2017 
Armao, J. J., Nyrkova, I., Fuks, G., Osypenko, A., Maaloum, M., Moulin, E., et al. (2017). Anisotropic SelfAssembly of Supramolecular Polymers and Plasmonic Nanoparticles at the Liquid Liquid Interface. J. Am. Chem. Soc., 139(6), 2345–2350.
Abstract: The study of supramolecular polymers in the bulk, in diluted solution, and at the solid liquid interface has recently become a major topic of interest, going from fundamental aspects to applications in materials science. However, examples of supramolecular polymers at the liquid liquid interface are mostly unexplored. Here, we describe the supramolecular polymerization of triarylamine molecules and their lighttriggered organization at a chloroform water interface. The resulting interfacial nematic layer of these 1D supramolecular polymers is further used as a template for the precise alignment of spherical gold nanoparticles coming from the water phase. These hybrid thin films are spontaneously formed in a single process, without chemical prefunctionalization of the metallic nanoparticles, and their ordering is improved by centrifugation. The resulting polymer chains and strings of nanoparticles can be coaligned with high anisotropy over very large distances. By using a combination of experimental and theoretical investigations, we decipher the full sequence of this oriented selfassembly process. In such a highly anisotropic configuration, electron energy loss spectroscopy reveals that the selfassembled nanoparticles behave as plasmonic waveguides.


Jamal, A., Nyrkova, I., Mesini, P., Militzer, S., & Reiter, G. (2017). Solventcontrolled reversible switching between adsorbed selfassembled nanoribbons and nanotubes. Nanoscale, 9(9), 3293–3303.
Abstract: We have demonstrated that solutions of 3,5bis(5hexylcarbamoylpentyloxy)benzoic acid decyl ester (BHPB10) can form metastable nanostructures on solid substrates and in the bulk. BHPB10 is an achiral molecule involving several distinct, strongly interacting groups (SIGs), one aromaticester ring and two amide groups per molecule. Specific solvents affect the interactions between particular SIGs, thus promoting various nanostructures: lamellae, nanoribbons, helical ribbons, or nanotubes. In cyclohexane, a solvent allowing for both interamide hydrogen bonds and mutual attraction of rings, the formation of nanotubes with a diameter of 28 +/ 5 nm was observed in the bulk and on surfaces. By contrast, in cyclohexanone, which suppresses interamide hydrogen bonds, flat nanoribbons with a specific width of 12 +/ 4 nm were formed on solid substrates after drying. By annealing in cyclohexane vapor, we followed the process of switching surface structures from nanoribbons to nanotubes and observed helical ribbons as the precursor of nanotubes. We also turned nanotubes back into nanoribbons by adding cyclohexanone, thus demonstrating reversible switching along the route: tubes. lamellae. flat ribbons. helical ribbons. tubes. We propose models explaining the observed nanostructures and their transformations, including the origin of spontaneous chirality of the helical ribbons. Our findings on the selfassembly in the achiral BHPB10 solutions provide insight into the influence of complementary intermolecular specific SIGbased interactions and demonstrate an effective route for tailoring the shape and size of nanostructures derived from the same building unit.


2014 
Nyrkova, I., Moulin, E., Armao, J. J., Maaloum, M., Heinrich, B., Rawiso, M., et al. (2014). Supramolecular SelfAssembly and Radical Kinetics in Conducting SelfReplicating Nanowires. Acs Nano, 8(10), 10111–10124.
Abstract: By using a combination of experimental and theoretical tools, we elucidate unique physical characteristics of supramolecular triarylamine nanowires (STANWs), their packed structure, as well as the entire kinetics of the associated radicalcontrolled supramolecular polymerization process. AFM, smallangle Xray scattering, and allatomic computer modeling reveal the twocolumnar “snowflake” internal structure of the fibers involving the pstacking of triarylamines with alternating handedness. The polymerization process and the kinetics of triarylammonium radicals formation and decay are studied by UVvis spectroscopy, nuclear magnetic resonance and electronic paramagnetic resonance. We fully describe these experimental data with theoretical models demonstrating that the supramolecular selfassembly starts by the production of radicals that are required for nucleation of doublecolumnar fibrils followed by their growth in doublestrand filaments. We also elucidate nontrivial kinetics of this selfassembly process revealing sigmoid time dependency and complex selfreplicating behavior. The hierarchical approach and other ideas proposed here provide a general tool to study kinetics in a large number of selfassembling fibrillar systems.


