Synthesis of Step-Growth Polymers

high reaction conversions ( 99.9%) as predicted using die Carodiers equation, 

absence of deleterious side reactions that result in loss of monomer functionality, 

The Carothers equation relates the number-average degree of polymerization to the extent of reaction and average functionality of a step-growth polymer. In the Carothers equation, the number-average degree of polymerization, X , relates to the extent of reaction, p, and average functionality, /avg, of the polymer system  

The molecular weight of a polymer will be reduced if either die extent of conversion or the average functionality is decreased. At 95% conversion of difunctional monomers, for example, Xn is only 20.25 The molecular weight is also related to a stoichiometric imbalance, r, which is normally defined to be less than 1.0  

The number-average molecular weight of a polymer may be controlled by offsetting the stoichiometry of two dissimilar mutually reactive difunctional monomers. The polymer will have the same endgroup functionality as that of the monomer used in excess. For a generic polymer made from a difunctional monomer AA with A functional groups and an excess of difunctional monomer BB widt B functional groups, r is defined as 

---

The synthesis of step-growth polymers—polytimides such as nylon and Kevlar, polyesters such as Dacron, polyurethanes such as spandex, and polycarbonates such as Lexan (Section 30.6)... 

Spychaj T, Pilawka R and Ukielski R (2004) New possibilities of chemical recycling methods in synthesis and/or modification of step-growth polymers, Proc 5 Int Conf Polymer Modification, Degradation and Stabilization MODEST, Lyon, CDROM abstract. 

Conditions that are important to all chemical reactions such as stoichiometry and reactant purity become critical in polymer synthesis. In step growth polymerization, a 2% measuring and/or impurity error cuts the degree of polymerization or the molecular weight in half. In chain growth polymerization, the presence of a small amount of impurity that can react with the growing chain can kill the polymerization. 

Imai Y (1996) A new facile and rapid synthesis of polyamides and polyimides by microwave-assisted polycondensation. In Hedrick JL, Labadie JW (eds) Step-growth polymers for high-performance materials. Am Chem Soc Washington, p421... 

Polymer synthesis is a complicated process that can be carried out applying different methodologies starting from appropriate monomers [193-196], The most important methods of polymer synthesis are step-growth polymerization and chain reaction polymerization [194,196],... 

When dwj fdi = 0, the curve has a maximum and / = I / In p. A series expansion of — 1 / In p gives p/(p — I) as the first term and this fraction approaches I /(p — I) as p approaches 1. This is the value of in linear step-growth polymerizations (Eq. 5-20). Thus, as a first approximation, the peak in the weight distribution of high conversion linear step-growth polymers is located at of the polymer if the synthesis was carried out under conditions where interchange reactions and molecular weight equilibration could occur. 

Early attempts to prepare main-chain metal-containing polymers mainly focused on the use of step-growth polycondensation processes (Scheme 1.1, Route B). These routes work well for the synthesis of carbon-based polymers when difunctional organic monomers are used because the latter are generally easily accessible in a high degree of purity. This allows the stringent stoichiometry and conver-... 

As already indicated in Section 3.1.3, besides chain and step growth polymerizations, new polymer structures can also be achieved by modifying a precursor polymer structure with new functionalities. Even though this is the base for a number of technically important polymers including polyvinyl alcohol and, for example, ion exchange resins, for many years, this method was not considered to be suitable for the reliable large-scale synthesis of well-controlled polymer architectures, mostly because it is very difficult to achieve very high... 

Whereas 2,5-dihydroxymethylfuran (DHMF) has been proposed frequently as a diol component for polyester synthesis, the high reactivity of the hydroxymethyl groups under acidic conditions primarily leads to resin formation, which is commercially exploited for the production of thermoset furan resins [55]. Although HMFA is more chemically stable than DHMF, it is also prone to resinification at high temperatures. In contrast, FDCA and derivatives have proven to be chemically stable under conditions relevant to polyester synthesis, making them the most versatile and industrially viable furan monomers for step growth polymers. 

Wright, L.W. and Brandner, J.D. (1964) Catalytic isomerization of polyhydric alcohols. II. The isomerization of isosorbide to isomannide and isoidide. Journal of Organic Chemistry, 29 (10), 2979-2982. Wu, J. (2012) Carbohydrate-Based Building Blocks and Step-growth Polymers Synthesis, Characterization and Structure-Property Relations. PhD thesis, Eindhoven Technical University. 

Wang S, McGrath JE. Synthesis of poly(arylene ether)s. In Rogers M, Long TE, editors. Synthetic methods in step-growth polymers. New York Wiley 2003. p. 327-74 [chapter 6]. 

Identify the monomers required for the synthesis of each step-growth polymer ... 

Asides from chain-growth, step-growth, and multi-step growth strategies, sequence-defined polymers may also be prepared using polymerization concepts inspired by biological polymerizations such as replication, transcription, and translation. For instance, sequence-defined templates can be used for monomer sequence regulation in non-natural polymerizations. Alternatively, catalytic molecular machines inspired by biocatalysts such as enzymes and ribozymes have been tested for the synthesis of sequence-controlled polymers. These developments are summarized in this last section of the chapter. 

Hecht and co-workers developed another class of polymers based on allgme-azide click chemistry. The synthesis of these new polymers was an A2-I-B2 step-growth polymerization, with A2 corresponding to the 2,6-diethynylpyridine monomer and B2 to the 3,5-diazidohenzoate monomer that reacted together under Cu-catalyzed 1,3-dipolar cycloaddition reaction conditions (Figure 5.22). 

Gaynor, S. G., and Matyjaszewski, K. (1997). Step-growth polymers as macroinitators for living radical polymerization synthesis of ABA block copolymers. Macromolecules, 30(14) 4241-4243. 

This study states that the uses of renewable somces which are vegetable oils, polymers synthesis is stepping forward. In this study we were reviewed about the different types of syntheses and the importance of polymer composites such as crossed-linked polymers and step-growth polymers from the vegetable oils. The polymer composites have achieved importance in industrial and biomedical applications. To our knowledge from various somces we have reviewed the preparation and applications of polymers from vegetable oil. 

---