influential factors, including the diluent, poly(ethylene glycol) (PEG) content, and cooling rate, were investigated. The results suggested that PEG could decrease the viscosity of UHMWPE/diluent apparently. The crystal density decreased when mineral oil was added, which made the melting point and crystallinity of UHMWPE lower. The crystallization rate and crystallinity also increased with the addition of PEG. However, the addition of excess PEG restrained crystal growth. PEG20000 in membranes could be extracted absolutely through the soaking of the membranes with fresh water for 7 days. With increasing PEG content, both porosity and pure water flux first increased and then decreased, reaching a maximum at a PEG mass fraction of 10%. The cooling rate had a direct effect the crystal structure. A slow cooling rate was good for crystal growth and diluent integration. Therefore, the pure water flux increased along with the temperature of the cooling medium, whereas porosity first increased and then decreased, reaching a maximum at 40°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Biodegradable aliphatic/aromatic copoly(ester-ether)s: the effect of poly(ethylene glycol) on physical properties and degradation behavior

A series of high molecular weight copolymers based on poly(L-lactic acid) (PLLA) as the biodegradable aliphatic segments, poly(butylene terephthalate) (PBT) as the rigid aromatic segments and hydrophilic poly(ethylene glycol) (PEG) as the soft segments were synthesized with the aim of developing novel polymer materials which could combine high physical properties with good biodegradability. Via direct melt polycondensation of terephthalic acid (TPA), 1,4-butanediol (BDO), poly(L-lactic acid) oligomer (OLLA) and PEG, biodegradable aliphatic/aromatic copoly(ester-ether)s, poly(butylene terephthalate-co-lactate-co-ethylene glycol) (PBTLG), were prepared. The effect of the introduction of PEG soft segments on the synthesis, mechanical properties and thermal stabilities as well as the degradation behaviors of the final copolymers was investigated. When the PEG units were incorporated into the polymer main-chains, the weight-average molecular weight of the copolymers increased from 53,700 g/mol to 177,000 g/mol and the tensile strength (σ) improved by nearly two times from 6.5 MPa to 12.8 MPa for PBTLG1000-0.5. The glass-transition temperature (T g) gradually decreased from 26.9 °C down to −5.5 °C and a depression of melting temperature was observed with the increase of PEG content. According to the in vitro hydrolytic degradation observation, all of the copolymers underwent significant degradation in phosphate buffer solution at 37 °C and the water absorption as well as the degradation rate of PBTLGs displayed a strong dependency on the PEG content.

Droplet size and morphology for the aqueous two‐phase polymerization of acrylamide in an aqueous poly(ethylene glycol) solution

AbstractA kind of polyacrylamide (PAM) latex product dispersed in an aqueous solution was successfully prepared through the aqueous two‐phase polymerization of acrylamide in an aqueous solution of poly(ethylene glycol) (PEG). The effects of various polymerization parameters on the size and morphology of droplets rich in PAM were systematically investigated. The droplet size and morphology was significantly influenced by the polymerization rate. The high polymerization rate caused the formation of stripe‐shaped droplets because of the aggregation of more droplets rapidly separated from the continuous phase. At the same time, the monomer partition behavior mainly relied on the temperature, and the PEG concentration also dramatically affected the droplet size and morphology. The increase in PEG concentration not only changed the monomer partition behavior and restrained droplet aggregation but also shortened the critical PAM radical chain length and accelerated the droplet formation. Furthermore, the stirring speed was also recognized as the correlative factor that affected the droplet stability and monomer diffusion rate from the continuous phase into the droplets. The addition of salt and alcohol altered the droplet stability and the final droplet size and morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Preferential Adsorption of Poly(ethylene glycol) on Hectorite Clay and Effects on Poly(N-isopropylacrylamide)/Hectorite Nanocomposite Hydrogels

