The mechanism requires that at least two different monomers participate. The following animation illustrates the polymerization of vinyl chloride initiated by radicals. After 75 per cent of the monomer molecules have reacted in this case the degree of polymerization n 12. This rate of propagation applies if the kinetic chain length is large and if the. Pdf reinvestigation of numerous ringopening polymerizations by means of malditof mass spectrometry has evidenced that cyclic polymers were formed. Radical chaingrowth polymerization of vinyl chloride. Properties of polymers, difference of chain growth and. The stiffer molecular chain of polystyrene and the dilution of polyisoprene chains slow down the rate and efficiency of formation of the highly crosslinked selfprotective layer. Stepgrowth polymerization forms polymers in a manner that is. Quizlet flashcards, activities and games help you improve your grades. Chain growth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. Chaingrowth polymerization for poly3hexylthiophene with a.
The in species represents the initiating radical, which might originate from a peroxide or azo initiator. Characteristics of chaingrowth polymerisation growth by addition of monomer only at one end or both ends of chain some monomer remains even at long reaction times different steps operate at different stages of mechanism i. Chain growth polymerisation the reaction starts rapidly at the beginning and high masses are attained at the end of the reaction about 500000 gmole. The limits of precision monomer placement in chain growth. The chemical reaction needs a catalyst and forms a free radical before polymerization is complete. Chain growth polymerization of styrene and methyl methacrylate study guide by vava55555 includes 11 questions covering vocabulary, terms and more.
Longer chain lengths give higher molecular weight mw and lower melt flow rates. Initiation, propagation, termination, and chain transfer molar mass of backbone chain increases rapidly at early stage. Plastic resins used in molding are formed by connecting many short units monomers into long, chain lengths polymers. Comparison of common polymerization methods stepgrowth chaingrowth anionic growth method cons. These 3 types of polymerization share 3 common steps.
Differences between step growth polymerization and chain growth polymerization. If the propagation step is much faster than the initiating step, two or more polymers differing in chain length and stereospeciflcity are obtained. 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. Objectives polymers national council of educational. This file is licensed under the creative commons attributionshare alike 4. By using a polytriazole, either as a small molecule or polymer, as core to effectively confine cu catalyst, linear polytriazole arms were synthesized for the first time with favored monomerpolymer reactions instead of random bimolecular reaction. Other articles where stepgrowth polymerization is discussed. Chaingrowth polymerizations require the presence of an initiating molecule that can be used to attach a monomer molecule at the beginning of the polymerization. Determine the concentration and mole fraction of polymers of chain length j in terms of initial.
In this chapter, we only discuss free radical chain 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. Polyphenylene ethynylene conjugated polyelectrolytes. Free radical polymerization is a type of chain growth polymerization, where the polymer is formed by consecutive addition of unsaturated monomer molecules to an active, free radical center. Differences between stepgrowth polymerization and chaingrowth polymerization step growth chain growth growth throughout matrix rapid loss of monomer early in the reaction similar steps repeated throughout reaction process average molecular weight increases slowly at low conversion and high. 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. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. Differences between stepgrowth polymerization and chaingrowth polymerization. The chain growth center of a ringopening polymerization can be a free radical, an anion, or a cation. The ionic chain polymerization will be discussed in chap.
Stepgrowth polymerization forms polymers in a manner that is quite different from chaingrowth polymerization. Polymers products that are commonly referred to as plastics by the general public are known to chemists as polymers. Free radical polymerization can be iniitated by thermal, chemical or photolytic decomposition of initiator molecules. Dhooge1,4 67th canadian chemical engineering conference, edmonton, 2225. Rubber and cellulose molecules have similar mass ranges, but fewer monomer units because of the monomers larger size. Chapter two, stepgrowth polymerization, version of 1505 75 2 stepgrowth polymerization 2. A polymer is a macromolecule which consists of small molecular units that are repeated over and over again to form a long chain. Initiation volume of nitrogen evolved from the decomposition of aibn chain growth. During propagation, only monomers react to the active site at the end of the growing chain. The characteristic of a chain polymer is that polymer growth. Chain growth polymerization involves the polymer growing by adding monomers on to the ends of the chain of the polymer.
The three steps in chainreaction polymerization are initiation, propagation and termination. Chaingrowth polymerization for the synthesis of polyfluorene. Chapter two, step growth polymerization, version of 1505 75 2 step growth polymerization 2. Chaingrowth 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. Many naturally occurring and some synthetic polymers are produced by stepgrowth polymerization, e. In this lab, the polystyrene is made by chain growth polymerization.
Other articles where step growth polymerization is discussed. Schanze department of chemistry, university of texas at san antonio, one utsa circle, san antonio, tx 78249. Dhooge, christopher barnerkowollik,2,3 european polymer federation, lyon, france, 0207072017. Compared to step growth polymerization, living chain growth polymerization shows low pdi, predictable molecular mass and controllable conformation. The presence of ggreek functional groups on the chains often enhances chainchain attractions, particularly if these involve hydrogen bonding, and thereby crystallinity and tensile strength. Plastic resins used in molding are formed by connecting. With chainreaction polymerization, there are three steps that takes two chemicals. Special issue in honor of professor krzysztof matyjaszewski. Polymerization, in polymer chemistry, is the process of reacting monomer molecules together in a chemical. In a stepgrowth polymerization, the molecular weight of the polymer chain builds up slowly and there is only one re action mechanism for the. Stepgrowth polymerization forms polymers in a manner that. This mechanism is known as chain growth and is shown schematically in figure 36 a, where a monomer unit is activated by initiator i and forms a chain very quickly. All molecules present monomer, oligomer, polymer can react with any other molecule. Intext questions there are two broad types of polymerisation reactions, i.
