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.
6 Key excerpts on "Condensation Polymerization"
- Shashanka Rajendrachari, Orhan Uzun(Authors)
- 2021(Publication Date)
- Bentham Science Publishers(Publisher)
...It is defined as a polymerization reaction in which bifunctional or polyfunctional monomers undergo an intermolecular condensation reaction with the elimination of byproducts like H 2 O, HCl, NH 3, etc. Bakelite, polyester (Dacron) and polyamide (Nylon 6,6) can be prepared by Condensation Polymerization. 5. DIFFERENCES BETWEEN ADDITION AND Condensation Polymerization Some of the differences between addition and Condensation Polymerizations are given below [ 13 ]. Table 2 Differences between addition and Condensation Polymerization. Addition Polymerization Condensation Polymerization This polymerization reaction involves addition of monomers This polymerization involves condensation reaction It is a chain reaction of monomers It precedes step wise Monomers with double bonds undergo addition polymerization Monomers with functional groups undergo Condensation Polymerization No by-products will be eliminated It involves elimination of by-products like H 2 O or HCl or NH 3 The reaction is spontaneous (fast) The rate of reaction is slow Addition polymerization results in thermoplastics Condensation Polymerization results in thermosetting plastics It is a chain growth polymerization It is a step growth polymerization Product yield does not depends upon duration of the reaction Product yield depends upon duration of the reaction. More the reaction time, more is the product 6. FREE RADICAL MECHANISM DURING ADDITION POLYMERIZATION [ 3 ] Addition polymerization takes place through the free radical mechanism and it involves three different stages: initiation, propagation, and termination [ 14, 15 ]. Initiation A free radical is an atomic or molecular species having an odd or unpaired electron...
eBook - ePubFundamentals of Polymer Science
An Introductory Text, Second Edition
- Michael M. Coleman, Paul C. Painter(Authors)
- 2019(Publication Date)
- CRC Press(Publisher)
...In this case no further condensations are possible and polymers are not formed. The structural units of addition polymers, in contrast, have the same molecular formula as their monomers, although the arrangement of bonds is different, as in ethylene and polyethylene: There are exceptions, however, and some polymerizations fit uneasily into these two categories. For example, polyurethanes, which are formed by the reaction of isocyanates and alcohols, are considered condensation polymers, even though water is not eliminated during the reaction: Furthermore, ring opening polymerizations must be regarded as addition polymerizations, but they form polymers that could also be synthesized by an appropriate condensation reaction, as in the polymerization of caprolactam: where the resulting polyamide could also be produced by polymerization of the appropriate amino acid: Figure 2.1 Schematic representation of step-growth polymerization. Accordingly, we prefer to adopt the classification given by Rempp and Merrill (Polymer Synthesis, 1986), where polymerization reactions are considered to be either step-growth (this category includes polycondensations) or chain polymerizations (which include ring opening polymerizations). One final thing needs to be kept in mind before we proceed to discuss the specifics of polymerization. In the following chapter we will discuss aspects of the kinetics of these reactions that will inherently assume that we are dealing with a batch process. In other words, we will consider a reaction “pot” into which we place monomer, which then reacts to form polymer and is therefore used up proportionally. In certain cases we might also have solvent, initiator, and perhaps one or two other additives present. These conditions are characteristic of most laboratory studies of polymerization that we will be concerned with here, as these provide the fundamental insights into mechanism and its relationship to the nature of the product...
- Enrique Saldivar-Guerra, Eduardo Vivaldo-Lima(Authors)
- 2013(Publication Date)
- Wiley(Publisher)
...In an addition polymer, the repeating unit has the same composition as that of the monomer; the only difference is the change of chemical bonds with respect to those of the monomer. On the other hand, in a condensation polymer, according to the original idea of Carothers, some atoms of the monomer are lost as a condensation compound when the monomers react to form the repeating unit of the polymer. Some years after the original Carothers classification, it became clear that some polymers, for example, polyurethane, which is synthesized by the reaction between a diol and a diisocyanate, would not generate any condensation molecule, so they could not be classified as a condensation polymer; still their chemistry and structure had much more in common with those of condensation polymers than with those of addition polymers; therefore, the criterion for classification of a polymer as one of condensation type was changed to include this type of cases. The modern accepted criterion determines that a condensation polymer is that which satisfies any of the following conditions: (i) some atoms of the monomer are lost as a small molecule during their synthesis or (ii) they contain functional groups as part of the main polymer chain, such as ester, urethane, amide, or ether. If a polymer does not satisfy any of these criteria then it is an addition polymer. 4 This issue is further discussed in Odian [8]. 1.2.2 Classification Based on Mechanism A second major classification of polymers was proposed by Flory [1] in 1953. This is based on the kinetic mechanism of the polymerization reaction. Flory classifies polymerizations into two categories: Step-growth polymerization; Chain polymerization. 1.2.2.1 Step-growth Polymerization The simplest scheme of this polymerization involves the reaction of a difunctional monomer AB, which contains both functional groups A and B in the molecule. For example, A can be an amine and B a carboxylic acid group...
