Measurement of Interfacial Width in a Poly(styrene)/Poly(2-vinylpyridine) Homopolymer Blend by Spatially Resolved Inelastic Electron Scattering

Abstract

This research uses spatially resolved electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) to determine an upper bound for the interfacial width of a solution-cast poly(styrene) (PS)−poly(2-vinylpyridine) (PVP) homopolymer blend. The measurement determines the fraction of nitrogen as a function of position across an unstained interface. The broadening effect of the incident-probe intensity distribution is deconvoluted from the raw data. In addition, a lower bound to the contribution of interfacial curvature to the interfacial width is estimated and also separated from the measured data. This leads to an upper bound to the interfacial width of 3.5 nm. The result is in agreement with independent measurements by neutron scattering reported in the literature. Dose-resolved measurements are made to demonstrate that the effects of mass loss during the present measurements are insignificant. Quantitative analysis of the carbon/nitrogen ratio is made on the basis of the background-subtracted C and N K-edges in PVP finding a value of 7.05 ± 0.20, in agreement with the stoichiometric value of 7.0.

Complex Morphology of the Intermediate Phase in Block Copolymers and Semicrystalline Polymers As Revealed by 1H NMR Spin Diffusion Experiments

“…Heterogeneous polymers are typically assumed to consist of well-organized structures exhibiting a continuous interphase layer. This interphase layer involves a smooth mobility gradient ,− in the range of 1 to 5 nm. ,− ,− Noting that the interphase affects the thermal and mechanical behavior of the material, knowledge of the structural and dynamical organization of the interphase region is of high interest for engineering applications and in the field of polymer crystal growth. In addition, the interphase impacts the dispersion of filler particles, such as carbon black or carbon nanotubes, which are widely used nowadays in high-performance polymer applications to increase the stiffness, longevity, or charge conductivity of the polymeric material. − …”

“…Techniques used to elucidate the structure and dynamics of the interphase include, but are not limited to, small-angle X-ray scattering, , neutron scattering, electron microscopy, (deuterium) NMR, , and dielectric spectroscopy, , as well as Monte Carlo , and molecular-dynamics − simulations. Most experimental techniques, however, do not provide insights on a molecular level, but provide data that are spatially averaged.…”

Inter‐diffusion between PMMA and PVDF during lamination studied by time‐of‐flight secondary ion mass spectrometry chemical imaging

“…Because of this, many analytical techniques have been developed to investigate the interface thickness or inter-diffusion distance between homopolymers and compatibilized homopolymers. 1 -9 For example, neutron reflectivity and small-angle neutron and x-ray scattering, forward recoil spectrometry, 1 -3 spatially resolved inelastic electron scattering, 4 transmission electron microscopy (TEM), 5 spatially resolved electron energyloss spectroscopy (EELS), 5 electron spectroscopic imaging (ESI), 7 x-ray photoelectron spectroscopy (XPS), 8 and the rheological technique have been used widely to study the interface of polymer blends. Bousmina et al 9 elucidated the diffusion of polystyrene (PS) in a PS/PS sandwichlike sample using rheological tools.…”

Spectroscopic Imaging of Soft-Soft and Hard-Soft Interfaces

“…where b is the Kuhn statistical segment length and χ is the Flory-Huggins interaction parameter. For the case, for example, of a polystyrene (PS) -poly(vinyl pyridine) (PVP) interface where b=0.67 nm and χ=0.11 [2], the interfacial width is 1.7 nm [3]. Clearly, the width of the interface increases as individual polymer molecules become more rigid (increasing b) and more soluble in each other (decreasing χ).…”

“…Light elements, however, lend themselves well to study by electron energy-loss spectroscopy (EELS) because of the accessible core-loss edges for C, N, and O as well as distinctive valence structure in the low-loss region. Spatially resolved EELS with varying degrees of spatial resolution have been used in studies of soft-soft [3][4][5][6][7] and hard-soft [8,9] interfaces exploiting both low-loss and coreloss signals.…”