Surface characterization hydrophilicity

One assembly example is polyethylenamine (PEI)-mediated self-assembly of FePt nanoparticles [56]. PEI is an all -NH-based polymer that can replace oleate/oleylamine molecules around FePt nanoparticles and attach to hydrophilic glass or silicon oxide surface through ionic interactions [52], A PEI/FePt assembly is readily fabricated by dipping the substrate alternately into PEI solution and FePt nanoparticle dispersion. Figure 10 shows the assembly process and TEM images of the 4 nm Fes8Pt42 nanoparticle self-assemblies on silicon oxide surfaces. Characterizations of the layered structures with X-ray reflectivity and AFM indicate that PEI-mediated FePt assemblies have controlled thickness and the surfaces of the assemblies are smooth with root mean square roughness less than 2 nm. 

Mori, H., Hirao, A., Nakahama, S., Senshu, K. Synthesis and surface characterization of hydrophilic-hydrophobic block copolymers containing poly(2,3-dihydroxypropyl methacrylate). Macromolecules 27, 4093 100 (1994)... 

Characterization of Laser-Treated Surface. When the irradiation of ArF laser to a PTFE film was conducted at fluences of 27 mJ cm"2 pulse with 10 Hz in a hydrazine vapor atmosphere, the PTFE surface became hydrophilic. Water contact angle (CA) was measured as the easiest but sensitive method for characterization of our laser processing. Compared with CA of 130° on PTFE before the irradiation, CA was changed to 25° upon irradiation of 3000 pulses at 27 mJ cm 2 pulse" (Table I). 

Ratner, B. D., Hoffman, A. S. Surface characterization of hydrophilic-hydrophobic copolymer model systems. I. A preliminary study, in Adhesion and Adsorption of Polymers, Part B (ed.) L. H. Lee, p. 691, New York, Plenum Press 1980... 

Tremendous efforts have been put into surface modification of polyurethane biomaterials to promote cell adhesion [41] and/or depress platelet adhesion [42,43], biofihn formation [44], or protein adsorption [45]. CA is the quickest indirect evidence of confirming these surface modifications. Cooper et al. [41] prepared a series of polyurethanes with surfaces functionalized with three hexapeptides to improve cell adhesion. The polar peptides on the surface increase the hydrophilicity and thus decreased CAs were observed. Again, CA is only an indirect proof of a successful surface modification since there are many factors that contribute to a change in CA. Many other surface characterization techniques must be combined to obtain a fuU picture of the surface properties of polyurethane biomaterials. 

Figure 1.15 High-resolution lateral surface characterization and the associated water structure for a hydrophilic SAM in pure water, (a] 12 x 12 nm area of the SAM showing faint periodicity and striped regions. The region indicated in the top-right corner corresponds to the location of the water structure measurement shown in [b], [b] Dissipation as a function of sample displacement away from the tip [zero on the x-axis is arbitrary). Oscillations in the dissipation signal are separated by approximately 2.2 A and are associated with the displacement of individual water layers between the tip and the sample [reused with permission from Jarvis copyright...

Kennedy et al. reported [79,80] that the amphiphilic materials consisting of hydrophic polyisobutylene (PIB) and hydrophilic poly(, V-dimethylac-rylamide) showed lower human blood monocyte adhesion than that of PIB and hydrophilic poly(2-hydroxyethyl methacrylate), for which the weight fractions between hydrophobic and hydrophilic components were identical. However, the amounts of various adsorbed proteins onto these samples were similar [79,80]. The relation between protein adsorption and cell adhesion has not yet been elucidated. The surface characterization methods that we employ were contact angle measurements, XPS, and SEM. There must be some structural differences among these samples of PAS that we could not detect using the aforementioned apparatus. Further studies on the surface structure of PAS by TEM and atomic force microscopy (AFM) in dry and wet conditions are now in progress. 

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