An aqueous-based surface modification of poly(dimethylsiloxane) with poly(ethylene glycol) to prevent biofouling

We report a simple modification of poly(dimethylsiloxane) (PDMS) surfaces with poly(ethylene glycol) (PEG) through the adsorption of a graft copolymer, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) from aqueous solution. In this approach, the PDMS surface was treated with oxygen plasma, followed by immersion into aqueous solution containing PLL-g-PEG copolymers. Due to the hydroxyl/carboxylic groups generated on the PDMS surface after oxygen plasma, the polycationic PLL backbone is attracted to the negatively charged surface and PEG side chains exhibit an extended structure. The PEG/aqueous interface generated in this way revealed a near-perfect resistance to nonspecific protein adsorption as monitored by means of optical waveguide lightmode spectroscopy (OWLS) and fluorescence microscopy.     

Thiophosphate/Phosphonate‐Containing Cross‐Linked PEGs and Their Use for the Stabilization of Silver Nanoparticles

A simple strategy was developed to obtain poly(ethylene glycol) (PEG)‐based materials incorporating phosphonate functions and thiophosphate groups from readily accessible symmetrical PEG compounds and trifunctional thiophosphates. These materials are obtained in a two‐step procedure, via the formation of THF soluble, hyperbranched PEG‐based polyazomethines that are subsequently functionalized with dimethylphosphite. The resulting materials are hydrolytically degradable, and upon exposure to aqueous solutions of silver acetate they afford stable colloidal solutions of silver.     

Solubility of amino acids in aqueous poly (ethylene glycol) solutions

The solubilities of amino acids have been measured in water and aqueous poly(ethylene glycol) (PEG) solutions as a function of temperature and PEG concentration. The free energies of transfer from water to aqueous PEG solutions forl-alanine,l-valine,l-isoleucine andl-leucine were positive, while those forl-phenylalanine andl-tryptophan were negative. The corresponding enthalpies of transfer were almost zero for all amino acids. The equilibrium constants of the binding of amino acids to PEG chain were estimated from the solubility data. Amino acids with larger hydrophobicity are bound more strongly to the PEG chain due to the hydrophobic interaction between the methylene groups of PEG and the side chain of amino acid. The equilibrium constants showed a correlation with the dynamic hydration number (n _DHN) which expresses the hydration properties of amino acids in aqueous solution.     

丙烯酰胺在聚乙二醇水溶液中聚合初期的液滴形成与成长过程

用动态激光光散射(DLS)在线观测了丙烯酰胺(AM)在聚乙二醇(PEG)水溶液中聚合初期液滴的出现、生长及聚并过程,考察了PEG分子量和浓度对聚合初期液滴尺寸的影响;用透射电镜(TEM)对聚合初期液滴形态的演变进行了观察,发现与DLS结果能很好吻合.用分光光度计对聚合体系分相点进行确定,采用溴化法测定了聚合体系临界分相时的转化率.随PEG分子量或浓度的升高,临界分相转化率逐渐减小;随温度的升高,临界分相转化率先减小后增大,在50℃左右出现最小值.用凝胶渗透色谱(GPC)对聚合体系临界分相时聚丙烯酰胺(PAM)的分子量进行了研究,变化趋势与临界分相转化率的变化一致.在上述基础上,提出了AM在PEG水溶液中聚合初期的液滴形成、成长机理.     

Effects of Ethylene Oxide Spacer Length on solution Properties of Water—Soluble Fluorocarbon—Containing Hydrophobically Associating Poly（Acrylic Acid—co—Rf—PEG Macromonomer）

Poly(acrylic acid)s (PAAs) modified with a series of fluorocarbon group (Rf) end-capped Poly(ethylene glycol) (PEG) macromonomers(number of ethylene oxide unit:1,9,23,45) and corresponding copolymers without fluorocarbon end groups were synthesized.It was found that the effect of the hydrophobic association of fluorocarbon groups on the solution viscosity prevailed over that of the hydrogen bond between grafted PEG and the backbone.Rheological measurement on the aqueous solutions of these poly(acrylic acid-co-Rf-PEG macromonomer) s demonstrated that the best thickening performance was shown when the number of ethylene oxide unit (EO number) was 23.     

