types of polymerization

1. Types of Polymerization
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2. Types of Polymerization
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Addition/Chain Growth Polymerization

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Addition/Chain Growth Polymerization

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Addition/Chain Growth Polymerization

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General Characteristics ofAddition/Chain Growth Polymerization

7. • ‘It requires presence of an initiating molecule that can
be used to attach a monomer molecule at the start of
polymerization.”
• There are 3 types of it
1. Free-radical chain growth polymerization
2. Anionic chain growth polymerization
3. Cationic chain growth polymerization
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8. Free Radical
• It is an atom, ion or molecule having unpaired valence
electrons.
• These unpaired electrons make free radical highly
chemically reactive toward other substances.
• A notable example of free radical is hydroxyl radical(HO•),
a molecule that has one unpaired electron on the oxygen
atom.
• In contrast, the hydroxyl anion (HO−) is not a radical,
since the unpaired electron is resolved by the addition of
an electron.
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9. Free Radical
• Free radicals may be created in a number of ways,
including synthesis with very dilute or reactions at very
low temperatures, or breakup of larger molecules.
• Free radicals play an important role in combustion,
polymerization, plasma chemistry, biochemistry, and many
other chemical processes.
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14. Termination of Radical Polymerization
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• The termination steps of free radical polymerization steps are of
two types: recombination and dis-proportionation.
• In a recombination step, two growing chain radicals form a
covalent bond in a single stable molecule. For the example of a
vinyl polymer,
• -------CH2–C°HR + -------CH2–C°HX → -------CH2–CH2X–CH2X–
CH2------- Termination by recombination increases the chain
length and therefore the molecular weight of the final polymer.[2]
• In a disproportionation step, one radical transfers a hydrogen
atom to the other to form two stable molecules:
• -------CH2–C°HX + -------CH2–C°HX → -------CH2–CH2X + -------
CH=CHX

15. Termination of Radical Polymerization
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• In a disproportionation step, one radical transfers a hydrogen
atom to the other to form two stable molecules:
• ----CH2–C°HX + ----CH2–C°HX → ---CH2–CH2X + ---CH=CHX

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22. Anionic Polymerization( initiation+Propagation)
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23. Anionic Polymerization(Chain Termination)
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Discussion about termination process of Anionic Polymerization
• Termination process in anionic polymerization is however not usually
spontaneous process.
• And unless some impurities are present or some strongly ionic substances are
added deliberately.
• Thus if polymerization is carried out under controlled condition and impurities
are avoided. The reaction proceeds till all the monomer is consumed.
• Studies have shown that polymerization may be restarted even after weeks by
adding fresh monomer.
• It is as if the polymer is living entity and called living polymer.
• Block co polymer can be prepared by this technique.

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32. TYPES
• Polymerization usually proceeds by the
reactions between two different functional
groups, for example, hydroxyl and carboxyl
groups, or isocyanate and hydroxyl groups.
• All step polymerizations fall into two groups
1. Two different bifunctional and/or polyfunctional
monomers in which each monomer possesses
only one type of functional group.
2. The second involves a single monomer
containing both types of functional groups.
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40. EXAMPLES
• The synthesis of polyamides illustrates both groups of
polymerization reactions. Thus polyamides can be
obtained from the reaction of diamines with diacids
• or from the reaction of amino acids with themselves:
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41. GENERAL DESCRIPTION
• The two groups of reactions can be represented in a
general manner by the equations
• where A and B are the two different types of functional
groups.
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