New measurement system based on small-angle neutron scattering for structural analysis of light-responsive materials

Abstract

With the increasing importance of light-responsive materials, it is vital to analyze the relationship between function and structural changes induced by light irradiation. Small-angle scattering (SAS) is effective for such structural analysis. However, quantitatively capturing local molecular structure formation and molecular reactions at a scale of less than 1 nm via SAS is difficult. In this study, to analyze the structure of non-equilibrium phenomena in light-responsive materials, a new sample environment has been developed for a time-of-flight small- and wide-angle neutron scattering instrument (TAIKAN), comprising a UV–Vis irradiation system, UV–Vis absorption measurement equipment and photodetector. Simultaneous measurement of small-angle neutron scattering and UV–Vis absorption was achieved. This system was used to demonstrate the in situ observation of UV–Vis irradiation-induced structural change of micelles formed by 4-butylazobenzene-4′-(oxyethyl)trimethylammonium bromide, which is a light-responsive surfactant, in an aqueous solution. The results showed that the present measuring system provides direct information on the interplay between changes in micelle structure and changes in molecular configuration.

Accelerated Recombination of Lophyl Radicals in Micelles: Rapid Controlled Self-Assembly of Micelles Formed by Amphiphilic Lophine Dimers and Release of Solubilized Substance by Photoirradiation

“…Furthermore, this system requires a unified understanding of hierarchical chemical phenomena at different scales, such as photochromic reactions, micellar morphology, and solubilizing ability. In the future, it is expected that SANS stroboscopic analysis 26) will be used to understand the system and to search for the optimal structure. This system is expected to contribute not only to drug delivery systems (DDS) , but also to a wide range of fields such as release control of active ingredients, efficient heat exchange control, and actuating systems.…”

“…In order to track the rapid photoisomerization of lophine dimers and the micelle structure change upon UV light irradiation, a new system of SANS docked with a UV lamp and a UV/Vis absorption spectrometer for inducing and monitoring the photochromic reaction of amphiphilic lophine dimers is develoed 22) . Therefore, this system in the SANS instrument (BL-15, TAIKAN) installed was constructed in the large neutron source of the J-PARC (Japan Proton Accelerator Research Complex) research facility in Japan 23,24) (Fig. 6) .…”

“…Recently, time-resolved structural analysis of the 3TEG-LPD micelle by the stroboscopic SANS revealed the morphological change with a time width of 0.5 s in the presence and absence of UV light irradiation 26) . This revealed that the morphological change in the micelles is faster than the recombination of the lophyl radicals.…”

Time-Resolved Structural Analysis of Fast-Photoresponsive Surfactant Micelles by Stroboscopic Small-Angle Neutron Scattering

“…26 Figure 2 shows a schematic of the in situ UV−vis irradiation system installed on TAIKAN. 27,28 SANS experiments were conducted under the UV irradiation at 365 nm (a half-width of 10 nm) using a mercury lamp (REX-250, Asahi Spectra Co., Ltd., Japan) with a narrow bandpass filter and a cold mirror module. UV light emitted from the mercury lamp are reflected by the quartz mirror, and the reflected light irradiates a sample.…”

“…In this method, the position of detected neutrons and the time of detection are stored as events in the raw data file. , This method allows us to create time-resolved SANS profiles with arbitrary time widths even after completing the measurement. The event-recording method is useful in time-resolved measurements. ,− Thus, stroboscopic SANS measurements can be easily performed, as shown in Figure …”