Sedimentation and diffusion of polyelectrolytes. Part II. Experimental studies with poly‐L‐lysine hydrohalides

Abstract

AbstractThe sedimentation, diffusion, and osmotic behavior of poly‐L‐lysine hydrochloride is examined over a wide range of ionic strengths and in solutions which range in relative composition from a swamping excess of added salt (suppression of charge effect) to salt‐free solutions (maximum effect). The charge effect is found to essentially obey the theoretical treatment proposed in Part I of this work. The frictional coefficient of the macroion in salt‐free solutions is comparable to that of the fully stretched chain. In excess of salt the friction is appreciably smaller, its magnitude not varying greatly with ionic strength. The molecular weight is determined osmotically and also from diffusion‐sedimentation, with the charge effect suppressed by addition of salt or eliminated through the use of non‐ionized forms of the polymer; a reasonable agreement is obtained between the methods. The influence of small ions on sedimentation is also examined. The secondary salt effect is found to be much smaller than that predicted theoretically; on the other hand, the substitution of different counterions in the absence of secondary salt effect gives rise to changes of the expected magnitude.