The Structure of Dipolar Polymer Brushes and Their Interaction in the Melt. Impact of Chain Stiffness

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.

Conformational properties of biocompatible poly(2-ethyl-2-oxazoline)s in phosphate buffered saline

The Kuhn segment length of PEtOx as a flexible macromolecule under physiological conditions is undoubtedly decreasing when approaching the LCST.

MODELLING OF POLYCOMB-DEPENDENT CHROMOSOMAL INTERACTIONS INVOLVED IN DROSOPHILA GENE SILENCING

The conditions of the chromosomes inside the nucleus in the Rabl configuration have been modelled as self-avoiding polymer chains under restraining conditions. To ensure that the chromosomes remain stretched out and lined up, we fixed their end points to two opposing walls. The numbers of segments N, the distances d1 and d2 between the fixpoints, and the wall-to-wall distance z (as measured in segment lengths) determine an approximate value for the Kuhn segment length kl. We have simulated the movement of the chromosomes using molecular dynamics to obtain the expected distance distribution between the genetic loci in the absence of further attractive or repulsive forces. A comparison to biological experiments on Drosophila Melanogaster yields information on the parameters for our model. With the correct parameters it is possible to draw conclusions on the strength and range of the attraction that leads to pairing.

MODELLING OF POLYCOMB-DEPENDENT CHROMOSOMAL INTERACTIONS INVOLVED IN DROSOPHILA GENE SILENCING

The conditions of the chromosomes inside the nucleus in the Rabl configuration have been modelled as self-avoiding polymer chains under restraining conditions. To ensure that the chromosomes remain stretched out and lined up, we fixed their end points to two opposing walls. The numbers of segments N, the distances d1 and d2 between the fixpoints, and the wall-to-wall distance z (as measured in segment lengths) determine an approximate value for the Kuhn segment length kl. We have simulated the movement of the chromosomes using molecular dynamics to obtain the expected distance distribution between the genetic loci in the absence of further attractive or repulsive forces. A comparison to biological experiments on Drosophila Melanogaster yields information on the parameters for our model. With the correct parameters it is possible to draw conclusions on the strength and range of the attraction that leads to pairing.