Properties of Poly(ethylene Oxide)

Bailey, F. E.; Koleske, JV

doi:10.1016/b978-0-12-073250-0.50010-6

Cited by 326 publications

(381 citation statements)

References 92 publications

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“…This is ascribed to the phase separation of the oligo(ethylene oxide) side chains with the water, known as the lower critical solution temperature behavior (42). However, in contrast to previously studied discotics (43), the temperature-induced oligo(ethylene oxide) side-chain aggregation does not result in the reappearance of a Cotton effect, affirming the loss of structuring hydrogen-bonding interactions at high temperatures.…”

Section: Resultscontrasting

confidence: 39%

Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water

Brunsveld

Vekemans

Hirschberg

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

197

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Bifunctional ureido-s-triazines provided with penta(ethylene oxide) side chains are able to self assemble in water, leading to helical columns via cooperative stacking of the hydrogen-bonded pairs (DADA array). Monofunctional ureido-s-triazines do not form such helical architectures. The presence of a linker, covalently connecting the two ureido-s-triazine units, is essential as it generates a high local concentration of aromatic units, favorable for stacking interactions. This hydrophobic stacking of the aromatic units occurs at concentrations as low as 5⅐10 ؊6 M and can be visualized by using fluorescence spectroscopy. The stacking generates a hydrophobic microenvironment that allows intermolecular hydrogen bonding to occur at higher concentrations because the hydrogen bonds are shielded from competitive hydrogen bonding with water. This hierarchical process results in the formation of a helical self-assembled polymer in water at concentrations above 10 ؊4 M. Chiral side chains attached to the ureido-striazine units bias the helicity of these columns as concluded from CD spectroscopy and ''Sergeants and Soldiers'' experiments.I n DNA, the well known double helical motif originates from self assembly and is directed by lateral hydrogen bonds between bases and stabilized by solvophobic interactions between the covalently linked bases perpendicular to the hydrogen bonds (1). Control over the intrinsic helicity of the structure is governed by the peripheral chirality in the sugar-phosphate backbone. In synthetic systems, noncovalent interactions have been used to obtain well defined self-assembled architectures in organic solvents (2-7). Peripheral chiral centers in assemblies (8-11) and chiral side chains attached to a polymer backbone (12-20) have been shown to bias chirality at the supramolecular level. Highly ordered multimolecular supramolecular structures stable in water, held together by hydrophobic interactions or with additional hydrogen bonding, are also known (21-25). However, it remains difficult to exploit directional noncovalent interactions in a cooperative way for the formation of discrete multimolecular assemblies stable in water. In this solvent, water molecules strongly compete with directional polar interactions such as hydrogen bonds, resulting in low association constants.The formation of helical self-assembled polymers in solution by both stacking and hydrogen bonding has recently been demonstrated by us (26, 27). Self-complementary apolar molecules 1 and 2 dimerize via strong cooperative 4-fold hydrogen bonding (ADAD) in chloroform (28), giving rise to the formation of a dimer by 1 and a random coil polymer by 2, the latter featuring viscous solutions at higher concentrations. Additional to the hydrogen bonding, solvophobic interactions between the aromatic surfaces arise for 1 and 2 in alkanes. Association via hydrogen bonding of the ureido-s-triazine functional groups leads to the formation of a large and planar aromatic core surrounded by six flexible chains, a structure that is conduciv...

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Section: Resultscontrasting

confidence: 39%

Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water

Brunsveld

Vekemans

Hirschberg

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

197

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“…A typical phase diagram of LCST polymer in water is given in Figure 1. Such phase behaviour has been described for various polymers in water, as for example polyethylene oxide [8] and [9], polypropylene oxide [10], poly N-isopropylaciylamide [11], polyvinyl methylether [12] or hydroxyalkyl cellulose [13], A possible structure of our "thermoassociative" macromolecule can be represented by the Figure 2. At temperature lower than the grafts LCST, the system is entirely water-soluble and behaves as usual macromol ecular solutions.…”

Section: Concept and Designmentioning

confidence: 99%

Reversible Thermoassociation of Water-Soluble Polymers

L'Alloret¹,

Maroy²,

Hourdet³

et al. 1997

Rev. Inst. Fr. Pét.

