In Situ Atomic Force Microscopy Imaging of Adsorbed Block Copolymer Micelles

Abstract

Atomic force microscopy has been used to study the in situ adsorption of an amphiphilic block copolymer from aqueous solution onto hydrophilic mica and hydrophobic silica substrates. Adsorption was studied as a function of concentrationsclose to and below the bulk critical micelle concentration the copolymers adsorb as single chains or "premicelle aggregates". As concentration is increased, micelles form into densely packed structures. At a given concentration, the ordering is higher for the strongly adsorbed micelles on silica. Competitive adsorption onto the hydrophilic silicon nitride AFM tip occurs. The substrate coverage of micelles on mica increases roughly linearly with scan time at low micelle concentration. Weak adsorption on mica was analyzed to provide a two-dimensional diffusion coefficient. The effect of tip oscillation frequency on the AFM images was investigatedshigher frequencies were required to image polymer aggregates on mica. Finally, force-distance curves provide information on the nanomechanical properties of the adsorbed polymer layers. Evidence is presented to show that micelles and aggregates adsorb to silica via the hydrophobic P block, while they adsorb to mica via the hydrophilic E block.

Reduction of protein adsorption to a solid surface by a coating composed of polymeric micelles with a glass-like core

“…Since inplane (parallel to the surface) structure is not detected, it is not possible to distinguish between a layer composed of adsorbed single C3Ms and a (bi)layer composed of a PEO brush layer on top of a layer composed of the more glass-like core material at the surface. Combining all data (AFM images, reflectometry, ellipsometry, and related measurements in literature) and the known literature on adsorption of polymeric micelles (for polymeric micelles, when both micelles and free polymers are present, it is the micelles that are adsorbed [26][27][28]), we conclude that our C3Ms adsorb as flattened single micelles. As they have an almost glass-like core [17] and a relatively high surface tension (as the core is hydrophobic), they do not rearrange into a bilayer structure.…”

“…Generally, polymeric micelles with a hydrophobic core tend to adsorb as whole micelles [25]. This gives rise to two possible adsorption states for C3Ms with a more glass-like core: on one hand as micelles adsorbed via their core (making flattened micelles) or on the other hand via their corona [26][27][28]. For C3Ms with a liquid-like core, a different structure may be observed, e.g.…”

Sequential pH‐Dependent Adsorption of Ionic Amphiphilic Diblock Copolymer Micelles and Choline Oxidase Onto Conductive Substrates: Toward the Design of Biosensors

“…The sensor crystals (Q-Sense) are AT-cut quartz with gold-plated polished electrodes. The quartz crystals were excited at their fundamental frequency (f 0 % 5 MHz) as well as at the 3rd, 5th, 7th, 9th, and 11th overtones, corresponding to 15,25,35,45, and 55 MHz, respectively. Before use, the crystals were cleaned according to the Q-Sense cleaning protocol by sequential ozone treatment for 10 min, then treatment by a mixture of Milli-Q water/NH 4 OH/H 2 O 2 ¼ 5:1:1 at 70 8C for 10 min, followed by rinsing with Milli-Q water, blowing by air flux, and again ozone treatment for 10 min.…”

“…The adsorption of diblock copolymer micelles onto planar surfaces has been intensively studied [16][17][18][19][20][21][22][23][24] for different substrates [25,26] as well as varying adsorption conditions. [27,28] However, such approaches have only rarely been used in the context of biosensor applications.…”

The Art of SPM: Scanning Probe Microscopy in Materials Science

“…A general area of research is related to the study of morphological changes of materials initiated by controlled changes of the environmental conditions. Researchers have followed the adsorption of amphiphilic block copolymer micelles, which can possibly be used as lubricants or detergents, from aqueous solution on hydrophilic and hydrophobic substrates; [27] the formation of cyanide species on a Au(111) electrode; and the dissolution and deposition process of gold in a broad pH range. [28] Others have characterized phospholipid layers formed by solution spreading, which are models for biological membranes; [29] analyzed the reversible switching between ordered and disordered structures of molecular layers of hexadecane on Au(111) surfaces; [30] tracked the reorganization of polycrystalline monolayers at the solid/liquid interface; [31] and correlated morphological changes of polypyrrole films as a potential cathode material for Li-ion batteries with their ion-exchange characteristics during continuous cycling.…”