condensation polymerization

(noun)

a polymerization mechanism in which monomers react to form dimers first, then trimers, longer oligomers, and eventually long chain polymers

Related Terms

Examples of condensation polymerization in the following topics:

  • Condensation Reactions

    • Other condensations, such as the acyloin condensation, are triggered by radical conditions.
    • In one type of polymerization reaction, a series of condensation steps takes place whereby monomers or monomer chains add to each other to form longer chains.
    • This is termed "condensation polymerization," or "step-growth polymerization," and occurs in such processes as the synthesis of polyesters or nylons.
    • The condensation of a diacid and diamine is an example of A-B polymerization.
    • Recognize the chemical principles of condensation reactions as they relate to polymerization.

  • Characteristics of Condensation Polymers

    • Condensation polymers form more slowly than addition polymers, often requiring heat, and they are generally lower in molecular weight.
    • The following examples of condensation polymers are illustrative.
    • Also, the polymerization reactions for Nylon 6 and Spandex do not proceed by elimination of water or other small molecules.
    • Step-growth polymerization is also used for preparing a class of adhesives and amorphous solids called epoxy resins.
    • Bisphenol A is prepared by the acid-catalyzed condensation of acetone with phenol.

  • Condensation Polymers

    • A large number of important and useful polymeric materials are not formed by chain-growth processes involving reactive species such as radicals, but proceed instead by conventional functional group transformations of polyfunctional reactants.
    • These polymerizations often (but not always) occur with loss of a small byproduct, such as water, and generally (but not always) combine two different components in an alternating structure.
    • The polyester Dacron and the polyamide Nylon 66, shown in the first diagram, are two examples of synthetic condensation polymers, also known as step-growth polymers.
    • Examples of naturally occurring condensation polymers are cellulose, the polypeptide chains of proteins, and poly(β-hydroxybutyric acid), a polyester synthesized in large quantity by certain soil and water bacteria.

  • Block Copolymerization

    • Several different techniques for preparing block copolymers have been developed, many of which use condensation reactions (next section).
    • At this point, our discussion will be limited to an application of anionic polymerization.
    • In the anionic polymerization of styrene, a reactive site remains at the end of the chain until it is quenched.

  • Anionic Chain-Growth Polymerization

    • Treatment of a cold THF solution of styrene with 0.001 equivalents of n-butyllithium causes an immediate polymerization.
    • This is an example of anionic polymerization, the course of which is described by the following equations.
    • Only monomers having anion stabilizing substituents, such as phenyl, cyano or carbonyl are good substrates for this polymerization technique.
    • A practical application of anionic polymerization occurs in the use of superglue.
    • When exposed to water, amines or other nucleophiles, a rapid polymerization of this monomer takes place.

  • Non-Ionic Reactions

    • Indeed, the study of free-radical polymerization of alkene monomers has opened the door to modern polymer chemistry.

  • Cationic Chain-Growth Polymerization

    • Polymerization of isobutylene (2-methylpropene) by traces of strong acids is an example of cationic polymerization.
    • This process is similar to radical polymerization, as demonstrated by the following equations.
    • Monomers bearing cation stabilizing groups, such as alkyl, phenyl or vinyl can be polymerized by cationic processes.
    • At low temperatures, chain transfer reactions are rare in such polymerizations, so the resulting polymers are cleanly linear (unbranched).

  • Synthesis of Addition Polymers

    • Indeed, cases of explosively uncontrolled polymerizations have been reported.
    • It is useful to distinguish four polymerization procedures fitting this general description.
    • Radical Polymerization The initiator is a radical, and the propagating site of reactivity (*) is a carbon radical.
    • Cationic Polymerization The initiator is an acid, and the propagating site of reactivity (*) is a carbocation.
    • Anionic Polymerization The initiator is a nucleophile, and the propagating site of reactivity (*) is a carbanion.

  • Ziegler-Natta Catalytic Polymerization

    • An efficient and stereospecific catalytic polymerization procedure was developed by Karl Ziegler (Germany) and Giulio Natta (Italy) in the 1950's.
    • In the case of ethylene, rapid polymerization occurred at atmospheric pressure and moderate to low temperature, giving a stronger (more crystalline) product (HDPE) than that from radical polymerization (LDPE).
    • Polymerization of propylene through action of the titanium catalyst gives an isotactic product; whereas, a vanadium based catalyst gives a syndiotactic product.

  • Esters

    • Esters are functional groups produced from the condensation of an alcohol with a carboxylic acid, and are named based on these components.
    • They are commonly synthesized from the condensation of a carboxylic acid with an alcohol:
    • Polymerized esters, or polyesters, are important plastics, with monomers linked by esteric units like this:
    • This process is the one that usually initiates condensation reactions.