Mechanically Interlocked Structure of Polyrotaxane Investigated by Contrast Variation Small-Angle Neutron Scattering

It has been shown that the thermodynamics of bicontinuous microemulsions can be tailored via the addition of various different amphiphilic polymers. In this manuscript, we now focus on comb-type polymers consisting of hydrophobic backbones and hydrophilic side chains. The distinct philicity of the backbone and side chains leads to a well-defined segregation into the oil and water domains respectively, as confirmed by contrast variation small-angle neutron scattering experiments. This polymer–microemulsion structure leads to well-described conformational entropies of the polymer fragments (backbone and side chains) that exert pressure on the membrane, which influences the thermodynamics of the overall microemulsion. In the context of the different polymer architectures that have been studied by our group with regards to their phase diagrams and small-angle neutron scattering, the microemulsion thermodynamics of comb polymers can be described in terms of a superposition of the backbone and side chain fragments. The denser or longer the side chain, the stronger the grafting and the more visible the brush effect of the side chains becomes. Possible applications of the comb polymers as switchable additives are discussed. Finally, a balanced philicity of polymers also motivates transmembrane migration in biological systems of the polymers themselves or of polymer–DNA complexes.

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Contrast-Variation Time-Resolved Small-Angle Neutron Scattering Analysis of Oil-Exchange Kinetics Between Oil-in-Water Emulsions Stabilized by Anionic Surfactants

Langmuir ◽

10.1021/acs.langmuir.9b02423 ◽

2019 ◽

Vol 35 (47) ◽

pp. 15192-15203

Author(s):

Yi-Ting Lee ◽

Lilo D. Pozzo

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Anionic Surfactants ◽

Contrast Variation ◽

Time Resolved ◽

Oil In Water ◽

Exchange Kinetics

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Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering. I. Application to industrial multi-component nanocomposites

Journal of Applied Crystallography ◽

10.1107/s1600576716016472 ◽

2016 ◽

Vol 49 (6) ◽

pp. 2036-2045 ◽

Cited By ~ 12

Author(s):

Yohei Noda ◽

Satoshi Koizumi ◽

Tomomi Masui ◽

Ryo Mashita ◽

Hiroyuki Kishimoto ◽

...

Keyword(s):

Form Factor ◽

Binary Mixture ◽

Neutron Scattering ◽

Dynamic Nuclear Polarization ◽

Small Angle ◽

Ternary Mixture ◽

Small Angle Neutron Scattering ◽

Nuclear Polarization ◽

Scattering Function ◽

Contrast Variation

Dynamic nuclear polarization (DNP) at low temperature (1.2 K) and high magnetic field (3.3 T) was applied to a contrast variation study in small-angle neutron scattering (SANS) focusing on industrial rubber materials. By varying the scattering contrast by DNP, time-of-flight SANS profiles were obtained at the pulsed neutron source of the Japan Proton Accelerator Research Complex (J-PARC). The concentration of a small organic molecule, (2,2,6,6-tetramethylpiperidine-1-yl)oxy (TEMPO), was carefully controlled by a doping method using vapour sorption into the rubber specimens. With the assistance of microwave irradiation (94 GHz), almost full polarization of the paramagnetic electronic spin of TEMPO was transferred to the spin state of hydrogen (protons) in the rubber materials to obtain a high proton spin polarization (PH). The following samples were prepared: (i) a binary mixture of styrene–butadiene random copolymer (SBR) with silica particles (SBR/SP); and (ii) a ternary mixture of SBR with silica and carbon black particles (SBR/SP/CP). For the binary mixture (SBR/SP), the intensity of SANS significantly increased or decreased while keeping itsqdependence forPH= −35% orPH= 40%, respectively. Theqbehaviour of SANS for the SBR/SP mixture can be reproduced using the form factor of a spherical particle. The intensity at lowq(∼0.01 Å−1) varied as a quadratic function ofPHand indicated a minimum value atPH= 30%, which can be explained by the scattering contrast between SP and SBR. The scattering intensity at highq(∼0.3 Å−1) decreased with increasingPH, which is attributed to the incoherent scattering from hydrogen. For the ternary mixture (SBR/SP/CP), theqbehaviour of SANS was varied by changingPH. AtPH= −35%, the scattering maxima originating from the form factor of SP prevailed, whereas atPH= 29% andPH= 38%, the scattering maxima disappeared. After decomposition of the total SANS according to inverse matrix calculations, the partial scattering functions were obtained. The partial scattering function obtained for SP was well reproduced by a spherical form factor and matched the SANS profile for the SBR/SP mixture. The partial scattering function for CP exhibited surface fractal behaviour according toq−3.6, which is consistent with the results for the SBR/CP mixture.

