With the great development of “living” radical polymerization (LRP), one can
now easily prepare linear polymers with different monomers and functional chain
ends. The past decade has seen a boost in new synthetic strategies for cyclic
polymers. Lepoittevin et al. [78] pioneered a new synthetic method for cyclization
of PSTY by combining NMRP and esterification. 4-Hydroxyl-2,2,6,6-tetramethylpyperidine-1-oxy (HTEMPO) and 4,4
0 -azobis(4-cyanovaleric acid) were used in a
combination, yielding linear PSTY with both hydroxyl and carboxylic acid chain
ends. Subsequently, the cyclization reaction was catalyzed by 1-methyl-2chloropyridinium iodide and triethylamine (Scheme 27). Because the esterification
reaction is not highly efficient, especially when used in polymer systems, this
method was only successful with low molecular weight PSTY (<4 kDa).
A fast and highly efficient chemical reaction could significantly advance the
synthesis of cyclic polymers. One of the most prevalent, highly efficient and
Scheme 24 Synthesis of cyclic poly(2-chloroethyl vinyl ether) through the coupling between
iodo- and styryl- groups
Scheme 25 Synthesis of cyclic PSTY through the coupling between iodo- and styryl- groups
Scheme 26 Synthesis of cyclic PSTY through the amidation between carboxylic acid and amine
groups
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Z. Jia and M.J. Monteiro
now easily prepare linear polymers with different monomers and functional chain
ends. The past decade has seen a boost in new synthetic strategies for cyclic
polymers. Lepoittevin et al. [78] pioneered a new synthetic method for cyclization
of PSTY by combining NMRP and esterification. 4-Hydroxyl-2,2,6,6-tetramethylpyperidine-1-oxy (HTEMPO) and 4,4
0 -azobis(4-cyanovaleric acid) were used in a
combination, yielding linear PSTY with both hydroxyl and carboxylic acid chain
ends. Subsequently, the cyclization reaction was catalyzed by 1-methyl-2chloropyridinium iodide and triethylamine (Scheme 27). Because the esterification
reaction is not highly efficient, especially when used in polymer systems, this
method was only successful with low molecular weight PSTY (<4 kDa).
A fast and highly efficient chemical reaction could significantly advance the
synthesis of cyclic polymers. One of the most prevalent, highly efficient and
Scheme 24 Synthesis of cyclic poly(2-chloroethyl vinyl ether) through the coupling between
iodo- and styryl- groups
Scheme 25 Synthesis of cyclic PSTY through the coupling between iodo- and styryl- groups
Scheme 26 Synthesis of cyclic PSTY through the amidation between carboxylic acid and amine
groups
316
Z. Jia and M.J. Monteiro