Fraction of segments in close contact with the surface

From this description of polymer configurations, a full characterization of the adsorption process clearly requires a knowledge of the amount of polymer adsorbed per unit area of the surface, T (mol m or mg m ), the fraction of segments in close contact with the surface, p, and the distribution of polymer segments, p z), from the surface towards the bulk solution. We also must know how far the seg-... 

For full characterization of the process of adsorption, it is necessary to know the amount of polymer adsorbed per unit area of the snrface, the fraction of segments in close contact with the surface, and the distribution of polymer segments. 

The bound fraction p represents the ratio of the number of segments in close contact with the surface (i.e. in trains) to the total number of segments in the polymer chain. The polymer bound fraction, p, can be directly determined using spectroscopic methods such as infrared (IR), electron spin resonance (ESR) and nuclear magnetic resonance (NMR). The IR method depends on measuring the shift in some absorption peak for a polymer and/or surface group [62-64]. The ESR and NMR methods depend on the reduction in the mobility of the segments that are in close contact with the... 

The polymer-bound fraction, p, can be directly determined using spectroscopic methods such as nuclear magnetic resonance (NMR). The method depends on the reduction in the mobility of the segments that are in close contact with the surface. By using a... 

Several methods can be used to determine the fraction of segments, (p), of the polymer chain actually in contact with the surface. Small-angle neutron scattering (SANS) and neutron reflectivity (NR) ellipsometry, electron paramagnetic resonance (EPR), IR, and NMR spectroscopy have all been used. Most suffer from the drawback that the distinction between bound and free segments close to the interface is often difficult to define. This distinction is important as the bound fraction effectively determines how well anchored the polymer is to the surface. 

The fraction of segments attached to the surface (bound fraction) increases monotonically for all molecular weights as the surface interaction energy increases. For energies above the transition point, the average number of surface contacts is proportional to N and the bound fraction approaches a constant, large value. The constant bound fraction results in adsorbed polymer dimensions which are independent of N, with the molecule lying close to the surface. 

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