Neutron Reflectometry on Interfacial Structures of the Thin Films of Polymer and Lipid

Abstract

ABSTRACT:Neutron reflectometry is a very powerful and essential technique for the studies on material interfaces due to its high spatial resolution, $a few tenths of nm, along the depth direction. The use of neutron as a probe is a big advantage for structural analysis on soft-materials, since the scattering contrast can be highly enhanced in hydrogenous materials such as polymers, surfactants, lipids, proteins, etc., without big changes in their physical and chemical properties by substituting all or part of the hydrogen atoms in the molecules with deuterium (a deuterium labeling method). Furthermore, the neutron reflectometry can explore deeply-buried interfaces such as solid/liquid interfaces in a non-destructive way, and make in situ measurements combined with various sample environments due to its high transmission to the materials. In this article, the neutron reflectometry is reviewed from the standpoint of researches on interfacial structures of the thin films of polymer and lipid, and its future prospects at a high-intensity pulsed-neutron source are presented. [doi:10.1295/polymj.PJ2007113] KEY WORDS Neutron Reflectometry / High Depth Resolution / Soft-material / Deuterium Labeling / Non-destructive Exploration / Deeply-buried Interface / In situ Measurement / At interfaces, materials often exhibit different structures or physical properties from in bulk because they interact directly with different materials or phases in a very narrow space. So far many interesting phenomena relevant to interfaces have been reported, e.g., lower surface glass transition temperature, de-wetting, surface segregation, etc., in the research field of softmaterials.1,2 Also, material interfaces contribute largely to many practical phenomena known as coating, painting, adhesion, lubrication, etc. In addition, the recent development of nano-technology makes the size of practical devices smaller, so that interfaces occupy the larger proportion of space in the devices, and then play an important role in the device performance. Therefore, strong demands to clarify the structures and physical properties of materials at interfaces have been rapidly grown.However, in reality it is generally difficult to observe detailed interfacial structure, since the interfacial region is very narrow and has considerably small volume in materials. The material interfaces are not always exposed to air surface, but are deeply buried in materials. Neutron reflectometry is a very powerful and indispensable technique to the studies on material interfaces because of its high spatial resolution, $a few tenths of nm, along the depth direction. Here, the neutron reflectometry is reviewed from the standpoint of soft-material researches by highlighting experimental examples on the thin films of polymer and lipid systems, and its future prospects at a highintensity pulsed-neutron source are presented. NEUTRON REFLECTOMETRYNeutron has unique properties as a probe for structural analysis of materials, compared with electromagnetic waves such as light or X-ray....

Block copolymer thin films: Characterizing nanostructure evolution with in situ X-ray and neutron scattering

“…This isotopic replacement is arguably the most important feature for polymer studies and is referred to as contrast variation or contrast matching [183]. By selectively manipulating the isotopic makeup of different polymer blocks, commonly by replacing hydrogen with deuterium, neutron scattering can provide highlyresolved information about individual domains of self-assembled BCPs [184][185][186]. For a more detailed explanation of neutron scattering theory and its advantages for BCP systems, the reader is directed to several sources [87,88,183,187,188].…”

“…As a complement to SANS, NR employs a reflection geometry to probe out-of-plane structures (specular reflection) [85,186]. wetting layer formed at the free surface (see Figure 10).…”

“…Furthermore, recent research has demonstrated the ability to measure in-plane features in thin films with spin echo resolved grazing-incidence scattering (SERGIS) [231,232]. Although there are still challenges associated with the use spin echo techniques with BCP thin films, most notably sample preparation and analysis issues [233], SERGIS offers a promising technique to track interactions between polymer domains [186]. Other scattering tools of potential interest for BCP thin film studies include ultra small-angle X-ray or neutron scattering (USAXS/USANS).…”

Neutron Reflectometry for Studying Proteins/Peptides in Biomimetic Membranes

“…Neutron reflectometry is a powerful and non-destructive technique that has been widely employed for studying biomolecular interactions. It has unique properties to provide quantitative structural and compositional details of the model interfaces without physical damage to the sample, which is impossible to achieve using other techniques [6,7].…”

An improved algorithm for reducing reflectometry data involving divergent beams or non-flat samples

“…Reflectometry has been very successfully exploited in analysing a wide variety of interfacial structures, with applications ranging from soft matter (Torikai et al, 2007) to magnetism (Saerbeck & Klose, 2012) and life sciences (Wacklin, 2010). A reflectometry experiment consists of measuring the ratio of reflected to incoming intensity as a function of the incident angle, , and the wavelength, .…”