Research

Polyampholytes (PAs) are macromolecules carrying both positively and negatively charged monomers. Historically, they were considered synthetic analogs of proteins. It is now established that almost 40% of the proteome comprises intrinsically disordered proteins (IDPs) or proteins with intrinsically disordered regions (IDRs). In contrast to the folded proteins, IDPs and IDRs are highly unstructured and undergo strong thermal fluctuations. This enables considering IDPs/IDRs as polyampholytes by applying the well-developed methods of the statistical physics of polymers. 

In globally non-neutral polyampholytes, the interplay between Coulomb correlation attractions of oppositely charged monomers and bare Coulomb repulsions between the chain segments due to their net nonzero charge results in an unusual type of conformations called necklaces. Necklace formation can be viewed as microphase separation within the single polymer chains. The addition of salt screens both Coulomb attractions and repulsions, leading to the appearance of the multicritical Lifshitz point on the scaling diagram of PAs/IDPs conformational regimes, which was constructed in our recent work [Macromolecules 2024]. We also speculate that, under physiological conditions, IDPs reside near the Lifshitz point, where they exhibit maximal conformational heterogeneity and susceptibility — properties essential for efficient signaling and regulation within the cell. We conjectured that their composition has been evolutionarily tuned in this way, consistent with the idea that “nature likes criticality”. 

Genetic mutations and abnormal posttranslational modifications alter the primary sequence of IDPs and may induce changes in their conformational behavior, including the pathological transition of disordered regions to folded states. The latter is associated with multiple diseases, ranging from neurodegenerative disorders to cancer to cardiovascular problems. We are interested in developing simple physical models of IDPs, which enable considering conformational transitions in them theoretically and in coarse-grained simulations. Our goal is to derive a fundamental understanding of the relationship between the primary sequence of IDPs and their conformational behaviors, including disorder-to-order transitions that serve as a prerequisite for pathologic protein aggregation.  

Charge carrier transport in conjugated polymers is controlled by the interplay of inter- and intra-chain hopping, which in turn is dependent on the polymer conformations. Introducing charges via intrinsic or extrinsic chemical doping enables beneficial tuning of the optoelectronic performance of the film. We apply scaling and field-theoretic methods of polymer physics to gain foundational predictions on the conformational statistics and conductivity of neutral and doped (ionic) conjugated polymers, providing a theoretical framework for the targeted design of soft electronic materials for flexible and stretchable electronic devices.   

We developed a theory of charge transport in isotropic bulks and solutions of conjugated polymers [Macromolecules 2025]. It was demonstrated that two approaches yield identical results: (i) a microscopic one, following the scaling method of de Gennes, based on considering the hopping diffusion of the charge along and between chains, and (ii) an approach based on calculating the resistance of an equivalent resistor ladder, with resistors representing intra-chain and inter-chain charge hopping. 

The unique ribbon-like shape of conjugated polymers promotes the formation of a variety of liquid-crystalline phases, not limited to uniaxial nematics but also including biaxial nematic and smectic (sanidic) phases. In our recent work [Macromolecules 2026], we considered polymer chains capable of torsion (twisting) and derived the so-called Lifshitz conformational entropy for such chains as well as the Edwards equation for them. This, in turn, enabled the development of a minimal theory for the uniaxial–biaxial nematic phase transition in melts of twistable polymer chains. Within a Maier–Saupe–type approach, this transition was predicted to be second order phase transition.

Microphase separation in polymer melts and the formation of polymer micelles in solutions and at interfaces are different manifestations of the same phenomenon — polymer self-assembly. This process is driven by thermodynamic factors and can be described theoretically. Theoretical polymer physics provides important guidelines that enable control over the size and morphology of the resulting structures by tuning chain length, composition, and architecture. Particular attention is paid to electrostatically stabilized microphase separation, in which the finite size of microphase-separated domains is determined by their excess Coulomb energy, in contrast to diblock copolymer microphases stabilized by the chemical connectivity of the blocks. A comprehensive review of this phenomenon is provided in our recent Viewpoint. [ACS Macro Lett. 2025] 

Another problem of interest is diblock-copolymer micellization at interfaces, where the reduced 2D dimensionality of the system leads to unique and often unexpected behaviors. [Macromolecules 2023] 

We also consider the kinetics of microphase separation within a dynamical field theory (RPA) approach. We developed a theory of electrostatic slowdown in spinodal decomposition. We showed that the decay into microphases proceeds via exponentially fast growth of periodic density modulations with an optimal wavelength, closely analogous to Cahn–Hilliard waves. The key distinction lies in the new scaling of the optimal growth rate with the quench depth, δχ: it is linear for decay into microphases, in contrast to the well-known quadratic dependence characteristic of systems undergoing macrophase separation. Interestingly, near the Lifshitz point, the optimal growth rate exponent was predicted to be 3/2, lying between the microphase and macrophase values of 1 and 2, respectively. The found growth rate exponents are universal and apply not only to electrostatic but also to block-copolymer systems undergoing spinodal decomposition into microphases or bicontinuous microemulsions. [J. Chem. Phys. 2026]

Polyelectrolyte complex coacervates are liquid polymer-rich phases forming as a result of associative phase separation in mixed solutions of polyanions and polycations. Complex coacervation is considered one of the physical mechanisms behind the intracellular organization and formation of membraneless organelles. Coacervates of synthetic polyelectrolytes are promising underwater adhesives, and micelles with coacervate cores serve as efficient drug delivery vehicles. We apply the modern methods of polymer physics to predict the relationship between the structure of the polyelectrolytes and the properties of the coacervate phases. The interplay between charge connectivity and their long-range Coulomb interactions makes the physics of these systems very rich, beautiful, and challenging. Our interests include (but are not limited to) the intra-coacervate microphase separation, liquid crystalline ordering, the role of the primary sequence of monomers, and coacervation-driven self-assembly. Some of our findings are summarized in the comprehensive review. [Annu. Rev. Condens. Matter Phys. 2021]