Aromatic-aliphatic copolyesters—I. Synthesis and characterization

Copolyesters have been synthesized by interfacial polycondensation of 2,2-bis(4-hydroxyphenyl)-propane or phenolphthalein as aromatic diol and ethylene glycol or polyethylene glycol as aliphatic diol in various mole ratios with terephthaloyl or isophthaloyl chloride. Chemical compositions, dilute solution viscosities and solubility behaviours of these polymers have been investigated. The introduction of aliphatic diol in aromatic polyesters influences T_g, softening point, chemical resistance and thermal stability.     

Thermophysical properties of binary liquid mixtures of polyether and n-alkane at 298.15 and 323.15 K: heat of mixing,heat capacity,viscosity, density and thermal conductivity

An apparatus for a rapid and simultaneous determination of the thermophysical properties excess enthalpy, isobaric heat capacity, kinematic viscosity, density and thermal conductivity has been developed. The experimental setup is subject of this paper. At 298.15 and 323.15 K, the systems ethylene glycol dimethyl ether–n-dodecane, diethylene glycol dimethyl ether–n-dodecane, triethylene glycol dimethyl ether–n-dodecane, tetraethylene glycol dimethyl ether–n-dodecane and diethylene glycol dibutyl ether–n-dodecane have been investigated. The experimental results are correlated and the macroscopic properties are interpreted.     

Relative permittivity of the binary mixtures of 2-methoxyethanol with diethylene glycol,triethylene glycol,tetraethylene glycol,and polyethylene glycol 200 at various temperatures

Relative permittivities at T = (293.15, 298.15, and 303.15) K in the binary liquid mixtures of 2-methoxyethanol with diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol 200 have been measured over the entire mixture compositions. The relative permittivity deviations (Δε) were calculated from these experimental data. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.     

Stability of boronic esters - Structural effects on the relative rates of transesterification of 2-(phenyl)-1,3,2-dioxaborolane

Relative rates of reaction of the achiral cyclic phenylboronic ester 2-(phenyl)-1,3,2-dioxaborolane with a wide variety of structurally modified diols, have been studied to understand the factors influencing the relative stabilities of boronic esters. It is found that the alkyl substituents on the α-carbons of diols slow down the transesterification, but produce thermodynamically more stable boronic ester. Six-membered boronic esters are thermodynamically more stable than their corresponding five-membered analogs. Amongst cyclic 1,2-diols, cis-1,2-cyclopentanediol displaces ethylene glycol instantaneously whereas trans-1,2-cyclopentanediol is totally unreactive, which suggests that the cis-stereochemistry of the 1,2-diol is a prerequisite for transesterification. Among the 1,5-diols, diethanolamine displaces ethylene glycol quite rapidly forming a more stable bicyclic chelate in which nitrogen is attached to boron by a coordinating bond (as evident by ¹¹B NMR spectroscopy). The oxygen atom of di(ethylene glycol) and the sulfur atom of 2,2′-thiodiethanol do not assist in displacing the ethylene glycol from their boronic esters.     

Time differential perturbed angular correlation (TDPAC) study of some hafnium glycolate complexes

Time differential measurements of the 133–482 keV γ—γ angular correlation of ¹⁸¹Ta have been performed in solid hafnium complexes of the type [Hf(glycol)₄] (glycol = p-chloromandelate, p-bromomandelate, b-naphthylglycolate and mandelate). The quadrupolar frequencies (ω_Q) were found to increase within the series. This behaviour was explained by supposing a dissipation of electronic density at the metal level, caused by an increase in intermolecular hydrogen bonding in the complexes throughout the series studied. These results seem to agree with complementary data from IR spectroscopic studies.     

Thermodynamic studies of some binary mixtures containing a self-associated component. II. Excess volumes of some mixtures of tetrahydrofuran with alcohols

Excess volumes of mixing, V^E, for binary mixtures of tetrahydrofuran (THF) with methanol, ethanol, n-butanol, tert-butanol, 2-bromoethanol and ethylene glycol have been determined from the experimental density measurements at 298.15 K over the entire composition range. The V^E data follow the order: ethylene glycol < 2-bromoethanol < methanol < ethanol < n-butanol < tert-butanol. The results have been explained in terms of self-association and the hydrogen bond-donating abilities of alcohols.     

