Chain growth polymerization an overview sciencedirect topics. The condensation process may or may not be accompanied by elimination. As you work through this course you will need various resources to help you complete some of the activities. Virtually all of the monomers described above are subject to radical polymerization. A step growth polymerization is the gradual growth of a polymer chain by the consecutive reaction of two bifunctional monomers. In the propagation stage, the process of electron transfer and consequent motion of the active. The monomer in stepgrowth polymerization will be consumed very quickly to dimer, trimer or oligomer. Following a comparison of chain growth and step growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step growth polymerization kinetics, synthesis and molecular weight distribution of some linear step growth polymers, and threedimensional network step growth polymers. The mechanism requires that at least two different monomers participate in the reaction. What is the difference between stepgrowth polymerisation, chaingrowth polymerisation and copolymerisation. A detailed discussion of several important step growth polymeriz ations follows in the next five chapters.
Chain growth and stepgrowth polymerization are described in. It is the addition of monomers to an evergrowing chain. Difference between chain growth and step growth polymerization. Principles of stepgrowth polymerization polycondensation and polyaddition. Chemical engineering 160260 polymer science and engineering lecture 6 mechanism and kinetics of free radical chain polymerization january 29, 2001. In this context, we noticed that a particular compound in our separate work 18 serves as a metastable monomer that is temporarily disabled for spontaneous polymerization in the absence of. 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. Intro to polymer chemistry exam 2 flashcards quizlet. Step growth polymerization refers to a type of polymerization mechanism in which.
Reaction engineering of step growth polymerization springerlink. Most anionic reactions have no inherent termination step. There is very little change in the molecular mass throughout the. What is the difference between step growth polymerisation, chaingrowth polymerisation and copolymerisation. By comparison, a wide variety of unsaturated monomers undergo chaingrowth polymerization. This is one of the earliest topics i was teaching in the polymer science and engineering course.
Chain growth system the characteristic of a chain polymer is that polymer growth takes place by monomer reacting only with the reactive centers. These polymerization techniques generate many important commodity polymers where their broad range of molecular weight distribution gives rise to important physical properties. Stepgrowth polymerization forms polymers in a manner that is quite different from. Since all the monomer molecules can interact with one another, the length of the chains increases more slowly during the course of polymerization. Stepgrowth polymerization forms polymers in a manner that is quite different from chaingrowth polymerization. Polymerization kinetics step growth slow can use statistical methods as well as kinetics to describe mol. 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. The resins to be presented have all been formed via the stepgrowth or chain. The distinct initiation, propagation, and termination steps of chaingrowth polymerization are meaningless in stepgrowth polymerization. The main difference between chain growth polymerization and step growth polymerization is that chain growth polymerization has a growth a polymer chain at its ends whereas step growth polymerization has a combination of oligomers to form a polymer chain. The mw and the mw distribution, referred to as polydispersity, are two fundamental factors that dictate the physical nature of polymeric materials. Step growth polymerization refers to a type of polymerization mechanism in which bifunctional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. 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.
Concentration of monomers decreases steadily throughout the reaction reaction is fast and polymer is formed at once. But in condensation polymerization, any molecule can react with any other. In the following example, the same bisphenol a intermediate used as a monomer for lexan serves as a. Equilibrium step condensation polymerizations, interchange reactions. A stepgrowth polymerization is a stepwise reaction between bifunctional or multifunction. In which in the first step a group of two monomer molecules combined to view the full answer previous question next question transcribed image text from this question. It is a chain reaction where free radicals or ionic groups are responsible for propagating the chain. The first six chapters present the principles of step growth polymerization. Polymers are giant molecules made of small units known as monomers. For example, aminocaproic acid has an amine group at one end and a carboxyl group at the other. Chain growth, or addition polymerization of vinyl monomers that contain an initiating group and a propagating group in the same molecule has been identified as a synthetic route to hyperbranched polymers. Feb 16, 2016 the process results in the formation of chain and ultimately a polymer is formed. First, we examine how the degree of polymerization.
