Polymeric general description

This chapter will describe how we can apply an understanding of thermodynamic behavior to the processes associated with polymers. We will begin with a general description of the field, the laws of thermodynamics, the role of intermolecular forces, and the thermodynamics of polymerization reactions. We will then explore how statistical thermodynamics can be used to describe the molecules that make up polymers. Finally, we will learn the basics of heat transfer phenomena, which will allow us to understand the rate of heat movement during processing. 

In summary, the meaning of the different forms of energy, the three laws of thermodynamics and the relationship between equilibrium and free energy are the framework for modern thermodynamics. In the next section we will apply these ideas to a general description of polymerization. 

Statistical methods are most widespread. Macromolecules with and without ring formation can be described by methods of combinatorial algebra [8]. Processes of polymerization (and simplest cases of destruction) are assumed to be random, that allows the derivation of the formulas for the number of JT-mers and the calculation of the weight fractions, the distribution functions, and the averaged molecular weight [8]. However, the problem of the general description of destruction is not still solved. 

The structures of the element trihalides EX3 are covered in a number of textbooks on structural inorganic chemistry (4, 5), and these will not be discussed in great detail here. It is, however, worth mentioning some of the salient structural features. In most cases, a molecular trigonal pyramidal EX3 unit consistent with VSEPR theory predictions is readily apparent in the solid-state structure, although there are usually a number of fairly short intermolecular contacts or secondary bonds present. A general description of the structures as molecularly covalent but as having a tendency toward macromolecular or polymeric networks is therefore reasonable. Only in the case of the fluorides is an ionic model appropriate. 

Equation (26) is the ideal copolymer composition equation suggested [203] early in the development of copolymerization theory but which had to be abandoned in favour of eqn. (23) as a general description of radical copolymerization. Only in this particular case are the rates of incorporation of each monomer proportional to their homopolymerization rates. It was shown that the reactivity of a series of monomers in stannic chloride initiated copolymerization followed the same order as their homopolymerization rates [202] and so eqn. (26) could be at least qualitatively correct for carbonium-ion polymerizations and possibly for reactions carried by carbanions. This, in fact, does not seem to be correct for anionic polymerizations since the reactivities of the ion-paired species at least, differ greatly. The methylmethacrylate ion-pair will, for instance, not add to styrene monomer, whereas the polystyryl ion-pair adds rapidly to methylmethacrylate [204]. This is a general phenomenon no reaction will occur if the ion-pair is on a monomer unit which has an appreciably higher electron affinity than that of the reacting monomer. The additions are thus extremely selective, more so than in radical copolymerization. There is no evidence that eqn. (26) holds and the approximate agreement with eqn. (25) results from other causes indicated below. 

Zieglei Natta catalysts. The metal oxide catalysts are, in fact, of a similar character to the Zieglei Natta types and a more generally descriptive term which covers all of these is coordination catalysts. This derives from the view that an essential step in the polymerization is coordination of the olefin with the transition metal. 

In 1963 Gee [133] published a modified version of his polymerization theory which in principle allows for the incorporation of small rings other than Ss. The general description of a ring addition reaction (Eq. 21) is given by Eq. (22) if no solvent is present ... 

Investigations of water-in-oil polymerizations employing new monomers or emulsifiers for which kinetic or colloidal characterization is incomplete, require careful nomenclature designation. Under such circumstances a general description such as Water-in-Oil Polymerization or Heterophase Polymerization is recommended until the physical and chemical nature of the polymerizations can be identified. The designations inverse-suspension, inverse-emulsion and inverse-microemulsion should be reserved for processes for which a relatively advanced level of understanding exists. 

Figure 22.2 General description of the uniaxial load/deformation behavior for (a) flexible plastics and (b) elastomers. Source Adapted with permission of John Wiley Sons, Inc., from Odian G. Principles of Polymerization. 4th ed. New York Wiley-Interscience 2004 [1].

Later, some other models were proposed based on ion [24 or dectron [25] bombardment. Poll et al. [26] also discussed the role of ion bombardment and pointed to a competition between etching and deposition proces%s in plasma polymerization. A more general description was given by Yasuda [3] (Fig. 8). 

As it is known through Ref. [157], within the framework of fractal analysis the polymerization kinetics is described by the general Eq. (79). The combination of the relationships (79) and (125) allows to obtain radical polymerization kinetics description within the framework of synergetics [166] ... 

Kozlov, G. V. Zaikov, G. E. The generalized description of local order in polymers. In book Fractals and Local Order in Polymeric Materials. Ed. Kozlov, G. Zaikov, G. New York, Nova Science Pubhshers, Inc. 2001, 55-63. 

General Description Polyethylenes consist of a family of thermoplastic resins obtained by polymerizing the gas ethylene [C2H4]. High molecular weight polymers (i.e., over 6,000) are the materials used in the plastics industry. Copolymers of ethylene with vinyl acetate, ethyl acrylate, and acrylic acid are commercially important,... 

General Description Polyvinyl Chloride (PVC) is produced by the polymerization of the gas vinyl chloride. It is one of the world s most widely used plastics. Polyvinyl Chloride by itself is hard, brittle, and difficult to process. With the addition of plasticizers and other additives the compound becomes flexible and much more versatile. The wide application of PVC results from the material s versatility since it can be used as a rigid compound or blended with plasticizers to produce flexible grades. 

In Fig. 46, the dependences S n (SF) in double logarithmic coordinates are shown for DMDAACh, synthesized at different c . As it follows from the data of this figure, all four MWD curves, shown in Fig. 45, are described by a sole generalized curve. This is the most important result, confirming an irreversible aggregation models using correctness for polymerization process description. 

Hence, the stated above results have shown the correctness of the description of MWD curves for polymers on the example of DMD/VACh within the frameworks of the dynamical distribution function of an irreversible aggregation cluster-cluster model. The obtaining of the generalized distribution curve (Fig. 46) confirms the possibility of polymerization process description within the frameworks of the indicated models and allows to predict MWD change kinetics as a function of the initial monomers concentration c and reaction duration t. 

The pol) merization details are given for a small scale laboratory polymerization and a larger pilot scale polymerization of PCL homopolymer. A general description for laboratory copolymerization th lactide or glycolide is also given. 

Reactions between alkynes and transition metal compounds yield a surprising variety of products (76, 77), indicating nonspecific mechanisms of formation. At least for the reaction of alkynes with metal carbonyls any simple polar mechanism must be excluded, in view of the insensitivity of the reactions to the degree of polarity of the solvents. A radical mechanism would perhaps be better suited for a general description but this has so far been rejected, since inhibition of the reactions with f-butylphenol or hydroquinone proved unsuccessful (78). Likewise, iron carbonyls react with diphenylacetylene, using ethyl acrylate, vinyl methyl ketone or vinyl acetate as the solvent, without polymerization of the vinyl compounds (79). These experiments, however, do not fully eliminate the possibility of a radical mechanism. 

Yech, G. S. (1979). The General Notions on Amorphous Polymers Structure. Local Order and Chain Conformation Degrees. N sokomolek.SoedA, 21 (Nil), 2433-2446. Perepechko, 1.1. (1978). Introduction in Physics of Polymers. Moscow, Khimiya, 312p. Kozlov, G. V, Zaikov, G. E. (2001). The Generalized Description of Local Order in Polymers. In Fractals and Local Order in Polymeric Materials. Kozlov, G. V., Zaikov, G. E., Ed., New York, Nova Science Pubhshers Inc. 55-63. 

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