Swelling equilibrium of poly(acrylamide) gels in aqueous salt and polymer solutions

The influence of some single salts (NaCl, KCl, Na₂HPO₄ and K₂HPO₄) and poly(ethylene glycol) (PEG) on the swelling of aqueous poly(arcylamide)-gels was studied at 25°C in more than 600 experiments. The chlorides and phosphates cause a different behavior at high salt concentrations: The polyacrylamide gels swell in aqueous solutions of sodium and potassium chloride whereas they shrink when chloride ions are substituted by hydrogen phosphate ions. These differences are due to differences in the interactions of chloride and hydrogen phosphate ions with the network groups. In aqueous solutions of poly(ethylene glycol) the gels shrink continuously with increasing polymer concentration. At constant PEG mass fraction in the liquid phase, the swelling of the gel decreases with increasing molecular weight of PEG. The experimental results (degree of swelling, partitioning of solutes to the coexisting phases) are correlated by combining a model for the Gibbs excess energy for aqueous systems of polymers and electrolytes with a modification of the phantom-network theory. The correlation gives a good agreement with the experimental data for the degree of swelling, whereas in most cases, there is only a qualitative agreement for the partitioning of the solutes.     

Sodium Chloride Molar Conductance in Different Poly(ethylene glycol)–Water Mixed Solvents

The molar conductivities of NaCl in several poly(ethylene glycol)(PEG)–water “mixed solvents” are presented as a function of the PEG content in solution. Three different PEG samples, a monodispersed one and two polydispersed ones, have been used. The comparison between the molar conductivity values in the mixed solvents and the corresponding ones in pure water shows that the only effect of PEG on the ions’ motions is an obstruction effect despite the variation of the macroscopic dielectric constant induced by PEG itself. A comparison between the molar conductivities and the corresponding mutual main diffusion coefficients shows a tight correlation between the two quantities. This correlation is possible only in the absence of electrostatic effects due to the presence of PEG.     

PROPERTIES OF SILK FIBROIN/POLY(ETHYLENE GLYCOL)400 BLEND FILMS

The blend film of silk fibroin (SF) and poly(ethylene glycol)400 (PEG400) with a blend ratio of 2/1 (wt/wt) wasprepared simply by dropping a little PEG400 into the SF solution and then casting the mixed aqueous solution at 50℃. Theresulting film exhibited much better mechanical properties in the dry and wet state than SF itself, owing to theconformational change of SF in the blends from the random coil to the β-sheet structure and intermolecular hydrogen bondformation between SF and PEG400. Thermogravimetric analysis showed that the initial thermal decomposition temperatureof the blend film was 170℃, which was 80℃ lower than that of SF (250℃) and 20℃ higher than that of PEG400 (150℃),and indicated a Strong interaction between two components of the blend. No crystalline peaks were observed in the X-raydiffraction curve of the blend film. Cell culture test showed that SF/PEG400 was a suitable substrate for the growth of humanumbilical vein endothelial cells (HUVEC).     

Poly(ethylene glycol)-conjugated phospholipids in aqueous micellar solutions: hydration, static structure, and interparticle interactions

By means of dielectric relaxation spectroscopy (DRS) and small-angle X-ray scattering (SAXS), we have investigated hydration behavior, solvent dynamics, and static structures of aqueous solutions of poly(ethylene glycol)-conjugated distearoyl phosphatidylethanolamine (DSPE-PEG) (molecular weight of PEG: M(PEG)= 2000, 5000, and 12,000 Da). A quantitative analysis of the bulk-water relaxation amplitude revealed the effective hydration number of a DSPE-PEG molecule per ethylene oxide monomer unit to be approximately 5.0-5.5, virtually independent of M(PEG). The overall hydration number of a DSPE-PEG molecule is ca. 20% higher than that of the corresponding normal PEG (without DSPE). This is attributed to both hydration of a charged head group of phosphoric acid in DSPE and a packing effect of PEG chains into micellar structures. The pair-distance distribution functions, p(r), extracted from the GIFT analysis of SAXS intensities show that the DSPE-PEGs form spherical-like micelles in water having the maximum diameter of approximately 16, 22, and 31 nm, respectively, for M(PEG) = 2000, 5000, and 12,000 Da and nearly identical aggregation numbers of 72 (+/-10%). The DSPE-PEG micelles behave as charged colloids whose interparticle interaction potential can be approximated by the screened Coulomb potential model. The extracted pair correlation function g(r) demonstrates that both electrostatic repulsion induced by the charged head group and excluded volume effects of the fully hydrated PEG layer contribute to repulsive interactions among the PEG-lipid micelles. This should be a key factor for the function of PEG lipids as a stabilizer of liposomes.     