2011 
Semenov, A. N., & Nyrkova, I. A. (2011). Endgrowth/evaporation living polymerization kinetics revisited. Journal of Chemical Physics, 134(11).
Abstract: Endgrowth/evaporation kinetics in living polymer systems with “associationready” free unimers (no initiator) is considered theoretically. The study is focused on the systems with long chains (typical aggregation number N >> 1) at long times. A closed system of continuous equations is derived and is applied to study the kinetics of the chain length distribution (CLD) following a jump of a parameter (Tjump) inducing a change of the equilibrium mean chain length from N(0) to N. The continuous approach is asymptotically exact for t >> t(1), where t(1) is the dimer dissociation time. It yields a number of essentially new analytical results concerning the CLD kinetics in some representative regimes. In particular, we obtained the asymptotically exact CLD response (for N >> 1) to a weak Tjump (epsilon = N(0)/N – 1


2010 
Moulin, E., Niess, F., Maaloum, M., Buhler, E., Nyrkova, I., & Giuseppone, N. (2010). The Hierarchical SelfAssembly of Charge Nanocarriers: A Highly Cooperative Process Promoted by Visible Light. Angew. Chem.Int. Edit., 49(39), 6974–6978.
Keywords: materials science; nanostructures; selfassembly; supramolecular chemistry; systems chemistry


Nyrkova, I. A., & Semenov, A. N. (2010). Twisted surfactant structures: an advanced theoretical model. Soft Matter, 6(3), 501–516.
Abstract: We analyze twisted membrane structures of chiral surfactants in the framework of the equilibrium theoretical approach based on a continuous elastic model. It is shown that both the surfactant ribbon width and its twist pitch can be defined by equilibrium factors, including the chiral elastic energy. We show however that the theoretically predicted dependencies of the ribbon geometrical parameters on the enantiomeric excess (ee) obtained for the unilamellar liquid membrane model are in partial, but qualitative disagreement with experimental data. The surfactant membrane model is then generalized in two directions: (i) we consider also multilamellar ribbons (of many bilayers), (ii) we allowed for the crystalline (Lbeta) state of the bilayers. The multibilayer crystalline structure of selfassembling twisted ribbons is consistent with recent results of Xray and other experimental studies on gemini surfactants, and, simultaneously, the theory developed for such ribbons yields the eedependencies of the twisted ribbon width and pitch that are in reasonable agreement with the data based on TEM images.


2009 
Nyrkova, I. A., & Semenov, A. N. (2009). Theory of chiral recognition in DNA condensation. Soft Matter, 5(5), 979–989.
Abstract: Collapse of long chiral Amacromolecules assisted by a chiral Badditive (where B associates with A) is considered theoretically. Based on a simple model we demonstrate that the compaction activity of B molecules can strongly depend on the sense of their chirality. The theory is applied to the DNA compaction in the presence of conformationally rigid divalent enantiomeric cations (SS and RR enantiomers).(1) It is shown that both chiral isomers of the dications adsorb well on the DNA surface, but the SS and RRbinding energies are different, reflecting their unequal stereocomplementarities (the 'boltandnut' effect). Unexpectedly, we find that the compaction activity of less strongly bound SS dication is significantly higher than that of its RR enantiomer. Moreover, the RR molecules tend to replace the SS enantiomers adsorbed on the DNA, so that SS compaction ability is significantly reduced in the presence of RR isomers. The theory thus provides a basis for explanation of recently observed dramatic stereoisomeric selectivity and antagonistic effects in DNA compaction.(1) The revealed chiral discrimination effects may serve as selection mechanisms leading to natural homochirality.


