Statistical physics of self-assembling structures in amphiphilic polymer systems
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Abstract EN:
Heteropolymer systems are of great importance in the polymer science due to promising prospects of their applications. We have examined solutions of polyamphiphilic chains with simple chemical structure which show, nevertheless, interesting features. It is well known that ordinary homopolymers are soluble in good solvents, but when the quality of the solvent gets poorer (for example, as temperature is lowered), the polymer chains form globules that sediment in time. Properties of an isolated (thus, not precipitating) globule were studied theoretically by Lifshitz and co-authors [1]. On the other hand, a couple decades ago it was experimentally discovered [2-6] that soluble globules can be formed in aqueous solutions of linear polymers, whose monomer units combine hydrophobic and hydrophilic properties. Colloidally stable mesoglobules were observed, in particular, in solutions of poly(N-isopropylacrylamide) (PNIPAM), poly(N-vinylcaprolactam) (PVCL), and other polymer chains with simple chemical structure of identical monomer units (Fig. 1). Though the nature of the monomers allow to qualify these macromolecules as linear amphiphilic homopolymers [7], solutions of such polymers behave as quite complicated systems: many experiments manifested existence of unprecipitable globules. [. . . ]
Abstract FR:
Les syst`emes h´et´eropolym´eriques ont une grande importance dans la science des polym`eres ´etant donn´e que ces syst`emes promettent de bonnes perspectives dans les applications. Nous avons examin´e les solutions de chaˆınes polyamphiphiles de structure chimique simple, qui pr´esentent n´eanmoins des caract`eres int´eressants. Il est bien connu que les homopolym`eres ordinaires sont solubles dans les bons solvants ; et lorsque la qualit´e de celui-ci baisse (par exemple, quand la temp´erature diminue), les chaˆınes polym´eriques forment des globules qui se s´edimentent avec le temps. L’´etude th´eorique des propri´et´es d’un globule isol´e (non pr´ecipit´e) a ´et´e accomplie par Lifshitz et ses collaborateurs [1]. D’un autre cˆot´e, il y a quelques d´ecades de ¸ca, il a ´et´e d´ecouvert [2–6] au cours d’exp´eriences r´ealis´ees sur des solutions de polym`eres lin´eaires ayant des unit´es monom´eriques r´eunissant les propri´et´es hydrophobes et hydrophiles que des globules solubles peuvent se former. On a ´etudi´e les solutions de PNIPAM (poly(N-isopropylacrylamide)), PVCL (polym`ere de caprolactame(N-vinyl)) et d’autres polym`eres dont les chaˆınes ont des monom`eres identiques et de structure chimique simples (Fig. 1). [. . . ]