Anionic‐coordinated polymerization of cyclobutene

Abstract

The terrdency of cyclo-olefins t o polymerize b y opening of the double bond decreases rapidly with increasing ring size. Thus, cyclopropene polymerizes spontaneously yielding high molecular weight polymers having polycyclopropane structure l ) . Higher cyclo-olefins, like cyclopentene or cyclohexene, on the other hand, may be converted only t o well defined cyclo-oligomers by the aid of acid catalysts2). No indications have been found about the polymerization of cyclobutene, which is unable t o undergo spontaneous polymerization.Catalysts acting through an anionic-coordinated mechanism do not homopolymerize cyclopentene and cyclohexenenot even t o oligomersprobably owing t o steric hindrance. However, using a comonomer which has a double bond free of substituents (ethylene) the effect of steric hindrance is reduced and a copolymerization can take place. I n fact, we have recently obtained high molecular weight copolymers employing catalysts of the anionic-coordinated type3). I n the case of cyclopentene we succeeded in preparing, under suitable conditions, crystalline cyclopentene-ethylene alternating copolymers with sterically ordered (erythroisotactic) structure.We have now observed t h a t catalytic systems acting through a n anionic-coordinated mechanism promote the polymerization of cyclobutene with a very good activity t o high molecular weight homopolymers.Depending on the nature of the catalyst, polymerization occurs b y the opening of the double bond, yielding polymers, whose macromolecules consist of regularly enchained cyclobutane rings (I) (polycyclobutylenamer-2 according t o the nomenclature of HUG GINS^)), whereas in other cases polymerization takes place by opening of the ring, and the resulting polymers have the structure of 1,4-polybutadienes (11) (polybuten-amer4)) :CH, -C H~ 1 +CH,-CH=CH-CH&- 224

A Catalyst for the Simultaneous Ring‐Opening Metathesis Polymerization/Vinyl Insertion Polymerization

“…To support these findings and identify the actual structure of the polymer, we compared the 13 C NMR spectra of poly(NBE) ROMP -co-poly(NBE) VIPco-poly(E) polymers with those of pure ROMP-derived poly(NBE) as well as of poly(NBE) ROMP -altpoly(E 3 ) formed by the alternating ring-opening metathesis copolymerization of NBE with COE ( Figure 1). [27,28] Poly(NBE) ROMP -altpoly(E 3 ) mimics one ROMPderived poly(NBE) repeat unit followed by three ethylene units.…”

“…Table 1, entry 8) and in the reaction temperature to T = 70 8C resulted in the formation of poly(COE) ROMP -copoly(E) (poly(COE) ROMP /poly(E) = 1:16). The absence of any additional peaks apart from those for linear poly(E) and poly(COE) ROMP in the 13 C NMR spectrum suggests a highly linear structure for the poly(E)-derived blocks.…”

Ein Katalysator für die Tandem‐Ringöffnungsmetathesepolymerisation/Vinylinsertionspolymerisation

“…[27,28] Poly(NBE) ROMP -alt-poly(E 3 ) simuliert eine ROMP-abgeleitete Poly(NBE)-Einheit, der drei Ethyleneinheiten folgen. Während keine Signale für Poly-(NBE) ROMP -poly(E), d. h. ÀCH=CHÀc-(1,2-C 5 H 8 )ÀCH=CHÀ (CH 2 ) n -Sequenzen, beobachtet wurden, können die 13 C-NMR-Signale bei d = 47.5 und 41.3 ppm den alternierenden, isotaktischen, VIP-abgeleiteten E-NBE-Diaden zugeordnet werden. Zusätzlich sind E-NBE-E-E-Sequenzen zu beobachten.…”

Ring Opening Metathesis Polymerization

“…Cyclic olefins form polymers (copolymers) of a high tacticity in a presence of this catalyst [14]. Catalytic systems prepared from compounds based on transition metals such as vanadium VCl 4 /Al(Hex) 3 ; V(Ac) 3 /AlC1(C 2 H 5 ) 2 ; titanium TiCl 4 /Al(C 2 H 5 ) 3 and TiCl 4 /AlCl 3 / Al(C 2 H 5 ) 3 [15]; molybdenum MoCl 5 /Al(C 2 H 5 ) 3 [16] as well as catalysts based on osmium, ruthenium, and iridium chlorides [17] were used in ROMP.…”