Random copolymer adsorption: Morita approximation compared to exact numerical simulations

TL;DR

This study compares an analytical Morita approximation method with numerical simulations to analyze the adsorption behavior of ideal random lattice copolymers with correlated sequences on homogeneous surfaces.

Contribution

It introduces a comparison between the Morita approximation and numerical simulations for copolymer adsorption, highlighting their quantitative agreement for various sequence correlations.

Findings

Good quantitative agreement between methods for Bernoullian and quasi-alternating sequences.

Both methods accurately predict free energy and conformational properties.

Correlation in sequences affects adsorption characteristics significantly.

Abstract

We study the adsorption of ideal random lattice copolymers with correlations in the sequences on homogeneous substrates with two different methods: An analytical solution of the problem based on the constrained annealed approximation introduced by Morita in 1964 and the generating functional (GF) technique, and direct numerical simulations of lattice chains averaged over many realizations of random sequences. Both methods allow to calculate the free energy and different conformational characteristics of the adsorbed chain. The comparison of the results for random copolymers with different degree of correlations and different types of nonadsorbing monomers (neutral or repelling from the surface) shows not only qualitative but a very good quantitative agreement, especially in the cases of Bernoullian and quasi-alternating random sequences.