2007 
Nyrkova, I. A., & Semenov, A. N. (2007). Correlation effects in dynamics of living polymers. Europhysics Lett., 79(6), 66007.
Abstract: Theoretically studying the dynamics of entangled living polymers which can reversibly break and recombine, we find a number of diffusioncontrolled regimes of essentially nonexponential stress relaxation. This behavior is in contrast to predictions of the classical theory of Cates and its more recent generalizations. The nonexponential relaxation is due to strong correlations between chain scissions and recombinations: multiple selfrecombinations are much more frequent than recombinations with other chains and are resulting in fast release of topological constraints (entanglement tube coarsening). The strong renormalization effect of correlations on the lifetime of a living chain (the time period tau(b) until the chain breaks and one of its fragments recombines with another chain) is also elucidated. We show that the correlation effects defining the dynamics are controlled by the activation energy for chain recombination and by the chain rigidity. Copyright (C) EPLA, 2007.


Nyrkova, I. A., & Semenov, A. N. (2007). Dynamic scattering of semirigid macromolecules. Physical Review E, 76(1), 011802.
Abstract: The polarized (VV) and depolarized (VH) dynamic light scattering functions of dilute solutions of semirigid macromolecules are calculated assuming that the scattering wave vector q_ is high compared to the chain Kuhn segment l: ql > 1. The terminal relaxation rate is Gamma proportional to q(8/3). Dynamics of both uniaxial and biaxial wormlike macromolecules (filaments) are considered. Biaxial macromolecules are characterized by two persistence lengths proportional to elastic constants for bending in two perpendicular directions (easy and hard bending). We showed that biaxiality may result in a significant broadening of the relaxation spectrum. A nonmonotonous q dependence of the depolarized scattering intensity is predicted. Analyzing the shorttime behavior of the dynamic structure factor for t < 1/Gamma, we show that it is characterized by two additional characteristic times: t(perpendicular to)proportional to q(4) and t(parallel to)proportional to q(8) reflecting the transverse and the longitudinal dynamics of polymer chains. The longitudinal motions (along the chain contour) increase the initial relaxation rate of the structure factor by a factor of 2. The longitudinal contribution to the dynamic structure factor is significant even for t > t(parallel to).


Nyrkova, I. A., & Semenov, A. N. (2007). Nonlinear scission/recombination kinetics of living polymerization. European Physical Journal E, 24(2), 167–183.
Abstract: Living polymers are formed by reversible association of primary units (unimers). Generally the chain statistical weight involves a factor sigma < 1 suppressing short chains in comparison with free unimers. Living polymerization is a sharp thermodynamic transition for sigma << 1 which is typically the case. We show that this sharpness has an important effect on the kinetics of living polymerization (onedimensional association). The kinetic model involves i) the unimer activation step (a transition to an assemblycompetent state); ii) the scission/recombination processes providing growth of polymer chains and relaxation of their length distribution. Analyzing the polymerization with no chains but unimers at t = 0, with initial concentration of unimers M greater than or similar to M* (M* is the critical polymerization concentration), we determine the time evolution of the chain length distribution and find that: 1) for M* << M << M*/sigma the kinetics is characterized by 5 distinct time stages demarcated by 4 characteristic times t(1), t(2), t(3) and t*; 2) there are transient regimes (t(1) less than or similar to t less than or similar to t(3)) when the molecularweight distribution is strongly nonexponential; 3) the chain scissions are negligible at times shorter than t(2). The chain growth is autoaccelerated for t(1) less than or similar to t less than or similar to t(2): the cutoff chain length (= polymerization degree < n >(w) N1 proportional to t(2) in this regime. 4) For t (2) < t < t (3) the length distribution is characterized by essentially 2 nonlinear modes; the shorter cutoff length N1 is decreasing with time in this regime, while the length scale N2 of the second mode is increasing. (5) The terminal relaxation time of the polymer length distribution, t*, shows a sharp maximum in the vicinity of M*; the effective exponent partial derivative ln 1/t*/partial derivative ln M is as high as similar to sigma(1/3) just above M*.


