Chemistry
Condensation Polymerization
Condensation polymerization is a process in which monomers join together, releasing small molecules such as water, as a byproduct. This reaction forms longer polymer chains through the formation of covalent bonds between the monomers. Unlike addition polymerization, condensation polymerization involves the elimination of a small molecule during the polymerization process.
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10 Key excerpts on "Condensation Polymerization"
eBook - PDFAn Introduction to Polymer Chemistry
The Commonwealth and International Library: Intermediate Chemistry Division
- D. Margerison, G. C. East, J. E. Spice(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
CHAPTER 3 Condensation Polymerization IN THIS chapter we propose to examine the process of conden-sation polymerization in some detail. As its name implies, the formation of polymer is accompanied by the production of a simple, low molecular weight substance such as water, hydrogen chloride, etc. Typical of condensation polymers are the polyesters, polyamides and polyurethanes in which the linkages formed in the condensation reaction are : -c -o -II o -N H -C -II o -N H -C -O -II o The reactions by which such polymers are prepared are the familiar condensation reactions described in the standard texts of organic chemistry, the only special requirement being that the monomers used must be polyfunctional. If each monomer possesses two functional groups only, linear polymers are pro-duced; three-dimensional network structures, on the other hand, are formed when the functionality of one or more of the reactants exceeds two. The following examples illustrate the above points more explicitly. 119 120 AN INTRODUCTION TO POLYMER CHEMISTRY PRODUCTION OF LINEAR POLYMERS The polyesters Polyesters are formed by the reactions between an alcohol and an acid or an acid chloride and by ester interchange. For example, the reaction between adipic acid and ethylene glycol to produce polymer proceeds by a series of successive conden-sations. The first stage is the formation of an hydroxy carboxy-lic acid in which the difunctionality of the reactants is pre-served in the product.
eBook - PDFElements of Polymer Science & Engineering
An Introductory Text and Reference for Engineers and Chemists
- Alfred Rudin(Author)
- 1998(Publication Date)
- Academic Press(Publisher)
This line of reasoning takes us into a more detailed consideration of polymerizations in this and succeeding chapters. 155 156 5 Step-Growth Polymerizations A condensation polymer is one in which the repeating unit lacks certain atoms which were present in the monomer(s) from which the polymer was formed or to which it can be degraded by chemical means. Condensation polymers are formed from bi- or polyfunctional monomers by reactions which involve elimination of some smaller molecule. Polyesters (e.g., 1-5) and polyamides like 1-6 are exam-ples of such thermoplastic polymers. Phenol-formaldehyde resins (Fig. 5-1) are thermosetting condensation polymers. All these polymers are directly synthesized by condensation reactions. Other condensation polymers like cellulose (1-11) or starches can be hydrolyzed to glucose units. Their chemical structure indicates that their repeating units consist of linked glucose entities which lack the elements of water. They are also considered to be condensation polymers although they have not been synthesized yet in the laboratory. In addition polymers, by contrast, the recurring units have the same structures as the monomer(s) from which the polymer was formed. Examples are polystyrene (1-1), polyethylene (1-3), styrene-maleic anhydride copolymers (1-26), and so on. The difficulty with these definitions is that the same macromolecular structure can be made by different reaction pathways. This situation occurs particularly when cyclic and linear monomers can produce the same polymer. Thus nylon-6 can be made by either of two reactions: H2C ~CH2 / ^CH2 H / I -H,0 HjC C=0 --f N -f C H j -^ C -^ — ^ H ^ N -f C H j -^ ^ C -O H (5-1) / nylon 6 0 0 H 2 C — N -H c-ominohexanoic acid coproloctom The polyamide made from caprolactam is technically an addition polymer by the above definition, while the product made from the amino acid would be a conden-sation polymer.