This file contains additional information such as exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. I think the exact statement is the degree of polymerization changes slowly when the convertion rate is low. Prediction of molecular weight distribution in chain growth. The principal steps in the chain growth mechanism are the. Explain the difference between a step growth and a chain growth polymerization. Mar, 20 applies the steadystate approximation to a chain growth polymerization to determine how the rate of reaction depends on initiator and monomer concentrations. The molecular weight is controlled by the feed ratio of 1 to the catalyst, even though the molecular weight distribution is broad. 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. 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.
We discuss this distribution further after we discuss chain reactions. In the model of chain growth polymerization, there is an assumption that all the functional groups have the same reactivity. Chain grow and free radical polymerization introduction chain growth polymerization monomers for chain. Augustine adu 2 p a g e polymerization aims and objectives. Augustine adu 1 p a g e kwame nkrumah university of science and technology, kumasi college of science department of chemistry pratical chemistry iv organic practial 2. Prediction of molecular weight distribution in chain. 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. Polyaddition and polycondensation occur in either group, but polyinsertion is a chain growth process exclusively. According to their growth mechanisms, polymerization reactions are divided into two major groups. The highest level of control over monomer placement achievable using chain growth polymerization techniques is obtained by addition of a nonhomopolymerizing monomer b, such as maleic anhydride, to a polymer of average length n a n, followed by subsequent chain extension 10,11,12. Step growth polymerization of colloidal monomers into chains. 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. Living polymerization free download as powerpoint presentation. Polymerization of resin is completed by one of two methods.
Differences between step growth polymerization and chain growth polymerization step growth chain growth growth throughout matrix rapid loss of monomer early in the reaction similar steps repeated throughout reaction process average molecular weight increases slowly at low conversion and high extents of reaction are. To quantify the resulting growth process, we relate the linear prism chains to polymer chains grown out of molecular monomers with. Pdf simultaneous chaingrowth and stepgrowth polymerization. All structured data from the file and property namespaces is available. Copy of 0510 quiz 3 introduction to polymers this week we saw a demonstration of nylon synthesis, we generally discussed stepgrowth or condensation and chaingrowth or addition polymerization and went through a list of about 30 common polymers and copolymers including their chemical structure. Berry professor and department chair of chemical engineering at west virginia university, where he has been teaching since 1981 explores the chemistry of synthesis, mechanisms of polymerization, reaction engineering of step growth and chain growth polymerization, polymer characterization, thermodynamics and structural, mechanical, thermal and transport behavior of polymers as melts, solutions. A step growth polymerization is the gradual growth of a polymer chain by the consecutive reaction of two bifunctional monomers. The mechanism requires that at least two different monomers participate in the reaction.
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. In this type of polymerisation, the molecules of the same monomer or. Prediction of molecular weight distribution in chain growth polymerizations volume 1767 ramiro infantemartinez, enrique saldivarguerra, odilia perezcamacho, maricela garciazamora, victor comparanpadilla. The mole fraction of polymer with a chain length j is just recalling m m o 1 p, we obtain r. 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.
At that time we noted that these classifications could be based on the following. Chain growth polymerization an overview sciencedirect. Draw the structures of monomers that can be polymerized by both processes. Polymerizations by a freeradical mechanism are typical freeradical reactions. Applies the steadystate approximation to a chain growth polymerization to determine how the rate of reaction depends on initiator and monomer concentrations. This assumption is very reasonable for this initiation mechanism. Chaingrowth polymerization forms polymers in such a manner that. Imaging the polymerization of multivalent nanoparticles in. The monomer is present throughout the polymerization but it decreases gradually. 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. In order to start such a reaction, an initiator is needed which has many at best 7 valence electrons like iodine for example.
The type of polymerization is dependent on the chemical groups the. Chain growth polymerization outline chain growth polymerization is a polymerization process or technique chain growth polymerization has the chemical equation. This represents a danger, for example during monomer transportation, since it may lead. Zieglernatta polymerization of olefins stereoselectivity. Chaingrowth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. The polymerization reaction kinetics of benzoxazine resins is described in this chapter. On the other hand, in chain growth polymerization, the monomer consumed steadily but the degree of polymerization could be increased very quickly after chain initiation. Chaingrowth polymerization article about chaingrowth. Chaingrowth polymerization for poly3hexylthiophene with a defined molecular weight and a low polydispersity akihiro yokoyama, ryo miyakoshi, and tsutomu yokozawa supporting information experimental. Suzukimiyaura coupling polymerization of 1 with amphos pd g3 in the presence of chain terminator 2 affords polyfluorene with pinbphcf 3 ends. These three types of reactions will be discussed in the following sections in considerable detail.
It is a kind polymerization where an active center free radical or ion is formed, and a plurality of monomers can be polymerized together in a short period of time to form a macromolecule having a large molecular weight. Chain growth polymerization for the synthesis of polyfluorene via suzukimiyaura coupling reaction from an externally added initiator unit akihiro yokoyama, hirofumi suzuki, yasuhiro kubota, kazuei ohuchi, hideyuki higashimura, and tsutomu yokozawa supporting information general. Stepgrowth polymerization forms polymers in a manner that is quite different from chain. Plastic resins used in molding are formed by connecting many. Living polymerization polymerization polymer chemistry.115 459 741 1166 930 66 1435 267 31 557 903 1237 384 148 1317 305 700 1204 438 1057 479 734 1176 977 1333 448 585 913 984 470