@article{rumyantsev_johner_2023, title={Salt-Added Solutions of Markov Polyampholytes: Diagram of States, Antipolyelectrolyte Effect, and Self-Coacervate Dynamics}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.3c00512}, abstractNote={Field-theoretic and scaling approaches are combined to predict conformational behaviors of single-chain globally neutral polyampholytes (PAs) in the presence of salt, the viscosity of their dilute solutions, and the rheology of condensed self-coacervate phases. To reveal the role of the monomer sequence, we consider PAs with Markov statistics of positive and negative charges. The diagram of globular regimes of single-chain PAs in Θ solvent is constructed with the coordinates of the charge blockiness and salt concentrations. For highly flexible chains, it contains six scaling regimes corresponding to low/high salt concentrations and (i) almost alternating, (ii) random correlated, and (iii) highly blocky sequences of ionic monomers. At increasing salt concentration, PAs of any sequence swell until reaching an ideal-coil size. The amplitude of the salt-induced globule-to-coil transition increases with increasing charge blockiness. So does the change in the viscosity of dilute PA solutions, indicating the sequence specificity in the antipolyelectrolyte effect. The similarity between the internal structure of the globules and macroscopic self-coacervate phases enables prediction of the viscosity of the latter. The respective scaling dependencies for self-coacervates of short unentangled and long entangled PAs are provided. Self-coacervate viscosity is the highest for the most blocky PAs and, for any sequence, decreases with the addition of salt. Our findings serve as important guidelines for understanding the dynamics of intracellular condensates, which form from polyampholytic disordered proteins/regions and exhibit the salt-induced viscosity drop described herein.}, journal={MACROMOLECULES}, author={Rumyantsev, Artem M. and Johner, Albert}, year={2023}, month={Jun} }
 @article{rumyantsev_2023, title={Scaling Theory of Circular Surface Micelles of Diblock Copolymers}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.3c00851}, abstractNote={Surface micelles of AB diblock copolymer have a three-dimensional (3D) core formed by B blocks and a two-dimensional (2D) corona consisting of A blocks strongly adsorbed and swollen at the air–liquid interface. A scaling theory of circular spherical micelles is developed by describing flat corona within the 2D Daoud–Cotton model. The power-law dependencies of their sizes and the aggregation number p on the block lengths NA and NB are predicted for the limits of starlike and crew-cut morphologies. Owing to the corona’s spatial confinement, the derived laws differ from those for usual micelles with 3D corona forming in the solution bulk. If solvent quality is Θ for 2D corona chains, theory predicts pst ∼ NA0 NB0.5 and pcc ∼ NA–0.67 NB0.83 for starlike and crew-cut micelles, respectively. In the recent systematic experiments [ J. Phys. Chem. Lett. 2022, 13, 5380], numerical fitting of the results (corresponding to a wide crossover region between crew-cut and starlike limits) with a single power law led to p ∼ NA–0.48 NB0.7; these empirical exponents fall within the range theoretically found herein. Our predictions for the core radius and corona thickness are in similar agreement with the experiment, both for Θ and a good solvent quality for the corona. Theory extension to micelles with quasi-planar 2D cores demonstrates that the core morphology weakly affects scaling laws. The developed approach provides insight into mechanisms controlling the interfacial self-assembly of diblock copolymers.}, journal={MACROMOLECULES}, author={Rumyantsev, Artem M.}, year={2023}, month={Jul} }
 @article{fang_rumyantsev_neitzel_liang_heller_nealey_tirrell_pablo_2023, title={Scattering evidence of positional charge correlations in polyelectrolyte complexes}, volume={120}, ISSN={["1091-6490"]}, DOI={10.1073/pnas.2302151120}, abstractNote={
            Polyelectrolyte complexation plays an important role in materials science and biology. The internal structure of the resultant polyelectrolyte complex (PEC) phase dictates properties such as physical state, response to external stimuli, and dynamics. Small-angle scattering experiments with X-rays and neutrons have revealed structural similarities between PECs and semidilute solutions of neutral polymers, where the total scattering function exhibits an Ornstein–Zernike form. In spite of consensus among different theoretical predictions, the existence of positional correlations between polyanion and polycation charges has not been confirmed experimentally. Here, we present small-angle neutron scattering profiles where the polycation scattering length density is matched to that of the solvent to extract positional correlations among anionic monomers. The polyanion scattering functions exhibit a peak at the inverse polymer screening radius of Coulomb interactions,
            q
            *
            ≈ 0.2 Å
            −1
            . This peak, attributed to Coulomb repulsions between the fragments of polyanions and their attractions to polycations, is even more pronounced in the calculated charge scattering function that quantifies positional correlations of all polymer charges within the PEC. Screening of electrostatic interactions by adding salt leads to the gradual disappearance of this correlation peak, and the scattering functions regain an Ornstein–Zernike form. Experimental scattering results are consistent with those calculated from the random phase approximation, a scaling analysis, and molecular simulations.