eBook - PDF- Sami Matar Ph.D., Lewis F. Hatch Ph.D., Sami Matar, Ph.D., Lewis F. Hatch, Ph.D.(Authors)
- 2001(Publication Date)
- Gulf Professional Publishing(Publisher)
CHAPTER ELEVEN Polymerization INTRODUCTION Polymerization is a reaction in which chain-like macromolecules are formed by combining small molecules (monomers). Monomers are the building blocks of these large molecules called polymers. One natural polymer is cellulose (the most abundant organic compound on earth), a molecule made of many simple glucose units (monomers) joined together through a glycoside linkage. ~ Proteins, the material of life, are polypeptides made of ~-amino acids attached by an amide 0 II --(- CNH-)-- linkage. The polymer industry dates back to the 19th century, when natural polymers, such as cotton, were modified by chemical treatment to pro- duce artificial silk (rayon). Work on synthetic polymers did not start until the beginning of the 20th century. In 1909, L. H. Baekeland prepared the first synthetic polymeric material using a condensation reaction between formaldehyde and phenol. Currently, these polymers serve as important thermosetting plastics (phenol formaldehyde resins). Since Baekeland's discovery, many polymers have been synthesized and marketed. Many modern commercial products (plastics, fibers, rubber) derive from poly- mers. The huge polymer market directly results from extensive work in synthetic organic compounds and catalysts. Ziegler's discovery of a coordination catalyst in the titanium family paved the road for synthe- sizing many stereoregular polymers with improved properties. This chapter reviews the chemistry involved in the synthesis of polymers. 301 302 Chemistry of Petrochemical Processes MONOMERS, POLYMERS, AND COPOLYMERS A monomer is a reactive molecule that has at least one functional group (e.g.-OH,-COOH,-NH2,-C=C-). Monomers may add to them- selves as in the case of ethylene or may react with other monomers hav- ing different functionalities. A monomer initiated or catalyzed with a specific catalyst polymerizes and forms a macromolecule~a polymer.
eBook - PDF- Robert O. Ebewele(Author)
- 2000(Publication Date)
- CRC Press(Publisher)
Chapter 6 Condensation (Step-Reaction) Polymerization I. INTRODUCTION Condensation Polymerization is chemically the same as a condensation reaction that produces a small organic molecule. However, as we sa w in Chapter 2, in Condensation Polymerization (i.e., production of a macromolecule) the functionality of reactants must be at least 2. Recall that functionality was defined as the average number of reacting groups per reacting molecule. To derive expressions that describe the physical phenomena occurring during Condensation Polymerization (polycondensation) — a tool vital to process design and product control — three approaches have been traditionally adopted: kinetic, stoichiometric, and statistical. Various degrees of success have been achieved by each approach. We treat each approach in the succeeding sections. Before then, we briefly discuss the overall mechanism of polycondensation reactions. II. MECHANISM OF Condensation Polymerization The mechanism of polycondensation reactions is thought to parallel that of the low-molecular-weight analogs. As a result of their macromolecular nature, polymers would be expected to have retarded mobility. It was therefore predicted, purely on theoretical arguments, that the chemical reactivity of polymers should be low. • The collision rate of polymer molecules should be small due to their low kinetic velocity. This should be accentuated by the high viscosity of the liquid medium consisting of polymer molecules. • Shielding of the reactive group within the coiling chain of its molecule should impose steric restrictions on the functional group. This would lead to a reduction in the reactivity of the reactants. Flory 1 has shown from empirical data that for a homologous series the velocity constant measured under comparable conditions approaches an asymptotic limit as the chain length increases.
eBook - PDFThe Elements of Polymer Science and Engineering
An Introductory Text for Engineers and Chemists
- Alfred Rudin(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
This line of reasoning takes us into a more detailed con-sideration of polymerizations in this and succeeding chapters. A condensation polymer is one in which the repeating unit lacks cer-tain atoms which were present in the monomer(s) from which the polymer was formed or to which it can be degraded by chemical means. Condensa-155 156 OH OH H O C H , Ο ] • 2 C H 2 0 ' (excess) A L K A L I N E CONDITION S CH Ο 5 Step-Growth Polymerizations ' R E S O L E ' T Y P E PRODUCTS C U R E HOCH NETWORK P O L Y M E R (b) OH 3 ΓOJ +2CH 2 0-ACIDIC CONDITIONS OH OH CH2 OH NOVOLAC TYPE PRODUCTS CURE with added hexamethylene tetramine NETWORK POLYMER Fig. 5-1. Phenol-formaldehyde polymers, (a) Character of resole^-type resins nor-mally produced with excess formaldehyde under alkaline conditions; (b) ''novolac^-type resins normally made with excess phenol under acidic conditions. (a) OH Ο 5.1 Condensation and Addition Polymers 157 tion polymers are formed from bi- or polyfunctional monomers by reac-tions which involve elimination of some smaller molecule. Polyesters (e.g., 1-5) and polyamides like 1-6 are examples of such thermoplastic polymers. Phenol-formaldehyde resins (Fig. 5-1) are thermosetting con-densation polymers. All these polymers are directly synthesized by con-densation reactions. Other condensation polymers like cellulose (1-8) or starches can be hydrolyzed to glucose units. Their chemical structure in-dicates that their repeating units consist of linked glucose entities which lack the elements of water. They are also considered to be condensation polymers although they have not been synthesized yet in the laboratory. In addition polymers, by contrast, the recurring units have the same structures as the monomer(s) from which the polymer was formed. Ex-amples are polystyrene (1-1), polyethylene (1-3), styrene-methyl meth-acrylate copolymers (1-35), and so on.