Spatial arrangement of alpha-cyclodextrins in a rotaxane. Insights from free-energy calculations

The rotaxane formed by alpha-cyclodextrins (alpha-CDs) threaded onto a poly(ethylene glycol) (PEG) chain was investigated in the gas phase and in an aqueous solution by means of molecular dynamics simulations. The free-energy difference between the three possible spatial arrangements of consecutive alpha-CD--viz.. head-to-head (HH), head-to-tail (HT), and tail-to-tail, was determined using free-energy perturbation calculations. These simulations reveal that the interaction of alpha-CD with the PEG chain is very similar in the two surroundings, whereas the mutual interaction of the macrocycles is stronger in the gas phase than in the aqueous solution. Moreover, difference in the overall interaction appears to stem primarily from changes in the electrostatic contribution. Analysis of intermolecular hydrogen bonds indicates that hydrogen bonds created between alpha-CD and water molecules weaken the hydrogen-bonding interaction of adjacent alpha-CDs. Comparison of the free-energy differences characteristic of the three possible spatial arrangements of contiguous alpha-CDs reveals that the HH motif of the rotaxane is the most stable in the gas phase due to the hydrogen-bond formation between the secondary hydroxyl groups of the two alpha-CDs, and the slight preference for the HT motif in aqueous solution, which can be related to the directionality of the dipole moment borne by the macrocycles in these two motifs.     

Modeling of Osmotic Pressure of Aqueous Poly(Ethylene Glycol) Solutions Using the Artificial Neural Network and Free Volume Flory Huggins Model

In this work, the modified Flory-Huggins coupled with the free-volume concept and the artificial neural network models were used to obtain the osmotic pressure of aqueous poly(ethylene glycol) solutions. In the artificial neural network, the osmotic pressure of aqueous poly(ethylene glycol) solutions depends on temperature, molecular weight and the mole fractions of poly(ethylene glycol) in aqueous solution. The network topology is optimized and the (3-1-1) architecture is found using optimization of an objective function with batch back propagation (BBP) method for 134 experimental data points. The results obtained from the neural network in obtaining of the osmotic pressure of aqueous poly(ethylene glycol) were compared with those obtained from the free volume Flory-Huggins model (FV-FH). The results showed that the modified Flory-Huggins model and also the artificial neural network can accurately predict the osmotic pressure of aqueous poly(ethylene glycol) solutions but the accuracy of ANN is much better than the modified Flory-Huggins model.     

Thermally switchable polyrotaxane as a model of stimuli-responsive supramolecules for nano-scale devices

A polyrotaxane consisting of many β-cyclodextrins (β-CDs) and a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with bulky end-groups was synthesized as a model of stimuli-responsive supramolecules for nanoscale devices. The polyrotaxane was reversibly soluble-insoluble in water in response to temperature. This was achieved through the assembled and dispersed states of β-CDs along the block copolymer. It is considered that intermolecular hydrogen bondings of β-CDs, as well as the PEG segment length of the copoloymer, are predominant factors for regulating such thermally switchable behavior of the polyrotaxane.     

Extraction of actinides in two-phase water-poly(ethylene glycol)—Salt systems in the presence of potassium phosphotungstate

Extraction of actinides has been examined in two-phase aqueous systems based on poly(ethylene glycol) (PEG) from sulfate solutions in the presence of potassium phosphotungstate, which forms strong complexes with ions of tri- and tetravalent transuranium elements. Extraction of these complexes by aqueous PEG solution is complete in contrast to that of penta- and hexavalent actinides. Conditions have been chosen for the separation of actinides in different oxidation states.     

Hydrodynamic radius of polyethylene glycol in solution obtained by dynamic light scattering

In order to compare the size characterizations in poly(ethylene glycol) (PEG) obtained by dynamic light scattering (DLS) and small angle neutron scattering (SANS), DLS experiments were performed in various PEG solutions to ascertain the hydrodynamic radius. Data from the experiments were analyzed by using a method to eliminate effects of PEG aggregation on dynamic correlation functions. The results of the analysis were then compared to the radii of gyration reported from SANS experiments. The relation between the hydrodynamic radius, obtained by DLS, and the radius of gyration, obtained by SANS, in PEG in solution was found to be in agreement with a previously obtained relation for PEG, where the radius of gyration was found by static light scattering.     

Gelation characteristics and applications of poly(ethylene glycol) end capped with hydrophobic biodegradable dipeptides

Poly(ethylene glycol) (PEG) end capped with biodegradable hydrophobic dipeptides shows versatile gelation behavior in a wide range of aqueous and organic solvents. This gelation characteristic is attributed to the aggregation of polymer chains induced by dipeptide end groups. Both PEG molecular weight and molecular structure of end groups control this aggregation by striking a balance between two opposing molecular interactions: solubility of the PEG segment which tends to dissolve the polymer while hydrophobic and intermolecular noncovalent interactions between the end groups induce aggregation. Morphologically, this aggregated structure forms interpenetrating nano sheets with characteristic microstructural features. These gels are biodegradable and possess physicomechanical characteristics suitable for biomedical applications. Furthermore, proteins and hydrophobic model drugs can be encapsulated within the gels from aqueous and organic solvents, respectively, and can be released in a controlled fashion which indicates the applicability of the gels as drug delivery vehicles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1917–1928     

