4160- 9-13-16 L11 - 4160 Addition Pollymerization-L11...

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4160- Addition Pollymerization-L11 09/13/2016 ° Copolymers Polymers with two different monomers in or attached to the main chain are called copolymers (three=terpolymers) Types (A,B represent comonomers) o Alternating: ABABAB o Random: AABABBBABABBAAABAABABB o Block: AAAAAAABBBBBBAAAAABBBBBB o Graft: Comonomer grafted onto existing chain ° ° Addition chain-growth polymerization Monomers are adding to the growing polymer one at a time o Like building a chain o Therefore: chain growth polymerization All atoms of the monomer remain with the polymer Growing chains sometimes combine with each other o Termination o Branching ° ° Role of catalysts Catalysts enable the addition of the next monomer to the growing chain
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Certain catalysts control the orientation of each monomer unit as it is added o Ziegler-Natta, Metallocene o These catalysts enable control of tacticity, branching, comonomer distribution, molecular weight distribution and other spatial orientation dependent structures ° ° Types of addition polymerization Initiator (part of molecule is incorporated into the polymer) o Free radical Most ommon Used to make polymers from “vinyl monomers” (monomers with double bonds) o Anionic “Living polymers” o Cationic Polyisobutylene ° ° Initiator chain-growth polymerization Three steps o Initiation o Propagation o Termination Frequently get branching
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