Dynamic atomic force microscopy methods

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

The silicon wafer hydrophobized with OTS was immersed into water to observe the surface in-situ by tapping-mode AFM. A large number of nano-size domain images were found on the surface. Their shape...

Nano bubbles on a hydrophobic surface in water observed by tapping-mode atomic force microscopy

α-Synuclein Membrane Interactions and Lipid Specificity

High-speed atomic force microscopy for nano-visualization of dynamic biomolecular processes

Blends of two polymers, poly(ethene-co-styrene) (PES) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), were examined with tapping mode atomic force microscopy (AFM) using various values of the driving amplitude A0 and set-point amplitude ratio rsp = Asp/A0, where Asp is the set-point amplitude. In height and phase images of PPO/PES blend samples, the relative contrast of chemically different regions depends sensitively on the rsp and A0 values. As the tip−sample force is increased from small to large, both phase and height images of PPO/PES blend samples can undergo a contrast reversal twice. This makes it difficult to assign the features of height and phase images to different chemical components without performing additional experiments. Phase and height images were interpreted by analyzing several factors that affect the dependence of phase shift and amplitude damping on rsp and A0.

Factors Affecting the Height and Phase Images in Tapping Mode Atomic Force Microscopy. Study of Phase-Separated Polymer Blends of Poly(ethene-co-styrene) and Poly(2,6-dimethyl-1,4-phenylene oxide)

Tapping mode atomic force microscopy measurements were performed for patterned self-assembled monolayers (SAMs) of −S(CH2)15CH3 and −S(CH2)15COOH groups on a polycrystalline Au substrate. Height and phase images of these SAMs were obtained as a function of the driving amplitude A0 and the set-point amplitude Asp. Factors influencing the contrasts of these images are discussed in terms of the simple approximation that the essential consequence of bringing the tip closer to the sample surface is to change the force constant of the cantilever.

On the factors affecting the contrast of height and phase images in tapping mode atomic force microscopy

Blends of poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) (SEBS) with isotactic polypropylene (i-PP) and with atactic polypropylene (a-PP) were prepared under different thermal treatments. On the basis of the phase imaging of tapping-mode atomic force microscopy (TMAFM), we investigated the nanostructures and the morphologies of these blends as well as their dependence on blending history. The observed macrophase separation in i-PP/SEBS blends is caused by the incompatibility of the two polymer components. The microphase separation of the SEBS component depends on the thermal treatment. The morphology of a-PP/SEBS blends exhibits domains that span a wide range of sizes from 15 μm down to 15 nm. Our work shows that TMAFM phase imaging is an important and competitive tool for studying the microphase separation of polymers.

Characterization of the Morphologies and Nanostructures of Blends of Poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) with Isotactic and Atactic Polypropylenes by Tapping-Mode Atomic Force Microscopy

Latex based upon fluorinated acrylates such as perfluorooctylethyl methacrylate (FMA) and perfluorooctylethyl acrylate (FA) and fluorine-free acrylates such as n-butyl methacrylate (BMA) was prepared by means of emulsion polymerization in the presence of octadecyltrimethylammonium bromide (C18TAB) and 2,2‘-azobis(2-amidinopropane) dihydrochloride (V50) as water-soluble azo initiator. Reaction calorimetric studies revealed that acetone addition, preferably 15−25 wt %, was the key to achieve high monomer conversion and to produce stable latex with average particle sizes varying between 50 and 300 nm. Monomer conversion was increased, and latex particle size was reduced when 2 wt % n-butyl acrylate (BA) was added together with fluorine-containing monomers. The reaction enthalpy of FMA was determined to be 62 kJ/mol with respect to 75 kJ/mol for the more reactive FA. Stable poly(perfluorooctylethyl methacrylate)/poly(n-butyl methacrylate) (PFMA/PBMA) latex blends were formed. According to tapping mode atomic ...

Latex Blends of Fluorinated and Fluorine-Free Acrylates: Emulsion Polymerization and Tapping Mode Atomic Force Microscopy of Film Formation

The microstructure of banded spherulites of a typical semirigid-chain polymer, poly(trimethylene terephtha- late), PTT, has been explored with microbeam X-ray diffraction. It is shown that during microbeam scans along the spherulite radius, different diffraction peaks exhibit oscillations with the same periodicity, which means that the lamellar twist is strictly uniform and regular. The twisted PTT crystals formed from the melt at 170 °C reveal a one-to-one correlation between the handedness and growth axis polarity. Thus, the lamellae are right-handed for the growth along the negative growth direction (−a) while they are left-handed for the positive growth direction (+a). This is in line with predictions of the KP-model, although the original model cannot explain why, for example left-handed crystals have to grow along (−a). The direction of the chain tilt in the lamellar crystal correlates with the lamellar handedness as postulated by the KP-model. However, the measured chain tilt in the crystal (4°) is too faint to be the primary source of the surface stresses required for twisted lamellar growth.

Georg Bar

Papers

Factors Affecting the Height and Phase Images in Tapping Mode Atomic Force Microscopy. Study of Phase-Separated Polymer Blends of Poly(ethene-co-styrene) and Poly(2,6-dimethyl-1,4-phenylene oxide)

On the factors affecting the contrast of height and phase images in tapping mode atomic force microscopy

Characterization of the Morphologies and Nanostructures of Blends of Poly(styrene)-block-poly(ethene-co-but-1-ene)-block-poly(styrene) with Isotactic and Atactic Polypropylenes by Tapping-Mode Atomic Force Microscopy

Latex Blends of Fluorinated and Fluorine-Free Acrylates: Emulsion Polymerization and Tapping Mode Atomic Force Microscopy of Film Formation

Exploring the Origin of Crystalline Lamella Twist in Semi-Rigid Chain Polymers: the Model of Keith and Padden revisited