Polystyrene latex segment density profiles

Several experimental parameters have been used to describe the conformation of a polymer adsorbed at the solid-solution interface these include the thickness of the adsorbed layer (photon correlation spectroscopy(J ) (p.c.s.), small angle neutron scattering (2) (s.a.n.s.), ellipsometry (3) and force-distance measurements between adsorbed layers (A), and the surface bound fraction (e.s.r. (5), n.m.r. ( 6), calorimetry (7) and i.r. (8)). However, it is very difficult to describe the adsorbed layer with a single parameter and ideally the segment density profile of the adsorbed chain is required. Recently s.a.n.s. (9) has been used to obtain segment density profiles for polyethylene oxide (PEO) and partially hydrolysed polyvinyl alcohol adsorbed on polystyrene latex. For PEO, two types of system were examined one where the chains were terminally-anchored and the other where the polymer was physically adsorbed from solution. The profiles for these two... 

Segment density profiles and hydrodynamic thickness measurements have been made for polyethylene oxides adsorbed on polystyrene latex. Comparison with theoretical models shows that the hydro-dynamic thickness is determined by polymer segments (tails) at the extremity of the distribution. It is also concluded that the sensitivity of the s.a.n.s. experiment precludes the measurement of segments in this region and that the experimental segment density profiles are essentially dominated by loops and trains. 

Figure 13 demonstrates the segment density profile of sodium poly(styrene sulfonate) adsorbed on polystyrene latex in NaCl solution [48]. The segment density profiles of Na poly(styrene sulfonate) do not practically depend on the surface charge. The shape of curve depends on the NaCl concentration. An increase of salt concenliation leads to an increase of the thickness of the adsorption layer, as predicted by theory. 

FIG. 13 Segment density profiles of sodium polystyrene sulfonate with M = 14 x 10 adsorbed in polystyrene negatively charged latex (1) and positively charged latex (2) in 0.5 N aqueous NaCl solution. (From Ref. 48.)... 

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