Polymer3.pdf - Ring Opening Polymerization A/Prof Cyrille Boyer A class of important compounds This is the ring-opening polymerization(ROP of cyclic

Polymer3.pdf - Ring Opening Polymerization A/Prof Cyrille...

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Ring Opening Polymerization A/Prof. Cyrille Boyer
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2 A class of important compounds This is the ring-opening polymerization (ROP) of cyclic monomers such as cyclic ethers, acetals, amides (lactams), esters (lactones), and siloxanes. Ring-opening polymerization is of commercial interest in a number of systems, including the polymerizations of ethylene oxide
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3 Thermodynamics of polymerization cycloalkanes at 25 o C The reaction are favoured thermodynamically for all except the 6-membered ring. The order of thermodynamic feasibility is 3,4 > 8 > 5,7
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4 Monomer selections Although the thermodynamic is favourable, cycloalkanes do not polymerize very well by ROP (do not forget the kinetics) Except cylcopropane (only short oligomers) Other alkanes do not polymerize Polymerization requires that there be a kinetic pathway for the ring to open and undergo reaction. The cycloalkanes do not have a bond in the ring structure that is easily prone to attack by an initiator species. The lactams, lactones, cyclic ethers and acetals, and other cyclic monomers present a difference in reactivity in comparison with cycloalkanes. The presence of a heteroatom in the ring provides a site for nucleophilic or electrophilic attack by an initiator species, resulting in initiation and subsequent propagation by ring opening.
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5 Cationic and Anionic Polymerization Z represents a functional group, such as O, NH, SiO, COO, and CONH in ethers, amines, siloxanes, esters, and amides, respectively. Alternative mechanism of cationic polymerization: activated monomer (AM) polymerization
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6 ROP and Radical Polymerization Ring-opening polymerization (ROP) is a chain polymerization, consisting of a sequence of initiation, propagation, and termination . Only monomer adds to the growing chains in propagation. Unlike step polymerization, monomer does not react with monomer and larger sized species do not generally react with each other in ROP. Many ring-opening polymerizations proceed as living polymerizations: i) polymer molecular weight increases linearly with conversion; ii) ii) the ratio of monomer to initiator; iii) block copolymers can be synthesized.
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