eBook - ePubBiermann's Handbook of Pulp and Paper
Volume 2: Paper and Board Making
- Pratima Bajpai(Author)
- 2018(Publication Date)
- Elsevier(Publisher)
...Sometimes the polyacrylic acid polymers are reacted with starch to form the superabsorbent polymers. Figure 18.3 Polymerization of dienes. The position of the double bond is variable; it may be a side group. Figure 18.4 Vinyl polymer structures. Figure 18.5 Acrylic ester structures. Another type of addition polymerization is the ring opening reaction. One example is the polymerization of ethylene oxide used to form polyethylene glycols and ethoxylated molecules used as surfactants. 18.3. Condensation Polymers The condensation mechanism is used to make polymers from monomers with two (or more for cross-linked polymers) reactive functional groups by a step-wise reaction. Each reaction step between two monomers produces a simple molecule, often water, but sometimes NH 3 or another molecule, as a side product. These reactions are common, well-known organic chemistry reactions. They are easily controlled reactions, unlike free radical reactions. The most common reactions of synthetic polymers are esterification (formation of ester linkages) and amidation (formation of amide linkages). Fig. 18.6 gives an example of each. In the case of nylon 6,6 (6 is the number of carbon atoms in each of the two monomers if a dicarboxylic acid and diamine were used to form it), it is possible to use a single compound to make the polymer, that is, H 2 N(CH 2) 5 COOH. It is apparent that monomers will react together initially and small polymers (oligomers) will react later. This means that after a short time essentially all of the monomers will be gone and oligomers will exist. These oligomers will then react to form short-chain polymers, then the short-chained polymers will react to form moderately long-chain polymers. The number average DP can be predicted as a function of the extent of reaction. The extent of reaction is the fraction of functional groups, which have participated in the polymerization reaction...
eBook - ePub- Marianne Gilbert(Author)
- 2016(Publication Date)
- Butterworth-Heinemann(Publisher)
...It is also possible to open other double bonds such as carbonyl carbon–oxygen and to open a wide range of rings in cyclic monomers. An example of the former is the polymerization of formaldehyde to give polyacetal (also known as polyoxymethylene and polyformaldehyde) (Eqn (2.2)). x CH 2 O → (CH 2 O) x (2.2) The other main type of polymerization is step reaction polymerization. This involves the reaction of pairs of functional groups on the monomers, sometimes with the elimination of a small molecule such as water (hence the former name Condensation Polymerization). An example of a step reaction is the production of polyamide 66 (Table 2.1). The reaction which occurs is shown in Eqn (2.3). x H 2 N(CH 2) 6 NH 2 + x HOOC(CH 2) 4 COOH ⇌ (HN(CH 2) 6 NHOC(CH 2) 4 CO) x + 2 x H 2 O (2.3) Removal of water drives the reaction to the right, and a linear polymer can be formed. Polymerization proceeds by a series of separate steps. Some general characteristics of the two types of polymerization described above are shown in Table 2.3. The two types of polymerization described above are also used to produce thermosetting plastics. For example, phenol formaldehyde resins are produced from phenol and formaldehyde, which initially react as shown in Eqn (2.4)...
- Anil Kumar, Rakesh K. Gupta(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
...7 Emulsion Polymerization 7.1 INTRODUCTION Emulsion polymerization is a technique of polymerization where polymer formation occurs in an inert medium in which the monomer is sparingly soluble (not completely insoluble). Traditionally, water is the inert medium and the initiator is chosen such that it is water soluble. Monomers undergoing step-growth reaction do not require any initiation and are not polymerized by this method. Emulsion polymerization is commonly used for vinyl monomers undergoing addition polymerization and, even among these, those that polymerize by the radical mechanism are preferably polymerized by this method. Water-based emulsions for ionic polymerizations are uncommon because of high-purity requirements. This discussion is therefore restricted to the polymerization of monomers following the radical mechanism only. The water-soluble initiator commonly used is potassium or sodium persulfate, and the usual recipe for emulsion polymerization is 200 parts by weight of water, 100 parts by weight of the monomer, and 2–5 parts by weight of a suitable emulsifier [ 1, 2 ]. The monomer should be neither totally soluble nor totally insoluble in the water medium and must form a separate phase. The emulsifier is necessary to ensure that the monomer is dispersed uniformly, as in a true emulsion [ 3, 4, 5, 6, 7, 8 ]. The polymer that is formed from emulsion polymerization is in the form of small particles having an average diameter around 5 μm. The particles form a stable emulsion in water. Their separation can be effected only through the evaporation of water, and once the water is evaporated, these particles coalesce to a solid mass...
