Conformation of macromolecules

Bovcy, F.A. Chain Structure ami Conformation of Macromolecules, Wiley New York, 1982. 

The properties such as b.p., m.p., v.p., etc., are dependent on the size and shape of macromolecules and also on the interaction between individual segments of molecules. They are also found to depend on conformations of macromolecules and thus on the structure of molecules. 

Computational chemists have developed several remarkably powerful and reliable computer codes, capable of describing the relative stability of various conformations of macromolecules, and details of the electronic structure of molecules of more modest size ( 1). The properties of molecules which can be obtained by use of these programs correlate with important features of chemical reactivity and the properties of materials. Molecular design, in pharmaceuticals, photochemistry, and general materials science can be made much more efficient by the routine use of these computational systems. However, their use is at present not widespread it is limited to a few large chemical companies. 

Bovey, F. A. Chain Stmcture and Conformation of Macromolecules Academic New York, 1982. 

See for example (a) J. C. Randall, Polymer Sequence Determination C NMR Method, Academic Press, New York 1977, (b) E. A. Bovey, Chain Structure and Conformation of Macromolecules, Academic Press New York, 1982 (c) A. E. Tonelli, NMR Spectroscopy and Polymer Microstructure ... 

F. A. Bovey, Chain Structures and Conformations of Macromolecules, Academic Press, New York, 1982. 

Birshtein,T.M., Ptitsyn.O.B. Conformations of macromolecules, Chapter 10. New York Wiley-Interscience 1966. 

Birshtein, T. M., Ptitsyn, O. B. Conformations of Macromolecules (in Russian) Moscow Nauka 1964... 

First of all we shall examine the preparation and properties of optically active polymers subsequently we shall briefly discuss the contribution given by the research on optically active polymers to the investigation on the stereospedfic polymerization and on the conformation of macromolecules in solution. 

Hesselink51 assumed that the conformation of macromolecules adsorbed on the interface consists of one train and two tails. The number of tails with i segments, n(i), is calculated from the partition function for the tail-train conformation, and the normalized segment density distribution p7(z) in tails is derived by methods analogous to those used in Hesselink s derivation of the segment density distribution in loops. The result is... 

Conformational factors play a role with large macromolecules. Changes in the conformation of macromolecules may affect the local environment and, thus, the retention energy of specific coordinating groups. Retention of metals at the surface or inside particles may be influenced by similar effects. 

Glassy materials can be deformed without fracture up to hundreds of percents. Under this so-called forced deformation, the conformations of macromolecules change but the structure of the dense network does not change. After the stresses have been removed, the sample is still in a deformed state, which is a metastable equilibrium state. The macromolecules in such a sample are frozen in a deformed state, so that on heating, when the crosslink number density decreases, forces are exerted and the sample can return to its initial form (Laius and Kuvshinskii 1963 Shishkin et al. 1963). 

The relaxation equation for conformation of macromolecule follows directly from the relation (7.23) of the previous section... 

One can see that the velocity gradients directly affect the mean orientation of segments, while the effect of the disturbed conformation of macromolecules (the end-to-end distance) can be neglected here in comparison with the latter. 

One can see that, in this approximation, disturbed conformation of macromolecules does not affect the mean orientation of segments in the steady state, that can be found from equation (10.15) as... 

Bird RB, Curtiss CF, Armstrong RC, Hassager O (1987b) Dynamics of polymeric liquids, vol 2 Kinetic theory, 2nd edn. Wiley, New York Birshtein TM, Ptitsyn OB (1966) Conformations of macromolecules. Interscience, New York... 

Bovey, F. A. and Kwei, T. K., Microstructure and Chain Conformation of Macromolecules , in Macromolecules - an Introduction to Polymer Science, Academic Press, New York, 1979, pp. 207-271. 

Chemically modified silica fillers with grafted methyl groups or methyl and silicon hydride groups, influenced the micro- and macrostructures of various copolymers. Changes in cross-linking, orderliness, crystallinity, microtacticity and conformation of macromolecules have been detected in the presence of fillers. Surface functionality of the silica filler determines the disposition of macromolecular chains at the interface. 

In the case of PDADMAC the dependence of f potential on the pressure was observed at the whole concentration range investigated (Fig. 7). Even at low PE concentration the conformation of macromolecules differs from the flat one. It can be a consequence of the high molecular weight of PDADMAC. 

The polymers were fractioned into 8-14 components by coacervate extraction from the benzene - methanol system. For fractions and nonfractioned polymers, characteristic viscosities [t ], were me-asured. Because that was the first example of studying conformations of macromolecules of this ty-pe in diluted solutions, authors of the work [56] paid much attention to selection of an equation, which would adequately describe hydrodynamic behavior of polymeric chains. Figure 10 shows de-pendencies of [q] on molecular mass (MM), represented in double logarithmic coordinates. Parame-ters of the Mark-Kuhn-Hauvink equation for toluene medium at 25°C were determined from the slo-pe and disposition of the straight lines. 

Small differences in Mco values, measured in polarized and non-polarized light, as well as low scat-tering asymmetry values close for different fractions testify about low polydispersity of the fractions and coil like conformation of macromolecules, which is of... 

N. Go and H. A. Scheraga,/. Chem. Phys., 51,4751 (1969). Analysis of the Contribution of Internal Vibrations to the Statistical Weights of Equilibrium Conformations of Macromolecules. 

Since the strength of an article made of discrete polymer molecules depends on the sum of intermolecular attractions, it is obvious that any process that increases the extent to which such macromoiccules overlap with each other will result in a stronger product. If the article is oriented, polymer molecules tend to become stretched out and mutually aligned. The number of intermolecular contacts is increased at the expense of intramolecular contacts of segments buried in the normal ball-like conformation of macromolecules. The article will be much stronger in the orienlalion direction. Examples are given below in Section 1.8. 

Considerations of minimum overlap of radii of nonbonded substituents on the polymer chain are useful in understanding the preferred conformations of macromolecules in crystallites. The simplest example for our purposes is the polyethylene (1-3) chain in which the energy barriers to rotation can be expected to be similar to those in /i-butane. Figure 4-2 shows sawhorse projections of the conformational isomers of two adjacent carbon atoms in the polyethylene chain and the corresponding rotational energy barriers (not to scale). The angle of rotation is that between the polymer chain substitutents and is taken here to be zero when the two chain segments are as far as possible from each other. 

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