Surface Heterogeneity of Polystyrene Latex Particles Determined by Dynamic Force Microscopy

Abstract

Atomic force microscopy (AFM) was employed to characterize the surface chemistry distribution on individual polystyrene latex particles. The particles were obtained by surfactant-free emulsion polymerization and contained hydrophilic quaternary ammonium chloride, sodium sulfonate, or hydroxyethyl groups. The phase shift in dynamic force mode AFM is sensitive to charge/chemical interactions between an oscillating atomic force microscope tip and a sample surface. In this work, the phase imaging technique distinguished phase domains of 50-100 nm on the surfaces of dried latex particles in ambient air. The domains are attributed to the separation of ion-rich and ion-poor components of the polymer on the particle surface.

Long-Ranged Attraction between Charged Polystyrene Spheres at Aqueous Interfaces

“…PS groups (and, hence, fewer charges). The AFM measurements on the commercial samples and on laboratory synthesized PS samples of different surface chemistry [13] all reveal surface inhomogeneities similar to those shown in Fig. 4, suggesting that the observed surface heterogeneity is not simply a defect of a particular particle sample.…”

“…With the cantilever tip in the attractive regime 2 -3 nm above a sphere's top surface, the phase delay of the oscillating cantilever is determined primarily by the van der Waals attraction between the cantilever tip and the almost flat top surface [12]. Because hydrophilic carboxyl-PS domains have a Hamaker constant different from that of hydrophobic neutral PS domains, the phase contrast images reveal the surface distribution of the ionizable carboxyl-PS groups [13]. Figure 4(c) shows the phase image simultaneously recorded with the height image shown in Fig.…”

Nanoscale investigation of the structural and chemical changes induced by oxidation on carbon black surfaces: A scanning probe microscopy approach

“…5b-5d and 6b, 6c, 6e, and 6f), we must first note that the measurement of this magnitude is rather sensitive to the morphology of the sample, in such a way that sharp variations in surface topography (e.g., those arising from steps or high vertical features) result in considerable changes in the measured phase. This kind of topography-dependent behavior is quite commonly encountered in the study of surface properties by scanning probe microscopies, and has been well documented not only in the case of phase imaging in tapping mode AFM [26,35,36] but also when mapping other properties such as adhesion [37][38][39] or friction [40]. In our case, we see this effect mainly at the edges of the CB particles (Figs.…”

“…To the best of our knowledge, this is the first time that the chemical modification of CB particles induced by surface oxidation or any other type of chemical treatment has been investigated on a local scale. Very recently, a related investigation on the surface chemistry of latex particles studied locally by phase contrast imaging in tapping mode AFM has been reported [26].…”

Removal of Benzene Using the Characteristics of Block Copolymers for Encapsulation

“…To investigate the morphology of the star copolymer, an atomic force microscopy (AFM: Nanoscope D-3000, Digital Instrument Inc, Santa Barbara, CA) measurement was carried out in the tapping mode under ambient conditions. Images were obtained at the light tapping force level corresponding to amplitude set point ratios between 0.80 and 0.99 (Tan et al 2005). …”