Adsorption properties of the polyelectrolytes poly-L-lysine (PL-L) and poly-DL-lysine (PL-DL) on hydrophobic (polystyrene latex, silver iodide) and hydrophilic (silica) negatively charged solid particles were studied.<br/>Adsorbed amounts as a function of concentration, ionic strength, surface charge, PI, chain length and chain charge density were determined. The adsorption of PI, on negatively charged polystyrene latex and silica was also monitored conductometrically and potentiometrically. Further flocculation and coagulation measurements were performed. Information about the secondary structure of adsorbed PL-L was obtained from proton titrations of PL-L and PL-DL adsorbed at polystyrene particles.<br/>The stereoregularity and secondary chain structure of PI, does not influence the adsorbed amount. At low constant adsorbed amount, there is no coil to helix transition in adsorbed PL-L, because of the charge contrast and hydrophobic interactions between PL and the surface. Only when the adsorbed amount is high at each pH, a transition takes place and adsorbed PL-L can be partly helical.<br/>At low pH and low ionic strength the adsorbed polyelectrolytes show a rather flat conformation and there is no pronounced effect of the hydrophobicity of the adsorbent. All negative surface groups form ion pairs with an -NH <sub>3</sub><sup>+</sup> group of PL, but the reverse is not the case. The adsorption of the basic polyaminoacids increases (i.e. loops and tails start to develop) if the pH is increased or if the ionic strength is raised. With the hydrophobic adsorbents the electrolyte effect persists up to very high concentrations. In the case of the hydrophilic silica no increase above 0.01 M salt was observed, because here hydrophobic interactions are absent. The ionic strength and pH dependence of the adsorption on hydrophobic substrates are in satisfactorily agreement with theoretical predictions.
|Qualification||Doctor of Philosophy|
|Award date||12 Sep 1984|
|Place of Publication||Wageningen|
|Publication status||Published - 1984|
- amino acids
- macromolecular materials