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. Compared to chaingrowth polymerization, where the production of the growing chaingrowth is based on the reaction between polymer with active center and monomer, stepgrowth polymerization doesnt have initiator or termination. In addition polymerization, there are three distinct steps. Step growth polymerization typically takes place between monomers containing functional groups that react in high yield to form new functionalities. Chain growth polymerization is basically a threestage process, involving initiation of active molecules, their propagation and termination of the active chain ends. Stepgrowth polymerization forms polymers in a manner that is quite different from chain growth polymerization. The distinct initiation, propagation, and termination steps of chaingrowth polymerization are meaningless in. The two most important step growth polymerizations are condensation and addition polymerization. Step growth polymerization is also known as condensation polymerization. Different steps operate at different stages of mechanism. During propagation, only monomers react to the active site at the end of the growing chain. Stepgrowth polymerscondensation polymers chemistry. Stepgrowth polymerization of inorganic nanoparticles.
Pdf reinvestigation of numerous ringopening polymerizations by means of malditof mass spectrometry has evidenced that cyclic polymers were formed. Propagation it is the middle step in chain polymerization where successive monomers are attached to the growing chain. Monomers are molecules having either unsaturated bonds or at least two functional groups per molecule. Putting them together polymer science learning center. Chain growth polymerization is a process in which the high molecular weight polymer is formed early in the polymerization process and the polymer yield the percentage conversion of the monomer into the polymer gradually increases with time. Step growth polymers are defined as polymers formed by the stepwise. This is known as step growth and is shown in figure 36 b. The products usually have a carbon backbone with pendant substituent groups ex. Mechanism of radical chain polymerization fundamental steps initiation, propagation. Stepgrowth polymerization refers to a type of polymerization mechanism in which bifunctional or multifunctional monomers react to form first dimers, then. The results indicate that as catalytic mechanisms dominate the kinetics chain growth mechanisms also overwhelm step growth mechanisms. Stepgrowth polymerization refers to a type of polymerization mechanism in which bifunctional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Compared to stepgrowth polymerization, living chaingrowth polymerization shows low pdi, predictable molecular mass and controllable conformation.
Ionic chain polymerization is a chaingrowth reaction where the active center is charged, either negatively, leading to anionic polymerization, or positively, leading to cationic polymerization. Chain growth polymerization has been successfully performed for many decades through conventional free radical, anionic, or cationic polymerization. Explain the difference between a step growth and a chain growth polymerization. In condensation polymerization, there is no termination step. Many naturally occurring and some synthetic polymers are produced by stepgrowth polymerization. In addition polymerization monomers only join at the active site of the chain. In chain growth or chain polymerization, the only chain extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical or ion. Monomer does not react with monomer and the different sized species such as dimer, trimer, and nmer do not react with each other. Made by faculty at the university of colorado boulder department of chemical and biological. In other words, addition of each monomer unit regenerates the active site. Stepgrowth polymerization forms polymers in a manner that is. Controlled stepgrowth polymerization ccs chemistry. Open systems kinetics of step growth polymerization chapter 2. Transformation of stepgrowth polymerization into living.
Chain growth polymerization or chain polymerization is a polymerization technique where unsaturated monomer molecules add onto the active site of a growing polymer chain one at a time. The growth of np chains was described by the kinetics and statistics of step growth 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. Equivalent terms are either chain polymerization or chain. Based on this mechanism, the choice of catalysts can impact both the rate of reaction and degree of polymerization length. Reaction engineering of step growth polymerization. Chain addition polymerization also referred to as chaingrowth polymerization technique is a chain reaction in which the growth of a polymer chain proceeds exclusively by reactions between monomerss and active sites on the polymer chain with regeneration of the active sites at the end of each growth step.
Following a comparison of chain growth 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 step growth polymers, and threedimensional network step growth polymers. Chain growth polymerization an overview sciencedirect. The process of step growth polymerization is a little more complicated than chain growth polymerization. Now let us look at an example for step growth polymerization for better understanding. Stepgrowth polymerization and stepgrowth polymers rro. Pdf simultaneous stepgrowth and chaingrowth cationic. The mechanism requires that at least two different monomers participate. Step growth polymerisation concentration of monomers disappears early in the reaction. Thus at 75 per cent completion, the average degree of polymerization is one quarter of that. In slurry polymerization, chain growth occurs as monomers dissolved in a hydrocarbon solvent add to growing chains also dissolved in the solvent.
