Micellization through complexation of oppositely charged diblock copolymers: Effects of composition, polymer architecture, salt of different valency, and thermoresponsive block

Abstract

The structural and electrical characteristics of polyelectrolyte complex micelles (PCMs) formed by mixing of oppositely charged double hydrophilic copolymers are studied by means of molecular dynamics simulations. In mixtures of linear diblock copolymers we found that the preferential aggregation numberNpof PCMs is a universal function of the ratioγ±of the total positive to total negative charges of the mixture. The addition of divalent salts ions induces a secondary micellization. In mixtures of copolymers bearing a common neutral thermoresponsive block, micelles with contracted corona consisting of thermoresponsive blocks and complex polyelectrolyte core are formed at low salt concentration and temperature far away the biphasic regime. At high salt concentration and temperature in the biphasic regime, reversed micelles are obtained. In equimolar mixtures of linear copolymers with miktoarm stars we found thatNpof PCMs decreases as the number of charged branches of miktoarm copolymer increases. The shape of micelles progressively changes from spherical to worm‐like with the increase of number of branches of miktoarm copolymers. Our findings are in full agreement with existing experimental and theoretical predictions and provides new and additional insights.

Dendrimer‐Based Polyion Complex Vesicles: Loops Make Loose

“…Recent Brownian Dynamics simulations seem to support such a two-step mechanism. [38] The forces keeping these initial complexes together are strong, and at low salt they therefore probably hardly rearrange internally; they are largely in a "frozen" state. Although they are overall near neutral, they have both negative and positive charges exposed which are needed to form the ionic bonds that bind these initial complexes together in the next assembly step.…”

Complexation of a Polyelectrolyte Brush with Oppositely Charged AB Diblock Copolymers: The Zipper Brushes

“…In this way, the total volume fraction of all type of units and counterions in the mixture is the same with the one we used in the micellization through complexation of opposite charged diblock copolymer chains and equal to Φ = 0.12. [ 26 ] The number of the complexed diblock copolymer chains in the zipper brush as a function of time τ is shown in Figure . As can be seen, the number of the complexed chains increases gradually with τ , reaching a plateau corresponding to 112 chains after ≈3.6 × 10 4 tau.…”

“…[25] To the best of our knowledge, there are no prior molecular simulations studies dealing with the structure of the zipper brushes. Here, we perform an exhaustive molecular simulation study of zipper brushes base on our previous work on the PEBs, [16] the complexation of oppositely charged double hydrophilic diblock copolymers, [26] the complexation of PEB with oppositely charges micelles, [27] and the complexation on mixed PEB. [25] We use molecular dynamics simulations using the Primitive model [25] (spherical charged particles and implicit solvent), to elucidate the effects of the grafted chains fraction of charged units a, the brush grafting density, the molecular weights of both grafted and diblock copolymer chains, and the salt concentration on the height and the internal stratification of zipper brush.…”

Impact of Copolymer Architecture on Demicellization and Cargo Release via Head-to-Tail Depolymerization of Hydrophobic Blocks or Branches

“…In recent years, polymeric micelles have emerged as highly effective cargo carriers, owing to their biocompatibility, facile preparation, tunable size and shape, prolonged stability in blood circulation, and enhanced in vivo retention at the target site [ 2 , 3 , 4 , 5 , 6 ]. Typically, polymeric micelles consist of pre-synthesized diblock copolymer chains, comprising a hydrophilic and a hydrophobic block, or a mixture of double hydrophilic diblock copolymers with neutral and oppositely charged blocks, that become hydrophobic upon complexation [ 7 , 8 ]. The hydrophobic segments form the micelle core, while the hydrophilic ones create the surrounding corona.…”