Interchain interactions, intermolecular

The absorption spectra of every molecular wire 470-474 in thin films were nearly identical to those in solution, which implied that the interchain interaction and/or intermolecular aggregation in the ground states might be suppressed in films possibly owing to truxene moieties with hexyl substituents. Their absorption spectra in films show an identical peak at about 309 nm owing to the n n electron absorption band of the truxene units. The absorption Xmax peaked at 400 nm for 470, 410 nm for 471, 415 nm for 472, 418 nm for 473, and 424 nm for 474, respectively. 

The Ksv values for these ions are similar to those for Cu2+ and it may be anticipated that binding to the polymer by all three ions occurs with comparable strength due to reasonably similar Coulombic interactions between the divalent ions and the polymer. Since the polymer fluorescence is known to be strongly attenuated when interchain or intermolecular interactions occur, it may be that all or part of the quenching observed for these ions may be attributed to aggregation effects induced by association of the divalent cations with the polymer. 

The cohesive energy Ecoij of a material is the increase in the internal energy per mole of the material if all of its intermolecular forces are eliminated [1,2]. The cohesive energy density ecoh> which is defined by Equation 5.1, is the energy required to break all intermolecular physical links in a unit volume of the material. In polymers, these physical links mainly consist of interchain interactions of various types, which will be discussed below. 

The Ecob of a polymer depends mainly on localized intermolecular (interchain) interactions similar to the intermolecular interactions determining the Tb of a simple liquid. Ecoh can thus also be expected to correlate fairly well with zeroth-order and first-order connectivity indices. 

Recall that melt index, by definition, is amount of polymer flowing through a given orifice under some specified conditions. Introduction of the polar acrylic acid unit into the polymer structure increases its polarity while at the same time disrupting the interchain bonding and crystalline nature of PE. Initially, the disruption of the interchain interaction of PE predominates. Consequently, flow is enhanced and melt index increases. Further increase in acrylic acid content results in the predominance of chain polarity and hence intermolecular attraction. This leads to a decrease in the flow properties. 

The calculations have included a more complete range of interatomic interchain interactions,and finally intermolecular forces have been taken into account as well. These are referred to in Table 2 as the 4 constant and 8 constant Urey-Bradley force field calculations. Generally speaking, the 4 constant calculations give good agreement with the X-ray method of measurement, which in fact gives a static modulus. The exception to this is the case of polyethylene, where the picture is further confused by the Raman and neutron data. 

Static 2D NOE spectroscopy was appUed in a first experiment showing that the technique can be used to measiu-e interchain interactions (107). This work was then continued by applying the technique imder MAS to investigate the intermolecular interactions responsible for the miscibibty in polybuta-diene/polyisoprene blends above the glass-transition temperature (108). It could be shown that intermoleciJar association can be probed by this technique and the results reveal the existence of weak intermoleciJar interactions between the polyisoprene methyl group and the vinyl side chain of the polybutadiene. 

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