Destruction of globules of Co- and homopolymer macromolecules in the presence of an amphiphilic substrate

The destruction of a globule in the presence of a dimeric substrate composed of a hydrophilic group OP and a hydrophobic group H with a high affinity to hydrophobic H units of a macromolecule has been studied. Globules of the homopolymer H macromolecule and the macromolecule of the HP copolymer with proteinlike statistics of monomer unit distribution along a chain have been investigated. The destruction of a globule in such systems begins with the transformation of the globule’s shape from spherical to disklike. At high substrate concentrations, the globule of the proteinlike copolymer is completely destroyed; under the same conditions, the homopolymer macromolecule forms a structure composed of two beads having a shape close to that of the oblate ellipsoid that are located symmetrically about a string connecting them.     

Computer simulation analysis of microstructure formation in monomer and polymer blends involving a glassy component

Monte Carlo and molecular dynamics simulations are performed for low-molecular-weight and polymeric A/B mixtures with a glassy component A. The possibility of a glass transition in the microregions enriched with A-molecules is taken into account by introducing a “freezing constraint”. Two types of this constraint are considered in the present paper: either the diffusion motion of a given A-particle is stopped if the concentration of A-units in some sphere around a given particle is larger than a certain critical value (constraint of G-type), or it is stopped if the concentration of “plasticizing” B-molecules in this sphere is lower than a certain critical value (constraint of P-type). It is shown that even for athermal A/B blends a “freezing constraint” of both types leads to the formation of well-separated microsegregated clusters of glassy A-units. The type of the final microstructure depends essentially on the type and the effective radius of the “freezing constraint”; both “frozen-in” and equilibrium microdomain structures can emerge.     

Polyelectrolyte Complexes Consisting of Macromolecules With Varied Stiffness: Computer Simulation

Monte Carlo simulations are employed in order to analyze the structure of polyelectrolyte complexes consisting of two identical but oppositely charged macroions with varying chain stiffness. It is shown that two complex structures can arise depending on the stiffness of the constituent chains. Stiff chains are organized into a “ladder” structure in which chains are located parallel to each other and monomeric units are arranged into ionic pairs according to their position in the chain. Flexible chains form a globular “scrambled‐egg” structure with a disordered position of monomer units. The conformational transition between the two structures proceeds as a phase transition.