A method for monitoring polymer reactions in very dilute solutions

Physical and/or chemical transformations in polymer systems can be studied by different analytical methods. However, most of them are applicable to sy stems of rather high concentration of polymer, or that takes long periods t o prepare samples. In this paper, the Toms effect (drag reduction (DR) in a dding very small amounts of a polymer to a solvent if flow takes part in a turbulent regime) is proposed as a method suitable for monitoring chemical reactions of polymers in very dilute solutions (down to tens of ppm). Then, by measuring the Toms effect, there is the possibility of observing slight changes occurring in the course of a reaction taking part in a dilute solu tion. This publication deals with two typical polymer-polymer transformatio ns - the formation of stereocomplexes between iso- and syndio-tactic poly(m ethyl methacrylate)s (PMMAs), as an example of physical transition, and den aturating of DNA, as an important chemical reaction. (C) 2001 Published by Elsevier Science B.V.