Polyelectrolytes: Theory, Properties and Applications

Structural Properties and Phase Behavior ... 7

For flexible chains, the form factors are usually represented by the Debye
function [25]

  22  i iT    

i

(^2222)
a b g
22 e 1 ; i a, b; e 1
; (1 ) ;.
6
u u
P qi uuu P q u
u xu u x u u q Nl q R
        
    

(9)

Here Rg is the chain radius of gyration and the cross term Pab is related to
Pa, Pb and PT by

P qT x P q^22 a  (1 x P q) b  2 (1x x P) abq. (10)

Note that the ionic strength of the solution is determined by the volume
fraction of added salt salt which enters in the expression of the Debye
screening length -^1. Recalling that both counter ions from the added salt and

from the ionization of A-monomers contribute to  one can write

(^23) B salt
4 l
xf
l

    .
We will focus on the partial structure factor of charged blocks Saa(q) to
analyze the effects of parameters impacting the structural properties and phase
behavior of the dispersed copolymer solution.

3. MACRO VERSUS MICROPHASE TRANSITIONS OF

NEUTRAL DIBLOCK COPOLYMERS IN SOLUTION

3.1. Symmetric Diblock Copolymers

The case where the two blocks have the same size leads to great
simplifications which, nevertheless preserve the basic features of the
investigated properties. The first simplification comes from the fact that only
two form factors enter in the formalism: PT(q) for the total chain and P1/2(q)
for each block

P qa  P qb  P1/ 2q; PPqab  (^2) TqP1/ 2q. (11)