Status: Professor, Department of Physics, Universidad Nacional del Sur, Bahia Blanca, Argentina

                   Daniel Vega's Faculty Homepage at UNS (in Spanish)

Doctoral Institution: Universidad Nacional Del Sur, Argentina
 
 
 
 

At present, my research activities at Princeton includes:

a) experimental characterization of asymmetric block copolymer solutions,
b) theory about the dynamics of star polymer melts and
c) cell-dynamic simulations of defect annihilation in block copolymer patterns.

 a) I am studying the phase behavior and dynamic properties of ternary mixtures composed of Styrene-poor diblock and triblock copolymers in selective solvents. Triblock copolymers in midblock-selective solvents can form physical gels. However, at low triblock contents (near the percolation threshold), bridging of chains between micelles can lead to macrophase separation. We find that adding a fraction of styrene-isoprene (SI) diblock to an SIS triblock copolymer in squalane can eliminate macrophase separation, yielding a wide range of stable, single-phase gels with a disordered arrangement of micelles. The plateau modulus of these triblock gels scales with the 2.2 power of polymer content, indicating the importance of entanglements in dictating the modulus. This work include rheological and Small Angle X-Ray Scattering (SAXS) characterization.

b) My research activities also include theory about the stress relaxation process in star polymer melts. Recently, using concepts of arm retraction and constrain release we have improved previous models by obtaining an expression to the time required for each star arm to escape from its original tube. We also show that several viscoelastic properties obtained through our model compare very well with experimental data.

c) Recently I began to simulate by computer the domain coarsening and defect annihilation in stripe patterns formed by block copolymers. By using cell dynamics simulations and the time dependent Guinbzburg-Landau equation (Cahn-Hilliard-Cook model) we start to study the orientational order parameter and the correlation length of stripe patterns formed by block copolymers.