Bulk state of polymers

Together with the reaction kinetics in the bulk state of polymer mixtures, we can conclude that, in general, chemical reaction proceeds inhomogeneously in polymeric media. As a consequence, a strain field associated with chemical reactions is generated in the polymer, and develops by this inhomogeneous kinetics. By using interferometry, the existence and relaxation of this strain field can be clarified, as described in the next section. 

The above discussion points out the difficulty associated with using the linear dimensions of a molecule as a measure of its size It is not the molecule alone that determines its dimensions, but also the shape in which it exists. Linear arrangements of the sort described above exist in polymer crystals, at least for some distance, although not over the full length of the chain. We shall take up the structure of polymer crystals in Chap. 4. In the solution and bulk states, many polymers exist in the coiled form we have also described. Still other structures are important, notably the helix, which we shall discuss in Sec. 1.11. The overall shape assumed by a polymer molecule is greatly affected... 

Finally, we turn from solutions to the bulk state of amorphous polymers, specifically the thermoelastic properties of the rubbery state. The contrasting behavior of rubber, as compared with other solids, such as the temperature decrease upon adiabatic extension, the contraction upon heating under load, and the positive temperature coefficient of stress under constant elongation, had been observed in the nineteenth century by Gough and Joule. The latter was able to interpret these experiments in terms of the second law of thermodynamics, which revealed the connection between the different phenomena observed. One could conclude the primary effect to be a reduction of entropy... 

The intention of this brief survey has been to demonstrate that besides the "classical" aspects of isotropic polymer solutions and the amorphous or partially crystalline state of polymers, a broad variety of anisotropic structures exist, which can be induced by definable primary structures of the macromolecules. Rigid rod-like macromolecules give rise to nematic or smectic organization, while amphiphilic monomer units or amphiphilic and incompatible chain segments cause ordered micellar-like aggregation in solution or bulk. The outstanding features of these systems are determined by their super-molecular structure rather than by the chemistry of the macromolecules. The anisotropic phase structures or ordered incompatible microphases offer new properties and aspects for application. 

If one considers that the surface state of polymer interacts with the surface state of water, not the bulk phase water, in the process of establishing the equilibrium, it is not surprising to find the same transition temperature for four... 

There has been increasing interest in recent years in using incoherent electronic excitation transport as a probe of molecular interactions in solid state polymer systems. The macroscopic properties of such systems arise from the microscopic interaction of the individual polymer chains. The bulk properties of polymer blends are critically dependent on the mixing of blend components on a molecular level. Through the careful adjustment of the composition of blends technological advances in the engineering of polymer materials have been made. In order to understand these systems more fully, it is desirable to investigate the interactions... 

In the bulk state each polymer molecule is surrounded by other polymer molecules of the same type. Expansion of a given chain to relieve long-range intramolecular steric interactions only serves to create an equal number of intermolecular steric interactions with neighboring chains. These opposing volume exclusion effects exactly counteract each other and so in a bulk amorphous polymer the polymer molecules adopt their unperturbed dimensions (i.e., a = 1). 

The limit of accuracy of H-NMR experiments carried out in dilute solution is around 1-5%, depending on the resolution of the spectrum, and of approximately 10% for C NMR. If the polymer to be investigated proved to be insoluble, solid-state NMR techniques are available for further investigation. Solid-state NMR methods are also very useful for determining bulk properties of polymers such as relaxation behavior of local motions and mutual arrangements of chains and chain segments. 

The conformational entropy defined by Eq. 1 is directly related to the flexibility or rigidity of given polymer chains. Thermodynamic properties of the bulk state are known to be largely affected by the flexibility of the polymer chain. The RIS information is fundamentally important in predicting bulk properties of polymers from a given first-order structure. A great deal of effort has been made to elucidate the role of conformational entropy in determining the phase transition behavior of chain molecules. 

C NMR. If the polymer to be investigated proved to be insoluble, solid-state NMR techniques are available for further investigation. Solid-state NMR methods are also very useful for determining bulk properties of polymers such as relaxation... 

Grafting with RIG can be initiated in a wide range of temperatures including subambient temperature, in monomers of various states such as bulk solution, emulsion, vapor, and even at solid state. Thus, RIG has been widely investigated for the preparation of PEMs and ion exchange membranes as bulk modification of polymer films can be achieved (Nasef and Hegazy 2004) unlike plasma-induced and UV-induced grafting, which produces surface modification in polymers (Finsterwalder and Hambitzer 2001). 

