Polycondensation and polyaddition

Block copolymers containing polysiloxane segments are of great interest as polymeric surfactants and elastomers. Polycondensation and polyaddition reactions of functionally ended prepolymers are usually employed to prepare well-defined block copolymers. The living polystyrene anion reacts with a,co-dichloropoly(dimethyl-siloxane) to form multiblock copolymers398. ... 

Note 1 Reactive end-groups in telechelic polymers come from initiator or termination or chain transfer agents in chain polymerizations, but not from monomer(s) as in polycondensations and polyadditions. 

Each reaction step causes the disappearance of two reactive sites, A and B, converted into a linking unit C, and leaves two reactive sites at the ends of any growing molecule irrespective of its size. The difference between polycondensation and polyaddition is only the formation of by-products during each reaction step. 

In addition to the repeat unit sequence, another area of current interest in polymer structural control (Fig. 1) may be the spatial or three-dimensional shapes of macromolecules. In fact, the recent development of star [181-184] and graft [185] polymers, as well as starburst dendrimers [126], arborols [186,187], and related multibranched or multiarmed polymers of unique and controlled topology, has been eliciting active interest among polymer scientists. In this section, let us consider the following macromolecules of unique topology for which living cationic polymerizations offers convenient synthetic methods that differ from the stepwise syntheses (polycondensation and polyaddition) [126,186,187]. 

The monomer feed is converted into Polyamide-6 by polycondensation and polyaddition reactions [930]. This reaction step can be realized by a complex reactor which can be modeled as a sequence of stirred tank and plug-flow reactors. An exemplary model flowsheet comprising two reactors (CSTR) with an intermediate water separation (Split) is shown in Fig. 5.20. Such a model of the reaction section can be analyzed by means of Polymers Plus, an extension of Aspen Plus for handling polymer materials [513]. 

The kinetics of polycondensation and polyaddition reactions follow the same general scheme, but both differ sharply from the kinetics of addition or chain polymerization. 

Until recently it has been customary to classify synthetic polyreactions as polymerb.ations, polycondensations and polyadditions [1]. According to the lUPAC nomenclature [2] the term polymerization is superior to the concepts of addition polymerization and condensation polymerization. Both these subordinate terms are very broadly defined and so far the classification of reactions bearing the features of polymerization and polycondensation is rather arbitrary. Only addition polymerizations are treated in this book. Processes of the polycondensation type are not described. 

The aspects relevant to the use of rosin as such, or one of the derivatives arising from its appropriate chemical modification as monomer or comonomer [12-14], have to do with the synthesis of a variety of materials based on polycondensations and polyaddition reactions of structures bearing such moieties as primary amines, maleimides, epoxies, alkenyls and, of course, carboxylic acids. These polymers find applications in paper sizing, adhesion and tack, emulsification, coatings, drug delivery and printing inks. 

Finally, reactive (polymerizable) moieties can be introduced that can be polymerized after deposition. For this purpose soluble precursors, low-molecular weight as well as polymeric ones, with one (polymerization reactions) or two (polycondensation and polyaddition reactions) such reactive groups are required. After evaporation of the solvent the reaction is initiated, yielding a linear polymer (side-chain for polymerizations main-chain for polycondensa-... 

Ideally, more reactive groups are introduced, at least two (polymerization reactions) or three (polycondensation and polyaddition reactions), to yield absolutely insoluble crosslinked layers (Fig. 9.3). The next layer can then be prepared without negative impact on the underlying one, and the process can in principle be repeated without limitation. 

Because it is the extraordinarily large size of the macromolecules which leads to their unusual properties, it would be most sensible to classify polymerization reactions in accordance with the way in which they affect the molecular size and size distribution of the final product, i.e., in terms of the mechanism of polymerization. On this basis, there appear to be only two basic processes whereby macromolecules are synthesized (Zhang et al., 2012 Penczek and Premia, 2012 Moore, 1978 Saunders and Dobinson, 1976 Odian, 2004b Penczek, 2002 Jenkins et al., 1996) (1) step-growth polymerization (polycondensation and polyaddition) and (2) chain-growth (chain) polymerization. 

Zhang, M., June, S.M., Long, T.E., 2012. Principles of step-growth polymerization (polycondensation and polyaddition). In Matyjaszewski, K., Moller, M. (Eds.), Polymer Science A Comprehensive Reference, vol. 5. Elsevier, Amsterdam, pp. 7-47. 

