Lamellae—Parking Garage Structure—Lamellae Transition in Densely Grafted Layers of Amphiphilic Homopolymers: Impact of Polymerization Degree

Abstract

By means of computer modeling, the self-organization of densely grafted macromolecules with amphiphilic monomer units as a function of macromolecular polymerization degree and solvent quality was studied and a diagram of state was constructed. The diagram contains fields of disordered distribution of monomer units and of prolonged aggregates, regions of lamellae with small and big domain spacing, and transition region. Within the transition region, the lamellae with different spacing coexist: the lamellae with big domain spacing are on the top of the grafting layer and the lamellae with small domain spacing are close to the grafting surface. The lamellae are connected with each other and form bicontinuous parking garage structure joining all side groups into a single cluster. The domain spacing of lamellae does not depend on the macromolecular length, but the width of the transition region decreases with the decrease of polymerization degree until total vanishing at relatively short macromolecules. The sharp switch between lamellae and bicontinuous structure opens the perspective for practical applications of densely grafted layers with amphiphilic monomer units.

Fundamental helical geometry consolidates the plant photosynthetic membrane

“…Remarkably, arrayed spiral ramps of alternating handedness connecting between sheets of nucleons were observed in molecular dynamics simulations of dense nuclear matter phases, termed “nuclear pasta,” predicted to exist in the inner crust of neutron stars and in core-collapse supernovae, which are some 14 orders of magnitude denser than the cellular environment (58, 72, 73). Twisted bridges similar to helical ramps were likewise observed in simulations of densely grafted polymer brushes of amphiphilic homopolymers (74). This geometry, based on a pitch-balanced arrangement of heterochiral helical elements, thus appears to be a universal means to connect between densely packed flat layers, irrespective of their composition, properties, or size scale (58).…”

Flowerlike Multipetal Structures of Nanoparticles Decorated by Amphiphilic Homopolymers

“…These transitions occur as the grafting density increases. At higher grafting densities, ultrathin micelles of various shapes (round, strips, layers) are built on the ABBA bilayer, and only after the macromolecules cover the grafting plane with a double ABBA – ABBA bilayer do they break off from the surface and form lamellae perpendicular to the grafting plane. − …”

“…The computer modeling of amphiphilic A - graft - B homopolymer’s layers grafted into a plane surface reveals that the microstructuring of such layers crucially depends on the solvent selectivity toward the relative position of different groups in monomer units. − …”

“…In the opposite situation where the solvent is poor for the side groups and good for the main chain, the densely grafted A - graft - B macromolecules self-assemble into lamella structures. − Depending on the solvent quality, these can be lamellas with a short period; lamellas with a long period; or a complex, garage structure in which lamellas with different periods are spaced according to height. At low grafting densities, the self-organization of amphiphilic homopolymers, caused by aggregation of hydrophobic pendants, leads to formation of ultrathin coatings and micelles of various shapes with a thickness of two to four monomer units .…”