Synthesis and characterization of a novel macromolecular surface modifier for polyethylene

A new macromolecular surface modifier, a copolymer of lauryl methacrylate (LMA) and poly(ethylene glycol) methyl methacrylate (PEGMA), was synthesized through free radical polymerization. The copolymer was characterized by nuclear magnetic resonance spectrum (1H-NMR) and thermogravimetric analysis (TGA). The copolymer was used to blend with polyethylene. The binary blends have been characterized by attenuated total reflection/Fourier transform infrared (ATR-FTIR), contact-angle measurements (CDA) and scanning electron microscopy (SEM). The results indicated that poly(ethylene glycol) methyl methacrylate-co-lauryl methacrylate (PEGMA-co-LMA) could diffuse preferably onto the surface of the polyethylene (PE) film, and thus can be used as an efficient surface modifier for PE.     

Synthesis of triphilic, Y-shaped molecular surfactants

Novel multiphilic molecules comprising three chains with antagonistic affinities have been synthesized. These ‘triphilic’ surfactants (FnHmEOy) contain a perfluorinated arm (Fn=C_nF_2n+1), a hydrocarbon arm (Hm=C_mH_2m+1), and a methyl-caped, poly(ethylene glycol) arm (EOy=CH₃(OC₂H₄)_yO). These moieties have variable lengths (n=5 or 7, m=8, 10, or 14, and y=2-7) and are interconnected in a Y shape; hence, each unit is directly connected to the other two. The key intermediates in the synthetic route are 3-F-alkyl-3-alkyloxypropanoic acids, on which the polar EOy chain is subsequently grafted. Monodisperse methyl-caped diethylene glycol (EO2) and triethylene glycol (EO3) led to the corresponding monodisperse triaffine surfactants. In parallel, a library of five F5H10EOy triaffines (y=3-7) has been obtained simultaneously when starting from the polydisperse methyl-caped poly(ethylene glycol) MPEG 350. Separation of pure individual compounds was achieved through column chromatography on silica gel. The relative concentration of the Z and E isomers has been quantified in the reaction mixtures of the intermediates and final products by ¹H NMR (Z largely predominant). Several products have been obtained in their isomerically pure form. Chemical characterization (¹H, ¹³C, and ¹⁹F NMR, elemental analysis) was consistent with the expected structures.     

Quantum-chemical study on thermal transformations of urea in ethylene glycol

Thermal decomposition of urea in ethylene glycol with formation of isocyanic acid and ammonia was studied at the B3LYP/6-311++G(df,p) level of theory. The decomposition process is efficiently catalyzed by monomeric and dimeric forms of ethylene glycol. Ethylene glycol dimer formed via intermolecular hydrogen bonding is a stronger acid than the monomeric species, which is responsible for the higher catalytic activity of the former. Ethylene glycol associates efficiently catalyze addition of ammonium to isocyanic acid in the synthesis of ethylene carbonate.     

Rate and thermodynamic studies of the interaction between water and iso-butyl cellosolve by ultrasonic methods

Ultrasonic absorption and velocity measurements in aqueous solution of iso-butyl cellosolve (ethylene glycol iso-butyl ether) as a function of the concentration are reported. The two relaxational absorptions have been attributed to the perturbation of the equilibria expressed by AB?A+B and Aα(1/n)A_n where A is the solute, B is the solvent, AB is the complex and A _n is the solute aggregate. The rate constants for each step have been determined. From the concentration dependence of the maximum excess absorption per wave length, the enthalpy change and the volume change for the reaction between the solute and the solvent have been determined for aqueous solutions of butyl cellosolve (ethylene glycol n-butyl ether), iso-butyl cellosolve and propyl cellosolve (ethylene glycol n-propyl ether). The results are consistent with a hydrogen bonding reaction. The effect of the ethers on water structure are considered and it is clear that the fraction of water molecules which can hydrogen bond to the solute decreases with the increasing hydrophobicity of the solute.     

