Polyelectrolyte shells of copolymer micelles in aqueous solutions: A Monte Carlo study

Abstract

Multimolecular micelles, formed by polystyrene-block-poly(methacrylic acid) in water, are studied by lattice Monte Carlo method. Electrostatic interactions are calculated in the mean-field approximation by solving the Poisson-Boltzmann equation. The model is parametrized according to available experimental data. The dependence of micellar size on pH and ionic strength is calculated and compared with experimental data. A special attention is devoted to the behavior in solutions with a low ionic strength.

Probing the Inhomogeneous Charge Distribution on Annealed Polyelectrolyte Star Polymers in Dilute Aqueous Solutions

“…Clearly, at all the varied solution pH, the local pH near the center of swollen P2VP star is higher than that near the periphery by ∼0.3, indicating lower proton concentration and ionization degree at the center than those near the terminal group if assuming constant p K a for all the monomers in the star. The observed decrease of ionization degree from the periphery to the center qualitatively agrees with the theoretical and computer simulation prediction of the ionization profile along the contour of branched PE arms, which is determined by the concentration of localized counterions inside the star PE in the osmotic regime. ,,− We contributed the lower ionization degree primarily to the higher segment density in the center of PE star, where it becomes more energetically unflavored to ionize the monomer due to intermonomer electrostatic repulsion. Similar effect of PE segment density on the local ionization degree was also observed with a linear quenched PE chain labeled with fluorophores at the different locations .…”

“…The shift of the onset transition pH to lower pH for a PE star suggested that the introduction of branched topology or increasing the arm number shifted the solvent toward poor conditions as predicted theoretically . The continuous transition of linear P2VP MM was consistent with the reported smooth transition for linear P2VP of M n < 30000, in contrast to a sharp transition reported at higher M n . , The smooth transition of P2VP stars in dilution solutions was consistent with the theoretical and computer simulation predictions. ,,− ,, Although we could not fully exclude the possible contribution of the polydispersity in the M n or the arm number of our P2VP stars, we considered the smooth transition was mainly resulted from the inhomogeneous counterion distribution along the arms, which is similar to the continuous conformational transition of PE brushes grafted on a colloidal particle or a solid surface. , …”

“…While much has focused on linear PEs, PEs bearing complex architectures, including branched PEs, ,− ionic dendrimers, , and PE brushes grafted on nanocolloids or planar solid substrates, , have recently gained noticeable research interests and emerged as new functional materials or building blocks for many practical applications. For instance, hyperbranched PEs show great promise in enhancing ion and molecule transport in the polymers as new energy storage and nanomedicine materials. , Complexes of lubricin and aggregan in synovial fluids are PE bottlebrushes and their branched topology is critical for the superlubrication of synovial fluids. , The structural dynamics of nonionic branched polymers have been predicted by scaling theories , and confirmed by recent experimental , and computer simulation studies. , Distinct structural characteristics of branched PEs in aqueous solutions from those of neutral branched polymers are expected due to the difference between long-range electrostatic interaction and short-range excluded volume interaction, respectively.…”

Surface Modification of Silicon Nanowire Based Field Effect Transistors with Stimuli Responsive Polymer Brushes for Biosensing Applications

“…Dong et al [67] determined that there is a dissociation gradient inside the PAA brushes. Increased charge regions are present at higher distances from the substrate surface being caused by the minimization of the system's free energy [68], an inhomogeneous polymer volume fraction, and the formation of a double layer at the brush-solution interface [69]. In addition, the presence of PAA can be considered as another capacitive layer occurring on the surface.…”

Solubilization of Charged Porphyrins in Interpolyelectrolyte Complexes: A Computer Study

“…However, to the best of our knowledge, the possibility to incorporate charged porphyrins into IPEC cores of such nanoparticles has not yet been investigated-either experimentally or by simulations. The question if, to what extent, and in which form the large disk-like molecules charged at their outermost periphery would be solubilized in compact IPEC is interesting, and the answer is not a priori obvious for the following reasons: Studies of electrostatic co-assembly of PEs [41,[49][50][51][52][53][54][55][56] show that the formation of core-shell associates with segregated domains requires not only the presence of opposite charges on PE blocks (natural prerequisite) but also moderate hydrophobicity of PE backbones and their partial incompatibility with the shell-forming block. From this point of view, 4-or 2-poly(vinyl pyridines) are good candidates because they are insoluble in their non-ionized form in neutral or alkaline solutions and readily soluble at low pH when they are protonated and strongly charged.…”