During propagation, only monomers react to the active site at the end of the growing chain. This is known as step growth and is shown in figure 36 b. In chaingrowth or chain polymerization, the only chainextension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical or ion. Long and others published stepgrowth polymerization find, read and cite all the research you need on researchgate. Chapter two, stepgrowth polymerization, version of 1505 75 2 stepgrowth polymerization 2. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. Chainreaction polymerization, sometimes called addition polymerization, requires an initiator to start the growth of the reaction. Condensation polymers form from the step growth polymerization. Propagation or growth of the active chain by sequential addition of monomers. Unlike in chain growth polymerization, the polymer chains here are not formed at the beginning.
It is much less sensitive to the effects of adventitious impurities than stepgrowth polymerization and ionic chaingrowth polymerization. Step growth polymerization is the formation of a polymer from bifunctional or multifunctional monomers. Following a comparison of chaingrowth and stepgrowth polymerization, focuses on the latter process by describing requirements for high molecular weight, stepgrowth polymerization kinetics, synthesis and molecular weight distribution of some linear stepgrowth polymers, and threedimensional network stepgrowth polymers. Anionic polymerization chain transfer to solvent ch 2 c. The other process, called stepgrowth polymerization, involves the buildup of molecular weight not in a chainlike fashion but in a stepwise fashion, by the random combination of monomer molecules containing reactive functional groups. Bulk polymerization is carried out in the absence of any solvent or dispersant and is thus the simplest in terms of formulation.
Stepgrowth polymerization is a very important method for the preparation of some of the most important engineering and specialty polymers. In a stepgrowth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one re action mechanism for the formation of polymer. Difference between chain growth and step growth polymerization. Here when molecules of monomers react to form a bond they replace certain molecules. Stepgrowth polymers have been known since the discovery of. Step growth polymerization mit opencourseware free. Step growth polymerization p olymerization mechanism in which bifunctional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. As in free radical polymerization, there are initiation and propagation steps. The net rate of production of free radicals is zero so that the initiation and termination rates are equal.
Stepgrowth polymerization request pdf researchgate. New polymers synthesis by organocatalyzed stepgrowth. Ch 26 stepgrowth polymers condensation polymerization. Stepgrowth polymerization typically takes place between monomers containing functional groups that react in high yield to form new functionalities. For example, aminocaproic acid has an amine group at one end and a carboxyl group at the other. Synthetic methods in stepgrowth polymers provides a concise source of information on synthetic techniques, purification, and characterization methods for stepgrowth polymers and also addresses future synthetic trends. Chain growth polymerization begins when a reactive species and a monomer react to form an active site. The activation energy for freeradical polymerizations is about the same as for stepgrowth reactions section 8. The electrophilic aromatic substitution reactions of ketones. Thus at 75 per cent completion, the average degree of polymerization is one quarter of that. Since, each step produces a distinct functionalised species and is independent of each other, this process is also called as step growth polymerisation. Novel, linear, highmolecularweight singlestrand heteroaromatic polymers and copolymers containing 9hxanthene moieties in the backbone were synthesized by metalfree superacidcatalyzed stoichiometric and nonstoichiometric stepgrowth polymerizations of carbonyl compounds bearing electronwithdrawing substituents with bisphenols. Chain growth polymerization an overview sciencedirect. Polymerization processes are categorized into two broad classes, according to their reaction mechanisms.
Converting step growth polymerization to chain growth free download as powerpoint presentation. The formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid is an example of this type of polymerisation. Pdf since its discovery in 2001, copper catalyzed azidealkyne click. Stepgrowth polymerization is also used for preparing a class of adhesives and amorphous solids called epoxy resins.
Virtually all of the monomers described above are subject to radical polymerization. Propagation proceeds in the usual manner, but there is no termination of the type that occurs when free radicals collide. The two most important stepgrowth polymerizations are condensation and addition polymerization. A good example is the freeradical polymerization of styrene, which is initiated by a free radical r that reacts with styrene.
Polymerization of vinyl polymers mechanism of free radical polymerization molecular weight control in stepgrowth polymerization cyclization versus. The growth of np chains was described by the kinetics and statistics of stepgrowth polymerization 2426, which, for a particular time, allowed the prediction of the aggregation number and the size distribution of np ensembles, similar to the degree of polymerization and polydispersity index pdi of polymers, respectively. Ppg industries has received a patent for a compound that is comprised of the reaction product of a highly branched polymer having terminal amine functional groups and a lactam, wherein the highly branched polymer is the stepgrowth polymerization reaction product of a polyfunctional first monomer having a first functional group and a polyfunctional second monomer having a second functional. Step growth polymerization refers to a type of polymerization mechanism in. Since all the monomer molecules can interact with one another, the length of the chains increases more slowly during the course of polymerization. Freeradical polymerization is the most widely used process for polymer synthesis.
Since this can be initiated by traces of oxygen or other minor impurities, pure samples of these compounds are often stabilized by small amounts of radical inhibitors to avoid unwanted reaction. Examples of such functional groups are carboxylic acids, which react with alcohols to form esters and with amines to form amides here r and r. Initiation of the active monomer, propagation or growth of the active chain by sequential addition of monomers, termination of the active chain to give the final polymer product. Stepgrowth polymerization and stepgrowth polymers rro. There are four principal mechanisms of chain growth polymerization. Let us do a comparative analysis of the two types of polymerization to understand them better. Polymerization kinetics step growth slow can use statistical methods as well as kinetics to describe mol. College level organic chemistry 2 chapter 26 including closed captioned video. Growth polymerization process modeling and product. The largest family of polymers 3, vinyl polymers, are produced by chain polymerization reactions. Objectives polymers national council of educational.
Freeradical polymerization is particularly suitable for polymerizing monomers containing carboncarbon double bonds. Understand quantitative model stepgrowth polymerization plans and how to predict properties of the product polymer with the essential information in stepgrowth polymerization process modeling and product design. The first six chapters present the principles of step growth polymerization. A huge variety of possibilities cytoskeleton proteins actin filament. In the case of chaingrowth reactions, which are generally exothermic, the heat evolved may cause the reaction to become too vigorous. Other articles where stepgrowth polymerization is discussed. At that time we noted that these classifications could be based on the following. Step growth polymerization is also known as condensation polymerization. All molecules present monomer, oligomer, polymer can react with any other molecule. Stepgrowth polymerization article about stepgrowth. Converting step growth polymerization to chain growth. These free radicals are added to another monomer forming another free radical. Growth regulated by regulating nucleation of new barbed ends.
Stepgrowth polymerization an overview sciencedirect topics. Chemical engineering 160260 polymer science and engineering. If you want to learn how to simulate stepgrowth polymerization processes using commercial software and seek an indepth, quantitative understanding of how to develop, use, and. Stiile colorado state university, fort collins, co 80523 as illustrated in the articles on chain polymerization, a chaingrowth polymerization is one in which each polymer chain, after being started by a free radical initiator, a cationic catalyst or an anionic catalyst, grows rapidly, producing a high molecular weight polymer. The process results in the formation of chain and ultimately a polymer is. It is used for most stepgrowth polymers and many types of chaingrowth polymers. In the following example, the same bisphenol a intermediate used as a monomer for lexan serves as a. Dendrimers, traditional convergent and divergent routes.
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