Polymer dynamics in hydrogenous systems by neutron reflectivity

Abstract

Neutron reflectivity is a powerful tool for exploring polymer dynamics above the glass-transition temperature at short diffusion times in layered thin-film systems. Recent studies of membrane-mediated interdiffusion in deuterium-labeled systems have shown that ultrathin membranes can track the position of the interface in binary polymeric diffusion couples and also can discriminate between perdeuterated and hydrogenous polymers of the same molecular weight. This report shows that similar dynamic information can be obtained for binary hydrogenous polystyrene (hPS) diffusion couples separated by an ultrathin (6-nm) isopentylcellulose cinnamate (IPCC) membrane on Si wafers (air//hPS/IPCC/hPS//Si, where "//" represents an interface between obviously different phases and "/" represents a dynamic interface between polymeric species). In particular, the air//hPS/IPCC/hPS//Si system provides the same information as perdeuterium-labeled polystyrene (dPS) diffusion couples separated by the same IPCC membrane (air//dPS/IPCC/dPS//Si). This technique has potential applications for the study of confinement effects on thin-film dynamics and macromolecular transport across membranes.

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

“…The specular X-ray reflectivity measurements were performed at the NIST Center for Neutron Research using Cu Kα radiation with a wavelength of 0.154 nm on a Bruker AXS-D8 Advance diffractometer. The thicknesses of the films were obtained by plotting the refraction-corrected successive minima vs minima index as described by Thompson et al Roughnesses of both the film and the substrate were obtained by fitting the experimental profiles with theoretical curves in Microsoft Excel. , …”

“…The thicknesses of the films were obtained by plotting the refraction-corrected successive minima vs minima index as described by Thompson et al 41 Roughnesses of both the film and the substrate were obtained by fitting the experimental profiles with theoretical curves in Microsoft Excel. 42,43 Results and Discussion…”

Effects of POSS nanoparticles on glass transition temperatures of ultrathin poly(t‐butyl acrylate) films and bulk blends

“…The presence of double layer structure was determined via the observation of single Bragg peak through XR measurements which performed at the NIST Center for Neutron Research using Cu–K α radiation with a wavelength of 1.542 Å on a Bruker AXS‐D8 Advance Diffractometer. The thickness of the films was obtained by analyzing the Kiessig fringe spacing following the method of Thomson et al This method was validated by also fitting the reflectivity curves with a single layer model with both a silicon/polymer and polymer/air roughness in Microsoft Excel …”

“…The thickness of the films was obtained by analyzing the Kiessig fringe spacing following the method of Thomson et al 44 This method was validated by also fitting the reflectivity curves with a single layer model with both a silicon/polymer and polymer/air roughness in Microsoft Excel. 45,46…”