Poly(N-isopropylacrylamide)/Laponite nanocomposite hydrogel (NC gel) was synthesized via in situ polymerization in the Laponite suspension containing PEG. The adsorption of PEG on Laponite platelets was characterized by zeta-potential, which decreased with the PEG adsorption. The tensile strength decreased and elongation at break increased with increasing PEG concentration. The effective network chain density of PNIPAm/Laponite NC gels determined from the equilibrium modulus G(e) decreased upon adsorption of PEG on the Laponite. All of these results revealed the preferential adsorption of PEG on the Laponite platelets occupying the active sites for the PNIPAm chain anchoring, which hindered their cross-linking effect in the NC gels. However, the temperature sensitive swelling behavior still remained in the PNIPAm/Laponite NC gels containing PEG with higher swelling volume below the LCST due to the lower cross-linker density. By adjusting the amount of added PEG, we can easily control the properties of the PNIPAm/Laponite NC gels.

Room-temperature Synthesis of Monodispersed SnO2 Nanoparticles by Liquid Phase Deposition

Abstract We have successfully tailored a soft solution process for the synthesis of monodispersed SnO2 nanoparticles, applying a liquid phase deposition technique from an aqueous reaction mixture without any post-annealing treatment. The synthesis was carried out by varying poly(ethylene glycol) (PEG) content in the reaction mixture. The XRD patterns of the nanoparticles exhibited the formation of SnO2 cassiterite phase, irrespective of the PEG content in the composition of the reaction solution, the reaction time, and the reaction temperature. The mean size and the standard deviation of SnO2 nanoparticles exhibited a decreasing trend with increasing PEG concentration.

Hydrogels assembled by inclusion complexation of poly(ethylene glycol) with alpha‐cyclodextrin

AbstractPolymeric hydrogels were prepared based on the inclusive complexation between α‐cyclodextrin (α‐CD) and poly(ethylene glycol) (PEG). Because the rheological property of a thermodynamic stable hydrogel should be gap‐independent, it is found in this work that the uniformed hydrogel can be distinguished from gel‐like aggregation by changing the plate gap during the rheological measurement. By this rheological method it is determined that suitable storage duration is necessary for the preparation of uniform hydrogels. However, the sonication technique after mixing CD and PEG solutions or increasing PEG concentration can shorten the time to form stable hydrogels. Moreover, the molecular weight of PEG should be high enough (≥8000 g/mol) for sol‐gel transition. The higher the molecular weight of PEG is, the longer storage time is needed to obtain a uniform hydrogel. From the observation by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) of prepared hydrogels, we concluded that the driving force of networks should be attributed to the crystallization of complexed α‐CDs in the α‐CD/PEG pseudo‐polyrotaxanes. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

PH-sensitive nanoparticles self-assembled from a novel class of biodegradable amphiphilic copolymers based on chitosan

A new type of biodegradable amphiphilic graft copolymers, PEG-g-hexanoyl chitosan, was synthesized by a facile scheme. The self-assemble properties of the copolymers were studied by TEM, fluorometry and dynamic light scattering. It was found that spherical nanoparticles of the copolymers could be formed through dialysis method. With the increase of PEG content in the copolymers, the average diameter of the nanoparticles decreased from about 180 to 40 nm. PEG fraction in the copolymers has little effect on the copolymer CAC. The micellization of the copolymers was strongly dependent of the medium pH. When pH was lowered from 7.2 to 6.8, the average diameter of the nanoparticles dramatically changed from about 180 to 60 nm.

Effects of vanillin and plasticizer on properties of chitosan‐methyl cellulose based film

AbstractChitosan‐methyl cellulose based films which incorporatate vanillin as an antimicrobial agent and polyethylene glycol 400 (PEG) as a plasticizer were developed in this study. The effects of vanillin and plasticizer concentration on mechanical, barrier, optical, and thermal properties of chitosan‐methyl cellulose film were evaluated. When the vanillin concentration was increased at a given PEG level, film flexibility decreased while tensile strength increased slightly. Vanillin increased the barrier to oxygen but not water vapor. Increasing vanillin content resulted in less transparency and a more yellowish tint. The bulky nature of vanillin reduced film crystallization. When PEG concentration was increased at a given vanillin level, it resulted in greater film flexibility but reduced film strength. Water vapor permeability (WVP) and oxygen permeability (OP) increased with increase in PEG content. PEG contributed less to the opacity, yellowness, and crystallization of the film than did vanillin. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis and water-swelling of thermo-responsive poly(ester urethane)s containing poly(ε-caprolactone), poly(ethylene glycol) and poly(propylene glycol)