eBook - PDF- John J. McKetta Jr(Author)
- 1993(Publication Date)
- CRC Press(Publisher)
892 Polymerization Polymerization Introduction Polymerization conditions and processes often differ greatly for the pro-duction of different high polymers or even in some cases the same polymers. Careful control of the operating conditions is needed in all cases to obtain high-quality products in an economical manner. The high polymers consid-ered here are those that have high molecular weights and that find uses as plastics, elastomers (or synthetic rubbers), synthetic fibers, adhesives, and surface coatings, such as paints or varnishes. The operating conditions for the production of a polymer affect the rates of polymerization and also at least some of the following structural features of the polymer molecules: molecular weight, cross-linking, linearity of the molecule, branching, and stereospecificity. These features have a major effect on the morphology or packing abilities of the molecules and hence on the physical properties of the polymers. The relationship between struc-tural features of the molecules and physical properties is considered in more detail later. Chemistry of Polymerization Based on the reactants used to produce the polymers, polymerizations are divided into two broad categories: polycondensations and addition polym-erizations. Polycondensation Polyesters, polyamides (or nylons), polyurethanes, phenolics, urea resins, and epoxies are important examples of polycondensations. Often but not always, two or more reactants are employed, and the average functionality of the reactants must be at least two. A functionality of one is defined as the ability of a molecule to form a single chemical bond with another mol-ecule. With a functionality of two, chemical bonds can be obtained with two other molecules. In the latter case, polymerization can occur and the polymer chain can increase in length (and molecular weight), forming so-called linear molecules.
eBook - PDFCompositional Analysis of Polymers
An Engineering Approach
- Aleksandr M. Kochnev, Oleg V. Stoyanov, Gennady E. Zaikov, Renat M. Akhmetkhanov, Aleksandr M. Kochnev, Oleg V. Stoyanov, Gennady E. Zaikov, Renat M. Akhmetkhanov(Authors)
- 2016(Publication Date)
- Apple Academic Press(Publisher)
TECHNICAL HINTS ONPOLYCONDENSATION G. E. ZAIKOV Russian Academy of Sciences, Moscow, Russia CHAPTER 5 CONTENTS 5.1 Process Overview ......................................................................................... 104 5.2 Kinetics of Polycondensation ...................................................................... 107 5.3 Effect of Catalysts on the Course of Polycondensation ............................... 112 5.4 Effect of Monomer Structure on the Polycondensation Process .................. 116 5.5 Copolycondensation ..................................................................................... 117 5.6 Basic Types of Polycondensation Reactions ................................................ 118 5.7 Crosslinking in the Polycondensation Process ............................................ 121 5.8 Technical Methods of Polycondensation Piloting ....................................... 123 References ............................................................................................................. 126 104 Compositional Analysis of Polymers: An Engineering Approach 5.1 PROCESS OVERVIEW The Condensation Polymerization, often called as polycondensation, is a con-densation reaction of a large number of monomer molecules or comonomers to the polycondensate macromolecules, during which water, hydrogen chloride, ammonia, and other simple compounds are released as byproducts. In the polycondensate macromolecules,the main chain is formed not only of carbon atoms but it also includes atoms of other elements such as oxygen, nitrogen, phosphorus, boron, or silicon. Polycondensation is a special case of substitution reaction, in which multifunctional molecules react with each other and the equilibrium conditions do not interfere with the formation of long-chain molecules. In contrast to the addition polymerization, the Condensation Polymerization is a gradual reaction.
