Conformational transitions coil-globule

The two examples of adsorbed side chain substituted macromolecules, i.e., the poly(n-butyl acrylate) brush and the tris(p-undecyloxybenzyloxo) benzoate jacketed polystyrene, demonstrate two rather complementary aspects of the interaction of such molecules with a planar surface. In the first case the two-dimension to three-dimension transition results in a cooperative collapse of an extended coil conformation to a globule. The second case shows a rather high degree ordering with a distinct orientation of the backbone in the substrate plane. Combination of both effects and partial desorption can lead to a repta-tion-hke directed motion as depicted schematically in Fig. 36. 

Macrosyneresis, in which the network polymer is contained only in one phase is not the only possibility for phase equilibria in networks. Under favorable conditions two polymer phases can coexist in a network with a diluent phase (50). The two polymer phases in equilibrium differ in the conformations of the network chains. The transition resembles the condensation of a real gas or, in macromolecules, an intramolecular transition due to long-range net attraction between segments in a poor solvent (coil-globule type transition [139)). 

Jennings, D.E., Kuznetsov, Y.A., Timoshenko, E.G. and Dawson, K.A. (2000) A lattice model Monte Carlo study of coil-globule and other conformational transitions of polymer, amphiphile, and solvent. J. Chem. Phys., 112, 7711-7722. 

Kiriy A, Gorodyska G, Minko S, Jaeger W, Stepanek P, Stamm M (2002) Cascade of Coil-Globule Conformational Transitions of Single Flexible Polyelectrolyte Molecules in Poor Solvent. J Am Chem Soc 124(45) 13454... 

The above analysis implies that the coil-globule transition is essentially a gas-liquid transition within a single chain. Unlike usual molecular gases, the translational entropy is absent due to the chain connectivity, and instead, the conformational entropy shows up. The collapsed state is a spherical droplet, that is, globule, to minimize the surface area, the size of which is self-adjusted to satisfy the mechanical balance between the inside and the outside of the globule. 

The study of conformational transition (i.e., coil-globule transition) of macromolecules is one of the central problems in polymer science [1-4],... 

In addition, the fluorescence microscopy experiments confirm that the coil-globule transition of the DNA molecule in most cases is the first-order phase transition [34-36]. Fluorescence microscopy allows us to monitor the conformational state for single molecule. Thus it is possible to construct the distribution of the ensemble of DNA molecules over the size. It was found that the distribution of DNA macromolecules over the size in the vicinity of the coil-globule transition point has two maxima corresponding to the two coexisting states, the coil and the globule [36], This fact directly indicates that the conformational coil-globule transition is the first-order phase transition [1-3,36],... 

The conformations of polymers in worse than 6-solvents the coil-globule transition... 

PEAA in solution, in general, experiences a coil-to-globule transition at a pH of 6.2 (107). The conformational transition of PEAA in the presence of dipalmitoylphosphatidylcholine (DPPC) vesicles shifted to 6.5 (107). Chen and colleagues... 

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