SFM Characterization of Poly(isocyanodipeptide) Single Polymer Chains in Controlled Environments:  Effect of Tip Adhesion and Chain Swelling

Abstract

Isolated slightly hydrophilic chains of poly(isocyanodipeptides) (PICs) adsorbed on mica were studied by intermittent contact mode-scanning force microscopy (IC-SFM) in an ambient atmosphere controlled both with respect to the relative humidity (RH) and the presence of CHCl 3 vapor. SFM revealed that the average chain height increases up to more than an order of magnitude with decreasing RH, leading to the highest value at RH ) 0%. This is due to both a minimization of the capillary forces between the SFM tip and the hydrophilic substrate surface and a collapse of the side chains in the poor solvent. In a saturated CHCl 3 vapor atmosphere, the chain heights increase up to twice this value, which is close to the polymer diameter measured by powder X-ray diffraction. This indicates that the PIC chains are solvated by CHCl 3 molecules, causing the swelling of the single polymers. Achieving a control over the thickness of the polymer chains is fundamental for their optimal observation by SFM. Moreover, the understanding of the conformational properties of single macromolecules adsorbed on surfaces under different environmental conditions is of importance for unraveling their physicochemical properties and their dynamics, including their reactivity.

Synthesis, Characterization, and Folding Behavior of β‐Amino Acid Derived Polyisocyanides

“…This is likely the result of the fact that the polymers adopt a collapsed conformation on the mica surface. [21] Histograms of the measured length distributions are shown in Figure 4 and the calculated molar mass data are summarized in Table 2. In these analyses, the degree of polymerization was derived from the contour lengths, assuming a 4 1 -type helix with a helical pitch of 4.6 .…”

Unconventional nanotubes self-assembled in alumina channels: morphology and surface potential of isolated nanostructures at surfaces

“…This difference in the width and height of tubular architectures adsorbed at surfaces visualized by SFM effect has been found to become dramatic when measurements of hydrophobic adsorbates supported on hydrophilic substrates are performed in an atmosphere characterized by a high relative humidity (Ji et al 1998;Zhuang et al 2005). Moreover, additional roles can be ascribed to the indentation of the nanotube by the probing SFM tip (Prokhorova et al 1998) and the adhesion of the SFM tip to the surface (VanNoort et al 1997;Samorì et al 2002).…”

Atomic Force Spectroscopies: A Toolbox for Probing the Biological Matter

“…The possibility to investigate physical and chemical properties at the nano-scale in some cases has been used to reveal structural features or conformational properties of complex molecules and aggregates. In literature a reduced number of papers devoted to this subject can be found, essentially devoted to polymers studies (Zhuang et al, 2005).…”