Atomic force microscopy hydrolysis

Regarding the spatial aspects of the enzymatic degradation of CA-g-PLLA, a surface characterization [30] was carried out for melt-molded films by atomic force microscopy (AFM) and attenuated total-reflection Fourier-transform infrared spectroscopy (ATR-FTIR) before and after the hydrolysis test with proteinase K. As exemplified in Fig. 3 for a copolymer of MS = 22, the AFM study showed that hydrolysis for a few weeks caused a transformation of the original smooth surface of the test specimen (Fig. 3a) into a more undulated surface with a number of protuberances of 50-300 nm in height and less than a few micrometers in width (Fig. 3b). The ATR-FTIR measurements proved a selective release of lactyl units in the surface region of the hydrolyzed films, and the absorption intensity data monitored as a function of time was explicable in accordance with the AFM result. 

L.K. Nielsen, J. Risbo, T.H. Callisen, and T. Bjorholm. Lag-burst kinetics in phospholipase At hydrolysis of DPPC bilayers visualized by atomic force microscopy. Biochim. Biophys. Acta, 1999, 1420, 266-271. 

Synthesis of a new modification of silica soluble in THF is described. At the first synthetic step, a hyperbranched polyethoxysiloxane (HBPES) is synthesized by heterofunctional condensation using triethoxysilanol previously generated in reaction mixture by neutralization of correspondent sodium salt with acetic acid. At this step, the process was monitored by IR spectroscopy, SEC, and Si NMR spectroscopy. At the second step, hydrolysis and intramolecular condensation involving silanol groups is carried out to yield silica sol macromolecules. A SAXS method was used to determine the size and fractal coefficient of trimethylsilated derivatives and silica sols obtained. An atomic-force microscopy imaging of silica sol supported on a mica substrate showed the silica sol particles to be predominantly spherical in shape. Prospects for theoretical, experimental and practical applications of silica sols are discussed. 

The microstructure of zso-phthalate polyester films before and after exposure at room temperature to an alkaline solution was studied using tapping mode atomic force microscopy (AFM) [133]. The results of structural characterization as well as chemical analyses using attenuated total reflection FT-IR, total carbon analysis and liquid chromatography-mass spectroscopy showed that the base-catalyzed hydrolysis of polyester was a heterogeneous process. The formation of pits occurs as a result of hydrolysis and the number and size of pits increases with exposure time. 

Surface initiation is a commonly used method to prepare hybrid materials. Poly(vinyl alcohol) bmshes have been obtained from surface-initiated ITP of VAc from a silicon wafer followed by hydrolysis of PVAc. The surface properties of the Si02-g-PVA and Si02- -PVAc were examined by atomic force microscopy. 

Besides the conditions of acid hydrolysis, the morphology and dimensions of the NCC also depend on the source from which they were extracted. Some of the main techniques used in the investigation of size and/or morphology of these nanofibers are dynamic light scattering (DLS), scanning electron microscopy with a field emission gun (FESEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) [22,25,67,68,69]. 

The origin of the differences in reactivity mentioned above must lie in the structure of the surface of the SAMs. In situ information on the composition of the reacting monolayers was obtained by the "inverted chemical force microscopy approach described in the introduction. In these experiments, the force required to pull the AFM tip coated with 1, 2, or 3 away from contact with an inert octadecanethiol SAM on flat Au(l 11) was followed in real time in situ during the hydrolysis. The Au(lll) substrates are atomically smooth over distances of several hundred nanometers with only occasional steps and depressions present (Figure 4). With highly ordered octadecanethiol SAMs on top of these substrates it is ensured that the interaction between tip and surface takes place between exactly the same functional groups at the tip apex and a homogeneous inert substrate. 

---