Effects of composition correlations on the adsorption of statistical copolymers / by Josiane Gerges Salameh.

Abstract

Based on the first order Markov chains, we have designed sequences of length N with a distribution in chemical composition of A-monomers ΦA and microstructure c. With a value of c in the vicinity of unity, the polymer sequences tend to be more blocky, whereas the chains are periodic in the extreme case of c = 1. Then, within the numerical method of matrices, we discuss the effect of microstructure on the adsorption transition of a tethered copolymer on a planar solid surface. Apparently, the influence is only detected in the critical region. In analogy with the chromatographic methods, we then numerically describe the capacities of such separations from the partition coefficient distributions. In fractionation according to chemical composition ΦA or to microstructure c, the full distribution is under study not only the mean value of the partition over the ensemble of sequences. In the second part of the thesis, we present the mechanical desorption of a diblock chain within two methods. Following the landau formalism that depends on the behavior of the non-equilibrium Landau free energy as a function of the order parameter, we compare the analytical potentials with the numerical results. Therefore, we show a difference in the transition’s nature between a diblock composed of a block of A-monomers linked to a block of B-monomers and a diblock in the flipped order. In the case of first order transition, we will evaluate the mean first passage time for a diblock chain adsorbed at the surface to overcome an energy barrier and take a stretched conformation within the framework of the dynamic Fokker-Planck equation.