Made by faculty at the university of colorado boulder department of chemical and biological. An example is adipic acid that has two functional groups, but both are carboxylic acid groups. These are quite general, and can easily be applied in such diverse and emerging fields as polymerization applications in photolithography and microelec tronics. What are some characteristics of a step growth polymerization with relation to time. Despite the amazing growth of scientific contributions in this field since 2002, to our surprise the possibilities to combine stepgrowth. Stepgrowth polymerization process modeling and product. This kind of step growth polymerization is often called a condensation process polymerization steps 1. Chaingrowth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. Stepgrowth polymerization journal of chemical education. 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. There is no termination step and the end groups of the oligomers and polymers are reactive throughout the polymerization process. There are many forms of polymerization and different systems exist to categorize them. Intro to polymer chemistry exam 2 flashcards quizlet.
Roughly speaking, these processes are analogous to the chain growth and step growth mechanisms of polymer assembly at the molecular level. 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. Many naturally occurring and some synthetic polymers are produced by step growth polymerization. The first six chapters present the principles of step growth polymerization. In chain growth polymerization, a polymer chain is formed at the beginning by the attachment of one monomer at a time. Step growth polymerization typically takes place between monomers containing functional groups that react in high yield to form new functionalities. 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. 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. By combining the above expression with carothers equation and solving for m one obtains. 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. The easiest way to visualize the stepgrowth mechanism is a crowd of people. 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 p olymerization mechanism in which bifunctional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. During polymerization, smaller molecules, called monomers or building blocks, are chemically combined to create larger molecules or.
Step growth polymerization this polymerization method typically produces polymers of lower molecular weight than chain reactions and requires higher temperatures to occur. 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. 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. Unlike addition polymerization, step wise reactions involve two different types of difunctional monomers or end group that react with one another, forming a chain. These 3 types of polymerization share 3 common steps. A difunctional monomer or equal molar amounts of two. At edge of cell to cause protrusion against load force to notice. High impact polystyrene hips acrylonitrile butadiene. 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. In chain growth polymerizations, an initiator, like a freeradical, reacts with monomers that carry a reactive double bond, such as in ethylene.
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. The monomer in stepgrowth polymerization will be consumed very quickly to dimer, trimer or oligomer. 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. Chemical engineering 160260 polymer science and engineering lecture 6 mechanism and kinetics of free radical chain polymerization january 29, 2001. 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. Stepgrowth polymerization forms polymers in a manner that is. Stepgrowth polymerization an overview sciencedirect. Stepgrowth polymerization forms polymers in a manner that.
The polymerization of unsaturated monomers typically involves a chain growth polymerization. The mechanism requires that at least two different monomers participate in the reaction. There exist, exceptionally, some polymerizations that proceed via chain reactions that, according to the definition, are not chain polymerizations. First, we examine how the degree of polymerization. Stepgrowth polymerization forms polymers in a manner that is quite different from chaingrowth polymerization. Chaingrowth polymerizations require the presence of an initiating molecule that can be used to attach a monomer molecule at the beginning of the polymerization. Synthesis of macromolecules by step growth polymerization 4 4. Two types of monomers can undergo step growth polymerizations.
Figure 41 molecular mass distributions in step growth polymerization. Since, each step produces a distinct functionalised species and is independent of each other, this process is also called as step growth polymerisation. Stepgrowth polymerization of inorganic nanoparticles. Most anionic reactions have no inherent termination step. Step growth polymerization process modeling and product design kevin seavey, y. In contrast with step growth polymerization, chain growth polymerization uses monomers that do not polymerize spontaneously without initiators 11, 17. This is a step growth polymerization not a chaintransfer or radical polymerization. Ni or pd catalyst for synthesis of conjugated polymers. 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. 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. Chemical engineering 160260 polymer science and engineering. Atom transfer radical polymerization atrp has proven to be a powerful technique to obtain polymers with narrow polydispersities and controlled molecular weight. 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. Nov 10, 2015 simultaneous step growth and chain growth cationic polymerization of styrenic monomers bearing carbazolyl groups.
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. Chain growth polymerization can be understood with the chemical equation. The technique is the most studied and utilized of the controlledliving radical polymerization techniques since a large number of monomers. Chemistry of industrial polymers chemistry of industrial polymers step growth polymerization. Stepgrowth polymerization article about stepgrowth. 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.
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. The formation of terylene or dacron by the interaction of ethylene glycol and terephthalic acid is an example of this type of polymerisation. Step growth polymerization is also used for preparing a class of adhesives and amorphous solids called epoxy resins. Dec 17, 20 an animation which explains step growth polymerization. Stepgrowth polymerization is a very important method for the preparation of some of the most important engineering and specialty polymers. Many naturally occurring and some synthetic polymers are produced by stepgrowth polymerization, e. Step growth polymerization, types of monomers, kinetics and equilibrium considerations, closed vs. Stepgrowth or addition polymerization involves the reaction between the functional. During propagation, only monomers react to the active site at the end of the growing chain. 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.
