The technique is the most studied and utilized of the controlledliving radical polymerization techniques since a large number of monomers. Chemistry of industrial polymers stepgrowth polymerization. First, we examine how the degree of polymerization. An example is adipic acid that has two functional groups, but both are carboxylic acid groups. Made by faculty at the university of colorado boulder department of chemical and biological. Step growth polymerization is the method most commonly employed, although hydrogenbonddriven polypseudorotaxane formation has also been reported from preformed polyurethane backbones in combination with 30crown10 or 42crown14 rings. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Elements of stepgrowth polymerization branching network. Stepgrowth polymerization is a very important method for the preparation of some of the most important engineering and specialty polymers. Living supramolecular polymerization established by combining energy. Monoliths from stepgrowth polymerization reactions. 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. This is a step growth polymerization not a chaintransfer or radical polymerization.
Mechanism of step polymerization bifunctional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers slow growth of chains requires high conversion of monomer to reach high molecular weight, p0. Mechanism of radical chain polymerization fundamental steps initiation, propagation. Chemistry of industrial polymers chemistry of industrial polymers step growth polymerization. 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. Stepgrowth polymerization journal of chemical education. Figure 41 molecular mass distributions in step growth polymerization.
Step growth polymerization is also used for preparing a class of adhesives and amorphous solids called epoxy resins. Synthesis of macromolecules by step growth polymerization 4. The distinct initiation, propagation, and termination steps of chain growth polymerization are meaningless in step growth polymerization. Understand quantitative model step growth polymerization plans and how to predict properties of the product polymer with the essential information in step growth polymerization process modeling and product design. A difunctional monomer or equal molar amounts of two. Step growth polymerization, types of monomers, kinetics and equilibrium considerations, closed vs. Step growth polymerisation this type of polymerisation is due to the condensation process which takes place in several steps.
The polymerization of unsaturated monomers typically involves a chain growth polymerization. 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. Polymerization is a process of reacting monomer molecules together in a chemical reaction to form linear chains or a threedimensional network of polymer chains 1. Precise immobilization of monomers in the supramolecular assemblies is a promising way for the controlled aabb step. The number distribution a is shown for three different extents of reaction, the mass distribution b shows a single narrow peak which progressively broadens and shifts to high molecular mass as.
For example, aminocaproic acid has an amine group at one end and a carboxyl group at the other. Nov 10, 2015 simultaneous step growth and chain growth cationic polymerization of styrenic monomers bearing carbazolyl groups. Converting monomer to long chain polymer is the final step in the polymer manufacturing sequence. Despite the amazing growth of scientific contributions in this field since 2002, to our surprise the possibilities to combine stepgrowth. 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. Two other types of monomers that combine via stepgrowth polymerization. Stepgrowth polymerization forms polymers in a manner that. Step growth polymerization and condensation polymerization step growth polymerization and condensation polymerization are two different concepts, not always identical. For example, a monomer conversion of p 99% would be required to achieve x n 100. Examples of polymers formed through step growth mechanism.
As such, the result is quite remarkable as it contradicts the traditional rules of step growth polymerization and shows the power of confined space in polymerization processes. During polymerization, smaller molecules, called monomers or building blocks, are chemically combined to create larger molecules or. Dec 17, 20 an animation which explains step growth polymerization. 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. There exist, exceptionally, some polymerizations that proceed via chain reactions that, according to the definition, are not chain polymerizations.
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. Difference between chain growth and step growth polymerization. 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 longchain polymers 5,1822. A rational strategy for the realization of chaingrowth. By combining the above expression with carothers equation and solving for m one obtains.
Transformation of stepgrowth polymerization into living chain. Chaingrowth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. 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. The monomer in stepgrowth polymerization will be consumed very quickly to dimer, trimer or oligomer. Many naturally occurring and some synthetic polymers are produced by step growth polymerization. The oldest polymers rejuvenated leen billiet, david fournier, filip du prez volume 50, issue 16, 31 july 2009, pages 38773886. Two types of monomers can undergo step growth polymerizations.
