Polymerization reactions an overview sciencedirect topics. Based on the chemical reaction involved, polymerisation is divided into two groups known as addition polymerization and condensation polymerization. There are two fundamental polymerization reactions. The two reactions of more importaces is combustion and halogenation, i. There are two types of polymerization known as stepreaction polymerization or condensation and chainreaction polymerization. Converting monomer to long chain polymer is the final step in the polymer manufacturing sequence. Suppose we have a container full of ethene ethylene monomers and we unpair the pi electrons by a suitable method, either by appropriate radiation, or a free radical initiator. Polymers can be formed by a variety of reaction pathways. Polymerization reactions are divided into two groups known as step reactions also called condensation reactions and chain reactions also known as addition reactions. Development of the concept of a chemical reaction had a primary role in defining the science of chemistry as it is known today. Small molecules react with each other to form larger structural units while releasing smaller molecules as a byproduct, such as water or methanol. 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. A section discusses reactor design and the another one describes strategies for reactor operation.
When discussing the progress of step polymerization, it is not meaningful to use conversion of monomer as a measure because the reaction will still proceed even though all the monomer has been consumed. There is a loss of some simple molecules such as water and alcohol due to the condensation mechanism. It is used for most stepgrowth polymers and many types of chaingrowth polymers. Viscosity increases as conversion increases, making heat removal and processing more difficult. Pdf ethylene polymerization reactions with zieglernatta. Ethylene molecules are joined together in long chains. Let us do a comparative analysis of the two types of polymerization to understand them better.
Polyvinyl chloride pipe fittings, clear film for meat packaging. Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. Comparison of common polymerization methods stepgrowth chaingrowth anionic growth method cons. Step reactions require bifunctional or polyfunc tional monomers, while chain reactions require the presence of an initiator. These polycondensation reactions may result in the loss of some simple molecules as water, alcohol, etc. This can induce chain branching through the terminal double bond propagation reaction. There are two basic types of polymerization, chain reaction or addition and step reaction or condensation polymerization. In this unit we will look at those formed by the process of free radical polymerization. Polymers are highmolecularweight compounds, fashioned by the aggregation of many smaller molecules called monomers. Learn about polymers learn about condensation and addition polymerization reactions the two main types of polymerization reactions synthesize nylon synthesize slime identify the monomers and polymer in. Other types of reaction have been substitution and elimination. An azo polymerization initiator is a compound having an azo group rnnr, which decomposes with heat and light, and forms carbon radical. Addition polymerization the key feature of addition polymerization is that monomers add to one another in such a way that the polymeric product contains all the atoms of the starting monomers.
Polymerization is a reaction where monomers are converted into a polymer. The plastics that have so changed society and the natural and synthetic fibres used in clothing are polymers. The halogen reaction is very important in organic chemistry because it opens a gateway to further chemical reactions. In condensation polymerization, there is no termination step. A large molecule macromolecule built up by repetitive bonding covalent of smaller molecules monomers generally not a well defined structure, or molecular weight. Ch08 reacns of alkenes landscape page 1 reactions of alkenes since bonds are stronger than bonds, double bonds tend to react to convert the double bond into bonds this is an addition reaction. Once the reaction starts, heating is stopped as the reaction is exothermic. For example, a diacid can be allowed to react with a diol in the presence of an acid catalyst to afford a polyester.
In the polymerization with a rate of initiation much smaller than that of propagation, the value of s ridt increases with an increase in the reaction time. There are two general types of polymerization reactions. Add one more ring to it and repeat many times it becomes a chai. But in condensation polymerization, any molecule can react with any other. Polymerization is the process of converting the single units monomers to linked monomers called polymers poly many by chemical reactions. The addition reaction may occur by way of radical, cationic, or anionic intermediates. Carothers, a great and tragic figure in the history of polymer science, suggested that most polymers could be classified into two broad categories, condensation or addition. The monomers in these cases must contain two or more functional groups. These two types of polymerization both create high molecular mass molecules from monomers through a chemical reaction. A terpolymer is a copolymer which contains three types of repeat units.