Thermo-responsive multiblock poly(ester urethane)s comprising poly(ε-caprolactone) (PCL), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. The copolymers were characterized by GPC, NMR, FTIR, XRD, DSC and TGA. Water-swelling analysis carried out at different temperatures revealed that the bulk hydrophilicity of the copolymers could be controlled either by adjusting the composition of the copolymer or by changing the temperature of the environment. These thermo-responsive copolymer films formed highly swollen hydrogel-like materials when soaked in cold water and shrank when soaked in warm water. The changes are reversible. The mechanical properties of the copolymer films were assessed by tensile strength measurement. These copolymers were ductile when compared to PCL homopolymers. Young's modulus and the stress at break increased with increasing PCL content, whereas the strain at break increased with increasing PEG content. The results of the cytotoxicity tests based on the ISO 10993-5 protocol demonstrated that the copolymers were non-cytotoxic and could be potentially used in biomedical applications.

Novel amphiphilic poly(ester‐urethane)s based on poly[(R)‐3‐hydroxyalkanoate]: synthesis, biocompatibility and aggregation in aqueous solution

AbstractBACKGROUND: The aim of this work was to develop polyhydroxyalkanoates (PHAs) for blood contact applications, and to study their self‐assembly behavior in aqueous solution when the PHAs are incorporated with hydrophilic segments. To do this, poly(ester‐urethane) (PU) multiblock copolymers were prepared from hydroxyl‐terminated poly(ethylene glycol) (PEG) and hydroxylated poly[(R)‐3‐hydroxyalkanoate] (PHA‐diol) using 1,6‐hexamethylene diisocyanate as a coupling reagent. The PEG segment functions as a soft, hydrophilic and crystalline portion and the poly[(R)‐3‐hydroxybutyrate] segment behaves as a hard, hydrophobic and crystalline portion. In another series of PU multiblock copolymers, crystalline PEG and completely amorphous poly[((R)‐3‐hydroxybutyrate)‐co‐(4‐hydroxybutyrate)] behaved as hydrophobic and hydrophilic segments, respectively.RESULTS: The formation of a PU series of block copolymers was confirmed by NMR, gel permeation chromatography and infrared analyses. The thermal properties showed enhanced thermal stability with semi‐crystalline morphology via incorporation of PEG. Interestingly, the changes of the hydrophilic/hydrophobic ratio led to different formations in oil‐in‐water emulsion and surface patterning behavior when cast into films. Blood compatibility was also increased with increasing PEG content compared with PHA‐only polymers.CONCLUSION: For the first time, PHA‐based PU block copolymers have been investigated in terms of their blood compatibility and aggregation behavior in aqueous solution. Novel amphiphilic materials with good biocompatibility for possible blood contact applications with hydrogel properties were obtained. Copyright © 2008 Society of Chemical Industry

Non‐covalently crosslinked hydrogels displaying a unique combination of water‐absorbing, elastic and adhesive properties