During propagation, only monomers react to the active site at the end of the growing chain. The reaction can be carried out in solution, in bulk melt, or in solid state. In this context, the present manuscript investigates the step growth polymerization of polyethylene 2,5furandicarboxylate, pef, a furanic polyester with structural similarity to polyethylene terephthalate, pet, using ethylene glycol eg, and 2,5furandicarboxylic acid fdca as monomers. 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.
A detailed discussion of several important step growth polymeriz ations follows in the next five chapters. Stepgrowth polymerization refers to a type of polymerization mechanism in which bifunctional. The polymerization in each monomerswollen particle continues until the monomer droplets are depleted and no monomer andor initiator is left step 4 polymerization in monomerswollen polymer particles. In chain growth polymerization, a polymer chain is formed at the beginning by the attachment of one monomer at a time. Synthesis of macromolecules by step growth polymerization 4 4. The mechanism requires that at least two different monomers participate. 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.
Growth proceeds by a step wise intermolecular reaction growth involves monomer units reacting with each other or with oligomers of any size the reactivity of a functional group is independent of the size of the molecule to which it is attached the reactivity of a functional group is independent of. At edge of cell to cause protrusion against load force to notice. In chain growth 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. The mechanism requires that at least two different monomers participate in the reaction. These are quite general, and can easily be applied in such diverse and emerging fields as polymerization applications in photolithography and microelec tronics. Classical polycondensation is a step growth process, but a living polymerization polycondensation must proceed by a chain growth rather than a step growth mechanism. Condensation polymerization get full description along. The polyester dacron and the polyamide nylon 66, shown here, are two examples of synthetic condensation polymers, also known as step growth polymers. Objectives polymers national council of educational. High molecular weight chains are only obtained near the very end of the reaction. The two most important step growth polymerizations are condensation and addition polymerization. Pdf simultaneous chaingrowth and stepgrowth polymerization.
Step growth polymerization this polymerization method typically produces polymers of lower molecular weight than chain reactions and requires higher temperatures to occur. Intro to polymer chemistry exam 2 flashcards quizlet. Chemistry 328n the carothers equation high molecular weights are hard to get this way if there are n o molecules at time 0 and n remaining at time t then the amount reacted is n 0n and we can define p as the conversion or fraction reacted then as. Unlike addition polymerization, step wise reactions involve two different types of difunctional monomers or end group that react with one another, forming a chain. What are some characteristics of a step growth polymerization with relation to time. Where in the cell is polymerization most important. The polyketals are synthesized via step growth polymerization, we therefore speculate that their low molecular weight is due to an imbalance of the reactants during the polymerization process. More often, we jostle around in one of several bulging crowds that merge haphazardly near the gate. 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. This is fully supported by the monte carlo simulation on the basis of the polymerization mechanism. Transformation of stepgrowth polymerization into living. There are two distinctive mechanisms during polymerization.
High impact polystyrene hips acrylonitrile butadiene. Stepgrowth polymerization article about stepgrowth. When we talk about condensation polymerization, it is a form of a step growth polymerization where smaller molecules or monomers react with each other to form larger structural units usually polymers while releasing byproducts such as water or methanol molecule. Atom transfer radical polymerization atrp has proven to be a powerful technique to obtain polymers with narrow polydispersities and controlled molecular weight. The first six chapters present the principles of step growth polymerization. New polymers synthesis by organocatalyzed stepgrowth. Here the covalent bonding occurs by an s n 2 reaction between a nucleophile, usually an amine, and a terminal epoxide. These 3 types of polymerization share 3 common steps. All molecules present monomer, oligomer, polymer can react with any other molecule. Pdf monoliths from stepgrowth polymerization reactions. Chemical engineering 160260 polymer science and engineering.
Stepgrowth polymerization of inorganic nanoparticles. Jan 30, 2012 an introduction to step growth polymerization. Cannot be used for polymers whose glass transition temperature is less than the polymerization temperature, or else aggregation will occur. There are many forms of polymerization and different systems exist to categorize them. 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 easiest way to visualize the stepgrowth mechanism is a crowd of people. Stepgrowth polymerization an overview sciencedirect topics. Stepgrowth polymerization process modeling and product.
