Cationic cyclopolymerization of new divinyl ethers: The effect of ether and ester neighboring functional groups on their cyclopolymerization tendency

Abstract

The cationic polymerization of two new divinyl ethers, 1-(2-vinyloxyethoxy)-2-[(2-vinyloxyethoxy)carbonyl]benzene (2) and 1,2-bis[(2-vinyloxyethoxy)carbonyl]benzene (3), as well as 1,2-bis(2-vinyloxyethoxy)benzene (1), with BF 3 OEt 2 in CH 2 Cl 2 at 0°C at low initial monomer concentrations ([M] 0 ϭ 0.15 and 0.075 M) gave soluble polymers with relatively high molecular weights and broad molecular weight distributions (MWDs), whereas reactions with the HCl/ZnCl 2 initiating system yielded soluble polymers with relatively narrow MWDs (weight-average molecular weight/number-average molecular weight Շ 1.6) under similar reaction conditions. An NMR structural analysis of the HCl/ZnCl 2 -mediated polymers from the divinyl ethers showed that poly(1) had virtually no unreacted vinyl ether groups throughout the polymerization (monomer conversion ϭ 28 -98%), whereas poly(2) and poly(3) possessed some amount of unreacted vinyl ether groups in the initial stage of the polymerization; the content of the vinyl groups of poly(2) was 18 mol % at a 15% monomer conversion, and the content of the vinyl groups of poly(3) was 31 mol % at an 18% monomer conversion. Therefore, divinyl ether 1 underwent cyclopolymerization exclusively to give almost completely cyclized polymers [degree of cyclization (DC) ϳ 100%], whereas divinyl ethers 2 and 3 exhibited a lower cyclopolymerization tendency [DC for poly(2) ϭ 82%; DC for poly(3) ϭ 69%]. The differences in the cyclopolymerization tendencies among the divinyl ethers can be explained by the differences in the solvation powers of the neighboring functional groups adjacent to the vinyl ether moiety with the active center: the ether oxygen of the ether neighboring group solvates intramolecularly with the active center to accelerate the intramolecular propagation, but such an interaction is less effective with the more electron-deficient oxygen attached to the carbonyl group of the ester neighboring group.

Cationic cyclopolymerization of 1,2‐bis(2‐vinyloxyethoxy)benzenes: Introduction of bulky substituents to increase cyclopolymerization tendency

“…In contrast, a number of divinyl ether monomers were reported to undergo cationic cyclopolymerization to form polymers containing cyclized repeating units in the polymer backbones 13, 14. Among them, 1,2‐bis(2‐vinyloxyethoxy)benzene ( 1 ) is a representative monomer for cationic cyclopolymerization of divinyl ethers (Scheme ) 15–22. Cyclopolymerization of 1 was first reported by Butler and Lien,15–17 and subsequently, many researchers used this monomer for the synthesis of poly(vinyl ether)s with crown ether‐like repeating units via its cationic cyclopolymerization18–20 and cyclocopolymerization 21, 22…”

Star-shaped cyclopolymers: A new category of star polymer with rigid cyclized arms prepared by controlled cationic cyclopolymerization and subsequent microgel formation of divinyl ethers

“…The broadening of polymer MWD in the course of cyclopolymerization of divinyl ethers comes from the occurrence of a minor extent of crosslinking and/or branching reactions to consume the pendant unreacted vinyl groups. 19,20,23,24 Figure 4 also shows the time-conversion plots (A), the M n (B), and M w /M n (C) of the product polymers vs. monomer conversion plots for the polymerization of 1 at 0 C. The polymerization proceeded smoothly and rather fast (conversion 5 100% at 10 min), and the M n s of the produced polymers increased in direct proportion to monomer conversion before and after the monomer addition with the polymer MWDs being narrow and were in good agreement with the calculated values assuming that one HCl molecule formed one polymer chain. The results of these plots in Figure 4 confirm living nature of the cyclopolymerization of 1 at 0 C. However, close inspection of the M n of the product polymers versus monomer conversion plots [ Fig.…”

“…In other words, the degree of cyclization for the poly(1) was over 97%, high value and similar to those of the reported cyclopolymers from other divinyl ethers. 19,20,23,24 To check living nature of the present cyclopolymerization systems, a fresh monomer feed (equivalent to the first stage) was added to the almost completely polymerized reaction mixture. The polymers obtained after the monomer addition were also soluble and the peak top of the MWD curves of the polymers clearly shifted toward high molecular weight region.…”

“…13,14 In contrast, cyclopolymerization of divinyl ethers is a polymerization route to produce so-called cyclopolymer, which is a linear polymer consisting of cyclized repeating monomeric units produced by propagation with intramolecular cyclization. [15][16][17][18][19][20] The incorporation of consecutive cyclic groups into the polymer backbones provides rigidity, and hence high thermal stability and high T g to the resulting polymers. [21][22][23] Our recent study showed that some of cyclopoly(divinyl ether)s possessed high T g (up to 200 C) and high thermal decomposition temperature (up to 300 C).…”

Cyclopolymerization of a bisacrylate through selective formation of a 19-membered ring

“…However, the low concentration often limits the yields of polymers. 4,9 Effective strategies for improvement of the cyclization tendency involve conformational orientation of two polymerization groups with cyclic structures [10][11][12][13][14][15][16][17][18][19][20][21] or templates such as metal cations 22,23 and selective alternating copolymerization. 24,25 In the most common method, namely, the design of oriented monomers, additional constraints by steric hindrance 12,13,19 and hydrogen bonding 17 are effective in improving the cyclization tendency.…”