Tetraethylene Glycol Monomethyl Ether Research Articles

A Consequence of Dispersity on the Self‐Assembly of Amphiphilic Homopolymers Containing Main‐Chain Azobenzene

AbstractThe self‐assembly of amphiphilic oligomers/polymers is a versatile and promising approach for creating nonspherical polymeric nanoparticles. Discrete amphiphilic oligomers/polymers with molecularly defined structures are ideal candidates for fabricating smart nanoparticles and for achieving a deeper understanding of structure‐controlled self‐assembly. Herein, discrete and disperse amphiphilic homopolymers of PAZOnTEG2n, with hydrophobic azobenzene are designed and synthesized as the main chains tethered with hydrophilic tetraethylene glycol monomethyl ether (TEG) units, to accurately investigate the impact of dispersity on their self‐assembly in solution. The discrete‐PAZO8TEG16 in DMF/water and in THF/water results in the formation of 2D lamellae, while the dispersed counterpart prefers to self‐assemble into spherical micelles. The significant difference is due to their distinction between interior structures of assembly. Furthermore, photoisomerization of azobenzene triggers dissociation/reassembly for discrete polymeric nanoparticles but no obvious change for the dispersed counterparts under irradiation with UV/vis light. This work reveals the influence of dispersity on the self‐assembly of amphiphilic polymers and stimuli‐responsive properties of their nanomaterials, which is desirable for universal applicability in fabricating smart 2D lamellas.

Vibrational and Nuclear Magnetic Resonance Properties of 2,2'-Biquinolines: Experimental and Computational Spectroscopy Study.

Experimental (IR, Raman and NMR) techniques and quantum chemical (DFT) methods have been applied to investigate the vibrational and NMR properties of a new ligand based on 2,2'-biquinoline (bq) functionalized with polar hydrophilic tetraethylene glycol monomethylether (TEG) chains (bq_TEG). Vibrational and NMR spectra of the ligand have been explained based on DFT computational data obtained at B3LYP/6-311+G(d,p) level of theory. For the spectroscopic analysis we started from the parent molecule 2,2'-biquinoline and explained the changes in the spectra of bq_TEG in close relation to the corresponding spectra of bq. Our data point to a trans conformation of bq_TEG in solid state, as wells as in liquid phase. The excellent agreement between the experimental and computed data allowed for a reliable assignment of the vibrational and NMR spectra, both for bq and bq_TEG.

Separation of Inorganic Anions and Phenolic Compounds Using Tetraethylene Oxide-Bonded Stationary Phases in Capillary Liquid Chromatography

Tetraethylene glycol monomethyl ether (TEGMM) and tetraethylene glycol (TEG) modified silica were synthesized and used in capillary liquid chromatography as stationary phases. The stationary phases were prepared by chemically bonding TEGMM or TEG on silica via reaction with 3-glycidyloxypropyltrimethoxysilane. The present stationary phases were successfully used for the separation of several inorganic anions and phenolic compounds. The TEG-modified silica stationary phase had a better selectivity and higher retention for five anions compared to TEGMM-modified silica stationary phase. The repeatability of retention time for the five anions was satisfactory on both stationary phases. By using 2 mM sodium chloride as eluent, the relative standard deviation values were in ranging from 0.68–3.21 and 2.00–2.16% for analytes in the TEG-and TEGMM-bonded stationary phase, respectively. It was found that the TEG-bonded stationary phase had hydrophilic properties due to the presence of the hydroxyl group at the end of the TEG chains.

Photochemically Induced Folding of Single Chain Polymer Nanoparticles in Water.

We pioneer the synthesis of fluorescent single chain nanoparticles (SCNPs) via UV-light induced folding based on tetrazole chemistry directly in pure water. Water-soluble photoreactive precursor polymers based on poly(acrylic acid) (PAA) bearing tetrazole, alkene and tetraethylene glycol monomethyl ether moieties, (PAAn(Tet/p-Mal/TEG)), or simply tetrazoles moieties, PAAn(Tet), were generated via RAFT polymerization. While tetrazole, ene, and acrylic acid containing polymers fold via dual nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) as well as nitrile imine-carboxylic acid ligation (NICAL), tetrazole and acrylic acid only functional prepolymers fold exclusively via NICAL. A detailed study of the underpinning photochemistry of NITEC and NICAL is also included. The resulting water-soluble SCNPs were carefully characterized via analytical techniques such as NMR, UV-vis, and fluorescence spectroscopy, as well as SEC and DLS.

Photoresponsive Amphiphilic Macrocycles Containing Main-Chain Azobenzene Polymers.

Herein, the first example of photosensitive cyclic amphiphilic homopolymers consisting of multiple biphenyl azobenzene chromophores in the cyclic main chain tethered with hydrophilic tetraethylene glycol monomethyl ether units is presented. The synthetic approach involves sequentially performed thermal catalyzed "click" step-growth polymerization in bulk, and Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) intramolecular cyclization from α-alkyne/ω-azide linear precursors. It is observed that such amphiphilic macrocycles exhibit increased glass transition temperatures (Tg ), slightly faster trans-cis-trans photoisomerization, and enhanced fluorescence emission intensity compared with the corresponding linear polymers. In addition, the cyclic amphiphilic homopolymers self-assemble into spherical nanoparticles with smaller sizes which possess slower photoresponsive behaviors in a tetrahydrofuran/water mixture compared with those of the linear ones. All these interesting observations suggest that the cyclic topology has a great influence on the physical properties and self-assembly behavior of these photoresponsive amphiphilic macrocycles in general.

Synthesis of uniform cyclodextrin thioethers to transport hydrophobic drugs.