eBook - PDF- Stoyko Fakirov(Author)
- 2008(Publication Date)
- Wiley-VCH(Publisher)
F. Cheung, A. Golovoy, H. van Oene, J. Appl. Polym. Sci. 40, 963 (1990) 94. M. F. Cheung, K. R. Carduner, A. Golovoy, H. van Oene, J. Appl. Polym. Sci. 40, 977 (1990) 95. E. V. Guinlock, R. A. Wolfe, J. C. Rosenfeld, J. Appl. Polym. Sci. 20, 949 (1976) 96. F. Pilati, C. Berti, M. Fiorini, M. Toselli, V. N. Ignatov, V. Tartari, C. Car- Taro, R. Pippa, A. Moro, POC’94, 6th International Symposium on Polymer Supported Reactions in Organic Chemistry, Venezia, Italy, 19-23 June 1994, p. 140 97. C. Berti, E. Marianucci, B. Sweileh, F. Pilati, M. Fiorini, 4th AIM Conference on Advanced Topics in Polymer Science, Gargnano (Bs), Italy, 2-7 June 1996, p. 40 Chapter 3 Model Studies of Transreactions in Condensation Polymers J. Devaux 1. Introduction Condensation polymers, as defined by Carothers [l], are those polymers ob- tained by a coupling reaction between polyfunctional monomers, involving the elimination of a small molecule, e.g., water. Later on [2], condensation polymers were defined as polymers with repeat units joined together by functional units of one kind or another, such as ester, amide, urethane, sulfide, and ether linkages. Other classifications, such as Flory’s [3], em- phasise the differences in polymerisation mechanisms for the distinction between polymers. A main characteristic of the condensation polymers lies in their polymerisation reaction, which progresses stepwise, through succes- sive equilibrated steps. End-groups of condensation polymers are usually reactive. As thermodynamic equilibria are always dynamic states, conden- sation polymers in thermodynamic equilibrium are “living” species, con- tinuously exchanging end-groups and chain linkages. As a consequence, in “pure” polycondensates this leads to equilibrium molecular weight distri- butions. The situation becomes more complex when two, or more, condensation polymers are mixed together, forming homogeneous binary phases.
eBook - PDF- Kuchanov, Dusek(Authors)
- 1992(Publication Date)
- CRC Press(Publisher)
SOME DEFINITIO NS The main differenc e between polyc ondensati on and polymerization processes from the kinetic point of view consi sts in the way of polymer chain formation [I] . B. A. Rozenberg and V 1./rzhak The polyc ondensatio n process proceeds according to gen eral kinetic equation: (1) In this case the functional groups of chains can react with each other. Ther efore, a chain is formed by as sembly of separate fragments. The polymerization proces s can be describ ed in the foll owing way: • * R i , j , k + MJ,n -R (i+l}, (j+n-l),k (2) i.e . the proces s of chain assembly is the result of a successiv e addit ion of single * units to the active propag ating chain R . . k' Her e R are polymer chains, M is l,J , monomer. First index char acterizes the number of monomer units, the second one -a number of functio nal groups and the third one -a number of active cent ers in a chain. Reactions ( 1) and (2) can be irrev ersible or reve rsible. For simplification we will consider below only irrevers ible reactions. The definition of thes e process es to our mind complete ly exhausts the kinetic aspect of the problem. However, there are some different definitions [2,3]. It is worth making two rema rks. The first one: in contrast to the widely spread definitio n of polyc ondensation as the process of polymer formation that was ac companied by elim inat ion of low molecular compounds, this feature of polycondensation can be ignored in the kinetic defin ition used her e. The second one: the polyaddition reactions withou t any elim inat ion of low molecu lar sub stances (like formation of epoxy-amin e or polyurethane polymers and so on) in used clas sif icat ion are also consider ed as polyconde nsatio n reactions. We also must note tha t the formati on of network polymers by crosslink ing of alre ady prepa red polymers can be formally describe d as polyc onde nsatio n or polymerizat ion process es [ 1 ] .
eBook - PDFIntroduction to Polymer Science and Chemistry
A Problem-Solving Approach, Second Edition
- Manas Chanda(Author)
- 2013(Publication Date)
- CRC Press(Publisher)
The gel particles so formed remain suspended in the medium and increase in number as reaction continues. At the experimentally observed gel point, the concentration of gel particles reaches a critical value and causes phase inversion as well as a steep rise in viscosity. The lower value of p c predicted by the statistical approach is also attributed to the occurrence of some wasteful intramolecular cyclization reactions not taken into account in the derivation and also in some cases to the limited applicability of the assumption of equal reactivity of all functional groups of the same type, irrespective of molecular size. 5.6.2.3 Molecular Size Distribution Expressions for molecular size distributions in multifunctional condensation leading to three-dimensional polymers are derived (Flory, 1941, 1946, 1953; Stockmayer, 1943, 1952, 1953) by following much the same approach as for linear polymers, though with much more dif fi culty. Only the results of these derivations will, however, be considered here. The derivations are based on three simplifying assumptions of ideal network formation: (1) all functional groups of the same type are equally reactive and independent of size of molecules to which they are attached; (2) all groups react independently of one another; and (3) no intramolecular reactions (cyclization) occur. 256 Chapter 5 Figure 5.8 A model for the process of gelation. (After Bobalek et al., 1964.) The simplest possible type of three-dimensional polymer is that formed by stepwise homopoly-merization of a multifunctional monomer, such as etheri fi cation of pentaerythritol, or by stepwise copolymerization of equimolar amounts of two monomers having the same functionality f , such as the condensation of a trihydric alcohol with an equimolar proportion of a tribasic acid, all three functional groups on each monomer being equally reactive.
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