2005 
Nyrkova, I. A., & Semenov, A. N. (2005). Multimerization: Closed or open association scenario? European Physical Journal E, 17(3), 327–337.
Abstract: We address the problem of classification of the type of association (multimerization) in solutions of identical unimers. Although the aggregation is still routinely characterized in terms of either “open association” or “closed association” models, neither of the two models can provide a fair description of many aggregation processes. We demonstrate that a realistic multimerization may show mixed basic features, i.e. simultaneously those typical of the classical open association and those typical of the classical closed association. In particular, we show that a living polymerization may seem to exhibit a critical micelle concentration (CMC), whereas the basic integral characteristics of a “closed” system with rather monodisperse micelles ((m(w)/m(n))(mic) = 1.02) may not imply a welldefined CMC. Therefore, a multimerization must be characterized by the detailed micelle size distribution that largely defines the equilibrium and dynamical properties of the system. To this end, we suggest a simple method of deriving the micelle size distribution c(m) (depending also on the total concentration of amphiphilic molecules) from the concentration dependence of just the mean aggregation number, m(w)(c). Our results thus invite a reconsideration of the basic methods used for interpretation of experimental data on micellization.


Nyrkova, I. A., & Semenov, A. N. (2005). On the theory of aggregation and micellization: PEOPVP copolymer in water. Faraday Discussions, 128, 113–127.
Abstract: We develop a theoretical approach to micellization of the PEOPVP blockcopolymer in water. This copolymer is a weak polyelectrolyte due to protonation of VP blocks. The theory accounts for nonlinear ion screening, and predicts strong position dependence of both ion concentration and the effective Debye length. We consider both the case when the local Debye length is small compared to the core radius and the case when it is large. We found that the effective (local) pH is not uniform even inside one micellar core, hence nonuniform protonation of the core with higher charge density near the surface. In many cases the core charge is concentrated in a relatively thin surface layer. Considering statistical weights of nonequilibrium micelles and their continuous evolution we show that kinetics of both formation and dissociation of typical blockcopolymer or surfactant micelles can be extremely slow. Thus micelle formation at the genuine (equilibrium) critical micelle concentration (c.m.c.) is totally suppressed (involves astronomical time scales) if the micelles are big enough. An 'apparent' critical micelle concentration (c.m.c.*) is introduced to account for this effect. The apparent c.m.c.* could be much higher than the genuine equilibrium c.m.c., i.e. a significant hysteresis is inherent in these systems. We also determine the ranges of metastability of micelles depending on the experimental timescales.


Nyrkova, I. A., & Semenov, A. N. (2005). On the theory of micellization kinetics. Macromolecular Theory And Simulations, 14(9), 569–585.
Abstract: We consider certain general features of aggregation (micellization) processes in solutions of amphiphilic molecules, in particular, blockcopolymers. We demonstrate that nonequilibrium effects can be very important for micellization. In particular, we show that micelle formation at the conventional (equilibrium) critical micelle concentration (CMC, c(c)) can be inhibited by high activation energy barriers. This is likely to be the case when the micelles are large. In this case an aggregation actually occurs at higher concentrations, above an apparent CMC, c(a). The concentration Ca can be much. higher than the equilibrium CMC. Hence significant hysteresis effects are inherent in amphiphilic systems since micelle formation and dissociation are activation processes. To further clarify this idea we consider relaxation of a micellar system after a, temperature jump (or a jump of another essential parameter) and discuss qualitatively different relaxation times corresponding to the relaxations of the micellar sizes and of the total number of micelles. We also discuss different kinetic pathways of micelle formation and relaxation and show that in certain cases the idealgas (combinatorial) contribution to the micelle free energy is significant for the kinetics.


