Ring-opening copolymerization of (R,S)-β-butyrolactone and ε-caprolactone using sodium hydride as initiator

Abstract

Abstract. Copolymers of racemic β-butyrolactone ((R,S)-BL) and ε-caprolactone (CL), were synthesized by ring-opening polymerization initiated by sodium hydride (NaH). The initiator exhibited a satisfactory catalytic activity, producing copolymers whose yields are greatly influenced by the feed monomer ratio, CL/BL. All polymers obtained were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide angle X-rays scattering, WAXS. The molar composition of copolyesters determined by 1 H-NMR spectra, showed that the incorporation of CL is favoured over the incorporation of (R,S)-BL. Gel permeation chromatography and 13 C-NMR spectra indicated that CL/BL copolymers had block sequence distribution. The TGA analysis of copolymers showed that these copolymers are stable up to temperatures near 200°C, followed by a decomposition process in two steps; the first one is attributed to the (R,S)-BL block degradation and the second to the remaining PCL block. The crystallization process of these copolymers was studied by DSC and WAXS showing that the amorphous (R,S)-BL segments chains did not affect the crystallinity of the PCL blocks.

Ring-opening polymerization of β-butyrolactone in the presence of alkali metal salts: investigation of initiation course and determination of polymers structure by MALDI-TOF mass spectrometry

“…Lactones are important monomers, which are easily polymerized by ring-opening mechanism giving biodegradable polyesters [1,2]. Anionic polymerization of β-lactones yields polyesters exhibiting potential utility in medicine and environmental protection [3][4][5][6][7].…”

New way of anionic ring-opening copolymerization of β-butyrolactone and ε-caprolactone: determination of the reaction course

“…All syntheses were carried out at room temperature in a 50 cm 3 reactor equipped with a magnetic stirrer and a Teflon valve enabling substrates delivery and sampling under argon atmosphere. Homopolymerization of BL and CL and their copolymerization mediated with NaH were carried out in bulk at 70 °C according to literature data [14]. Polymerization of CL initiated with anhydrous KOH activated 12C4 in THF solution at room temperature was performed according to the method described previously [14].…”

“…Homopolymerization of BL and CL and their copolymerization mediated with NaH were carried out in bulk at 70 °C according to literature data [14]. Polymerization of CL initiated with anhydrous KOH activated 12C4 in THF solution at room temperature was performed according to the method described previously [14]. Potassium hydroxide was obtained in the reaction of pure potassium hydride with distilled water in THF.…”

“…The crystallization process was studied by DSC and WAXS showing, that the amorphous PBL segments chain do not affect the crystallinity of the PCL blocks. However, the course of copolymerization proposed by authors [14] seems to be questionable.…”

“…In the literature one may found examples of application of anionic polymerization to obtain the copolymers comprising of CL and BL blocks [11][12][13]. Till now, only one paper presents the possibility of the anionic copolymerization of BL and CL by use of low toxic sodium hydride as initiator [14]. The mentioned process was conducted in bulk containing both monomers at 70 °C.…”