Microphase Separation within a Comb Copolymer with Attractive Side Chains: A Computer Simulation Study

Computer simulation modelling of a flexible comb copolymer with attractive interactions between the monomer units of the side chains is performed. The conditions for the coil-globule transition, induced by the increase of attractive interaction, ε, between side chain monomer units, are analysed for different values of the number of monomer units in the backbone, N, in the side chains, n, and between successive grafting points, m. It is shown that the coil-globule transition of such a copolymer corresponds to a first-order phase transition. The energy of attraction (ε) required for the realisation of the coil-globule transition decreases with increasing n and decreasing m. The coil-globule transition is accompanied by significant aggregation of side chain units. The resulting globule has a complex structure. In the case of a relatively short backbone (small value of N), the globule consists of a spherical core formed by side chains and an enveloping shell formed by the monomer units of the backbone. In the case of long copolymers (large value of N), the side chains form several spherical micelles while the backbone is wrapped on the surfaces of these micelles and between them.

Primary Sequences of Protein-Like Copolymers: Levy Flight Type Long Range Correlations

We consider the statistical properties of primary sequences of two-letter HP copolymers (H for hydrophobic and P for polar) designed to have water soluble globular conformations with H monomers shielded from water inside the shell of P monomers. We show, both by computer simulations and by exact analytical calculation, that for large globules and flexible polymers such sequences exhibit long-range correlations which can be described by Levy-flight statistics.Comment: 4 pages, including 2 figures; several references added, some formulations improve

Probing Polyelectrolyte Elasticity Using Radial Distribution Function

We study the effect of electrostatic interactions on the distribution function of the end-to-end distance of a single polyelectrolyte chain in the rodlike limit. The extent to which the radial distribution function of a polyelectrolyte is reproduced by that of a wormlike chain with an adjusted persistence length is investigated. Strong evidence is found for a universal scaling formula connecting the effective persistence length of a polyelectrolyte with its linear charge density and the Debye screening of its self-interaction. An alternative definition of the electrostatic persistence length is proposed based on matching of the maximum of the distribution with that of an effective wormlike chain, as opposed to the traditional matching of the first or the second moments of the distributions. It is shown that this definition provides a more accurate probe of the affinity of the distribution to that of the wormlike chains, as compared to the traditional definition. It is also found that the length of a polyelectrolyte segment can act as a crucial parameter in determining its elastic properties.Comment: 15 pages, 19 figure

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

On the θ-behaviour of a polymer chain

By means of a cluster expansion method it is shown that the presence of higher-order collisions in a polymeric coil leads to : a) the renormalization of the second virial coefficient of monomer interaction; b) the existence of specific corrections due to chain finiteness which are the main corrections near the θ-point. These corrections lead to the existence of a finite θ-region for finite chains. The θ-behaviour of inhomogeneous polymers (polymers with defects, branched polymers) is also discussed.L'application d'une méthode de développement en amas à l'étude d'une pelote polymérique montre que la présence des collisions d'ordre élevé entraîne : a) une renormalisation du coefficient du second viriel de l'interaction des monomères; b) l'existence de corrections spéciales liées au fait que la chaîne est finie. Ces corrections sont près du point 0, elles entraînent l'existence d'une région 0 finie pour des chaines finies. Le comportement 0 de polymères hétérogènes (polymères avec défauts, polymères ramifiés) est aussi considéré

Topologically Driven Compatibility Enhancement in the Mixtures of Rings and Linear Chains

The thermodynamics of the bicomponent melts of linear chains A and unknotted unentangled closed chains B (trivial rings) is considered within the framework of the usual Flory approach. It is shown that such melts exhibit a compatibility enhancement in comparison with the corresponding melts of linear chains. The reason for such effect is due to the topological entropy gain of mixing of A- and B-chains: if B-chains are unentangled since the A-chains play the role of a “diluent” softening the topological restrictions imposed on the B-chains. This result is in agreement with recent experimental findings of McKnight et al

Statistics of copolymer sequences obtained by polymeranalogous reactions of homopolymer globules

For the first time the macrokinetics of polymeranalogous reaction in a homopolymer globule is considered theoretically. Using mathematical apparatus of the theory of markovian stochastic processes we examined the statistical characteristics of the chemical structure of the emerging copolymers. It is shown that when the reaction is kinetically-controlled the sequence distribution of monomeric units in copolymer chains follows Bernoullian statistics. In the opposite regime, when the reaction is diffusion-controlled it is proved that the resulting primary structure is described by the Levy flight distribution. Such copolymers with nonmarkovian character of the alteration of units in macromolecules can not be synthesized in the bulk or in concentrated solutions by means of standard synthetic polymerization procedures

Interaction of Colloidal Particles with Macromolecules: The RISM Integral Equation Theory

A microscopic theory of the mixtures of polymer chains and colloidal particles immersed in a common solvent is developed on the basis of the RISM integral equation technique. The obtained general equations enable the calculation of the correlation functions and thermodynamic characteristics of the system at an arbitrary ratio of the components. The theory is used for a comprehensive study of interaction of small spherical particles with flexible polymer chains in the regimes of weak and strong adsorption of the macromolecules on the surface of the particles. The temperature and concentration regions characterized by different effect of the polymer on stability of the colloidal dispersion are determined. The corresponding temperature–concentration diagrams of state are constructed