Polyester Synthesis at Moderate Temperatures via the Direct Polycondensation of Dicarboxylic Acids and Diols Catalyzed by Rare-Earth Perfluoroalkanesulfonates and Bis(perfluoroalkanesulfonyl)imides

Abstract

Recently, we reported that scandium trifluoromethanesulfonate [Sc(OTf)3] and scandium trifluoromethanesulfonimide could catalyze polycondensations of dicarboxylic acids and diols. Although these polycondensations were one-step and occurred at the moderate temperature of 35 °C, they required large amounts of the catalysts (ca. 1 mol %) and long reaction times (>100 h). Therefore, scandium catalysts having stronger electron-withdrawing ligands (scandium perfluorooctanesulfonate, scandium nonafluorobutanesulfonate, and scandium bis(nonafluorobutanesulfonyl)imide [Sc(NNf2)3]) were synthesized, and their catalytic efficiencies were tested. We have now demonstrated and report herein that scandium catalysts with the stronger electron-withdrawing ligands could catalyze the polycondensation of adipic acid and 3-methyl-1,5-pentanediol under conditions of a moderate temperature, a short time period, and a lesser amount of catalyst. Other rare-earth-metal catalysts containing ligands with strong electron-withdrawing abilities were also synthesized, and their catalytic efficiencies were tested using the aforementioned polycondensation. As a result, thulium bis(nonafluorobutanesulfonyl)imide [Tm(NNf2)3] was a more effective catalyst than was Sc(OTf)3, Sc(NNf2)3, thulium trifluoromethanesulfonate [Tm(OTf)3], or thulium trifluoromethanesulfonimide [Tm(NTf2)3]. Our work now makes it possible to synthesize aliphatic polyesters of M n > 1.0 × 104 at a moderate temperature (60 °C), within a short period of time (6 h), and using a small amount of catalyst (0.05−0.1 mol %).

The effect of microwave irradiation on the kinetics and activation thermodynamics of ring‐opening polymerization of ε‐caprolactone

“…Nf 2 NH was obtained from Mitsubishi Materials Electronic Chemicals (Akita, Japan). Sc(NTf 2 ) 3 and Sc(NNf 2 ) 3 were prepared according to a literature report …”

“…To the best of our knowledge, no study has dealt with the activation thermodynamics of microwave‐assisted polymerizations, which forms the basis of the study reported herein, in which we characterize the ROP of ε‐caprolactone at relatively low temperatures (50–70 °C) controlled by microwave heating and catalyzed by the super Brønsted acids, trifluoromethanesulfonimide (Tf 2 NH), and nonafluorobutanesulfonimide (Nf 2 NH), and by the Lewis acids, scandium trifluorobutanesulfonimide (Sc(NTf 2 ) 3 ) and scandium nonafluorobutanesulfonimide (Sc(NNf 2 ) 3 ) . These compounds are also effective catalysts of dehydration polycondensations of dicarboxylic acids and diols . To investigate the ROP kinetics of ε‐caprolactone, we performed temperature studies to obtain the Arrhenius and Eyring thermodynamic parameters.…”

Microwave-assisted low-temperature dehydration polycondensation of dicarboxylic acids and diols

“…Scandium bis(nonafluorobutanesulfonyl)imide (Sc(NNf 2 ) 3 ) was prepared in our laboratory according to the procedure described in the literature. 26 Measurements 1 H-NMR spectra were recorded at 27 1C using a Bruker Analytik DPX200 spectrometer (Bruker BioSpin, Kanagawa, Japan, 200 MHz). The number-average molecular weight (M n ) and the polydispersity index (M w /M n ) of each polyester were estimated using a size exclusion chromatography system that included a Tosoh DP8020 pump system, an RI (Tosoh, Tokyo, Japan, Tosoh RI-8020) detector and a Tosoh TSKgel SuperMultiporeHZ-M column calibrated with polystyrene standards.…”

“…Therefore, we next focused on identifying more active catalysts and found that scandium and thulium bis(nonafluorobutanesulfonyl)imide ((Sc(NNf 2 ) 3 ) and (Tm(NNf 2 ) 3 )) were more efficient catalysts and allowed us to obtain high-molecular-weight polyesters (M n 42.0Â10 4 ) from adipic acid (AdA) and 3-methyl-1,5-pentanediol (MPD) at 60 1C in a short period of time (24h) and with a smaller amount of catalyst (0.1 mol%) than had previously been possible. 26 Rapid syntheses that depend on microwave irradiation have attracted interest because they are environmentally benign. Since first reported in 1986, 27,28 microwave irradiation has been used to shorten the reaction time of organic syntheses, to decrease the levels of side products and to improve the yields and/or chemoselectivities of the products.…”

Catalysts and temperature driven melt polycondensation reaction for helical poly(ester-urethane)s based on natural L-amino acids

“…Fully aliphatic polyesters are biocompatible and enzymatically biodegradable and they are largely used for biomedical applications . Aliphatic polyesters from adipic acid, succinic acid, sebacic acid, and 1,4‐cyclohexane dicarboxylic acid are some of the important examples. Recently, renewable dicarboxylic acid resources based on isohexide, galactaric, mannitol, itaconic, and furan were also explored for the production of greener polyesters.…”