Cationic polymerization of lactones in the presence of hydroxyl‐containing compounds

Abstract

The mechanism of cationic polymerization of lactones in the presence of hydroxyl-containing compounds (hydroxomechanism) has been studied taking as an example the polymerization of &propiolactone, 8-caprolactone, glycolide and lactide. In this mechanism chain propagation proceeds via preliminary chain transfer t o the monomer. This transfer accelerates the process, decreases the molecular weight of the polymer, narrows the molecular-mass distribution and enhances the general stability of the system. Die kationische Polymerisation von Laetonen in Gegenwart von hydroxylhaltigenVerbindungen Der Mechanismus der kationischen Polymerisation von Lactonen in Gegenwart hydroxylhaltiger Verbindungen (Hydroxomechanismus) wurde am Beispiel der Polymerisation von 8-Propiolacton, e-Caprolacton, Glycolid und Lactid untersucht. Bei diesem Mechanismus erfolgt das Kettenwachstum iiber eine vorhergehende Kettenubertragung auf das Monomer. Diese ffbertragungsreaktion beschleunigt den Prozell, verringert die rel. Molekulmasse des Polymers, verschmalert die Molekulmassenverteilung und erhoht die allgemeine Stabilitat des Systems. Icamuonnas nonuncepuaayua naxmnoe e npucymemeuu z u a p o m w o a e p w a q u x coeaunenuii Ha IIpFlMepe UOJIFlMepFla~FlH ~-llpOllFlOJIaKTOHa, &-KallpOJIaKTOHa, rJIHKOJIklAa Fl JIaKTHAa PaCCMOTpeH MeXaHL13M KaTllOHHOa llOJIHMepH3a~FlFl JlaKTOHOB B IlPHCYTCTBHH rFl~pOKCFlJICO~ep?Ka~HX COenFlHeHMa -, ,~HAPOKCOMeXaHH3M". B TOM ~e x a~~l a~e POCT qenn ~~O F~C X O A F~T nyTena npensapmenbHo€i nepefiaqa qenti H a MoHoMep. nepexon Ha Hero ysennwsaeT CKOPOCTH npoqecca, yMemruaeT MoneKympHsxe Macm nonmepa, cymaeT MoseKynspHo-Maccosoe paCllpe~eJIeHFle Fl YBenFlqFlBaeT 06rqym CTa6FlJIbHOCTb CFlCTeMbI. in the presence of hydroxyl-containing compounds K%z: process without HC Acta Polymeriu 34 (1983) Heft 11/12

Reversible Kinetics and Thermodynamics of the Homopolymerization of l-Lactide with 2-Ethylhexanoic Acid Tin(II) Salt

“…The polymerizations in both contributions were performed at temperatures where crystallization accompanied polymerization. However, this same result was also reported for amorphous poly-(D,L-lactide) by Lyudvig et al, 38,39 who attributed the decreasing rates to a "gel effect" resulting from hydrogen bonding. 38 On the basis of the thermodynamic calculations of Kulagina et al, 25 which infer from free energy calculations that at T < 200 °C the monomer equilibrium amount is less than 0.5%, Eenink discounted the influence of equilibrium on the rates.…”

“…However, this same result was also reported for amorphous poly-(D,L-lactide) by Lyudvig et al, 38,39 who attributed the decreasing rates to a "gel effect" resulting from hydrogen bonding. 38 On the basis of the thermodynamic calculations of Kulagina et al, 25 which infer from free energy calculations that at T < 200 °C the monomer equilibrium amount is less than 0.5%, Eenink discounted the influence of equilibrium on the rates. However, direct measurements in our work conclude that monomer equilibrium is of greater consequence and suggest that some of the decreases found in polymerization rates at high conversion may be attributed to chemical equilibrium.…”

Kinetics of the ring‐opening polymerization of D,L‐lactide using zinc (II) octoate as catalyst

“…1, Y is quite linear up to conversion values around 90% ( R 2 = 0.926 in the worst case). Such behavior has been previously reported 24, 37, 38. In our case, the loss of linearity is due to the limited accuracy of our experimental evaluation of the residual monomer amount by GPC for high conversions 39.…”

Mechanistic study of boron trifluoride catalyzed ε‐caprolactone polymerization in the presence of glycerol

“…When an alcohol is present in the system, the cationic ring‐opening polymerization of lactones may operate according to an alternative mechanism to the ACE one. As early as the 1980s, Belen'kaya et al13 noted that the addition of ethylene glycol caused a sharp increase in the polymerization rate when they performed ε‐caprolactone polymerization with (CH 3 CH 2 ) 3 O + SbF 6 − as the catalyst. They proposed that the addition of the alcohol converted the process to a mechanism by which chain growth occurred through terminal hydroxyl groups by preliminary transfer of a proton to the monomer.…”