Abstract
By using the numerical lattice Scheutjens–Fleer self-consistent field (SF-SCF) method we have studied the effect of the restricted flexibility of grafted chains on the structure and mutual interaction of two opposing planar conventional and A-type dipolar brushes. Brushes are immersed in the solvent consisting of chains similar to the grafted ones. The increase of the chain rigidity enhances the segregation of grafted chains in a A-type dipolar brush into two populations: backfolded chains with terminal monomers near the grafting surface and chains with the ends at the brush periphery. The fraction of backfolded chains grows by an increase of the Kuhn segment length. It is shown that two opposite A-type dipolar brushes from semi-rigid chains are attracted to each other at short distances. The attraction becomes more pronounced and begins at larger distances for more rigid chains with the same brush characteristics: polymerization degree, grafting density, and dipole moments of monomer units. This attraction is connected with the dipole-dipole interactions between chains of oncoming brushes with oppositely directed dipoles penetrating deeply into each other upon contact. This effect of the chain rigidity is opposite to that for conventional brushes without dipoles in the chains. For such brushes, an increase in the chain rigidity leads to the enhanced repulsion between them.
Highlights
Polymer brushes are layers of polymer chains with the end link firmly connected to the surface
A-type brushes were not considered in these works. Another goal of the present work is to study the influence of the limited flexibility of the grafted chains and free chains in the polymer matrix on the internal structure and interaction of brushes. The formulation of this problem is motivated by the results of further atomistic molecular dynamics (MD) modeling [25], which demonstrated the difference in the structure of brushes formed on the surface of cellulose nanocrystals (CNC) particles by grafted OLA and oligohydroxybutyrate (OHB) in melts of polylactic acid (PLA) and polyhydroxybutyrate (PHB)
The goal is to determine the effect of two factors on the brush structure: the limited flexibility of chains (p > 1) and the dipole-dipole interactions of longitudinal dipoles in A-type brushes (τ > 0)
Summary
Polymer brushes are layers of polymer chains with the end link firmly (almost irreversibly) connected to the surface. Another goal of the present work is to study the influence of the limited flexibility of the grafted chains and free chains in the polymer matrix on the internal structure and interaction of brushes The formulation of this problem is motivated by the results of further atomistic MD modeling [25], which demonstrated the difference in the structure of brushes formed on the surface of CNCs particles by grafted OLA and oligohydroxybutyrate (OHB) in melts of PLA and polyhydroxybutyrate (PHB). The effect of such parameters as the polymerization degree N, grafting density σ, parameter τ of the dipole-dipole interactions, and the Kuhn segment length p on the brush structure will be studied.
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