Group-Transfer Polymerization of Various Crotonates Using Organic Acid Catalysts

Abstract

Various poly(alkyl crotonate)s (PRCrs) were synthesized by group-transfer polymerization (GTP) using organic superacid catalysts such as 1-[bis(trifluoromethanesulfonyl)methyl]-2,3,4,5,6pentafluorobenzene (C 6 H 5 CHTf 2 ) and 1-trimethylsiloxyl-1-methoxy-2-methyl-1-propene (MTS) as an initiator. Under the optimized reaction conditions, the corresponding poly(ethyl crotonate) (PEtCr) was obtained with a narrow molecular weight distribution (MWD = 1.14) in quantitative yield (>99%). The thermal stabilities of the PRCrs obtained by organic acid-catalyzed GTP were generally superior to those of poly(alkyl methacrylate)s. The glass-transition temperature (T g ) of poly(methyl crotonate) (PMeCr) (122 °C) was higher than that of poly(methyl methacrylate) (PMMA) prepared by GTP (104 °C). The 5% weight loss temperature (T d5 ) of PMeCr (359 °C) was also higher than that of PMMA (304 °C). The values of the total light transmittance (T t ) (reaching 91.9%) and haze (<5%) of the PRCr films were similar to those of both PMMA films and glass plates. ■ EXPERIMENTAL SECTIONMaterials and Reagents. Methyl crotonate (MeCr), ethyl crotonate (EtCr), n-butyl crotonate ( n BuCr), isopropyl crotonate ( i PrCr), isobutyl crotonate ( i BuCr), sec-butyl crotonate ( s BuCr), tert-

Kinetic modeling study of the group-transfer polymerization of alkyl crotonates using a silicon Lewis acid catalyst

“…1 shows a plausible polymerization mechanism for the GTP of crotonates using a silicon LA catalyst. 8 First, a crotonate coordinates to a silicon LA catalyst, following which the activated monomer (active species) is generated. The activated monomer reacts with the initiator or the living polymer, which possesses a structure similar to that of the initiator at the polymer chain-end.…”

“…Despite the living-polymerization characteristics of a GTP system, the use of EC as a monomer substrate resulted in a decline of the propagation reaction, with unreacted monomer remaining in all cases, as summarized in Table 1, except for the case of a low feed ratio between the monomer and initiator (entries 9-14 in Table 1). Furthermore, a previous report 8 stated that the GTP of alkyl crotonates generated not only polymers of a terminal cyclic form, via a well-known cyclization termination reaction, but also polymers of a linear form, via an acid treatment of a living polymer, as observed through the MALDI-TOF-MS analysis of the resulting polymers upon a halt of the polymerization reaction with unconsumed monomer remaining. This result suggests that some protic acids are produced in situ, which causes the protonation of a living polymer to occur in situ.…”

“…[3][4][5][6][7] Recently, we reported the group-transfer polymerization (GTP) method for the homopolymerization of various alkyl crotonates using only an organic acid catalyst, such as N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide (Tf 2 NSiMe 3 ), which is a silicon Lewis acid (LA), and 1-trimethylsiloxyl-1-methoxy-2-methyl-1-propene (MTS) as the initiator. 8,9 In general, organocatalysis without metal compounds is beneficial for industrial applications because of the well-known advantages of metal-free polymeric products and processes. 10,11 However, the alkyl crotonate GTP mentioned above is usually performed at low temperatures ( preferably −40°C or below) because high reaction temperatures, even ambient temperatures, accelerate termination reactions such as cyclization and/or isomerization of propagating chain-end groups.…”

Production and Polymerization of Biobased Acrylates and Analogs

“…Recently, Takenaka and Abe performed the GTP of n ‐alkyl crotonates using organic superacids instead of HgI 2 , thereby avoiding the use of a highly toxic catalyst. [ 557 ] Depending on the SKA, it is possible to control the disyndiotacticity of poly(EtCr) and this stereocontrol greatly influences the final properties of the material: T g = 201 °C for a 92% disyndiotactic poly(EtCr) and T g = 82 °C for a 53% disyndiotactic poly(EtCr). [ 558 ] Finally, the Chen group applied the Lewis pair polymerization and frustrated Lewis pair polymerizations concepts to MeCr with success, obtaining quantitative conversions, high M n (10 to 160 kg mol −1 ) and narrow dispersities at room temperature.…”

Unique acrylic resins with aromatic side chains by homopolymerization of cinnamic monomers

“…Additionally, organic-acid-catalyzed GTP systems were developed by Chen and co-workers and Kakuchi et al for the polymerization of (meth)acrylates [30][31][32] . In the last year, we applied such an organic-acid-catalyzed GTP system to the polymerization of various alkyl crotonates 33,34 . The GTP system in our study used an organic acid such as N-(trimethylsilyl)bis(trifluoromethanesulfonyl)imide (Tf 2 NTMS) as a catalyst and a silyl ketene acetal such as 1-methoxy-1-(trimethylsiloxy)-2methyl-1-propene (MTS) as an initiator ( Supplementary Fig.…”