A detailed discussion of several important step growth polymeriz ations follows in the next five chapters. Chemistry of industrial polymers stepgrowth polymerization. The distinct initiation, propagation, and termination steps of chain growth polymerization are meaningless in step growth polymerization. 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. 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. 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. For example, aminocaproic acid has an amine group at one end and a carboxyl group at the other. Stepgrowth polymerization an overview sciencedirect topics. Monoliths from stepgrowth polymerization reactions. Cannot be used for polymers whose glass transition temperature is less than the polymerization temperature, or else aggregation will occur. 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. Mechanism of radical chain polymerization fundamental steps initiation, propagation.
The oldest polymers rejuvenated leen billiet, david fournier, filip du prez volume 50, issue 16, 31 july 2009, pages 38773886. For example, a monomer conversion of p 99% would be required to achieve x n 100. Converting monomer to long chain polymer is the final step in the polymer manufacturing sequence. 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. Difference between chain growth and step growth polymerization. A rational strategy for the realization of chaingrowth. Two other types of monomers that combine via stepgrowth polymerization. Stepgrowth polymerization forms polymers in a manner that is quite different from chain. The mechanism requires that at least two different monomers participate. Step growth polymerization and condensation polymerization step growth polymerization and condensation polymerization are two different concepts, not always identical. Polymerization kinetics step growth slow can use statistical methods as well as kinetics to describe mol. Objectives polymers national council of educational. In step growth polymerization, oligomers are formed at the beginning and are later combined together, forming the polymer chain. Condensation polymerization get full description along.
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. Synthesis of macromolecules by step growth polymerization 4. Transformation of stepgrowth polymerization into living chain. 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. Step growth polymerisation this type of polymerisation is due to the condensation process which takes place in several steps.
Classical polycondensation is a step growth process, but a living polymerization polycondensation must proceed by a chain growth rather than a step growth mechanism. The reaction can be carried out in solution, in bulk melt, or in solid state. 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. The bisphenol a groups are reacted with proton acceptors such as naoh to obtain the polymerization functional groups. Post polymerization or how to make a graft copolymer examples. Synthetic methods in stepgrowth polymers request pdf. New polymers synthesis by organocatalyzed stepgrowth. We rarely board airplanes by joining the back of a single wellordered line. Stepgrowth polymerization and stepgrowth polymers rro.
The two most important step growth polymerizations are condensation and addition polymerization. All molecules present monomer, oligomer, polymer can react with any other molecule. Elements of stepgrowth polymerization branching network. In the following example, the same bisphenol a intermediate used as a monomer for lexan serves as a. Here the covalent bonding occurs by an s n 2 reaction between a nucleophile, usually an amine, and a terminal epoxide. Jan 30, 2012 an introduction to step growth polymerization. Where in the cell is polymerization most important. Living supramolecular polymerization established by combining energy. Pdf simultaneous chaingrowth and stepgrowth polymerization. Stepgrowth polymerization american chemical society.
Why pdi is usually greater than 2 in real polymerization system. The polymer size is dependent on the percent conversion. Simultaneous chaingrowth and stepgrowth polymerizationa new route to cyclic polymers. Transformation of stepgrowth polymerization into living. Open systems kinetics of step growth polymerization chapter 2. Stepgrowth polymerization refers to a type of polymerization mechanism in which bifunctional.
Made by faculty at the university of colorado boulder department of chemical and biological engineering. 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. Step growth polymerization of inorganic nanoparticles. There are two distinctive mechanisms during polymerization. The degree of polymerization dp was depending more significantly on the monomer arrangement, that is, the crystal structure, then on stoichiometry. 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.
Reaction engineering of step growth polymerization springerlink. 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. The polyester dacron and the polyamide nylon 66, shown here, are two examples of synthetic condensation polymers, also known as step growth polymers. Stepgrowth polymerization request pdf researchgate. This is fully supported by the monte carlo simulation on the basis of the polymerization mechanism.
These polymers are then processed to make various kinds of plastic products. Examples of polymers formed through step growth mechanism. More often, we jostle around in one of several bulging crowds that merge haphazardly near the gate. 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. High molecular weight chains are only obtained near the very end of the reaction. 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 fact polyurethane polymerizes with addition polymerization because its polymerization produces no small molecules, but its reaction mechanism corresponds to a step growth polymerization.1078 1069 802 360 510 861 1105 452 244 957 1060 1426 570 1212 546 312 1546 1051 1119 913 49 1443 781 850 774 970 1051 1265 983 948 905 1025 1089 84 817 1276 103 677 181