Conformational Properties of End-Grafted Bottlebrush Polymers

Scaling analysis combined with free-energy calculations and molecular dynamics simulations of a coarse-grained bead-spring model have been used to study the structural properties of planar brushes formed by bottlebrush polymers tethered by ends to a flat surface. We find that the height H of end-grafted bottlebrushes undergoes a sequence of conformational changes emerging from the overlap between molecules at subsequent length scales upon increasing the number of bottlebrushes per unit surface area sigma. We establish a relation between H and the structural parameters of bottlebrush architecture: degree of polymerization of backbone N-bb and side chains N-sc as well as grafting density z of side chains. We find that nonoverlapping bottlebrushes exhibit the behavior of isolated polymers in a good solvent with the height that is sigma-independent and scales as proportional to (1 + zN(sc))N-2/5(bb)3/5. Weakly overlapping bottlebrushes are similar to end-grafted linear polymers (z = 0), and the height in this regime is proportional to sigma(1/3) (1 + zN(sc))N-2/3(bb). Strongly overlapping bottlebrushes undergo a further increase in height, which is given by proportional to sigma(2/7)z(6/7) N-bb.

Automated summary

The study reveals that the height of end-grafted bottlebrushes undergoes conformational changes with increasing number of bottlebrushes per unit surface area, and the height is influenced by structural parameters. Bottlebrushes with different degrees of overlap exhibit distinct behaviors.