Polymer backbone bond energy

It is interesting to note that methane, ethane, and ethylene are all gases hexane, octane, and nonane are all liquids (at room conditions) while low molecular weight PE is a waxy solid. This trend is primarily due to an increase in the mass per molecule and to an increase in the London forces per polymer chain. The London force interaction between methylene units is about 8 kcal/mol. Thus, for methane molecules the attractive forces are 8 kJ/mol for octane it is 64 kJ/mol and for PE with 1000 ethylene (or 2000 methylenes) it is 2000 methylene units X 8 kJ/mol per methylene unit = 16,000 kJ/mol, which is well sufficient to make PE a solid and to break backbone bonds before it boils. (Polymers do not boil because the energy necessary to make a chain volatile is greater than the primary backbone bond energy.)... 

In a real polymer chain, rotation around backbone bonds is likely to be hindered by a potential energy barrier of height AEr. If AEr < RT, the population of the... 

Physical properties of polymers, including solubility, are related to the strength of covalent bonds, stiffness of the segments in the polymer backbone, amount of crystallinity or amorphousness, and intermolecular forces between the polymer chains. The strength of the intermolecular forces is directly related to the CED, which is the molar energy of vaporization per unit volume. Since intermolecular attractions of solvent and solute must be overcome when a solute (here the polymer) dissolves, CED values may be used to predict solubility. 

In a typical analysis of a polymer chain, the experimental values of configuration-dependent properties and their temperature coefficients are compared with the results of rotational isomeric state calculations. These comparisons yield values of the energies for the various rotational states about the backbone bonds, and these conformational preferences can then be used to predict other configuration-dependent properties of the chains. It is also possible to obtain such conformational information from potential energy calculations, using the methods of molecular mechanics.39,46 52... 

A close connection exists between the presence of a flexible polymer skeleton and the flexibility of the bulk material. Macromolecular flexibility is often defined in terms of the glass-transition temperature, Tg. Below this temperature, the polymer is a glass, and the backbone bonds have insufficient thermal energy to undergo significant torsional motions. As the temperature is raised above the Y g, an onset of torsional motion occurs, such that individual molecules can now twist and yield to stress and strain. In this state the polymer is a quasi-liquid (an elastomer) unless the bulk material is stiffened by microcrystalfite formation. Thus, a polymer with a high Tt is believed to have a backbone that offers more resistance to bond torsion than a polymer with a low 7 g. 

With higher energy excitation, M-CO bond dissociation occurs (e.g., eq. 19). This type of reactivity does not necessarily lead to polymer backbone degradation. 

For the polymer backbone, this coefficient is exclusively associated with the structure of macromolecules and potentials of internal rotation around internal bonds of the backbone. This dependence gives information about energy of the chain conformation and mutual transitions. 

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