Mechanisms of Step Growth Polymerization

Kinetic considerations are of paramount importance in understanding the mechanism of step-growth polymerization. As stated in Chapter 1, chain-growth polymerizations take place in discrete steps. Each step is a reaction between two functional groups for instance, in a polyesterification reaction it is a reaction between -COOH and -OH. The increase in molecular weight is slow. The first step is a condensation between two monomers to form a dimer ... [Pg.279]

The reaction mechanism of step-growth polymerizations differs considerably from the mechanism of chain-growth reactions. Whereas in... [Pg.50]

The dimer formed still has reactive groups. Hence, the polymerization will continue to take place in a stepwise fashion. Each step in this type of polymerization is identical and, therefore, the rate and mechanism of each step remains same as in the initial step. Polyestrification reactions are examples of step growth polymerization... [Pg.125]

Gandon S, Mison P, Sillion B (1996) Mechanism of step-growth thermal polymerization of arylacetylene. In Hedrick JL, Labadie JW (eds) Step-growth polymers for high performance materials, new synthetic methods. Am Chem Soc Symp Series 624 306... [Pg.177]

The bicyclic RSGP mechanism shown in Figure 5.3 has an important implication for the interpretation of diagnostic data of the luminous gas phase. Namely, any species identified in the plasma phase are intermediate species of step growth polymerization but not precursors of black box plasma polymerization. [Pg.71]

This is an addition reaction that proceeds via a mechanism of step growth (stagewise) polymerization. The most common isocyanates are toluene diisocyanate (TDI) and methylene bis 4-phenylisocyanate (MDI). TDI is cheaper and is mostly used for flexible foams, but MDI competes because of its lower vapor pressure and reduced sensitivity in handling. Polyfunctional isocyanates are added for cross-linking. The interesting reaction between isocyanate... [Pg.184]

Mechanism and Kinetics of Step-Growth Polymerization and, the molecular weight distribution is ... [Pg.409]

If the mechanism of termination is disproportionation then the degree of polymerization is the same as the kinetic chain length. The initial reaction between the radical and the first monomer molecule is fast and so only subsequent additions need be considered. The molecule M, has been formed by (/ - 1) addition reactions. The probability that one of these reactions has taken place is a and so using the analogy of step-growth polymerization the probability that (/ - 1) successive addition reactions have taken place is The probability that the last reaction is... [Pg.42]

Mechanism of Step-Growth Thermal Polymerization of Arylacetylene... [Pg.306]

To a different extent, the theory of step-growth polymerization was also applied to interpret the kinetics and the mechanism of OA of NPs, in which NPs with common... [Pg.118]

Step-growth polymerizations can be schematically represented by one of the individual reaction steps VA + B V —> Vab V with the realization that the species so connected can be any molecules containing A and B groups. Chain-growth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. These three types of reactions will be discussed in the following sections in considerable detail. For now our purpose is to introduce some vocabulary rather than develop any of these beyond mere definitions. The principal steps in the chain growth mechanism are the following ... [Pg.347]

Both modes of ionic polymerization are described by the same vocabulary as the corresponding steps in the free-radical mechanism for chain-growth polymerization. However, initiation, propagation, transfer, and termination are quite different than in the free-radical case and, in fact, different in many ways between anionic and cationic mechanisms. Our comments on the ionic mechanisms will touch many of the same points as the free-radical discussion, although in a far more abbreviated form. [Pg.404]

Step-growth polymerization is characterized by the fact that chains always maintain their terminal reactivity and continue to react together to form longer chains as the reaction proceeds, ie, a -mer + -mer — (a + )-mer. Because there are reactions that foUow this mechanism but do not produce a molecule of condensation, eg, the formation of polyurethanes from diols and diisocyanates (eq. 6), the terms step-growth and polycondensation are not exactly synonymous (6,18,19). [Pg.435]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...