Interaction intrachain

For large interchain separations (8 A < R < 30 A), the LCAO coefficients of a given molecular orbital are localized on a single chain, as intuitively expected. The lowest excited state of these dimers results from a destructive interaction of the two intrachain transition dipole moments, whereas a constructive interaction prevails for the second excited stale. This result is fully consistent with the molcc-... 

Later we will describe both oxidation and reduction processes that are in agreement with the electrochemically stimulated conformational relaxation (ESCR) model presented at the end of the chapter. In a neutral state, most of the conducting polymers are an amorphous cross-linked network (Fig. 3). The linear chains between cross-linking points have strong van der Waals intrachain and interchain interactions, giving a compact solid [Fig. 14(a)]. By oxidation of the neutral chains, electrons are extracted from the chains. At the polymer/solution interface, positive radical cations (polarons) accumulate along the polymeric chains. The same density of counter-ions accumulates on the solution side. 

Fig. 18.—Antiparallel packing arrangement of 2-fold poly(ManA) (15) helices, (a) Stereo view of two unit cells roughly normal to the hoplane. The helix at the center (filled bonds) is antiparallel to the two in the back (open bonds). Intrachain hydrogen bonds stabilize each helix. Association of helices through direct hydrogen bonds involve the carboxylate groups for parallel chains, but involve the axial hydroxyl groups for antiparallel chains, (b) A view of the unit-cell contents down the t-axis highlights the interactions between the helices.

FlC. 20.—Parallel packing arrangement of 6-fold, curdlan I (17) helices, (a) Stereo view of two unit cells approximately normal to the 6c-plane. The helix is stabilized by intrachain 4-0H---0-5 hydrogen bonds. There are only van der Waals interactions between the helices. 

Note that when the concentration of added salt is very low, Debye length needs to be modified by including the charge contribution of the dissociating counterions from the polyelectrolytes. Because the equilibrium interaction is used, their theory predicts that the intrinsic viscosity is independent of ion species at constant ionic strength. At very high ionic strength, the intrachain electrostatic interaction is nearly screened out, and the chains behave as neutral polymers. Aside from the tertiary effect, the intrinsic viscosity will indeed be affected by the ionic cloud distortion and thus cannot be accurately predicted by their theory. 

The transition of the compressibility, and other properties of the polyelectrolyte brnshes, is most likely accounted for in terms of the transition in the binding mode of the connterion to the polyelectrolytes, from the loosely bonnd state to the tightly bound one, which rednces inter- and intrachain repulsive interactions. The following snpports this ac-connt (1) At the critical density, = 0.20 chain/nm, the separation distance between polyelectrolyte chains, d, is 2.4 nm. This distance is close to the snm, 2.6 nm, of the chain diameter, 1.3 nm, and the size of two hydrated connterions, 1.32 nm, indicating that the abrupt... 

Lee et al. [60] investigated the adhesion of a single pair of DNA strands. They identified two types of forces interchain forces associated with Watson-Crick base pairing between complementary strands, and intrachain forces associated with the elasticity of single strands. For studying interchain interactions, complementary oligomers (ACTG)s and... 

We will describe a systematic approach to renormalize the intrachain interactions towards a coarser level for three different modifications of polycarbonates. The advantage of examinig three modifications of the same polymer gives a first hint of the sensitivity of the method. The three modifications of the polycarbonate are BPA-PC, BPZ-PC, and TMC-PC. The structures are given in Fig. 6.1. Although the backbone sequence is the same they have re-... 

The hydrodynamic interaction is introduced in the Zimm model as a pure intrachain effect. The molecular treatment of its screening owing to presence of other chains requires the solution of a complicated many-body problem [11, 160-164], In some cases, this problem can be overcome by a phenomenological approach [40,117], based on the Zimm model and on the additional assumption that the average hydrodynamic interaction in semi-dilute solutions is still of the same form as in the dilute case. 

With a few exceptions, the crystal structure of the salts based on the type I mixed chains consists of parallel arrangements of those chains. In most cases the magnetic behavior of these salts is dominated by ferromagnetic (FM) interactions, due to intrachain D+ A coupling. Several of these salts exhibit metamagnetic (MM) behaviors due to the coexistence of weaker antiferromagnetic (AF) intrachain interactions. 

The magnetic behavior of [Fe(Cp )2][Ni(edt)2] is consistent with the coexistence of FM intrachain interactions, due to D+A intrachain short contacts, with AF interchain interactions, resulting from the D+A- and A A interchain contacts, as predicted by the McConnell I mechanism [44], In this case the interchain interactions must be particularly large as they seem to be the dominant interactions at high temperatures. The value of the critical field, 14 kG, much higher than any of the... 

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