Step-growth polymerization process

Step-growth polymerization processes must be carefully designed in order to avoid reaction conditions that promote deleterious side reactions that may result in the loss of monomer functionality or the volatilization of monomers. For example, initial transesterification between DMT and EG is conducted in the presence of Lewis acid catalysts at temperatures (200°C) that do not result in the premature volatilization of EG (neat EG boiling point 197°C). In addition, polyurethane formation requires the absence of protic impurities such as water to avoid the premature formation of carbamic acids followed by decarboxylation and formation of the reactive amine.50 Thus, reaction conditions must be carefully chosen to avoid undesirable consumption of the functional groups, and 1 1 stoichiometry must be maintained throughout the polymerization process. 

Step-growth polymer industry, 2 Step-growth polymerization processes, design of, 13 Step-growth polymers applications for, 2 histoiy of, 1 -2... 

When the reactants involved in a step growth polymerization process are mutually immiscible, we can employ an interfacial polymerization method. Two solutions, each containing one of the monomers, are layered one on top of the other. This creates a phase boundary that forms wth the least dense liquid on top. The different monomers can then meet and polymerize at the interface. A commonly demonstrated example of this is the manufacture of nylon 610 by the interfacial reaction between an aqueous solution of hexamethylenediamine with sebacoyl chloride dissolved in carbon tetrachloride. Because the reaction only occurs at the interface, it is possible to pull the products from this interface to isolate the final product. 

Based on the classical definitions given in organic chemistry, the step-growth polymerization process can involve either condensation steps or addition steps. The former proceeds with elimination of by-products while the latter takes place without elimination of by-products. This is illustrated by Eqs (2.1) and (2.2), for the particular case of difunctional molecules ... 

Seavey, K. C., and Liu, Y. A., "Step-Growth Polymerization Process Modeling and Product Design". Wiley, New York (2008). 

This is a step-growth polymerization process. The additions to the double bonds involve a series of hydrogen exchange reactions... 

Basic properties of step-growth polymerization processes... 

Reaction injection molding (RIM) is suitable for some step-growth polymerization processes in which no condensation byproducts are generated, and reactions are very rapid (e.g., polyurethane synthesis from diisocyanates and diols or multifunctional alcohols) ... 

Poly (etheretherketone) or PEEK, the structure of which is shown in Fig. 16.2, was originally developed primarily for composite applications. It is produced by the step-growth polymerization process of dialkylation of bisphenolate salts. PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained at high temperatures. It has a glass transition temperature or Tg at about 143 °C and melts around 343 °C. It is highly resistant to thermal... 

Step-growth polymerization processes are much slower than chain-reaction processes. Because they also typically have higher activation enthalpies, heating is often required to attain satisfactory rates of polymerization. Finally, step-growth polymers generally have lower average molar masses than polymers formed by chain-reaction polymerization. 

Step-Growth Polymerization Process Modeling and Product Design... 

Chemistry of Crosslinked Polymer Synthesis Table 2.1 The step-growth polymerization process... 

This technique is generally used in mildly exothermic reactions when less viscous products are formed and therefore, mixing, heat transfer, and control of the process is easy, e.g. in step-growth polymerization processes. On the other hand, the application of this method offers some disadvantages when the viscosity of the mass reaction increases because heat transfer and mixing become difficult. 

Figure 16 Equation describing the number average degree of polymerization for a step-growth polymerization process. (See Ref. 33 and references therein.)...

TPE (co)polymers from step-growth polymerization processes can be used as compatibilizers for melt blending of the respective polymers, e.g., polyesters with polyamides or polycarbonate. The interfacial chemical reactions between... 

Polyurethanes are prepared in step-growth polymerization processes similar to that used for preparing polyesters. In fact, many polyurethane materials are hybrids of ester linkages and urethane linkages. If a polyisocyanate is substituted for the polycarboxylic acid shown in Figure 2, the result is a polyurethane. The urethane hnkage is obtained by the reaction of an alcohol with an isocyanate. (The urethane linkage is also known as a secondary carbamate.)... 

Baughman) in 1991 and 1995, respectively, published by Academic Press, San Diego, California, on industrial water reuse and wastewater minimization (with James G. Mann) in 1999, published by McGraw-HiU, New York, and on step-growth polymerization process modeling and product design (with Kevin Seavey) in 2008, published by John Wiley and Sons, New York. 

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