A reasonable way to approach the occurrence of inherent surface modifications is through repetition of a caveat already stated in this article Namely, that under equilibrium conditions, the surface and bulk compositions of polymers are never equal. Even in so (chemically) simple a polymer as polyethylene (PE), surface and bulk compositions must differ. This is due to the thermodynamic demand to minimize the surface free energy y. As usual, that value is given by ... 

The shear viscosity in polymer melts and solutions has been investigated for more than a half century. The blending process of polymers is generally performed in the molten state, particularly in shear flow. It is thus necessary to understand the flow (or better rheological) characteristics of polymer melts [66-70]. In both reactive and non-reactive blends, the shear viscosity of each polymer, and thus viscosity ratio, and bulk viscosity of polymer blend system needs to be understood. 

With the advent of small-angle neutron scattering, molecular dimensions can now be determined in the bulk state. A polymer scientist determined the following data on a new deuterated polymer dissolved in a sample of... 

Reaction kinetics was monitored for two cases photodimerization of anthracene in the bulk state of binary polymer mixtures, and photopolymerization of methyl methacrylate (MMA) monomer containing a photoreactive polymer as a minor component in the liquid state. 

A basic approach for the description of polymer chains in the continuum is the Gaussian thread model [26, 31]. Treating interactions among monomers in a mean-field-like fashion, one obtains the self-consistent field theory (SCFT) [11, 32-36] which can also be viewed as an extension of the Hory-Huggins theory to spatially inhomogeneous systems (like polymer interfaces in blends, nucrophase separation in block copolymer systems [11, 13], polymer bmshes [37, 38], etc.). However, with respect to the description of the equation of state of polymer solutions and blends in the bulk, it is stiU on a simple mean-field level, and going beyond mean field to include fluctuations is very difficult [11, 39-42] and outside the scope of this article. 

The majority of chemical reactions involved in reactive blending results from two functional polymers provided that the functional groups are able to react at the extrusion conditions including melt temperature, shear stress, and bulk state of the reacting polymer mixture. 

The L-L binodal curve can be calculated by the chemical potential equivalence of components between the dense phase and the dilute phase after phase separation, on the basis of the mixing free energy from the bulk amorphous state to the solution state of polymers, as given by... 

To the contrary, study of the second moment and various relaxation times of the resonance line as a function of temperature and other parameters often yidLds important data on the polymer such as degree of crystallinity, chain axis orientation, and degree of molecular motion. Indeed, so-called wide-line NMR has been one of the primary methods of characterizing the bulk state of polymeric systems. Nonetheless, it might be assumed that if a high-resolution NMR spectrum of a solid could be obtained, new detail on the nature of the solid state might be uncovered. Recent advances in magnetic resonance have now made possible the partial realization of this... 

Two of the most important functions in the application of neutron scattering are the use of deuterium labelling for the study of molecular confomiation in the bulk state and the use of deuterium solvent in polymer solutions. In the following, we will consider several different applications of die general fomuda to deuteration. 

The term polymer is derived from the Greek words poly and meros, meaning many parts. We noted in the last section that the existence of these parts was acknowledged before the nature of the interaction which held them together was known. Today we realize that ordinary covalent bonds are the intramolecular forces which keep the polymer molecule intact. In addition, the usual type of intermolecular forces—hydrogen bonds, dipole-dipole interactions, and London forces—hold assemblies of these molecules together in the bulk state. The only thing that is remarkable about these molecules is their size, but that feature is remarkable indeed. 

In this chapter we examine the flow behavior of bulk polymers in the liquid state. Such substances are characterized by very high viscosities, a property which is directly traceable to the chain structure of the molecules. All substances are viscous, even low molecular weight gases. The enhancement of this property due to the molecular structure of polymers is one of the most striking features of these materials. 

The subscript 0 on 1 implies 0 conditions, a state of affairs characterized in Chap. 1 by the compensation of chain-excluded volume and solvent effects on coil dimensions. In the present context we are applying this result to bulk polymer with no solvent present. We shall see in Chap. 9, however, that coil dimensions in bulk polymers and in solutions under 0 conditions are the same. 

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