Methyl and ethyl thioether groups were introduced at all primary positions of α-, β-, and γ-cyclodextrin by nucleophilic displacement reactions starting from the corresponding per-(6-deoxy-6-bromo)cyclodextrins. Further modification of all 2-OH positions by etherification with iodo terminated triethylene glycol monomethyl ether (and tetraethylene glycol monomethyl ether, respectively) furnished water-soluble hosts. Especially the β-cyclodextrin derivatives exhibit very high binding potentials towards the anaesthetic drugs sevoflurane and halothane. Since the resulting inclusion compounds are highly soluble in water at temperatures ≤37 °C they are good candidates for new aqueous dosage forms which would avoid inhalation anaesthesia.

Hydrogen bonding directed self-assembly of small-molecule amphiphiles in water.

Compounds comprising one or two quadruply hydrogen bonding units, 2-ureido-4[1H]-pyrimidinone (UPy) and tris(tetraethylene glycol monomethyl ether) moieties, were reported to form highly stable hydrogen-bonded assemblies in water. Compound 1, containing one UPy, assembles into vesicles, and compound 2, containing two UPy units, forms micelles. The aggregates disassemble reversibly when the solution pH is raised to 9.0 or above. The results demonstrate the utility of hydrogen bonding to direct the self-assembly of small-molecule building blocks in aqueous media.

Using Light To Tune Thermo-Responsive Behavior and Host–Guest Interactions in Tegylated Poly(azocalix[4]arene)s

Polymers consisting of azocalix[4]arenes in the main chain and tetraethylene glycol monomethyl ether chains in the lower rim of the calix[4]arene units have been prepared. The polymers undergo reversible photoisomerization between the trans and the cis forms, the extent of which depends on the solvent. A lower critical solution temperature (LCST) type behavior is observed for aqueous solutions of the polymers, which is strongly affected by the molar mass and concentration. More importantly, the same polymers exhibit an upper critical solution temperature (UCST) type transition in alcohols. It is shown that the temperature of the phase transition in alcohols decreases proportionally to the decrease in the trans content of the samples thus offering a unique possibility to reversibly tune the UCST behavior by adjusting the irradiation exposure time. An exciting photoassisted writing on solutions of the polymer in alcohols is demonstrated. Furthermore, the host–guest complex formation with a low molar mass guest is influenced by the photostationary state of the polymers.

Thermodynamic and spectroscopic study on molecular interaction in aqueous solution of tetraethylene glycol monomethyl ether

As part of a systematic study on thermodynamic properties for aqueous solution of alkoxyethanols, this paper reports data of densities and viscosities for aqueous solution of tetraethylene glycol monomethyl ether (CH3(OCH2CH2)4OH) as a function of composition at T=(293.15, 303.15, 313.15, 323.15, and 333.15) K under atmospheric pressure. Surface tension was also measured to investigate surface activity of tetraethylene glycol monomethyl ether at 303.15K. Fluorescence emission of probe pyrene in aqueous solution of tetraethylene glycol monomethyl ether was recorded in a Hitachi F-4500 spectrofluorometer at room temperature with the purpose of investigating the polarity change of solution environment. UV–vis spectra for aqueous solution with varied concentrations of tetraethylene glycol monobutyl ether were recorded to reflect molecular interactions. The excess molar volumes, viscosity deviations, and the excess energies of activation for viscous flow were calculated according to the experimental data. These data have been correlated by the Redlich–Kister type equations to obtain their coefficients and standard deviations. The results indicate that molecular interaction between tetraethylene glycol monomethyl ether and water is stronger than that between triethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and ethylene glycol monomethyl ether with water.

Dendritic, Nanosized Building Block for Siloxane‐Based Materials: A Spherosilicate Dendrimer

A spherosilicate dendrimer (DMS-1) with closely spaced reaction sites (Si-H groups) on the dendrimer surface has been synthesized by stepwise silylation of double-four-ring silicate with chlorotriethoxysilane (ClSi(OEt)(3)) and subsequently with chlorodimethylsilane (ClSiHMe(2)). DMS-1 consists of a maximum of 40 Si atoms in the interior frameworks and 24 reactive Si-H groups on the surface. Because DMS-1 is spherical and about 1.5 nm in diameter, it can be regarded as the smallest well-defined silica-based nanoparticle. DMS-1 also forms molecular crystals and is soluble in typical organic solvents. A molecularly ordered silica-based hybrid can be prepared by heating a cast film of DMS-1 at 180 °C for 5 days. The surface of DMS-1 can be modified by hydrosilylation with 1-hexadecene, triethoxyvinylsilane, and allylic-terminated tetraethylene glycol monomethyl ether. More than 20 Si-H groups out of 24 react with these reagents. The solubilities of the products depend on the modification. DMS-1 is not only a building block for nanohybrids, but also the smallest and most precisely designed siloxane-based nanoparticle.

Amphiphilic, Regioregular Polythiophenes

The synthesis, characterization, and solid-state morphology of regioregular, amphiphilic polythiophenes based on 3-dodecyl-3‘-(3,6,9,12-tetraoxatridecanyl)-2‘,5-bithiophene are described. These polythiophenes form stable monolayers on the water subphase of a Langmuir trough and are transferable (Langmuir−Blodgett deposition) to solid substrates to give highly ordered thin films. Mixing of the amphiphilic, regioregular polythiophenes with a nonconducting poly(ethylene glycol), in a 50/50 weight percent ratio, results in the formation of a semiconducting network of polythiophene in the Langmuir−Blodgett film. The solution-cast films of the amphiphilic, regioregular polythiophenes exhibit liquid-crystalline lamellar mesophases with thermotropic transitions at 0, 60, and 120 °C. These transitions are attributed to the melting of the tetraethylene glycol monomethyl ether side chains, the dodecyl side chains, and the polythiophene backbones, respectively. DSC, X-ray diffraction, and optical microscopy were used...