The Influence of Crown Ether and Alcohol on Unsaturation and Molar Mass of Poly(propylene oxide)s Prepared by Use of Potassiumt-Butoxide: Reinvestigation of Chain Transfer Reactions

Abstract

Potassium t-butoxide dissolved in tetrahydrofuran effectively initiates homogeneous polymerization of propylene oxide at room temperature. Unsaturation and molar mass (M n) of the polymers prepared depend on the presence of additives, such as macrocyclic ligand 18-crown-6 (L) and t-butanol. Application of the ligand alone results in distinct increase of unsaturation and decrease of M n, whereas use of t-BuOH leads to simultaneous decrease of unsaturation and M n. Activation of t-BuOK/t-BuOH system with the ligand causes further decrease of unsaturation, that is, from 12.0 to 3.5 mol % for OK/OH (1/3) and OK/OH/L (1/3/2) systems, respectively. Unexpectedly, M n of the polymers obtained does not practically change (~4800). This result differs from that reported earlier for neat PO polymerization initiated potassium 1-methoxy-2-propoxide/1-methoxy-2-propanol, in which in the presence of the same ligand M n increases to ~12 400 for the same ratio of reagents. The mechanism of studied processes was discussed.

Ring opening polymerization of styrene oxide initiated with potassium alkoxides and hydroxyalkoxides activated by 18-crown-6: determination of mechanism and preparation of new polyether-polyols

“…It was proposed that the first series of peaks at m/z, for example 897. 8 We proposed that the polymerization course is similar to that initiated with (I7), but in this case star-shaped macromolecules are formed (Scheme 6).…”

“…In the anionic polymerization of propylene oxide and other oxiranes complexation of the cation causes a marked activating effect. As a result one observes positive impact on reaction rate, lower unsaturation level in the polymer [8] and higher yield of the final product [9].…”

Application of cesium hydroxide monohydrate for ring opening polymerization of monosubstituted oxiranes: characterization of synthesized polyether-diols

“…It was also worth noting that PPOs synthesized in the presence of KOH/ H 2 O/18C6 [8] or t-BuOK/t-BuOH/18C6 [14] systems have very low unsaturation and M n due to chain transfer reaction to hydroxylic compound.…”

“…Especially interesting are polyether-and copolyether-diols or triols prepared from oxiranes, i.e., ethylene oxide (EO), propylene oxide (PO) or 1,2-butylene oxide (BO), which are applied for fabrication of polyurethane elastomers or foams [6]. Many initiators were used for anionic ring-opening polymerization of oxiranes, e.g., potassium hydroxide [7,8] or potassium alkoxides [9][10][11][12][13][14][15]. In industry, the most frequently used are KOH/1,2propylene glycol or glycerol systems, which allow to obtain PPO-diols or PPO-triols with M n = 2000-6000 at 110 °C [6,16].…”