Showing papers by "Ann-Christine Albertsson published in 1994"

Synthesis of copolymers of 1,3-dioxan-2-one and oxepan-2-one using coordination catalysts

Abstract: A new type of copolymer is synthesized in a bulk polymerization from 1,3-dioxan-2-one and oxepan-2-one (ϵ-caprolactone) using either Sn-oct, ZnAc2, Bu2SnO, or Bu3SnCl as the catalyst. SEC analysis shows that it is possible to achieve high molecular weights and narrow molecular weight distributions. 13C-NMR analysis confirms the existence of copolymers. Conversion studies have been made and reactivity ratios, r1 and r2, have been determined to distinguish between the reactivities of 1,3-dioxan-2-one and oxepan-2-one. The Finemann-Ross method and the Kelen-Tudos method were used to calculate the ratios and the agreement was good between the methods. The composition of the copolymer agrees with the feed composition at high conversions. Thermal analysis of copolymers by DSC shows crystalline melting resulting from a somewhat blocky copolymer. The glass transition temperatures of the copolymers are in agreement with the Fox equation. The corresponding blends of the two homopolymers show a constant melting point and glass transition temperature. A nonionic insertion mechanism and a Lewis acid alcoholysis mechanism are discussed. © 1994 John Wiley & Sons, Inc.

Synthesis and Characterization of Biodegradable Homopolymers and Block Copolymers Based on 1,5-Dioxepan-2-one

Abstract: Homopolymers of 1,5-dioxepan-2-one (DXO) and block copolymers of DXO and e-caprolactone (e-CL) have been synthesized with aluminum isopropoxide as an initiator in toluene and THF. The homopolymerization is first order with respect to both monomer and initiator, and the end-group analysis agrees with a coordination insertion mechanism based on the acyl-oxygen cleavage of the DXO ring. Living poly(e-caprolactone) (PCL) and poly(1,5-dioxepan-2-one) (PDXO) chains are very efficient macroinitiators for the polymerization of DXO and e-CL, respectively, with formation of block copolymers of a narrow molecular weight distribution

Degradation of enhanced environmentally degradable polyethylene in biological aqueous media: mechanisms during the first stages

Abstract: Degradation of enhanced environmentally degradable polyethylene in biological aqueous media: mechanisms during the first stages

Copolymers of 1,5-dioxepan-2-one and L- or D,L-dilactide: Hydrolytic degradation behavior

Abstract: The degradation of two series of copolymers made of 1,5-dioxepan-2-one (DXO) and L-or D,L-dilactide has been investigated. In vitro degradation of the six copolymers with different ratios of the ingoing components was followed using size exlusion chromatography (SEC), nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The copolymers with a high content of lactic acid units showed a higher rate of hydrolysis than the DXO-rich copolymers. The copolymer morphology also affects the rate of degradation as seen in the differences between amorphous and semicrystalline samples. The effect of electron beam sterilization was studied as well as the degradation products formed using the gas chromatography-mass spectrometry (GC–MS) technique. The major degradation products resulted from ester bond cleavage. Kinetics of the in vitro degradation indicate a complex hydrolysis, probably a mixture of an uncatalyzed and catalyzed mechanism. © 1994 John Wiley & Sons, Inc.