Chain polymerization polycondensation

Alongside the radical distinction of the mechanism of this process from that of chain polymerization, linear polycondensation features a number of specific peculiarities. So, for instance, the theory of copolycondensation does not deal with the problem of the calculation of a copolymer composition which normally coincides with the initial monomer mixture composition. Conversely, unlike chain polymerization, of particular importance for the products of polycondensation processes with the participation of asymmetric monomers is structural isomerism, so that the fractions of the head-to-head and head-to-tail patterns of ar-... 

Yokozawa, T. Yokoyama, A. Chain-growth polycondensation The living polymerization process in polycondensation. Prog. Polym. Sci. 2007, 32, 147-172. 

Until now the discussion has centered on the addition polymers obtained fiom unsaturated monomers by reaction of the C=C or C=0 double bond. However, polymers obtained by other methods (ring-opening polymerization, polycondensation, etc.) offer interesting stereochemical phenomena also. As a rule, in these classes of macromolecular compounds the monomer units are clearly defined, the direction of the chain is often distinguishable and the stereo-isomeric elements present in the chain already preexist in the monomer. There are, however, numerous exceptions and further clarification is called for. 

Note 2 The earlier term polycondensation was synon5nnous with condensation polymerization. It should be noted that the current definitions of polycondensation and eondensative chain polymerization were both embraced by the earlier term polycondensation. 

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. 

ADMET has been shown to be a step-growth polycondensation reaction [31[. The kinetics of step-growth polymerization and consequences thereof are completely different than those of chain polymerizations. Since ROMP and many other single-site transition metal-catalyzed polymerizations discussed in this book proceed... 

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

Phthalic anhydride, maleic anhydride, fumaric acid, isophthalic acid, ethylene glycol, propylene glycol, diethylene glycol, styrene Bulk polycondensation followed by free-radical-initiated chain polymerization Construction, automotive applications, marine applications... 

This broad definition allows fw a variety of polymerization mechanisms, and it is formally possible for dispersion polymerizations to be anionically or cation-ically initiated, or to be stepwise rather than chain polymerizations. These types of dispersion polymerizatitm are less commcn and are outside the scope of this chapter, which is devoted largely to radically initiated systems. A recent review [2] covers polycondensations by dispersion methods. 

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. 

Lim et al. used a palladium complex for the cationic polymerization of TH F and the ROMP of NB [10]. The same group also showed that even condensation and chain polymerization could be performed simultaneously in one step (Scheme 11.45). This was achieved by the use of unimolecular compounds which can simultaneously act both as an initiator for chain polymerization, and as an end-capper for condensation polymerization. The method provides a simple means of combining NMRP with a condensation polymerization to yield interesting and useful block copolymers [207]. Another interesting new system for the combination of chain (AROP of CL) and step (dehydration polycondensation) polymerizations for polyester-based new material, in which scandium trifluoromethane sulfonate catalyzed both polymerization modes, was reported by Takasu et al. (Scheme 11.46) [208]. 

The aim of this chapter is to describe the possibilities offered by the miniemulsion process for performing chain polymerization, polyaddition, polycondensation, and modifications of polymers, and to outline the current trends in this field of research. Whilst the different polymerization types performed in miniemulsion are discussed in detail, descriptions of so-called secondary or artificial miniemulsions (i.e., miniemulsions with a preformed polymer) will not be included at this point... 

Yokozawa, T., and H. Shimura. 1999. Condensative chain polymerization. II. Preferential esterification of propagating end group in Pd-catalyzed CO-insertion polycondensation of 4-bromo-phenol derivatives. / Polym Sci A 37 (14) 2607-2618. 

Recently, typical step-reaction polymerizations, as in polyesters, polyethers, and polyamides, have been forced into chain-reaction mechanisms by designing complex chain ends that react fast with the monomer only. Under the proper conditions, the step reaction can be suppressed almost completely. Such chain-growth polycondensation may even yield living polymers with narrow molar-mass distribution. A link to the initial literature is given in the General References for this section. 

Whereas the monomers shown in Scheme 6.11 are specifically suited for chain polymerization reactions through the moieties external to the ring and thus give rise to polymers or copolymers with the heterocycle pendant to their backbone, the monomers shown in Schemes 6.12 and 6.13 give rise to polycondensate architectures in which the heterocycle is an integral part of the backbone. 

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... 

The hrst section covers the basic principles and characteristics necessary for polymer preparation by polymerization, being either (a) stepwise polymerization of bifunctional monomers by polycondensation, stepwise polyaddition and ringopening processes, or (b) chain polymerization of vinyl monomers by free radical, cationic, anionic, and coordination addition processes. Both of these polymerization techniques are used for polymer preparation from monomer. The goal of the polymerization technique is to obtain polymers with specific structures and properties -this generally requires specialized polymerization conditions. Also described are the factors affecting the rates of homo- and copolymerizations and the reactivity ratios of different comonomers. 

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