Random coil macromolecule

Mucus is a network of linear, flexible, and random-coil macromolecules. 

Although in the discussion presented above we assumed, either explicitly or implicitly, the existence of a parallel relationship between [> ] and for interrupted helices, no definitive answer to the validity of this assumption is as yet known. As is well known (40), the [q] and of randomly coiled macromolecules are fairly accurately related to each other by the Flory-Fox empirical equation... 

The question arises as to whether or how closely Eq. (D-8) is obeyed by non-randomly coiled macromolecules, especially, by polypeptides in the helix-coil transition region. An answer has been given by a recent work by Norisuye (S3), who measured [fj] and for two high-molecular-weight samples of PBLG... 

It can be shown that the < 2> of an interrupted helical polypeptide is expressed by Eq. (C-3) for mean-square dipole moment of a random-coil unit. Precisely, this replacement is permissible if we neglect excluded-volume effects. Nagai (107) has shown theoretically that these effects on < 2> are virtually absent in randomly coiled macromolecules, even when they are appreciable on the molecular dimensions. It is our belief that Nagai s conclusion may apply to interrupted helical polypeptides as well. 

Cottrell,F.R., Merrill,E. W Smith,K. A. Intrinsic viscosity and axial extension ratio of random-coiling macromolecules in a hydrodynamic flow field. J. Polymer Sci. Pt. A-2 8,289-294 (1970). 

The dilute solution properties of polymers discussed so far had to do with randomly coiled macromolecules. In some cases, however, dissolved polymer molecules tend to assume a completely stretched rod-like shape. 

Unified theory of crystallisation processes, 706 Unit of a physical quantity, 53 Unperturbed random-coil macromolecule, 248 Unperturbed state, 246 Unperturbed viscosity coefficient, 791 Unstable flow, 578 Unzippering, 769... 

Fig. 3-11. Schematic representation of randomly coiling macromolecules in solution. In a good solvent (right) the interaction with the polymer is thermodynamically favorable, resulting in expansion whereas in a poor solvent the coil js rather compact (left) (Brown, 1966). 1966. TAPPI. Reprinted from Tappi 49(8), pp. 367-368, with permission.

In solutions of normally encountered randomly coiled macromolecules the formation of spontaneously birefringent phases is not expected. (Phase separation does occur when the interaction between solute molecules is strong.) Here, we have investigated solutions of the polyelectrolyte sodium carboxymethylcellulose in water, which are rubberlike at high concentrations 12). (Materials that form such solutions are commonly called gums.)... 

One must obviously ask which of the three assumptions with which the behavior of the CMC gels could be explained has to be altered. In the first place, the assumption about the elasticity of the network has to be somewhat modified since the individual microcrystals are much stiffer than the individual CMC molecules. The deformation of the former requires elastic energy while in deforming randomly coiled macromolecules the entropy changes. We have been able to show (11) that for a network of stiff rods,... 

In analytical practice, the logarithm of sample molar masses, or molar volumes, is plotted versus retention volumes in calibration dependences of low molecular substances while values or effective hydrodynamic volumes, are used as size parameters in gel chromatography of macromolecules [12,13]. is often called universal calibration parameter because in ideal gel chromatography of randomly coiled macromolecules, it enables the transfer of data from one polymer to another regardless of both the physical (linearity, branching, tacticity, etc.) and the chemical (composition) structure of macromolecules [12]. The hydrodynamic volume of a particular polymer is proportional to the product of its molar mass and limiting viscosity number [ij], in the solvent that is used as mobile phase [ij]Mm. 

The discussion of the chain statistics permits one, thus, to have a more quantitative description of a flexible, linear macromolecule. The random coil of a sufficiently long molecule can be compared in mass-density and randomness to an ideal gas at atmospheric pressure. The elastic compression and expansion of gases are caused by changes in entropy. It will be shown below that corresponding behavior exists for the extension and contraction of random-coil macromolecules (entropy or rubber elasticity, see Sect. 5.6.5). Combining many random coils into a... 

In both schemes, a polymer solution with random coiled macromolecules is represented it is implied that the solvent is capable of dissolving the pol5nner, but no indication is given on whether the solvent is a "good" or "theta" or "poor" solvent for the polymer, in Flory s sense [14]. In other words, the intensity of the polymer-solvent interactions, which play an important role in the subsequent steps of the solution blending process, is not specified. And in most of the papers discussing the structure and the properties of PLSN prepared from solution, the rationale behind the choice of the adopted solvent (or solvents) is not illustrated. 

In the model presented by Hammond, the HS, tied together by a polydiacetylene backbone, are oriented laterally in lameUar-like hard domains oriented in random directions before stress is applied, and possibly forming spherulitic type superstructures. The SS are randomly coiled macromolecules spaced between the hard domains. At low moderate strains, when the material is stretched, stress is transferred to the hard domains. The HS orient perpendicular to the stress direction. Upon removal of the stress, the SS relaxation allows the hard domains to return in a random orientation. This results in a small residual hard domain orientation. Therefore, the two-phase microstructure of the material is not highly interconnected. It consists of discontinuous hard domains dispersed throughout a continuous SS phase [364]. 

A hydrocarbon chain is in a constant thermal motion, and without external force field, the chains fluctuate around the most stable position given by the distribution of possible conformations at the temperature. The action of external forces at the ends of a molecule causes displacements of chains from their equilibrium conformations and evokes retractive forces. For a hydrocarbon chain of M = 14,000, extended length 125.5 nm, and the end-to-end distance r = 1 mn, the maximum exerted force is 10 MPa. The level of forces exerted by the random coil macromolecules are much lower than the theoretical strength of the primary bonds. The presence of strong intermolecular interactions, such as hydrogen bonds in polyamides, affects the retractive force substantially, causing a restriction of the number of possible chain conformations. In addition, the transitions... 

The -dependent amplitudes are dominated by the first term tor the lowest angles at which internal modes are visible. The values ot the relaxation rates have been calculated by Akcasu et al. Observation ot the internal modes of random-coil macromolecules in dilute solution by light scattering is now routine. For example, see Kim et al. ... 

Flory P J (1978) Statistical thermodynamics of mixtures of rodKke particles. 5. Mixtures with random coils, Macromolecules 11 1138-1141. 

Factors able to affect optical activity of a randomly coiled macromolecule in solution when external... 

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