Thermal gelation or gel melting: (ethylene glycol)113‐(l‐alanine)12 and (ethylene glycol)113‐(l‐lactic acid)12

When PEG (M.W.～5000 Daltons) is conjugated to poly(l ‐alanine), the polymer aqueous solutions (<10.0 wt.%) undergo sol‐to‐gel (thermal gelation), whereas it is conjugated to poly(l ‐lactic acid), the polymer aqueous solutions (>30.0 wt.%) undergo gel‐to‐sol (gel melting) as the temperature increases. In the search for molecular origins of such a quite different phase behavior, poly(ethylene glycol)‐poly(l ‐alanine) (PEG‐PA; EG₁₁₃‐A₁₂) and poly(ethylene glycol)‐poly(l ‐lactic acid) (PEG‐PLA; EG₁₁₃‐LA₁₂) are synthesized and their aqueous solution behavior is investigated. PEG‐PAs with an α‐helical core assemble into micelles with a broad size distribution, and the dehydration of PEG drives the aggregation of the micelles, leading to thermal gelation, whereas increased molecular motion of the PLA core overwhelms the partial dehydration of PEG, thus gel melting of the PEG‐PLA aqueous solutions occurs. The core‐rigidity of micelles must be one of the key factors in determining whether a polymer aqueous solution undergoes sol‐to‐gel or gel‐to‐sol transition, as the temperature increases. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, , 52, 2434–2441     

基于Diels-Alder点击反应构建壳聚糖-O-聚乙二醇接枝共聚物

通过Diels-Alder(D-A)反应,合成了具有规整化学结构的接枝共聚物,壳聚糖-O-聚乙二醇(CS-O-PEG).D-A反应所需双烯体(呋喃环)通过糠基硫醇与端甲基丙烯酸酯聚乙二醇之间的巯基-丙烯酸酯(thio-acrylate)反应合成得到;马来酰亚胺基丙酸通过活泼酯法偶联到十二烷基硫酸钠-壳聚糖复合物(SCC)羟基上,从而获得亲双烯体.采用红外光谱(FTIR)和核磁共振(1H-NMR)表征了中间产物与最终产物的结构,并用原位核磁监测D-A反应及其逆反应过程.结果表明,聚乙二醇双烯体可在水介质中温和条件下定量接枝到壳聚糖羟基上,反应具有点击特征;同时,聚乙二醇与壳聚糖之间的连接键在高温下(90℃)可通过D-A逆反应而发生断裂.     

PEG链段对聚乙二醇接枝聚苯胺结构与性能的影响

将苯胺(An)与甲氧基聚乙二醇邻氨基苯基醚氧化共聚,制备了梳状接枝共聚物PAn-g-PEG.研究了梳状接枝共聚物的UV-Vis、微观结构、热稳定性和溶解成膜性等随侧链聚乙二醇(PEG)链段的变化规律.结果表明随PAn-g-PEG中PEG链段长度和含量的提高,共聚物的溶解性和成膜性能显著提高,电子导电率缓慢降低,热稳定性变差.共聚物具有微相分离结构,其形态随PEG链段的改变分别为“海-岛相”和“双连续相”;提高PEG链段长度和含量,PAn-g-PEG能形成稳定的水溶性分散体系,并能浇注成柔韧平整的导电高分子自支撑膜.     

Properties of polyethylene glycol supported tetraarylporphyrin in aqueous solution and its interaction with liposomal membranes

5,10,15,20-Tetrakis(4-hydroxyphenyl)porphyrin was functionalized by covalent attachment of poly(ethylene glycol) (PEG) chains of various molecular weights, 350, 2000, and 5000 Da. The properties of PEG-functionalized tetraarylporphyrins in aqueous solution and their interactions with liposomes have been studied. Electronic absorption spectroscopy, dynamic light scattering, atomic force microscopy, and fluorescence quenching were used to monitor aggregation of porphyrin chromophores and behavior of the attached PEG chains in the aqueous solution. The tendency for aggregation of porphyrin chromophores in aqueous solution and the efficiency of fluorescence quenching by KI decrease with increasing length of PEG chain linked to the porphyrin ring. The experimental results indicate that polymer clusters are present in aqueous solution of all pegylated porphyrins. The interactions between the pegylated porphyrins and phosphatidylcholine liposomes in the aqueous solution were studied using the fluorescence methods. The apparent binding constants of porphyrin chromophores to liposomes were determined. The degree of binding was found to be dependent on the molecular weight of the attached polymer.     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...