Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004     

Positron annihilation and differential scanning calorimetry studies of polyacrylamide and poly(dimethylacrylamide)/poly(ethylene glycol) blends

Positron annihilation lifetime spectroscopy and differential scanning calorimetry (DSC) measurements were performed for blends of polyacrylamide (PAM) and poly(ethylene glycol) (PEG) and blends of poly(dimethylacrylamide) (PDMAM) and PEG. The samples were prepared by codissolution in a concentration range of 0–100 wt % PEG. The thermal behavior, characterized by DSC measurements, showed similar variations of the glass‐transition temperatures (T_g's) with the PEG concentration for the two systems. Pure PAM and PDMAM presented T_g's of 188 and 111 °C, respectively. A relatively small and nearly linearly decreasing T_g was observed for the two systems in the range of 20–80 wt % PEG. PEG crystals were present in all blend compositions, and no melting point depression was observed. The thermal results pointed to the partial miscibility of the blends. The degree of crystallinity of PEG increased with increasing PEG concentration for the PDMAM/PEG systems. The ortho‐positronium lifetime (τ₃) increased with increasing PEG concentration for both blends. However, the parameter of the ortho‐positronium formation probability (I₃) decreased with the PEG concentration. The product τI₃, which was proportional to the total free volume fraction, was approximately constant with the PEG concentration for PDMAM blends and increased with the PEG concentration for PAM systems. This result may be interpreted as a consequence of a more heterogeneous structure in PAM blends. Scanning electron microscopy micrographs of blends with 40 and 80 wt % PEG provided evidence of the regions associated with PEG crystallites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1493–1500, 2003     

Synthesis and characterization of poly(ethylene glycol) methyl ether endcapped poly(ethylene terephthalate)

Linear and branched poly(ethylene terephthalate) (PET) copolymers with polyethylene glycol) (PEG) methyl ether (700 or 2000 g/mol) end groups were synthesized using conventional melt polymerization. DSC analysis demonstrated that low levels of PEG end groups accelerated PET crystallization. The incorporated PEG end groups also decreased the crystallization temperature of PET dramatically, and copolymers with a high content of PEG (>17.6 wt%) were able to crystallize at room temperature. Rheological analysis demonstrated that the presence of PEG end groups effectively decreased the melt viscosities and facilitated melt processing. XPS and ATR-FTIR revealed that the PEG end groups tended to aggregate on the surface, and the surface of compression molded films containing 34.0 wt% PEG were PEG rich (85 wt% PEG). PEG end-capped PET (34.0 wt% PEG) and PET films were immersed into a fibrinogen solution (0.7 mg/mL BSA) for 72 h to investigate the propensity for protein adhesion. XPS demonstrated that the concentration of nitrogen (1.05%) on the surface of PEG endcapped PET film was statistically lower than PET (7.67%). SEM analysis was consistent with XPS results, and revealed the presence of adsorbed protein on the surface of PET films.     

Interaction between poly(ethylene glycol) and water as studied by differential scanning calorimetry

The interaction between poly(ethylene glycol) (PEG) and water was studied by differential scanning calorimetry (DSC). The DSC curves of PEG–water systems were classified into three groups according to the difference in molecular weight. The melting peaks of eutectic mixture appeared for PEG with molecular weight higher than 1000. The eutectic point temperature shifted to higher temperatures and the eutectic point composition shifted to lower concentrations of PEG with increasing molecular weight. The maximum hydration number per ethylene glycol (EG) unit was estimated as 1.6, 2.4, and 3.3 for samples with molecular weights 400, 1540, and 70,000, respectively. No thermal change was found in PEG1540‐water system for a narrow weight fraction range of 0.585–0.605 for overall measuring temperatures due to perfect supercooling. The glass transition temperature shifted to higher temperatures with increasing molecular weight of PEG. A modified Flory–Huggins equation was used to fit curves for experimental liquidus data in phase diagrams. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 496–506, 2001     

Ion conductivity studies of blends of poly(methyl methacrylate)-g-poly(ethylene glycol) and poly(ethylene glycol) complexed with LiCF3 SO3

Polymer electrolytes which are adhesive, transparent, and stable to atmospheric moisture have been prepared by blending poly(methyl methacrylate)-g-poly(ethylene glycol) with poly(ethylene glycol)/LiCF₃ SO₃ complexes. The maximum ionic conductivities at room temperature were measured to be in the range of 10⁻⁴ to 10⁻⁵ s cm⁻¹. The clarity of the sample was improved as the graft degree increased for all the samples studied. The graft degree of poly(methyl methacrylate)-g-poly(ethylene glycol) was found to be important for the compatibility between the poly(methyl methacrylate) segments in poly(methyl methacrylate)-g-poly(ethylene glycol) and the added poly(ethylene glycol), and consequently, for the ion conductivity of the polymer electrolyte. These properties make them promising candidates for polymer electrolytes in electrochromic devices. © 1996 John Wiley & Sons, Inc.     

Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)

Multiwall carbon nanotube (MWNT) was grafted with polyacrylate‐g‐poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid‐treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880–6887, 2006     

Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO₂ separation selectivity over H₂. The CO₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer‐rich and PEG‐rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2–4 μm in proportion to PAMAM dendrimer concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Side‐chain crystallization behavior of graft copolymers consisting of amorphous main chain and crystalline side chains: Poly(methyl methacrylate)‐graft‐poly(ethylene glycol) and poly(methyl acrylate)‐graft‐poly(ethylene glycol)

Graft copolymers consisting of amorphous main chain, poly(methyl methacrylate) (PMMA), or poly(methyl acrylate) (PMAc), and crystalline side chains, poly(ethylene glycol) (PEG), have been prepared by copolymerization of PEG macromonomers with methyl methacrylate or methyl acrylate (MMAx or MACx, respectively). Because of the compatibility of PMMA/PEG and PMAc/PEG, from small‐angle X‐ray scattering results, the main and side chains in graft copolymers were suggested to be homogeneous in the molten state. Differential scanning calorimetry (DSC) cooling scans revealed that PEG side chains for graft copolymers with large PEG fractions were crystallized when the sample was cooled, with a cooling rate of 10 °C/min. The spherulite pattern observed by a polarized optical microscope suggested the growth of PEG crystalline lamellae. Crystallization of PEG in MMAx was more restrained than in MACx. From these results, we have concluded that the crystallization behavior of the grafted side chains is strongly influenced by the glass transition of a homogeneously molten sample as well as dilution of the crystallizable chains. Domain spacings for isothermally crystallized graft copolymers were described by interdigitating chain packing in crystalline–amorphous lamellar structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 79–86, 2005     

Viscoelastic properties of single poly(ethylene glycol) molecules.

The viscoelastic properties of single poly(ethylene glycol) (PEG) molecules were measured by analysis of thermally and magnetically driven oscillations of an atomic force microscope (AFM) cantilever/molecule system. The molecular and monomer stiffness and friction of the PEG polymer were derived using a simple harmonic oscillator (SHO) model. Excellent agreement between the values of these two parameters obtained by the two approaches indicates the validity of the SHO model under the experimental regimes and the excellent reproducibility of the techniques. A sharp minimum in the monomeric friction is seen at around 180 pN applied force which we propose is due to a force induced change in the shape of the energy landscape describing the conformational transition of PEG from a helical to a planar state, which in turn affects the timescale of the transition and therefore modifies the measured internal friction. A knowledge of the viscoelastic response of PEG monomers is particularly important since PEG is widely used as a linker molecule for tethering groups of interest to the AFM tip in force spectroscopy experiments, and we show here that care must be exercised because of the force-dependent viscoelastic properties of these linkers.     

叶酸和聚乙二醇接枝作基因载体用壳聚糖的合成与表征

本研究将叶酸和聚乙二醇接枝到四种不同分子量的壳聚糖氨基侧链上,以改善壳聚糖的靶向性和水溶性作基因载体。用FTIE、1HNMR、UV-Vis、DSC和TEM对产物进行了表征,结果表明,叶酸和聚乙二醇被成功地接枝到壳聚糖上,所制得的载体有望作为潜在的肿瘤细胞靶向基因载体。     

Synthesis and characterization of polyphenylenes with polypeptide and poly(ethylene glycol) side chains

We report a novel approach for fabrication of multifunctional conjugated polymers, namely poly(p‐phenylene)s (PPPs) possessing polypeptide (poly‐l ‐lysine, PLL) and hydrophilic poly(ethylene glycol) (PEG) side chains. The approach is comprised of the combination of Suzuki coupling and in situ N‐carboxyanhydride (NCA) ring‐opening polymerization (ROP) processes. First, polypeptide macromonomer was prepared by ROP of the corresponding NCA precursor using (2,5‐dibromophenyl)methanamine as an initiator. Suzuki coupling reaction of the obtained polypeptide and PEG macromonomers both having dibromobenzene end functionality using 1,4‐benzenediboronic acid as the coupling partner in the presence of palladium catalyst gave the desired polymer. A different sequence of the same procedure was also employed to yield polymer with essentially identical structure. In the reverse sequence mode, low molar mass monomer (2,5‐dibromophenyl)methanamine, and PEG macromonomer were coupled with 1,4‐benzenediboronic acid in a similar way followed by ROP of the L‐Lysine NCA precursor through the primary amino groups of the resulting polyphenylene. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1785–1793     

