Eur. Phys. J. E 4, 515-519

Microphase separation at two length scales

R.J. Nap¹, C. Kok¹, G. ten Brinke¹ and S.I. Kuchanov<sup>2

1</sup>  Department of Polymer Chemistry and Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
²  Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Miusskaya Square 4, Moscow 125047, Russia

nap@chem.rug.nl

(Received 25 August 2000)

Abstract
The possibility of microphase separation at two different length scales in monodisperse AB block copolymer melts consisting of a homopolymer A block and either a linear alternating AB copolymer block (poly(A)_m-block-poly(B-alt -A)_n) or an AB comb copolymer block poly(A)_m-block-poly(A- graft -B)_n, is investigated. An analysis of the structure factor reveals that in the parameter space of n and m three different cases can be distinguished: I) The structure factor has only one minimum corresponding to the short length scale (i.e. the characteristic length of the repeating unit of the alternating or comb block). II) The structure factor has only one minimum corresponding to the long length scale (the characteristic length of the blocks). III) Two minima are present leading to a competition between microphase separation at the short and the long length scale. Depending on the choice of n and m, one of these three possibilities will occur.

PACS
36.20.-r - Macromolecules and polymer molecules.
64.60.Cn - Order-disorder transformations, statistical mechanics of model systems.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001