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Using the Gaussian Ansatz for the monomer-monomer correlation functions we derive a set of the self-consistent equations for determination of the conformational state in the bead-and-spring copolymer model. The latter is based on the Edwards type effective free energy functional with arbitrary two-body interaction matrix. The rate of conformational changes in kinetics may be expressed via the instantaneous gradients of the variational free energy functional in the space of the averaged dynamical variables. We study the equilibrium and kinetics for some periodic and random aperiodic amphiphilic sequences in infinitely diluted solution. Typical equilibrium phase diagrams are elucidated and the conformational structure of different states is discussed. The kinetics of compaction of an amphiphilic copolymer to the globular state proceeds through formation of locally frustrated non-equilibrium structures. This leads to a rather complicated multistep kinetic process. We observe that even a small modification in the primary sequence of a copolymer may significantly change its kinetic folding properties., Comment: 16 pages, 25 PS figures

In recent experiments involving PNIPAM copolymers it has been observed that stable spherical nanoparticles are being formed by association of several chains in poor aqueous solution instead of aggregation. This type of mesoscopic structures called mesoglobules has an extremely monodispersed size distribution. Previously we have studied theoretically formation of clusters consisting of several chains in dilute solutions of amphiphilic heteropolymers. We have seen that the mesoglobules often possess an essentially micellar structure. In the current work we argue that formation of mesoglobules is strongly sequence and concentration dependent. In particular, by means of lattice Monte Carlo simulation we consider structures formed by a number of tri-block sequences and their certain mutations. For sequences consisting of two hydrophilic ends with a hydrophobic middle the size distribution of the resulting particles is rather narrow, i.e. mesoglobules are being formed. However, in the case of sequences with two hydrophobic ends and a hydrophilic middle a new type of structures seems to be prevalent. These consist of small mesoglobules interconnected by hydrophilic bridges. Clearly, on increasing the concentration these networked structures would play an important role resulting in a rapid onset of a gel-like behaviour., Comment: RevTeX, 4 pages, 7 PS figures. Accepted for publication in Colloids and Surfaces A

By means of continuous space Monte Carlo simulation we study conformational structures formed by star and comb heteropolymers during kinetics of folding from the coil to the globule, as well as the corresponding equilibrium states on going from the good to the poor solution. Particular examples of combs with hydrophobic backbone and hydrophilic side-groups (and vice versa), as well as stars with flexible and semi-stiff arms are studied. It is interesting to note that star-like conformations naturally appear for a comb polymer with a strongly hydrophobic backbone. We emphasise the crucial difference in the spatial distribution of hydrophobic and hydrophilic monomers within the globular states for the above mentioned two types of combs. In case of stars, the non-equilibrium states during kinetics of the coil-to-globule transition correspond to formation of localised pearls within flexible arms, whereas semi-stiff arms prefer to join with each other remaining essentially extended. These studies present natural extension of our previous works on the equilibrium and kinetic properties of linear and ring heteropolymers based on the Gaussian self-consistent method and lattice Monte Carlo technique. However, in studying polymers with more nontrivial topology continuous space simulation has some essential advantages., Comment: RevTeX, 5 pages, 10 PS figures. Accepted for publication in Colloids and Surfaces A

We study conformations assumed by single diblock star copolymers in a poor solvent by means of the Gaussian variational theory and Monte Carlo simulation in continuous space. Cases of stars with internal and external hydrophobic blocks are analysed. While in the former case the collapsed state has an obvious micellar shape, the latter case exhibits two nontrivial conformational structures. Apart from the equilibrium state of a globular hydrophobic core with hydrophilic daisy loops, one also finds here a metastable state of outstretched hydrophilic blocks with hydrophobic subglobules at their ends. Such a state appears to be rather long-lived during the kinetics of collapse of a swollen star. The plots of monomer densities and other observables computed by both techniques are found to be in good agreement with each other., Comment: RevTeX, 13 pages, 20 PS figures. Accepted for publication in Macromol. Theory Simul