Photochemistry of nonconjugated bichromophoric systems III. Synthesis and photoreaction of poly(ethylene glycol) biscoumarinyloxyacetates

A series of poly(ethylene glycol) biscoumarinyloxyacetatea have been synthesized and their intramolecular photochemical cyclodimerizations have been studied. It was found that only syn-HT configuration products were obtained when these bisesters were directly irradiated in chloroform, and the yields of the products decreased with the increase of the chain length. This photocyclization reaction is a convenient and effective method to synthesize macrocyclic compounds.     

Poly (caprolactone)/poly (ethylene glycol) pervaporation blend membranes: Synthesis,characterization, and performance

Poly (caprolactone) membranes with addition of different poly (ethylene glycol) concentrations were prepared for separation of water/isopropanol azeotropic mixture by pervaporation process. Different characterization tests including Fourier transform infrared, scanning electron microscopy, water contact angle, and thermogravimetric analysis were carried out on the prepared membranes. In addition, the effect of poly (ethylene glycol) PEG content on the swelling degree and the performance of the prepared membranes in pervaporation process were investigated. According to the obtained results, all the membranes were water selective and the blend membrane containing 3 wt% PEG exhibited the best pervaporation performance with a water flux of 0.517 kg/m² hour and separation factor of 1642 at the ambient temperature. Hydrophilicity improvement of the blend membranes was confirmed by constant decrease in water contact angle of the membranes as PEG content increased in the casting solution. Scanning electron microscopy cross‐sectional images indicated that the blend membranes containing PEG had a closed cellular structure. Furthermore, mechanical and thermal properties of the membranes decreased by adding PEG.     

紫外光交联可降解聚对二氧环己酮/聚乙二醇薄膜制备与表征

以2,2-二甲氧基-2-苯基苯乙酮(DMPA)为引发剂,将四臂端丙烯酸酯聚对二氧环己酮(PPDO-4AC)和聚乙二醇双丙烯酸酯(PEG-DA)经紫外光照射制得PPDO/PEG交联薄膜.研究了光照时间和DMPA用量对PPDO/PEG交联薄膜凝胶含量的影响.DSC研究表明共聚物中两组分的相容性较好,Tg随着共聚物中PEG链...     

Diffusion of ethylene glycol accompanied by reactions in poly(ethylene terephthalate) melts

Diffusion coefficients of ethylene glycol (EG) have been measured in poly(ethylene terephthlate) (PET) melts by a quartz-spring sorption apparatus. A simple mathematical model was developed to investigate the sorption behavior accompanied by chemical reactions of EG and PET at high temperatures. Diffusion coefficients are deduced from experimental data for an asymptotically thin sample in order to minimize the effects of reactions. The diffusion coefficient of EG is strongly dependent on the vapor pressure of EG and temperature but not on the molecular weight of PET in this experimental range (degree of polymerization 80–120). The diffusion coefficient of EG in PET melt at 265°C is 2.58 × 10^?7 cm²/s at the limit of zero concentration of EG. The activation energy for diffusion is 38.4 kcal/gmol, and the heat of solution for sorption is ?44.9 kcal/gmol. The concentrations of the volatile materials resulting from reactions in PET-EG system were analyzed with gas chromatography. In addition, a fit of the current model to experimental data yields frequency factors for the polymerization reaction (k₁) and the acetaldehyde formation reaction (k₂) to be 5.84 × 10⁸ cm³/mol ? min and 3.90 × 10¹¹ min^?1, respectively.     

Sodium Alginate and Poly(ethylene glycol) Blends: Thermal and Morphological Behaviors

Sodium alginate (SA) was blended with varying amounts of poly(ethylene glycol) (PEG) viz., 10, 20, 30, 40 and 50 wt % by using water as a solvent. The obtained SA/PEG blends have been characterized for thermal behavior by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and surface morphology by scanning electron microscopic (SEM) methods. DSC analysis indicates the increase in glass transition temperature (T_g) of the blends with an increase in PEG content in the blend, which is due to chain entanglement. TGA results reveal the enhancement of thermal stability of SA/PEG blends in terms of the onset of degradation and percentage of weight loss. SEM photomicrographs shows the two phase morphology. This result indicates the immiscible nature of the SA/PEG blends.     