Since, each step produces a distinct functionalised species and is independent of each other, this process is also called as step growth polymerisation. Simultaneous chaingrowth and stepgrowth polymerizationa new route to cyclic polymers. Many naturally occurring and some synthetic polymers are produced by stepgrowth polymerization, e. Polymerization yields finely divided, stable latexes and dispersions to be used directly in coatings, paints, and adhesives. Stepgrowth polymerization forms polymers in a manner that is. In chain growth polymerizations, an initiator, like a freeradical, reacts with monomers that carry a reactive double bond, such as in ethylene. In the case of a condensation reaction, two monomers combine with the loss of a. Step growth polymerization typically takes place between monomers containing functional groups that react in high yield to form new functionalities. Post polymerization or how to make a graft copolymer examples.
Chain growth polymerization can be understood with the chemical equation. The bisphenol a groups are reacted with proton acceptors such as naoh to obtain the polymerization functional groups. In contrast with step growth polymerization, chain growth polymerization uses monomers that do not polymerize spontaneously without initiators 11, 17. Examples of such functional groups are carboxylic acids, which react with alcohols to form esters and with amines to form amides.
Stepgrowth polymerization forms polymers in a manner that is quite different from chaingrowth polymerization. Most anionic reactions have no inherent termination step. 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. In fact polyurethane polymerizes with addition polymerization because its polymerization produces no small molecules, but its reaction mechanism corresponds to a step growth polymerization.
Step growth polymerization process modeling and product design kevin seavey, y. In the following example, the same bisphenol a intermediate used as a monomer for lexan serves as a. Synthetic methods in stepgrowth polymers request pdf. These polymers are then processed to make various kinds of plastic products. In stepgrowth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one reaction mechanism for the formation of polymer. Stepgrowth polymerization and stepgrowth polymers rro. Polymerization is usually highly favourable in thermodynamic terms, mainly on energetic grounds because ordering molecules into linked chains is a process where the entropy is decreased. Stepgrowth polymerization american chemical society. As such, the result is quite remarkable as it contradicts the traditional rules of step growth polymerization and shows the power of confined space in polymerization. In step growth polymerization, oligomers are formed at the beginning and are later combined together, forming the polymer chain. The distinct initiation, propagation, and termination steps of chaingrowth polymerization are meaningless in stepgrowth polymerization. The formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid is an example of this type of polymerisation. Why pdi is usually greater than 2 in real polymerization system.
Chaingrowth polymerizations require the presence of an initiating molecule that can be used to attach a monomer molecule at the beginning of the polymerization. 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 of inorganic nanoparticles. Stepgrowth polymerization request pdf researchgate. Chemical engineering 160260 polymer science and engineering lecture 6 mechanism and kinetics of free radical chain polymerization january 29, 2001. 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 degree of polymerization dp was depending more significantly on the monomer arrangement, that is, the crystal structure, then on stoichiometry.
Stepgrowth or addition polymerization involves the reaction between the functional. This kind of step growth polymerization is often called a condensation process polymerization steps 1. Ni or pd catalyst for synthesis of conjugated polymers. Reaction engineering of step growth polymerization springerlink. The polymer size is dependent on the percent conversion. Made by faculty at the university of colorado boulder department of chemical and biological engineering. We rarely board airplanes by joining the back of a single wellordered line. Stepgrowth polymerization an overview sciencedirect. Open systems kinetics of step growth polymerization chapter 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. Stepgrowth polymerization forms polymers in a manner that is quite different from chain. There is no termination step and the end groups of the oligomers and polymers are reactive throughout the polymerization process. Polymerization kinetics step growth slow can use statistical methods as well as kinetics to describe mol. Roughly speaking, these processes are analogous to the chain growth and step growth mechanisms of polymer assembly at the molecular level.
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