Thermodynamic and optical studies of some ethylene glycol ethers in aqueous solutions at T = 298.15 K

Experimental results of density (ρ), speed of sound (u), and refractive index (n_D) have been obtained for aqueous solutions of ethylene glycol monomethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMME), and diethylene glycol monoethyl ether (DEGMEE) over the entire concentration range at T = 298.15 K. From these measurements, the derived parameters, apparent molar volume of solute (?_V), excess molar volume (V^E), isentropic compressibility of solution (β_S), apparent molar isentropic compressibility of solute (?_KS), deviation in isentropic compressibility (Δβ_S), molar refraction [R]_1,2 and deviation in refractive index of solution (Δn_D) have been calculated. The Redlich–Kister equation has been fitted to the calculated values of V^E, Δβ_S and Δn_D for the solution. The results obtained are interpreted in terms of hydrogen bonding and various interactions among solute and solvent molecules.     

Excess molar volumes and deviations of the relative permittivity of the binary mixtures of 2-propoxyethanol with diethylene,triethylene, and tetraethylene glycols at various temperatures

Densities and relative permittivities at T = (293.15, 298.15, and 303.15) K in the binary liquid mixtures of 2-propoxyethanol with diethylene glycol, triethylene glycol, and tetraethylene glycol have been measured over the entire mixture compositions. These data have been used to compute the excess molar volumes and deviations of the relative permittivity. The results are discussed in terms of intermolecular interactions in the bulk of studied the binary mixtures.     

Synthesis of polyurethanes from phosphorus-and nitrogen-containing diols obtained on the basis of tetrakis(hydroxymethyl)phosphonium chloride

Phosphorus- and nitrogen-containing diols have been prepared by condensing tetrakis-(hydroxymethyl)phosphonium chloride with secondary cyclic amines such as morpholine and pyperidine. The newly prepared diols were characterized by elemental analysis, hydroxyl values, i.r. and pmr spectroscopy. Linear polyurethanes have been prepared from phosphorus- and nitrogen-containing diols viz bis (hydroxymethyl)-N-morpholinomethylphosphine oxide or bis(hydroxymethyl)-N-pi-peridinomethylphosphine oxide and 4,4′-diphenylmethanediisocyanate; when ethylene glycol is present, copolyurethanes with different phosphorus content are also obtained. The homo- and copolyurethanes have been examined, special attention being paid to the thermogravimetric analysis data and their combustibility (oxygen index).     

Cytotoxicity assessment of palbociclib-loaded chitosan-polypropylene glycol nano vehicles for cancer chemotherapy

The delivery of drugs in nanosized carriers arises as a very attractive solution. This study reports the in vitro cytotoxic effect of palbociclib loaded chitosan cross-linked polypropylene glycol nanocarriers. The nanocarriers were prepared by ion gelation using calcium chloride, calcium oxalate, and sodium tripolyphosphate as cross-linking agents. The influence of the cross-linking agent on the size and morphology of the chitosan- polypropylene glycol nanocarriers was studied by Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), and Atomic Fluorescence Microscope (AFM). Tripolyphosphate assisted carriers was found higher amount palbociclib encapsulation capacity compared with other two carriers. The drug releasing behavior was studied at pH 6.8 which was based on the bulk erosion principal of the carriers. Palbociclib loaded chitosan-polypropylene glycol carriers were found to show excellent drug releasing kinetics and biocompatibility in in-vitro analysis. The unloaded chitosan-polypropylene glycol carrier was identified to have less inherent cytotoxicity, whereas the loaded carriers are as active as equal to pure palbociclib against the MCF-7 cancer cell line. The palbociclib loaded nanocarriers were studied to determine their potential anticancer activity against the MCF-7 cell line. The IC₅₀ values of three carriers chitosan-polypropylene glycol -I, chitosan-polypropylene glycol -II and chitosan-polypropylene glycol -III was observed 55.4, 51.0 and 38.7 mg/μL respectively. The effect of palbociclib uptake was evaluated by confocal microscopy using acridine orange/ethidium bromide and 4, 6-diamidino-2-phenylindole staining. Palbociclib loaded chitosan-polypropylene glycol nanocarriers show promise as potential candidates for cancer therapeutic applications.     