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Small Angle Neutron Scattering from Nanophase Titanium As A Function of Oxidation

MRS Proceedings ◽

10.1557/proc-132-21 ◽

1988 ◽

Vol 132 ◽

Cited By ~ 4

Author(s):

J. A. Eastman ◽

J. E. Epperson ◽

H. Hahn ◽

T. E. Klippert ◽

A. Narayanasamy ◽

...

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Scattering Length ◽

Contrast Variation ◽

Gas Condensation ◽

Pressure Oxygen ◽

Scattering Centers ◽

Scattering Lengths ◽

Contrast Matching

ABSTRACTNanophase titanium, prepared by the gas-condensation method both as aggregated powder and in lightly compacted discs, has been studied by conventional small angle neutron scattering, and by use of contrast variation methods. The contrast has been changed (a), isotopically, by means of deuterated/protonated solvents distilled into the specimen and (b) by progressive incremental oxidation of the Ti particles using fixed doses of low-pressure oxygen. It was shown that some evolution of the small angle pattern for lightly compacted nanophase Ti occurred over a period of several months at 300 K. Contrast matching by external solvent works well and has allowed the scattering lengths of oxidized and unoxidized specimens to be followed. The results imply that the scattering from metal and oxide can be separated under suitable conditions. The partial oxidation experiments indicate that there is both a fast and slow oxidation at 300 K. Also, during slow oxidation, high scattering length density scattering centers were formed whose number increased, but whose size remained the same at about 2 nm; these centers are tentatively assumed to be TiO2.

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Variation of Solvent Scattering-Length Density in Small-Angle Neutron Scattering as a Means of Determining Structure of Composite Materials

MRS Proceedings ◽

10.1557/proc-376-303 ◽

1994 ◽

Vol 376 ◽

Author(s):

Rex P. Hjelm ◽

Wesley Wampler ◽

Michel Gerspacher

Keyword(s):

Composite Materials ◽

Carbon Black ◽

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Scattering Length ◽

Contrast Variation ◽

Length Scales ◽

Excluded Volume Effects ◽

Component Form

ABSTRACTAs part of our work on the structure of composite materials we have been exploring the use of small-angle neutron scattering using the method of contrast variation to dissect the component form, structure and distribution. This approach has resulted in a new look at very old problemreinforcement of elastomers by carbon black.Using this approach we studied an experimental high surface area (HSA) carbon black and a gel of "HSA-bound" rubber in cyclohexane/deuterocyclohexane mixtures. HSA in cyclohexane is found to be short rodlike particle aggregates. The aggregates have a shell-core structure with a high density graphitic outer shell and an inner core of lower density amorphous carbon. The core is continuous throughout the carbon black aggregate, making the aggregate a stiff, integral unit. Contrast variation of swollen composite gels shows that there are two length scales in the gel structure. Above 10 Å, scattering from carbon black predominates, and below 10 Å the scattering is from both carbon black and the elastomer. The HSA in the composite is completely embedded in polyisoprene. An estimate of the carbon black structure factor shows strong exclusion of neighboring aggregates, probably from excluded volume effects. The surface structure of the carbon black is unaltered by the interactions with elastomer and appears smooth over length scales above about 10 Å. These results show that contrast variation can provide information on composite structure that is not available by other means. This information relates to the reinforcement mechanism of elastomers by carbon blacks.

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Structural evolution in metallomicroemulsions – the effect of increasing alcohol hydrophobicity

Dalton Transactions ◽

10.1039/c8dt02031k ◽

2018 ◽

Vol 47 (40) ◽

pp. 14211-14217

Author(s):

Alison Paul ◽

Ian A. Fallis ◽

Emily C. Stokes ◽

Stephen M. King ◽

Peter C. Griffiths

Keyword(s):

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Structural Evolution ◽

Microemulsion System ◽

Contrast Variation

Small-angle neutron scattering and contrast variation has been employed to quantify how a series of alcohols with increasing hydrophobicity exert different abilities to structure a model toluene based metallomicroemulsion – a microemulsion system stabilised with a metallosurfactant.

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