Zur Übertragungsreaktion bei der anionischen Polymerisation von Oxiranen. II. Zur Kettenübertragung bei der Copolymerisation von Propylen‐ und Ethylenoxid

Abstract

Der EinfluB des Ethylenoxidgehalts bei der anionischen Copolymerisation rnit Propylenoxid auf das AusmaS der Ubertragungsreaktion, d. h. der Isomerisierung des Propylenoxids zum Allylalkohol wird untersucht. Die Reduzierung der Doppelbindungsbildung rnit steigendem Ethylenoxidgehalt wird rnit Hilfe der Geschwindigkeitskonstanten aller ablaufenden Parallelreaktionen erklart. R peaKyuu nepedauu yenu npu afiuonnoii nonu~iepuaayuu omupanos. I I . 0 nepeaauu yenu npu cononu.~epuaayuu o m c u nponufiena c ozucbw amufiena HccnenosaHo Bnnumie conepHtaHm OKHCM ~T M J I~H~ npn amoHHot cononn~eplraaqrn~ c oKmbm nponHneHa Ha CTeneHb peaKqm nepeaoca, T. e. n3o~epn3aqnm O H H C~ nponmeHa B annnnbHMt c n n p~. YMeHbrueHne 06pa30-Bcex npoTeHaIoqmx napannenbmx peafcgtii. BaHHR A B O~H M X CBH3eR C BO3paCTaIoqHM COHepWaHHeM OKNCH 3TEJIeHa 06'buc~xe~cu C I I O M O q b I O KOHCTaHT CHOpOCTefi On the chain transfer reaction in the anionic polymerization of oxiranes. I I . The chain transfer in the copolymerization of propylene and ethylene oxides The influence of ethylene oxide concentration on the extent of transfer reaction, i.e. the isomerization of propylene oxide to allylic alcohol, in the course of the anionic copolymerization of ethylene and propylene oxides is investigated. The decrease in the formation of double bonds with increasing ethylene oxide concentration is explained in terms of the rate constants of all parallel reactions.

The influence of initiator and macrocyclic ligand on unsaturation and molar mass of poly(propylene oxide)s prepared with various anionic system

“…Conversely, the polyethers for flexible PU foams, having a low concentration of terminal OH groups, have high unsaturation. Similar influence of hydroxyl groups on the transfer reaction was reported in several works [8,[15][16][17][18][19]. The explanation of this phenomenon is based on the strong affinity of the alkoxide for hydroxyl groups.…”

Reactive amphiphilic block copolymers for the preparation of hybrid organic/inorganic materials with covalent interactions

“…As a consequence of the transfer reaction PEEGE homopolymer with an allylic end group is formed which was identified in the tailing of the SEC peak. [47][48][49][50][51][52][53][54] The protecting group of the PEEGE block was removed by an acidic ion exchange resin (AmberlystÒ 15). Complete deprotection was proven by 1 H NMR spectroscopy in DMSO by the absence of the acetal protection group (signals at d ¼ 4.6, 1.2, and 1.1 ppm).…”

Polyethers Based on Short-Chain Alkyl Glycidyl Ethers: Thermoresponsive and Highly Biocompatible Materials

“…Despite the many advantages like highly controlled polymerization, high end-group fidelity as well as a large variety of mono- and multifunctional nucleophilic initiators, AROP has one major drawback when applied to the polymerization of glycidyl ethers. Under anionic conditions, the weakly acidic methylene protons in the α-position to the epoxide ring are easily abstracted by the nucleophilic polyether chain end, resulting in a chain-transfer reaction analogous to propylene oxide. , This side reaction leads to the undesired aforementioned allylic initiator structure (Scheme ) and consequently to a loss of control over molecular weights and polymer end groups. The extent of this side reaction, which is likewise observed for alkylene oxide monomers and has been discussed in a detailed manner for propylene oxide, can generally be reduced by utilization of crown-ethers, ambient or at least low polymerization temperature, and the use of Pearson soft (HSAB) counterions. − …”