1997 
Nyrkova, I. A., Semenov, A. N., & Joanny, J. F. (1997). Highly anisotropic rigidity of ''ribbonLike'' polymers .2. Nematic phases in systems between two and three dimensions. Journal De Physique Ii, 7(6), 825–846.
Abstract: Various extensions of Onsager theory based on the second virial approximation are constructed in order to describe nematic Pphases in ribbon polymer solutions. If the average coil shape is anisotropic and the concentration is not too high, the coils can be considered as anisotropic solid objects and an ordinary expansion over the coil concentration can be performed. This first approach can be applied to study pancake nematic ordering. At higher concentrations and when the polymer chains are rather long, the polymer solution can be considered as a solution of short fragments connected into chains with a particular statistics reflecting the polymer structure with two rigidities: a similar virial expansion can be constructed. This last approach allows the consideration of the various symmetries of the nematic phases simultaneously. We also take into account the correlation correction to the mean field result which provides an essential additional angular dependence to the interaction free energy. Scaling arguments are applied in the case where the intracoil correlations are very strong, or if the coils interact as opaque objects. The methods developed here will be used in further publications to study liquid crystalline ordering in solutions of ribbon chains.


Nyrkova, I. A., Semenov, A. N., & Joanny, J. F. (1997). Highly anisotropic rigidity of ''ribbonlike'' polymers .3. Phase diagrams for solutions. Journal De Physique Ii, 7(6), 847–875.
Abstract: The behavior of solutions of polymer chains with anisotropic rigidity is considered theoretically. The diagrams of different scaling regimes and the phase diagrams for polymers with arbitrary contour length L, inplane rigidity l, and out of plane rigidity l(2) are obtained. Two new types of nematic structures in addition to ordinary nematic with ordering of tangent vectors are found for the regime of moderate second rigidity l(2) (l less than or equal to l(2) less than or equal to l(3)/d(2)): a pancake nematic (with ordering of the normals to the planes of main flexibility of the chains) and a biaxial nematic (when both tangent and normal vectors are ordered). We also found smectic A and smectic C phases in addition to three nematic phases. The scaling (modified blob) and meanfield with correlation corrections approaches are developed and used when appropriate. Order parameters, correlation radii and chain sizes are discussed for most of the regimes.


1996 
Nyrkova, I. A., Semenov, A. N., Joanny, J. F., & Khokhlov, A. R. (1996). Highly anisotropic rigidity of ''ribbonlike'' polymers .1. Chain conformation in dilute solutions. Journal De Physique Ii, 6(10), 1411–1428.
Abstract: We discuss the solution properties of polymers with a highly anisotropic rigidity which bend rather freely in a plane (the plane of main flexibility) and are extremely rigid in the direction perpendicular to this plane. Examples of these polymers are the ladder polymers recently synthesized or living polymers formed by the aggregation of peptide rodlike fragments. These polymers have a much higher out of plane persistence length l(2) than their inplane persistence length l. In the first paper of this series, we mostly investigate the conformation of single chains in solution (at extremely low concentrations). The conformation of an isolated chain with a highly anisotropic rigidity essentially depends on the dimensionless parameter Ohm = l(2)d(2)l(3) where d is the chain diameter. For small values of Ohm, (l(2) similar to l), the chain behaves as a standard semiflexible chain with isotropic rigidity. For large values of Ohm, (Ohm greater than or similar to 1), the chain adopts a onedimensional rodlike conformation at length scales smaller than l, an anisotropic disclike conformation at intermediate scales (corresponding to a contour length L such that l less than or similar to L less than or similar to l(2)) and a threedimensional swollen coil conformation at larger length scale. In the intermediate range of Ohm, l(2)/d(2) less than or similar to Ohm less than or similar to 1, the same three regimes are expected but the excluded volume interactions do not play any role in the disclike regime. At the end of the paper we discuss qualitatively the possible liquid crystalline phases (with nematic or smectic symmetry) which can emerge in these solutions at higher concentration.