Macromolecular chemistry university of texas at austin. 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. Step growth polymerization is the formation of a polymer from bifunctional or multifunctional monomers. Polymerization processes are categorized into two broad classes, according to their reaction mechanisms. Polymer science submitted by 1st year 2nd semester group. Stiile colorado state university, fort collins, co 80523 as illustrated in the articles on chain polymerization, a chain growth 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. Draw the structures of monomers that can be polymerized by both processes. Mar, 20 applies the steadystate approximation to a chain growth polymerization to determine how the rate of reaction depends on initiator and monomer concentrations. 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. Chain polymerization is a polymerization mechanism in which monomer molecules add onto an active site of a growing polymer chain one at a time iupac. Kinetic considerations are of paramount importance in understanding the mechanism of stepgrowth polymerization. A difunctional monomer or equal molar amounts of two.
Step growth polymerization, types of monomers, kinetics and equilibrium considerations, closed vs. In a stepgrowth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one reaction mechanism for the formation of polymer. Step growth polymerization is also used for preparing a class of adhesives and amorphous solids called epoxy resins. Chain growth polymerization mechanism in polyurethane. Examples of such functional groups are carboxylic acids, which react with alcohols to form esters and with amines to form amides.
Step growth polymerisation this type of polymerisation is due to the condensation process which takes place in several steps. What is the difference between stepgrowth polymerisation. In contrast with step growth polymerization, chain growth polymerization uses monomers that do not polymerize spontaneously without initiators 11, 17. Nov 10, 2015 simultaneous step growth and chain growth cationic polymerization of styrenic monomers bearing carbazolyl groups. Addition polymerization, on the other hand, is a polymerization in which the growth of polymer chains proceeds by addition reactions between molecules of any size iupac. A rational strategy for the realization of chaingrowth. Simultaneous step growth and chain growth cationic polymerization of styrenic monomers bearing carbazolyl groups article pdf available in polymer 129 september 2017 with 3 reads. Chaingrowth, or addition polymerization of vinyl monomers that contain an initiating group and a propagating group in the same molecule has been identified as a synthetic route to hyperbranched polymers. Stepgrowth polymerization forms polymers in a manner that. Chain addition polymerization also referred to as chain growth polymerization technique is a chain reaction in which the growth of a polymer chain proceeds exclusively by reactions between monomerss and active sites on the polymer chain with regeneration of the active sites at the end of each growth step. Some researchers are working on the transformation of two polymerization methods. The process results in the formation of chain and ultimately a polymer is formed. The number of growing polymer chains is restricted because the incoming. Pdf simultaneous chaingrowth and stepgrowth polymerization.
The other process, called step growth 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. Thus at 75 per cent completion, the average degree of polymerization. All molecules present monomer, oligomer, polymer can react with any other molecule. Poly3000ceic8104 polymer science week 4 chain polymerization. Chemical engineering 160260 polymer science and engineering. Unlike in chain growth polymerization, the polymer chains here are not formed at the beginning. Here the covalent bonding occurs by an s n 2 reaction between a nucleophile, usually an amine, and a terminal epoxide. The distinct initiation, propagation, and termination steps of chain growth polymerization are meaningless in step growth polymerization. Now, we call a polymerization an addition polymerization if the entire monomer molecule becomes part of the polymer. These are quite general, and can easily be applied in such diverse and emerging fields as polymerization applications in photolithography and microelec tronics. Chain growth and step growth polymerization are described in. In step growth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one reaction mechanism for the formation of polymer. Chemistry of industrial polymers chemistry of industrial polymers step growth polymerization. Jun 27, 2017 main difference chain growth polymerization vs step growth polymerization.
Ps or pvc aka most like chain growth polymerization. Stepgrowth polymerization an overview sciencedirect topics. Stepgrowth polymerization journal of chemical education. Chemistry of industrial polymers stepgrowth polymerization. Controlled radical polymerization guide sigmaaldrich.
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