AbstractBACKGROUND: Stringent requirements must be satisfied by biomedical adhesives, including biocompatibility, adhesion, cohesiveness and processability. The ability to change mechanical properties in response to environmental changes may also be desirable. In the present work the water‐absorbing, adhesive and mechanical properties of blends based on hydrogen bonding complexes between poly(N‐vinyl pyrrolidone), poly(ethylene glycol) (PEG) and poly[(methacrylic acid)‐co‐(ethyl acrylate)] were investigated. These blends, consisting of pharmaceutical‐grade components, exhibit pH‐sensitive swelling and dissolution, along with rubber‐like elasticity and bioadhesion.RESULTS: Polymer blend films remained intact at pH = 5.6 but underwent dissolution at pH = 7.4, the difference being attributed to deprotonation of acidic side‐chains, with loss of hydrogen bonding and development of charge repulsion. Sol release was primarily due to PEG. Films swelled at low pH instead of dissolving, in a manner that was pH‐dependent but PEG‐independent. Films displayed elastic properties comparable to cured elastomers when mildly swollen, with modulus and ultimate strength decreasing with increasing PEG content. Dry films were nearly tack‐free, but became more adhesive with increasing water content, up to a point where the film dissolved.CONCLUSION: Due to their biocompatibility and dissolution/mechanical properties, the bioadhesive polymer blends investigated may be suitable for numerous biomedical applications. Copyright © 2008 Society of Chemical Industry

Biodegradable polyetheresteramides synthesized from ε-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol)

Biodegradable aliphatic polyetheresteramides copolymers (PEEAs) were synthesized from ϵ-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol) (PEG) by melt-polycondensation method. FTIR, 1H NMR, differential scanning calorimeter, wide-angle X-ray diffraction, and thermogravimetric analysis/differential thermogravimetry were used to characterize the PEEAs. The tensile testing, water absorption and hydrolytic degradation behavior were also studied. With the increase in PEG content, the water absorption increased. The rate of hydrolytic degradation depended on the copolymers' hydrophilicity and crystallinity. PEEAs with a relatively low content of PEG still retain good tensile properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Poly(vinylidene fluoride-hexafluoropropylene)-based membranes for lithium batteries

Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) copolymer membranes were prepared by a phase inversion technique with poly(ethylene glycol) as an additive and tetrahydrofuran or acetone or dimethylformamide as solvent. The morphology, ionic conductivity and uptake of electrolyte solution by the polymer membranes were studied. The amount of intake of electrolyte solution by the polymer membranes increases with the increase of PEG content. The morphology and ionic conductivity of the polymer membranes (PM) are correlated with the physical properties of the solvents used in the phase inversion process. The cycling behavior of the membrane was examined with Li/LiCoO 2 cells.

Temperature and pH sensitive hydrogels composed of chitosan and poly(ethylene glycol)

Chitosan based semi-interpenetrating polymer network (semi-IPN) hydrogels containing different amounts of poly(ethylene glycol) (PEG) were prepared. The crosslinking of the hydrogels was achieved by using a naturally occurring nontoxic cross-linking agent genipin. The swelling behaviour of these hydrogels was studied by immersing the films in deionized water at 25, 37 and 45 °C and in media of different pHs at 37 °C. Swelling was found to be dependent on temperature, pH of the medium and the amount of PEG in the gel. States of water in the hydrogels swollen in deionized water at 37 °C were determined using Differential Scanning Calorimetry (DSC). The equilibrium water content and the amount of freezing water in the swollen hydrogels increased with the increase in PEG concentration in the gels.

Encapsulation and controlled release of lysozyme from electrospun poly(ε-caprolactone)/poly(ethylene glycol) non-woven membranes by formation of lysozyme–oleate complexes

In this study, the concept of hydrophobic ion pairing was adopted for incorporating lysozyme into electrospun poly(epsilon-caprolactone) (PCL)/poly(ethylene glycol) (PEG) non-woven membranes. The solubility of lysozyme in organic solvent was enhanced through the formation of lysozyme-oleate complexes, which could be directly loaded into PCL/PEG membranes using electrospinning technique. The resultant PCL/PEG nanofibers have a compact structure with an average diameter ranged from about 0.4 microm to 0.9 microm. The addition of PEG into the PCL nanofibers not only improved the hydrophilicity of the membrane, but also played an important role on in vitro lysozyme release rate. It was found that the release rate of lysozyme was enhanced with the increase of PEG content. In addition, the increase of salt concentration in the release medium accelerated lysozyme release. It has also been shown that the released lysozyme retained most of its enzymatic activity.

