Nanoscale characterization of surface-modified and surface-grafted polymers using environmental control scanning force microscopy

With the development of multiple scanning probe microscopy (SPM) methods, polymer surface characteristics can be imaged and measured with nanoscale spatial resolutions that approach the characteristic length scales of polymer molecules. Applying these relatively new nanoscale SPM methods to specific polymer surfaces requires novel methodologies with careful interpretations. In this thesis, novel scanning force microscopy (SFM) operating procedures and corresponding data analyses and interpretations were developed while characterizing surface-modified and surface-grafted polymers. Surface characterization was performed with SFM along with other instrumentation to verify SFM measurements and to correlate SFM measurements with polymer properties.; In Chapter 1, the mechanisms and sensitivity of polymer surface characterization using SFM are discussed. Chapter 2 describes the instrumental aspects of environmental control scanning force microscopy and nanoindentation methodologies. Chapter 3 describes the surface-modified systems of plasma-treated polydimethylsiloxane (PDMS) PDMS tubing which was plasma treated prior to biomedical implantation was characterized in a novel way using SFM and nanoindentation to determine depth and severity of treatments. Chapter 4 describes collaborative efforts to graft poly(ethylene glycol) (PEG) directly to silicon surfaces. SFM methods along with other surface-sensitive techniques were used to verify the grafting success, and to correlate molecular weight with chain conformation. Chapter 5 describes how the surface grafting procedure of PEG onto silicon can be applied to SFM tip modifications for various applications. Chapter 6 highlights the efforts made to map relative adhesion and energy dissipation using Pulsed Force Mode SFM (PFM). Patterned self-assembled monolayers (SAMs) were prepared as chemically heterogeneous substrates, where the effect of adsorbed water could be measured while varying humidity. These developments were then applied to mechanically heterogeneous polymer films to illustrate the ability to extend the capabilities of scanning force microscopy of polymer surfaces.