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TH ERMO ASSOCIATION RÉVERSIBLE DE POLYMÈRES HYDROSOLUBLESThe thermoassociative phenomenon was also studied by Small Angie Neutrons Scattering (SANS, using copolymers composed by a deuterated polyacrylate backbone and protonated polyethyl ene oxide grafts. The scattering properties of our system were studied by varying the temperature, the salinity and the polymer concentration of the solution. A good agreement between the microscopic characteristics of the solutions and their rheological properties was found. TERMOCOMBINACIÓN REVERSIBLE DE POLIMEROS HIDROSOLUBLESLos polimeros hidrosolubles se utilizan corrientemente corno agentes de espesamiento para controlar la reologìa de los fluidos acuosos, en distintos sectores de la industria. No obstante, sus propiedades se debilitan a medida que aumenta la temperatura. Para hacer trente a este problema se ha desarrollado el concepto de polfmeros "termocombinativos" solubles en el agua. Nuevos sistemas anfifilos de este gènero se pueden obtener por injerto en una estructura hidrófila de las cadenas laterales que dejan de ser solubles por encima de una temperatura critica infe rior de solución (Lower Critical Solution Temperature = LCST). Las soluciones semidiluidas de estos copolimeros presentan pro piedades de espesamiento reversibles a medida que aumenta la temperatura y alcanza un valor critico cercano de la temperatura de LCST de las cadenas laterales. Este comportamiento se puede poner en relación con la agregación de elementos de injertos por encima de su temperatura LCST en microsectores hidrófobos que conducen a la formación de una reticulación tridimensional. Con temperaturas màs elevadas, la viscosidad de la solución cizallada con valor constante alcanza un valor maximo. Esto se puede inter pretar en términos de reorganización de la red fisica debido al esfuerzo de cizallamiento, que pasa de una estructura con "combinaciones intermoleculares" principalmente a un sistema con un numero incrementai de "combinaciones intramoleculares". Habida cuenta de la diversidad de los polfmeros solubles en el agua que presentan una separación de fases al proceder a un recalentamiento (LCST), se han realizados distintos copolfmeros "termocombinados" [1] and [2], utilizando un polielectrolito, o sea una estructura hidrófila neutra. Con objeto de proceder a la aplicación de estos sistemas en la industria del petróleo, se han desa rrollado copolfmeros que contienen àcidos sulfónicos de propano 2-acrilamida 2-metil (AMPS) utilizando el óxido de polietilene (PEO) corno elemento de injerto LCST. En el presente artfculo figura una descripción generai de su comportamiento reológico. Sus propiedades se pueden controlar, ya sea variando las caracterfsticas de la solución (concentración de polimero, salinidad, etc.) o por modificación de la estructura quimica del copolimero (relación de injertos, masa molecular, etc.). Este estudio reológico ha demostrado la potencialidad de los sistemas "termocombinativos", particularmente para la industria del petróleo [3]. En la actualidad existe la po...

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“…Thus, from a qualitative standpoint, the effect of molecular weight is similar to that of the polymer concentration; low molecular weights enable the development of different impact morphologies, while increasing the molecular weight progressively suppresses secondary atomization and breakup/splashing, until only the dry rebound regime can be observed. The similarity between the effects of the molecular weight and of the polymer concentration on the impact morphology is justified because both of these parameters affect the relaxation time of polymer solutions [21][22][23].…”

Section: Resultsmentioning

confidence: 99%

Dilute polymer solution drops impacting on heated surfaces: New impact morphologies and impact regime maps

Lakhanpal¹,

Bertola²

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The impact morphology of dilute polymer solution drops on a heated surface is studied experimentally by means of high-speed imaging, with respect to the following parameters: surface temperature; impact Weber number; polymer concentration; polymer molecular weight. In addition to impact morphologies observed in Newtonian drops (deposition, rebound, secondary atomisation and breakup/splashing), three new impact regimes have been identified: (i) a single satellite droplet ejected in the direction of bouncing but tethered to the main drop by a thin liquid filament; (ii) a splashing-like behaviour (semi-splashing), where the rim instability generates satellite droplets tethered to the lamella by thin liquid filaments; (iii) a spray-like behaviour (semi-spray), where a fine secondary atomisation generated upon impact is quickly absorbed back into the drop globule. Experiments were carried out using drops of aqueous polyethylene oxide (PEO) solutions, with mass concentrations of 100 ppm, 200 ppm and 400 ppm, and PEO molecular weights of 2 MDa, 4MDa, and 8MDa. The impact morphology on a polished aluminium surface with temperatures ranging between 160°C and 400°C was investigated for impact Weber numbers between 20 and 170, taking side view images of impacting drops at a rate of 1,000 frames per second. KeywordsDrop Impact; Heated Surfaces; Polymer Solutions; Impact Regime Map. IntroductionThe dynamics of liquid drops impinging on a heated surface is a phenomenon of interest in many areas of engineering, including spray cooling, inkjet printing for advanced manufacturing applications, quenching of alloys in the steel industry and nuclear reactor safety. Despite several decades of research, this phenomenon is understood only to a limited extent and requires further research; specifically, the development of impact regime maps (IRMs) is of practical interest because they provide a consolidated understanding of the impact behaviour and represent a tool of practical use in the design of nozzles, print heads, etc. A quantitative and comprehensive IRM also presents an important test case for the development and validation of theoretical models describing specific features, such as transitions between different impact regimes. Currently, an extensive body of literature on the behaviour of Newtonian drops impacting on heated surfaces exists. The first IRM produced [1] identified most of the impact regimes, however lacked clear quantitative description on the initiation and extent of these regimes. This work was soon followed by a detailed investigation that allowed production of three distinct IRMs corresponding to Weber numbers of 20, 60 and 220 and for surface temperatures ranging from 100° to 300°C [2]. Although this work included substantial information on the spreading behaviour of a drop and its heat transfer characteristics, the IRMs were far from being fully comprehensive, particularly lacking information on all possible impact regimes that can be realised as well as the transitional boundaries. This was partly ...

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Properties of Poly(ethylene Oxide)

Cited by 326 publications

References 92 publications

Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water

Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water

Reversible Thermoassociation of Water-Soluble Polymers

Dilute polymer solution drops impacting on heated surfaces: New impact morphologies and impact regime maps

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