Synthesis, characterization and hydrolytic degradation study of polyetheresteramide copolymers based on ε-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol)

In this paper, a new kind of biodegradable aliphatic polyetheresteramide copolymers (PEEA) based on epsilon-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol) (PEG) were synthesized by melt polymerization method. The obtained copolymers were characterized by 1H-NMR. The thermal properties of PEEA copolymers were studied by DSC and TGA/DTA under nitrogen atmosphere. The water absorption and hydrolytic degradation behavior was also studied in detail. With the increase in PEG content or the decrease in caprolactone content, the water absorption of the copolymers increased accordingly. For the hydrolytic degradation behavior, with the increase in PEG content or caprolactone content, the degradation rate increased then.

Synthesis and characterization of biodegradable elastic hydrogels based on poly(ethylene glycol) and poly(ε-caprolactone) blocks

Novel biodegradable elastic hydrogels, based on hydrophilic and hydrophobic polymer blocks, were synthesized via the radical crosslinking reaction of diacrylates of poly(ethylene glycol) (PEG) and poly(e-caprolactone) (PCL). PEG and PCL diols were diacrylated with acryloyl chloride in the presence of triethylamine, with the reaction confirmed by FT-IR and1H-NMR measurements. The diacrylate polymers were used as building-blocks for the syntheses of a series of hydrogels, with different block compositions, by simply varying the feed ratios and molecular weights of the block components. The swelling ratio of the hydrogels was controlled by the balance between the hydrophilic and hydrophobic polymer blocks. Usually, the swelling ratio increases with increasing PEG content and decreasing block length within the network structure. The hydrogels exhibited negative thermo-sensitive swelling behavior due to the coexistence of hydrophilic and hydrophobic polymer components in their network structure, and such thermo-responsive swelling/deswelling behavior could be repeated using a temperature cycle, without any significant change in the swelling ratio.In vitro degradation tests showed that degradation occurred over a 3 to 8 month period. Due to their biodegradability, biocompatibility, elasticity and functionality, these hydrogels could be utilized in various biomedical applications, such as tissue engineering and drug delivery systems.

Synthesis and Erosion Properties of PEG‐Containing Polyanhydrides

To tailor the erosion rate of polyanhydrides while retaining their surface erosion characteristics, new three-component polyanhydrides of sebacic acid, 1,3-bis(p-carboxyphenoxy)propane and poly(ethylene glycol) were synthesized. The hydrophilicity of the polymer increased and its mechanical strength decreased with increasing PEG content. Correspondingly, the erosion rate increases with increasing PEG content, whereas it decreases with increasing specimen thickness. This indicates that the incorporation of poly(ethylene glycol) into traditional two-component polyanhydrides retains their surface erosion properties while making the erosion rate tunable. The new polyanhydrides hold potential for drug delivery applications.

Mechanical properties of layered poly(ethylene glycol) gels

Poly(ethylene glycol) (PEG) hydrogels have become a popular material for biomedical applications because of their versatility in use and design. As these gels are readily crosslinked under UV, microfabrication techniques have been investigated to manufacture complex three dimensional structures to better mimic the in vivo environment. This work investigated whether a layering technique to fabricate gels offered sufficient strength between the layers to perform similarly in mechanical testing to unlayered gels. Two mechanical tests were performed: tensile tests and peel tests. The tensile tests, which examined sample gels whose test sections were crosslinked for different durations, demonstrated no statistical differences in elastic modulus between sample and control gels. As expected, a statistical increase in the elastic modulus was found with increased PEG concentration. Comparison of the yield stress between samples and controls illustrated differences with total crosslinking duration, which may be due to the decreased molecular weight of the chains with decreased crosslinking time. In peel tests, no statistical differences of maximum peel force were found between samples and controls. However, an increase in the maximum peel force was found with increasing concentration of PEG. Overall, this study demonstrates that the layering process described for the PEG gels has minimal impact on the tested mechanical properties of the system. As mechanical properties are critical to the design of tissue engineered devices, these results demonstrate that this fabrication method may be appropriate for further study as a scaffold for complex cellular systems.