Hierarchical self-assembly of nanoparticles in polymer matrix and the nature of the interparticle interaction

Abstract

Using small angle X-ray scattering (SAXS), we elucidated the spatial organization of palladium (Pd) nanoparticles (NPs) in the polymer matrix of poly(2-vinylpyridine) (P2VP) and the nature of inter-nanoparticle interactions, where the NPs were synthesized in the presence of P2VP by the reduction of palladium acetylacetonate (Pd(acac)2). The experimental SAXS profiles were analysed on the basis of a hierarchical structure model considering the following two types of interparticle potential: (i) hard-core repulsion only (i.e., the hard-sphere interaction) and (ii) hard-core repulsion together with an attractive potential well (i.e., the sticky hard-sphere interaction). The corresponding theoretical scattering functions, which were used for analysing the experimental SAXS profiles, were obtained within the context of the Percus-Yevick closure and the Ornstein-Zernike equation in the fundamental liquid theory. The analyses revealed that existence of the attractive potential well is indispensable to account for the experimental SAXS profiles. Moreover, the morphology of the hybrids was found to be characterized by a hierarchical structure with three levels, where about six primary NPs with the diameter of ca. 1.8 nm (level one) formed local clusters (level two), and these clusters aggregated to build up a large-scale mass-fractal structure (level three) with the fractal dimension of ca. 2.3. The scattering function developed here is of general use for quantitatively characterizing the morphological structures of polymer/NP hybrids and, in particular, for exploring the interaction potential of the NPs on the basis of the fundamental liquid theory.

Kinetics and Mechanism of In Situ Metallization of Bulk DNA Films

“…During UV irradiation, an increase in the scattering intensities over the q range of Å with little changes in intensity at lower q was observed. This is consistent with the formation of isolated spherical particles, where the significant change in scattering is within the region corresponding to the form factor for isolated spheres [ 24 – 26 ]. If significant aggregation or inter-particle interaction was observed, an increase in the low- q scattering intensity would be seen together with a peak-like distortion at the q position corresponding to the particle diameter [ 24 – 26 ].…”

“…This is consistent with the formation of isolated spherical particles, where the significant change in scattering is within the region corresponding to the form factor for isolated spheres [ 24 – 26 ]. If significant aggregation or inter-particle interaction was observed, an increase in the low- q scattering intensity would be seen together with a peak-like distortion at the q position corresponding to the particle diameter [ 24 – 26 ]. To both quantify the final particle size and further highlight that the scattering is indeed related to isolated particles, the measurement from 2910 seconds was fitted to Eq.…”

Mechanism of silica–lysozyme composite formation unravelled by in situ fast SAXS

“…A general expression for such an effective structure factor for particles within an aggregate/droplet was proposed originally by Hashimoto and co-workers [43]. Several variations and applications of this concept are furthermore known [37,44]. For the purpose of the analysis of our data, we further extended the expressions originating from Hashimoto et al as we show below in a final form.…”

“…If we write the structure function of an aggregate (“template”) as S agg ( q ) and the internal arrangement within this aggregate as S int ( q ), then similar to Hashimoto et al [43] and Lin et al [44], we can express the scattering intensity by the generalized Eq. 23, in which “” denotes a convolution operation of the functions:…”

Nanoparticle self-assembly: from interactions in suspension to polymer nanocomposites

“…was based on a purely 'geometrical' measurement of aggregation from the combination of TEM and smallangle scattering, Lin et al140 have recently attempted to extract thermodynamic potentials from a multi-scale aggregated structure of palladium-NPs in low-mass poly(2-vinylpyridine) (P2VP). By small-angle scattering, they have observed three different levels of structure, ranging from individual NPs forming small aggregates, which themselves cluster quite densely on larger scales, described by a fractal dimension of about 2.3.…”