1. Second International Workshop On Soft Condensed Matter Physics andSecond International Workshop On Soft Condensed Matter Physics and
Biological SystemsBiological Systems
2828––3030April 2010, Fez, MoroccoApril 2010, Fez, Morocco
Extended study of the phase
separation between
phospholipids and grafted
polymers onto a bilayer
biomembrane
I. Joudar, K. El Hasnaoui, H. Kaïdi
H. Ridouane, H. Qamar, M. Benhamou
Laboratoire de Physique des Polymères et Phénomènes Critiques
Faculté des Sciences Ben M’sik, P.O. Box 7955, Casablanca,
Morocco

2. We reexamine here the study of the phase separation between
phospholipids and anchored polymer chains onto a fluid membrane,
under a change of some suitable parameter (temperature). The
purpose is to quantify the important e ects of the solvent quality andff
the polydispersity of the grafted chains on the segregation
phenomenon. First, we elaborate a theoretical model that allows us
the determination of the mixing free energy expression. From the
latter, we extract the phase diagram shape in the composition
temperature plane. Second, we compute the structure factor and
discuss the role of the strong fluctuations of composition near the
consolute point. The main conclusion is that, the polymer chains
condensation is very sensitive to the solvent quality and polydispersity
of the anchored chains.
Abstract

3. Biomembrane with anchored polymer chains
Studied system
Objective
The aim is the study of the effects of polydispersity and solvent quality on
the phase separation between phospholipids and anchored polymer chains
by more than one points.

4. Notations
Free energy
: Volume fraction of anchors ;: Volume fraction of anchors ; : That of phospholipid molecules.That of phospholipid molecules.
TT : Absolute temperature.Absolute temperature.
aa : area of the phospholipids polar-heads ;area of the phospholipids polar-heads ; AA : that of anchors.that of anchors.
: Areas ratio.Areas ratio.
Good solvents :Good solvents : Theta solvents :Theta solvents :
Segregation parameter :Segregation parameter :
Coefficients a and b :Coefficients a and b : They depend on the chemical details andThey depend on the chemical details and
membrane characteristicmembrane characteristic

5. Phase diagram
Spinodal curve :Spinodal curve :
⇓
0,0 0,2 0,4 0,6 0,8 1,0
0
10
20
30
40
Good solvents
Φ
χ c
0,0 0,2 0,4 0,6 0,8 1,0
0
10
20
30
40
Theta solvents
Φ
χ c

6. Structure factor
Definition :Definition :
Small distances behavior :Small distances behavior :
Correlation length :Correlation length :
Integration constant :Integration constant :

7. Perspectives
Extention of the study to charged systems.Extention of the study to charged systems.
Dynamic study.Dynamic study.
Extension to more than membrane.Extension to more than membrane.