Studies on elementary reactions in the polymerization of 1,2‐epoxycyclohexane with organozinc compounds as initiators

Abstract

1,2-Epoxycyclohexane (1) was found to behave differently from propylene oxide (PO) in polymerization reactions with organozinc compounds as initiators. A chair-type complex, [Z~I-MP],~, is the only compound that shows high catalytic activity for both polymerization of 1 and PO, following an anionic coordination mechanism. On the other hand, the polymerization of 1 with ZnEt, or (EtZnOMe), as initiator proceeds according to a cationic mechanism. Cationic polymerization of 1 with ZnEt, has two modes of termination reaction resulting in the formation of terminal units containing vinyl ether and ally1 ether moieties. The initiation and propagation mechanism of 1 by [Zn-MP]22 is similar to that of PO, but chain transfer reaction takes place in the polymerization of 1 owing to the low stability of the growing chain end. By using [ZXI-MP],~ as initiator, it was possible to prepare a block copolymer consisting of an isotactic sequence of monomeric units of PO and a syndiotactic sequence of monomeric units of 1. 0 1990, HUthig & Wepf Verlag, Basel CCC 0025-1 16X/90/$03.00 P -

Polymerization of cyclohexene oxide using yttrium isopropoxide and a bimetallic yttrium-aluminium isopropoxide as initiators

“…The polymerization of such cis-oxiranes leads to polymers with trans-structure implying the inversion of configuration of the attacked asymmetric carbon atom 1) . Cyclohexene oxide is easily polymerized by cationic initiators, for example aluminum alkyls 2) or diethylzinc 3,4) . Due to commercial application such as photocrosslinking of epoxy resins, numerous works were devoted to the photoinitiated cationic polymerization of cyclohexene oxide and its derivatives [5][6][7] .…”

“…Polymerization of cyclohexene oxide is generally very hard with classical initiators like CsOH, ZnEt 2 -H 2 O, or ZnEt 2 -ROH 4,8) which usually polymerize well other epoxides, e. g., propylene oxide. Some complex zinc initiators bearing methoxypropanol groups allowed to prepare poly(CHO) composed of syndiotactic and isotactic blocks 4,9) .…”

Stereoselective Ring‐Opening Polymerization of Heterocyclic Monomers

“…The activity differs significantly, depending on the alcohol used. Syndiotactic polymerization of cyclohexene oxide by the similar Zn catalyst was also reported (9,10). Al and Zn porphiryns (3,4) are effective initiators for living polymerization of propylene oxide (11).…”

Photo-initiated polymerization of cyclohexene oxide by dirhenium decacarbonyl

“…Accordingly, poly(CHO)s prepared by Re(CO) 15 X have a syndiotactic structure. 11,12 The [ 13 C]NMR spectrum of poly(CHO) prepared by Re 2 (CO) 10 is shown in Fig 6. The peaks at 76.64 ppm con®rm the disyndiotactic con®guration, e g -RR-SS-enchainments, and the peaks at about 30 and 22 ppm are due to the methylene carbons furthest from the oxygen atom. 10,13 Suggested polymerization mechanism A suggested mechanism for the photo-initiated polymerization of (1) by Re 2 (CO) 10 which is consistent with the photoreactions of Re 2 (CO) 10 with weak nucleophiles 14,15 is shown in Scheme 1.…”