Polymerization plays a key role in chemical microencapsulation. The basic mechanism of this method is to put a polymer wall (can be multilayer) through polymerization on a core material, which is in a form of small liquid droplets, solid particles, or even gas bubbles or to embed the core material in a polymer matrix through polymerization. Interfacial polymerization is one of the most important methods that have been extensively developed and industrialized for microencapsulation. According to Thies and Salaun, interfacial polymerization includes live types of processes represented by the methods of emulsion polymerization, suspension polymerization, dispersion polymerization, interfacial polycondensation/polyaddition, and in situ polymerization. This chapter is only focnsed on interfacial polycondensation and polyaddition in a narrow sense of interfacial polymerization. 

Both interfacial polycondensation and polyaddition involve two reactants dissolved in a pair of immiscible liquids, one of which is preferably water, which is normally the continuous phase, and the other one is the dispersed phase, which is normally called the oil phase. The polymerization takes place at the interface and controlled by reactant diffusion. Researches indicate that the polymer film occurs and grows toward the organic phase, and this was visually observed by Yuan et al. In most cases, oil-in-water systems are employed to make microcapsules, but water-in-oil systems are also common for the encapsulation of hydrophilic compounds. Even oil-in-oil systems were applied to prepare polyurethane and polyurea microcapsules. ... 

Equations 15.1 through 15.5 illustrate the main polymers and reactant systans of microcapsule making through interfacial polycondensation and polyaddition. The thus-prepared microcapsules... 

Polyphosphoesters form another interesting class of biomaterials that is composed of phosphorous-incorporated monomers (Figure 30.4m). These polymers consist of phosphates with two R groups (one in the backbone and one side group) and can be synthesized by a number of routes including ring-opening polymerization, polycondensation, and polyaddition. - - ... 

The solvolytic processes hydrolysis, alcoholysis, glycolysis, and aminolysis are suitable for recycling of products of polycondensation and polyaddition [13]. Since these are balanced-reaction processes, the primary material can be broken down into its monomers at a high temperature and with appropriate additives. A differentiation is drawn between summative and selective solvolytic processes. These processes are applied to polyesters, st5renics, and pol3mrethanes on a large scale as of today, and other (selective) polymers solvolysis solutions are under development. 

According to DIN 60001-T4, the synthetic fibers are divided into materials synthesized by different chain building processes polymerization, polycondensation, and polyaddition. Polymerization is subjected to monomers containing a vinyl group (double bond) in the molecular structure. The chain reaction will be induced by radical reaction. Polycondensation... 

Because of their free electron pairs or electron shell vacancies heteroatoms are particularly susceptible to attack by catalyst. Since heteroatom-containing groups react both by polycondensation and polyaddition mechanisms, they are especially readily catalyzed. The polymerization of rings with heteroatoms (lactams, lactones, trioxane, etc.) can also be easily initiated. On the same basis, however, deactivation of the chain can also occur frequently in these substances therefore, only low degrees of polymerization can be obtained. On the other hand, the activation of cycloalkanes in polymerization reactions proceeds with difficulty. The following discussion will therefore concentrate on the polymerization of rings and monomers with multiple bonds. 

Microfluidic systems (microreactors) provide great benefits, such as precise fluid-manipulation [1] and high controllability of rapid and difficult to control chemical reactions (see Part 2, Bulk and Fine Chemistry). Advantages of microreaction technology have been utilized in polymer chemistry notable examples include the synthesis of fine solid polymeric materials [2,3] and excellent control of exceptionally reactive polymerization through mainly radical and cationic polymerization reactions (see Chapters 13-15). Other polymerizations using microreaction technology are still in their infancy, vhich include step polymerization, that is, polycondensation and polyaddition and other non-radical polymerizations. 

Step-growth polymerizations in extruders, both polycondensations and polyadditions, are far less investigated than chain growth reactions. Because the polymer has to remain thermoplastic, only bifunctional monomers should be used, and the molecular weight can be controlled by the addition of a small amount of monofunctional monomers. For both polycondensation and poly-addition reactions the feeding should be very accurate and stochiometrically correct, because otherwise the conversion and therefore pressure built up will be seriously restricted. 

The chemistry of main chain elastomers is limited to step-growth reactions, i.e., polycondensation and polyaddition reactions, which demand the highest purity of the starting materials and experimental conditions which exclude side reactions. 

The chemistry of polymer production consists of three basic reaction types, polymerisation, polycondensation and polyaddition, thus the number of operations/processes used remains reasonably small. These include preparation, the reaction itself and the separation of products. In many cases cooling, heating, or the application of vacuum or pressure is necessary. The unavoidable waste streams are treated in recovery and/or abatement systems or disposed of as waste. 

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