Chemoenzymatic polymer-supported liquid phase synthesis of glucose γ-aminobutyric ester

A concise, polymer-supported solution synthesis of 6-O-(γ-aminobutyryl)-d-glucose has been achieved. Glucose was attached to polyethylene glycol monomethyl ether (MPEG) through an α,α′-dioxyxylyl diether linker, and, subsequently, the HO-6 hydroxyl of the glucose was regioselectively esterified with γ-aminobutyric acid by a lipase-catalyzed reaction.     

Introduction of phosphorus into the polyethyleneterephthalate molecule via disodium 1,2-dicarbomethoxyethylphosphonate—I. A study on the influence of the modifier-disodium 1,2-dicarbomethoxyethylphosphonate-on the properties of the pre-condensate

The effect of the concentration of disodium 1,2-dicarbomethoxyethylphosphonate as modifier in the trans-esterification stage of polyethyleneterephthalate preparation has been studied. It has been found that trans-esterification proceeds normally at modifier concentrations of up to 9% by weight, in respect of the combined weights of dimethylterephthalate and ethylene glycol, thus affording a precondensate with good characteristics.     

Fluorinated derivatives of a polyaspartamide bearing polyethylene glycol chains as oxygen carriers

In this paper the synthesis and characterization of new fluorinated polymers based on a polyaspartamide bearing polyethylene glycol (PEG) chains, are reported. The starting material was the α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA), a water soluble and biocompatible polymer, that has been derivatized with both polyethylene glycol (with a molecular weight of 2000 Da) and 5-pentafluorophenyl-3-perfluoroheptyl-1,2,4-oxadiazole. By varying the amount of the fluorinated oxadiazole, three samples have been prepared and characterized by FT-IR, ¹H NMR, ¹⁹F NMR and UV-VIS spectroscopy. Size exclusion chromatography analysis of these copolymers revealed the occurrence of a self-association process in aqueous medium. The value of critical aggregation concentration has been evaluated by performing a tensiometric study, whereas the size of these aggregates has been determined by photon correlation spectroscopy. Oxygen solubility studies in aqueous solutions of these fluoropolymers showed their ability to maintain high oxygen levels in solution. The biocompatibility of these fluoropolymers has been evaluated by performing an in vitro viability assay on human chronic myelogenous leukaemia cells (K-562), chosen as a model cell line, and haemolysis experiments on human red blood cells. All these properties suggest the potential use of these fluoropolymers as artificial oxygen carriers.     

Thermal transformations of urea in ethylene glycol: II. Reaction of isocyanic acid with ethylene glycol associates

The reaction of isocyanic acid with ethylene glycol associates was studied by the B3LYP/6–311++G(df,p) quantum chemical method. The reaction mechanism includes formation of pre- and post-reaction complexes and cyclic asymmetric late transition states. The energy barrier decreases with increase in the degree of association of ethylene glycol.     

PEG-supported pyridylthioesters for racemization-free amide synthesis: a reagent that allows simultaneous product formation and removal from the polymer

Pyridylthioesters anchored to a modified poly(ethylene glycol) of M_w 5000 Da have been prepared in high yields. The thioesters were employed as a convenient starting material for the liquid-phase synthesis of various enantiomerically pure amides. This new methodology allowed to perform simultaneously the reaction with the poly(ethylene glycol)-supported reagent and the traceless removal of the final product from the polymer support in a single step. The products were obtained in high yield and purity.     

Bis(fluorenono)phanes: a new class of perspective macrocyclic receptors

Two representatives of a novel class of cyclophanes containing two fragments of 2,7-dioxy-9H-fluoren-9-one bridged by triethylene glycol and p-xylyl linking units have been prepared. X-Ray analysis shows that the former has an anti-conformation and the cavity is self-filling with fluorenone moieties.