Amphiphilic Multiblock Copolymers: From Intramolecular Pearl Necklace to Layered Structures

Abstract

We report on three-dimensional Monte Carlo simulations of dilute solutions of multiblock copolymers made of regularly spaced hydrophobic and hydrophilic blocks in the limit of long chains with a large number of blocks. Using a lattice model we investigate the effects of the ratio of hydrophobic to hydrophilic block lengths and impact of the quality of the solvent on the intramolecular structure of the copolymers. In poor solvent and for given block lengths the simulations show evidence for the existence of different kinds of intramolecular self-assemblies depending on solvent quality: Micelles, chains of micelles, tubes, and layered structures are revealed by both statistical properties and visualization. The form factor signature of the different structures has been identified and is discussed in connection with its experimental observability. The existence region of the different conformations in terms of energy and entropy is summarized in a phase diagram.

Coarse-grained models for macromolecular systems

“…For a precise operational definition of cell polymer dynamics the reader is referred to Ref. [34]. In this algorithm, Rouse type moves dominate the dynamics for dilute solutions whereas reptation moves dominate the dynamics at melt densities, just as expected for real polymers [5].…”

“…The probability is negligible beyond N c ≥ 30. The inset shows the total fraction of small clusters (N c < 5) as a function of E i (From [34]). …”

“…Solid line: analytical form factor of a 2d-platelet. Note that the curves are normalized by N H and shifted vertically by one order of magnitude for clarity (From [34]). using a slowly increasing energy ramp.…”

“…Note that for P sub > 0.3, F H (q) ≈ F cluster (q) as most H blocks belong to a single cluster. For P sub = 0.3, F cluster (q) can be fitted to the analytical form factor of a polydisperse sphere of radius R s = 1.85 (not shown, see [34]). For lower q values, the behaviours of F H (q) and F cluster (q) depart from each other for P sub = 0.3: F H (q) shows a well-defined correlation distance at q c ≈ 1.2 (≈ 5.2 lattice units in real space), which becomes more pronounced for longer chains and disappears for short chains (single intramolecular micelle).…”

“…For the other two cases, the situation is quite different. The distances d p = 2 q P can be associated with the tube diameter and the sphere diameter of the hole due to the presence of the H core (see [34] for more details).…”