Regioregular Polymerization of Fluorine-Containing Epoxides

Abstract

Epoxides bearing fluorine (F)-containing substituents on ethylene oxide were polymerized under mild conditions to give regioregular polyethers. To alleviate the electron-withdrawing effect of fluoroalkyl or fluoroaryl groups, more than one unit of methylene spacer had to be introduced into a side chain for regioregular polymerization with high activity. Optically active isotactic polyethers were obtained from enatiopure monosubstituted ethylene oxides as a result of regioselective ring opening via successive cleavage of the less substituted carbon-oxygen bond. Obtained optically active isotactic polyethers were investigated through circular dichroism (CD) spectra or optical rotatory dispersion (ORD) spectra in solution states. As a result, no evidence for the formation of helical conformation was detected in both the F-substituted and the corresponding hydrogen (H)substituted optically active isotactic polyethers.

Designing Cooperative Hydrogen Bonding in Polyethers with Carboxylic Acid Pendants

“…29,30 It is known that the initiation step can involve hydrogen or the t-butyl group from Al(i-Bu) 3 besides the desired iodine group, as shown in Figure 3a. 31,32 As a representative example, P(t-BGA) 10 (entry 1 in Table 1) was selected to determine the degree of initiation from each group. It can be observed that the majority of the peaks originated from the initiation of iodine; for example, the observed m/z of 2034.25 can be assigned to a homopolymer comprised of the iodine initiator (126.90) and 10 monomers (188.22), with Na + as the counterion (Figure 3b).…”

“…Encouraged by the successful polymerization of the t -BGA monomer using MAROP, we further explored the mechanistic details by analyzing the initiation steps using matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) analysis (Figures and S13). As demonstrated in previous reports, the MALDI-ToF was employed for evaluation of the absolute molecular weight and end group analysis as well as the polymer topologies, which provides a convenient means to assess the relative contents of polymers with different initiating species. , It is known that the initiation step can involve hydrogen or the t -butyl group from Al­( i -Bu) 3 besides the desired iodine group, as shown in Figure a. , As a representative example, P­( t -BGA) 10 (entry 1 in Table ) was selected to determine the degree of initiation from each group. It can be observed that the majority of the peaks originated from the initiation of iodine; for example, the observed m / z of 2034.25 can be assigned to a homopolymer comprised of the iodine initiator (126.90) and 10 monomers (188.22), with Na + as the counterion (Figure b).…”

Utilization of catecholic functionality in natural safrole and eugenol to synthesize mussel-inspired polymers

“…Polymerization reaction of 2 using Lewis acid triisobutylaluminium as a catalyst and methyltriphenyphosphonium bromide (I) as an initiator 38,39,52 gave ring opened polymer 6 in excellent yields (Scheme 2), ( Table 1). The 1 H NMR spectra (Fig.…”

“…However, using the same standards, GPC has been extensively used to determine the molar masses of polymers/copolymers derived from epoxide containing a range of substituents. 38,39,53,54 The measured molar masses have then been compared with the theoretical values as described for the current polymers. Thus, the living-like polymerization of SO is jeopardized by a signicant contribution of the chain transfer process to the monomer.…”

“…It is reported that the initiation process involved the attack by not only bromide but also by the isobutyl group and hydride as shown in Scheme 3, 39,52 thereby leading to three polymers having bromide, isobutyl, and hydride end groups. 52 i Bu 3 Al can work both as a hydride as well as an isobutyl anion in the ringopening reaction.…”