The key feature of addition polymerization is that monomers add to one another in such a way that the polymeric product contains all the atoms of the starting monomers. 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. Condensation mechanism refers to combining of smaller molecules to obtain larger molecules. Bulk polymerization is carried out in the absence of any solvent or dispersant and is thus the simplest in terms of formulation. Difference between chain growth and step growth polymerization. Apply their knowledge of polymerization reactions to the synthesis of nylon and slime.
This type of reaction involves the repetitive condensation between two bifunctional monomers. Classification of polymerization reaction addition and. Condensation polymerization is a reaction that joins two functional groups such as an alcohol and a carboxylic acid and forms a second small molecule such as water. A condensation polymerization is a form of stepgrowth polymerization. Ethylene polymerization reactions with many zieglernatta catalysts exhibit a number of features that differentiate them from polymerization reactions of. Difference between addition and condensation polymerization. With chainreaction polymerization, there are three steps that takes two chemicals. The chemical reaction in which high molecular mass molecules are formed from monomers is known as polymerization. R t decreases at high conversion due to the trommsdorf effect, making the reaction hard to control. The concept of a chemical reaction dates back about 250 years. This type of polymerisation generally involves a repetitive condensation reaction between two bifunctional monomers. In addition polymerization, there are three distinct steps.
Addition polymerization an overview sciencedirect topics. The concepts here are explained in brief, for further details and clarification on the topic of polymerization reaction download byjus the learning app. With chain reaction polymerization, there are three steps that takes two chemicals. The choice of reactor type is determined not only by practical considerations such as scale of production and propensity for fouling, but also by the specific polymerization kinetics. A wellknown example of a condensation reaction is the esterification of carboxylic acids with alcohols. Freeradical polymerization frp is a method of polymerization by which a polymer forms by the successive addition of freeradical building blocks. Chemical reaction polymerization reactions britannica. The initiation step of ionic polymerization reactions has a much smaller activation energy than the equivalent step for freeradical polymerizations. Chaingrowth polymerizations involve the steps of chain initiation, chain propagation, and termination.
Finally, reactor control and optimization are dealt with. Addition polymerization is the successive addition of alkene monomers to one another. Polymer synthesis classification polymerization reactions can be classified into two or three basic types. Find materials for this course in the pages linked along the left. However, products made by solution polymerization also lend themselves to the production of waterborne secondary acrylic dispersions and powder coatings. Chemical reaction chemical reaction polymerization reactions. Growth polymerization applies to monomers with functional groups such as. Following its generation, the initiating free radical adds nonradical monomer units, thereby growing the polymer chain. Step reaction polymerization condensation this type of polymerization normally employs two difunctional monomers that are capable of undergoing typical organic reactions. In addition polymerization monomers only join at the active site of the chain.
So far we have seen that there are two types of the polymerization reaction, how the polymerization of monomers take place and the addition and condensation mechanism. The formed carbon radical is excellent in reactivity, and progresses polymerization and halogenation reactions of different types. A polymer which contains only a single type of repeat unit is known as a homopolymer, while a polymer containing two or more types of repeat units is known as a copolymer. 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.
B reaction is that used to make cocacola bottles i. The second type of polymerization reaction produces condensation polymers, which are formed when monomers are linked together with the release of a smaller molecule, such as water or hydrogen chloride. Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules. Characteristics of this type of polymerization are that chain growth occurs only by the addition of monomers to the active chain end, generally at a high speed, and that only the monomer and polymer are present during the reaction. Step growth polymerization, types of monomers, kinetics and equilibrium considerations, closed vs. There are two types of polymerization known as step reaction polymerization or condensation and chain reaction polymerization. In addition polymerization, the monomers add to one another in such a way that the polymer contains all the atoms of the starting monomers. Step growth polymerization is the formation of a polymer from bifunctional or multifunctional monomers. Chain growth polymerization is the formation of polymers from unsaturated monomers. The process of joining small molecules to form a large molecule is known as polymerization.
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