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Cationic polymerization of cyclocarbonates
Author(s) -
Kricheldorf Hans R.,
WeegenSchulz Bettina,
Jenssen Jörg
Publication year - 1992
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19920600111
Subject(s) - lewis acids and bases , chemistry , cationic polymerization , ether , polymer chemistry , triflic acid , polymerization , trimethylsilyl , boron trifluoride , living cationic polymerization , ring opening polymerization , medicinal chemistry , organic chemistry , polymer , catalysis
Trimethylenecarbonate (TMC) and neopentane diol carbonate (NPC) were polymerized with two groups of initiators, proton and carbenium ion donors or Lewis acids. Initiation with methyltriflate, triflic acid or triethyloxonium tetrafluoroborate in solution gave satisfactory yields (up to 90%) but only low molecular weights (M n < 5000), due to rapid back‐biting degradation. IR‐ and NMR‐spectroscopy demonstrate that the propagation steps involve alkylation of the carbonyl oxygen and cleavage of the alkyl‐0 bond by analogy with lactones. Whereas borontribromide and trichloride form solid complexes with NPC or TMC, but do not initiate a polymerization, boron trifluoride is a good initiator. High yields (up to 99,5%) and high molecular weights (M w > 10 5 ) were obtained. However, in analogy to triflic acid initiated polymerizations all polycarbonates contain ether groups. The molar fraction of the ether groups increases with the reaction temperature. High molecular‐weight polycarbonates containing ether groups were also obtained with other strong Lewis acids such as SnCl 4 , SnBr 4 and TiCl 4 . In contrast, weak Lewis acids such as Bu 2 SnBr 2 Bu 3 SnOMe and Sn(II)2‐ethylhexanoate yield polycarbonates free of ether groups. This finding and the NMR‐spectroscopically identified endgroups suggest that these weak Lewis acids initiate an insertion mechanism.