Stereospecific Polymerization of Dialkyl Muconates through Free Radical Polymerization:  Isotropic Polymerization and Topochemical Polymerization

Abstract

Radical polymerization of dialkyl muconates (dialkyl 2,4-hexadienoates) was investigated in an isotropic (amorphous) state, that is, solution or bulk polymerization, and in a crystalline state. In the bulk polymerization at 120 °C in the presence of a radical initiator, high molecular weight polymers of more than 105 were obtained in high yields, compared with those in solution polymerization. Three kinds of isomers, cis,cis-, cis,trans-, and trans,trans-muconates, showed similar polymerization reactivities. The microstructure in the polymers was determined by 1H and 13C NMR spectroscopies to be 84−91%, 6−13%, and 2−4% for trans-1,4-, cis-1,4-, and 1,2-structures, respectively, which depended on the polymerization temperature. In contrast with the bulk (in the melt) and solution polymerizations, we discovered that diethyl cis,cis-muconate underwent highly stereospecific polymerization in a crystalline state under UV irradiation via a topochemical polymerization mechanism. The resulting polymer was of ultrahigh molecular weight ([η]) = 103 cm3/g) with high stereoregularity and crystallinity. This polymer has been clarified to be a tritactic polymer, trans-1,4-meso-diisotactic or trans-1,4-meso-disyndiotactic polymer.

Degradable Polymers Prepared from Alkyl Sorbates and Oxygen under Atmospheric Conditions and Precise Evaluation of Their Thermal Properties

“…Diethyl muconate was prepared by the method previously reported. 38 (2E,4E)-2,4-Hexadiene (HD), methyl acrylate, methyl methacrylate, methyl crotonate, vinyl acetate, styrene, and α-methylstyrene were commercially available and distilled before use. 2,2 -Azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMVN) and 2,2 -azobis(isobutyronitrile) (AIBN) were purchased from Wako Pure Chemical Industries, Ltd., Osaka, and recrystallized from methanol.…”

“…43 The radical on the C4 carbon of RS preferably reacts with oxygen, because the homo-propagation slowly proceeds between the stable RS radical with a conjugated structure and the sterically hindered RS monomer as the internal diene compound. 38,39 The 5,2 propagation is suppressed because of less affinity for a reaction with oxygen (i.e., k 3 k 4 in Scheme 2). As a result, an alternating propagation proceeds with a high selectivity, leading to the formation of an exclusive 5,4 polymer.…”

“…The homopolymerization also proceeds only at a considerably low rate under the conditions in this work, that is, at a low temperature and a low monomer concentration. 38 In the case of the muconate polymerization, a molecular oxygen behaviors as a terminator rather than comonomer.…”

Polymer Structure Control Based on Crystal Engineering for Materials Design

“…For example, the ethyl and halo-or methoxybenzyl esters of (Z, Z)-muconic acid polymerize (1a-1d) to give the corresponding diisotactic polymers, [40][41][42] while most of the other ester derivatives isomerize to the corresponding EE isomers or have no reaction. The 4-methoxybenzyl ester of (E, E)-muconic acid (3a) provides a disyndiotactic polymer with a structure identical to that obtained from the (Z, Z)-muconic ester (1e).…”

Topochemical Polymerization of 1,3-Diene Monomers and Features of Polymer Crystals as Organic Intercalation Materials

“…[29 -34] In earlier work, our interest was focused on (i) the synthesis of high molecular weight polymers from muconates as the internal diene monomers and (ii) the control of the tacticity through free-radical polymerization in solution. [35] We examined the effects of the geometry of the isomers and of the alkyl ester substituents on the polymerization reactivity and the tacticity of the polymer. The bulk polymerization of all the geometric isomers, (Z,Z)-, (E,Z)-, and (E,E)-muconates, was carried out in the presence of a radical initiator to give high-molecular weight polymers in high yields.…”