Autori: ’’Static and dynamic light scattering of maleic acid copolymers

Editorial: Elsevier Science Ltd., Polymer, 41, p.3683-3692, 2000.

Rezumat:

Se studiaza solutii apoase de copolimeri alternanti acid maleic-acetat de vinil, intr-un domeniu larg de concentratii de polimer C si sare Cs, cu ajutorul difuziei luminii statica si dinamica. In functie de C si Cs functia de autocorelare a cimpului electric este caracterizata de unul sau doua moduri de relaxare. Aceasta ne permite sa definim regimul diluat si semidiluat intr-o diagrama C-Cs. Modul de relaxare rapid are o comportare obisnuita pentru polielectroliti in solutie. Modul de relaxare lent poate fi asociat cu aparitia unor agregate. Forta motoare propusa pentru agregare este lactonizarea, care scade solubilitatea in apa. In final are loc o separare de faza dupa o perioada de timp de ordinul saptaminilor, in functie de C si Cs. We study aqueous solutions of maleic acid-vinyl acetate alternating copolymers in a wide range of polymer C and salt Cs concentrations by means of static and dynamic light scattering. depending on C and Cs, the decay of the autocorrelation function of the scattered electric field is characterized by one or two modes of relaxation. This feature allows one to define the dilute and semi-dilute regimes in a diagram C-Cs. The fast mode of relaxation has the usual behavior reported for polyelectrolyte solutions. The slow mode of relaxation can be linked with the occurence of chain aggregation. The proposed driving force for the aggregation is the lactonization of the monomers thet decreases their solubility in water. Ultimetely a phase separation occurs after a time of several weeks that depends on C and Cs.

Cuvinte cheie: difuzia luminii statica si dinamica; copolimeri ai acidului maleic; polielectroliti in solutie // Static and dynamic light scattering; Maleic acid copolymers; Polyelectrolyte solutions