          }, number={32}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Fang, Yan N. and Rumyantsev, Artem M. and Neitzel, Angelika E. and Liang, Heyi and Heller, William T. and Nealey, Paul F. and Tirrell, Matthew V. and Pablo, Juan J.}, year={2023}, month={Aug} }
 @article{yu_liang_nealey_tirrell_rumyantsev_pablo_2023, title={Structure and Dynamics of Hybrid Colloid-Polyelectrolyte Coacervates: Insights from Molecular Simulations}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.3c01079}, abstractNote={Electrostatic interactions in polymeric systems are responsible for a wide range of liquid–liquid phase transitions that are of importance for biology and materials science. Such transitions are referred to as complex coacervation, and recent studies have sought to understand the underlying physics and chemistry. Most theoretical and simulation efforts to date have focused on oppositely charged linear polyelectrolytes, which adopt nearly ideal-coil conformations in the condensed phase. However, when one of the coacervate components is a globular protein, a better model of complexation should replace one of the species with a spherical charged particle or colloid. In this work, we perform coarse-grained simulations of colloid–polyelectrolyte coacervation using a spherical model for the colloid. Simulation results indicate that the electroneutral cell of the resulting (hybrid) coacervates consists of a polyelectrolyte layer adsorbed on the colloid. Power laws for the structure and the density of the condensed phase, which are extracted from simulations, are found to be consistent with the adsorption-based scaling theory of hybrid coacervation. The coacervates remain amorphous (disordered) at a moderate colloid charge, Q, while an intra-coacervate colloidal crystal is formed above a certain threshold, at Q > Q*. In the disordered coacervate, if Q is sufficiently low, colloids diffuse as neutral nonsticky nanoparticles in the semidilute polymer solution. For higher Q, adsorption is strong and colloids become effectively sticky. Our findings are relevant for the coacervation of polyelectrolytes with proteins, spherical micelles of ionic surfactants, and solid organic or inorganic nanoparticles.}, journal={MACROMOLECULES}, author={Yu, Boyuan and Liang, Heyi and Nealey, Paul F. and Tirrell, Matthew V. and Rumyantsev, Artem M. and Pablo, Juan J.}, year={2023}, month={Sep} }
 @article{rumyantsev_zhulina_borisov_2023, title={Surface-Immobilized Interpolyelectrolyte Complexes Formed by Polyelectrolyte Brushes}, volume={12}, ISSN={["2161-1653"]}, DOI={10.1021/acsmacrolett.3c00548}, abstractNote={A scaling theory of interaction and complex formation between planar polyelectrolyte (PE) brush and oppositely charged mobile linear PEs is developed. Counterion release is found to be the main driving force for the complexation. An interpolyelectrolyte coacervate complex (IPEC) between the brush and oppositely charged mobile PEs is formed at moderate grafting density and low salt concentration. At higher grafting density mobile chains penetrate the brush, but the brush structure is controlled by the balance between entropic elasticity and nonelectrostatic short-range interactions, as happens in a neutral brush. An increase in salt concentration beyond the theoretically predicted threshold leads to the release of the guest polyions from the brush. For brushes with moderate grafting density, complexation with oppositely charged guest polyions is predicted to trigger lateral microphase separation and formation of the finite-size surface IPEC clusters. Power law dependencies for the cluster dimensions on the brush grafting density, PE length, and salt concentration are provided.}, number={12}, journal={ACS MACRO LETTERS}, author={Rumyantsev, Artem M. and Zhulina, Ekaterina B. and Borisov, Oleg V.}, year={2023}, month={Dec}, pages={1727–1732} }