Grafted Polyrotaxanes: Scaling Theory and Molecular Dynamics Simulations

Abstract

We analyze the scaling properties of grafted polyrotaxanes and compare the resulting scaling laws with molecular dynamics simulations. These molecules display a resemblance to bottle brushes, but the mobility of the rotors yields a backbone tension that is uniform along its contour. Properties like brush extension, backbone tension, and rotor mobility as functions of rotor density and degree of polymerization of grafted chains are well covered by a simple scaling model. The dynamics of rotor release after a breakup of the polyrotaxanea process recently observed in laboratory experi-mentsis studied in detail. It consists of three stages: a rapid backbone retraction, a driven rotor expulsion, and a diffusive transport. The complexity of this process, which may be exploited for drug delivery systems, is asking for further in-depth simulation studies.

Influence of Molecular Structure on the In Vivo Performance of Flexible Rod Polyrotaxanes

“…We infer from these PK data that PPG block coverage by HP-β-CD is more important for increasing circulation time than overall molecular weight due to a rotaxanation-induced increase in rigidity of the PR to produce a more rodlike structure . Similar results have been reported for flexible rod PEG–PCL micelles that display long circulation properties by aligning with blood-flow and avoiding macrophage uptake .…”

“…We infer from these PK data that PPG block coverage by HP-β-CD is more important for increasing circulation time than overall molecular weight due to a rotaxanation-induced increase in rigidity of the PR to produce a more rodlike structure. 38 Similar results have been reported for flexible rod PEG–PCL micelles that display long circulation properties by aligning with blood-flow and avoiding macrophage uptake. 5 Slow PR clearance from blood is likely not due to PEG shielding effects since the longest circulating agent, PR5, has the shortest PEG blocks (average of 3 units on each side), while the PRs with the longest PEG blocks (PR1 and PR2) are rapidly cleared.…”

Nanopores as Switchable Gates for Nanoparticles: A Molecular Dynamics Study

“…Meanwhile, brush research is increasingly branching out into specialized topics, including brushes made of dendrimers, − brush-decorated macromolecules for drug delivery, , or switchable (environment-responsive) surface layers. − If brushes are grafted onto nonplanar surfaces, such as spheres , or concave surfaces of considerable curvature, additional features emerge as a result of geometrical restrictions.…”

Topological Effects in Isolated Poly[n]catenanes: Molecular Dynamics Simulations and Rouse Mode Analysis

“…To simulate polymers in good solvent conditions, the model of Kremer and Grest is adopted for all molecules, including linear and cyclic polymers, as well as macrocycles within poly­[ n ]­catenanes. This model precludes chain crossings, enforcing topological restrictions, which makes it suitable for MIPs. ,,− The impact of segment stiffness is studied by introducing an angle-bending potential between neighboring (covalent) bond vectors to model flexible, semiflexible, and stiff segments; unless otherwise stated, all segments are completely flexible. See Supporting Information for additional details.…”