Radical ring-opening polymerization of .alpha.-cyclopropylstyrenes. Polymerization behavior and mechanistic aspects of polymerization by the molecular orbital method

Abstract

Synthesis and radical polymerization of substituted a-cyclopropylstyrenes [l-(4-substituted phenyl)-1-cyclopropylethylene; 3a (X = OMe), 3b (X = H), and 3c (X = Cl)] were carried out. 3a-c were prepared by the Wittig reaction of the corresponding cyclopropyl aryl ketones. The radical polymerization of 3 was performed in the presence of an appropriate radical initiator (3 mol % vs monomer) at 60-120 O C . The molecular weight of the polymer obtained decreased while the conversion of the monomer increased, as the polymerization temperature rose. The structure of the polymer was determined to consist only of the unit formed by selective 1,5-ring-opening polymerization. The ratio of the observed rates of polymerization was estimated to be 3c:3a:3b = 2.0:1.61. The effect of a para substituent on the rate of polymerization was not the same as that of para substituted styrenes. The electron density of vinyl 8-carbon of 3 decreased in the following order: 3a > 3b > 3c, being the same as that of para substituted styrenes from 13C NMR analysis and molecular orbital calculation. The rate of polymerization was suggested to be affected by the polarity of the monomers (3). The dipole moment as an index of polarity well explained the order of the rate of polymerization. 3 showed shrinkage similar to those of common cyclic monomers with similar molecular weights; 7.23-8.56%. This value was consistent with the occurrence of the selective radical ring-opening polymerization of 3. T g of the polymers (4) obtained was lower by 94-102 O C than corresponding poly-(para-substituted styrenels.

Free radical ring-opening polymerization of cyclic allylic sulfides: Liquid monomers with low polymerization volume shrinkage

“…1,2-Propanedithiol (9) was synthesized by modifying the procedure reported by Culvenor and Davies. 29 Propylene oxide was reacted with carbon disulfide in sodium hydroxide in methanol to give the propylene trithiocarbonate (10). Instead of using alcoholic potassium hydroxide to hydrolyze the trithiocarbonate, ethanolamine was added directly to the neat trithiocarbonate and the liberated dithiol (9) was distilled directly from the reaction in over twice the yield reported for the hydroxide method (64 vs 26%).…”

“…Over the last 20 years, free radical ring-opening polymerization has been seen as a solution to the problem of polymerization volume shrinkage. Reports, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] patents, [15][16][17][18] and reviews 19,20,21 in this field appear regularly in the literature, and a monograph 22 also has been published. Whereas much work continues on ketene acetal 23 and vinylcyclopropane derivatives, 24 we have developed novel cyclic allylic sulfide monomers such as the activated monomer 1 5,15,25 and the unactivated monomers 2-4.…”

Synthesis and radical ring‐opening polymerization of adamantane‐containing bifunctional vinylcyclopropane undergoing volume expansion on polymerization

“…The cyclobutane formation is considered a possible reason for the large volume shrinkage. To reduce the generation of recyclization units, a bulky substituent, such as a phenyl group on a cyclopropane ring, can be used . Sugiyama et al reported that introducing the bulky phenoxycarbonyl or adamantyloxycarbonyl group reduced the cyclobutane unit formation, and the 1,5‐ring‐opened reaction proceeded quantitatively on to RROP, where the volume expansion (4%–6%) was successfully achieved .…”

“…[2][3][4][5] However, the vinylcyclopropane RROP causes a volume shrinkage (11%-17%), which is greater than that of a common cyclic monomer. [6][7][8][9][10] The detailed investigation of the polymer structure revealed that the polymer is involved, not only in the proposed 1,5-adduct unit but also in cyclobutane unit, which is formed via backbiting of the propagating radical to a double bond of the main chain. 8 The cyclobutane formation is considered a possible reason for the large volume shrinkage.…”

“…To reduce the genera-tion of recyclization units, a bulky substituent, such as a phenyl group on a cyclopropane ring, can be used. [8][9][10] Sugiyama et al reported that introducing the bulky phenoxycarbonyl or adamantyloxycarbonyl group reduced the cyclobutane unit formation, and the 1,5-ring-opened reaction proceeded quantitatively on to RROP, where the volume expansion (4%-6%) was successfully achieved. 11,12 This phenomenon may be explained not only by the suppression of the cyclobutane unit formation but also by the transition of the denser crystalline monomer structure to a free-volume enlargement of the amorphous polymer during polymerization.…”