Thermo-Responsive Hydrogels Based on Branched Poly(L-lactide)-poly(ethylene glycol) Copolymers

Summary: Branched poly(L -lactide)-poly(ethylene glycol) (PLLA-PEG) block copolymers were synthesized from trifunctional PLLA and amine functionalized methoxy poly(ethylene glycol)s. The copolymers in water formed hydrogels that showed thermo-responsive behavior. The hydrogels underwent a gel to sol transition with increasing temperature as determined with the vial tilting method and oscillatory rheology. For all copolymers, the transition temperature increased with increasing copolymer concentration. The transition temperature of corresponding branched copolymers also increased with increasing PEG molecular weight, and surprisingly decreased with increasing molecular weight of the PLLA branches. In general, the gel-sol transition is explained by disruption of micellar or aggregate interactions because of partial dehydration and shrinkage of the PEG chains. An increase in the molecular weight of the PLLA branches led to the formation of micelles and aggregates as observed with DLS at low concentrations. It is speculated that the non-uniform size distribution and possible crystallization of longer PLLA blocks may have a negative effect on the formation of micellar packing upon gelation, allowing the disruption of micellar or aggregate interactions to occur at lower temperatures. The transition temperature of the gels could be tuned closely to body temperature by varying the concentration of the solution or the molecular weight of the PEG block and the PLLA blocks, which implies that these polymers may be used as injectable systems for in-situ gel formation.     

Easily grafted polyurethanes with reactive main chain functional groups. Synthesis,characterization, and antithrombogenicity of poly(ethylene glycol)-grafted poly(urethanes)

A novel synthesis of poly(ethylene glycol) (PEG)-grafted poly(urethanes) (PURs) is described based on a precursor PUR containing free amino groups in the main chain. Three different poly(urethane) backbones were prepared: a homopoly(urethane) comprised of N-Bocdiethanolamine (BDA) and 4,4′-methylenebis(phenyl isocyanate) (MDI), a copoly(urethane) (COPUR) consisting of BDA, N-benzyldiethanolamine and MDI, and a poly(urethane urea) (PUU) that was prepared from BDA, MDI, and ethylenediamine as the chain extender. The M_n of these poly(urethanes) ranged from 32,000 to 72,000 g/mol. PEG (750, 1,900, and 5,000 g/mol) was grafted onto the boc-deprotected poly(urethanes) via the chloroformate. Films of the polymers were spin cast from dilute solutions, annealed, and the surfaces analyzed by goniometry. Water contact angle data indicates increasing PEG surface coverage of the poly(urethanes) with increasing PEG molecular weight. Reorientation of the polymer films is evidenced by contact angle hysteresis. Polymer thrombogenicity, which was studied using blood perfusion experiments, shows that COPUR-g-PEG5000 and PUU-g-PEG5000 exhibit very little platelet adhesion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3441–3448, 1999     

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

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

Photocrosslinked hydrogels based on copolymers of poly(ethylene glycol) and lysine

A group of new, water-soluble poly(ether-urethane)s, derived from poly(ethylene glycol) and the amino acid L -lysine, provide pendent carboxylic acid groups along the polymer backbone at regular intervals. The carboxylic acid groups were utilized for the attachment of acrylate and methacrylate pendent chains (hydroxyethyl acrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, and aminoethyl methacrylamide), leading to functionalized polymers. The pendent chains were attached via ester and/or amide bonds having different degrees of hydrolytic stability. The attachment reactions proceeded with high yields (up to 95%). The functionalized polymers were subsequently photopolymerized (UV irradiation) to obtain crosslinked hydrogels. Crosslinked membranes with the highest degree of mechanical strength were obtained when the crosslinking reaction was performed in dioxane with benzoin methyl ether (0.1 wt %) as the initiator. the crystallinity, thermomechanical properties, and hydrolytic stability of the crosslinked membranes were studied. All membranes were transparent and highly swellable (equilibrium water content: 64–88%). The tensile strength in the swollen state ranged from 0.15 to 1.09 MPa. Under physiological conditions (phosphate buffered water, 0.1M, pH 7.4, 37°C) the hydrolytic stability of the hydrogels varied depending on the bonds used in the attachment of the acrylate pendent chains: Hydrogels with hydroxyethyl acrylate pendent chains dissolved within 30 days, while hydrogels containing aminoethyl methacrylamide pendent chains remained unchanged throughout a 30 day period. Using high molecular weight FITC-dextrans as model compounds, complete release from the swollen hydrogels required between 60 and 150 h. Overall, the evaluation of poly(ethylene glycol)-lysine derived, photocrosslinked hydrogels indicated that these materials provide a range of potentially useful properties. © 1994 John Wiley & Sons, Inc.