| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 봄 (04/14 ~ 04/15, 전경련회관) |
| 권호 | 30권 1호, p.337 |
| 발표분야 | 고분자 합성 |
| 제목 | Kinetic and Mechanistic Studies of L-Lactide Polymerization in Supercritical dimethylether |
| 초록 | Introduction Recently, cloud point measurements by Lee et al. observed that Poly(L-Lactide) (PLLA) was readily soluble in polar dimethyl ether (DME), due to the specific interaction between the hydrogen atom in the DME and the ester group in the polymers. Thus, the ring-opening polymerization of L-lactide (L-LA) in supercritical dimethyl ether (DME) should be feasible up to high degrees of monomer conversion and high MWs in the homogeneous phase. It has been demonstrated that lactone polymerization using aluminum and tin alkoxides proceeds via a coordination insertion mechanism. When Sn(Oct)2 are used as catalyst, without alkoxide (or hydroxide) groups in a pure state, it has been proposed that they react with alcohol and convert to tin alkoxide, which are the active species in the polymerization. Until now, in coordination insertion mechanism of lactone initiated with tin-based initiation systems in solution, in bulk, and in supercritical CO2 (scCO2) with heterogeneous phase, the structure of the active species, the equilibria between them, and their contribution to propagation and intra-/inter-molecular transesterification are known. However, nothing is known about the mechanism and the kinetics of homogeneous ring-opening polymerization of L-LA in scDME . In this paper, we will report preliminary results about the ring-opening polymerization of L-LA initiated by 1-dodecanol/Sn(Oct)2 in scDME. This research may illustrate the structure of the active species, the equilibria between them, and their contribution to propagation in scDME as reaction medium. Experimental Section Polymerization Procedure in Supercritical DME. Polymerization was conducted in a 40 mL stainless steel high-pressure cell equipped with a magnetic stirring bar and an electrically heating mantle. L-LA (6.0 g), DoOH solution (0.019ml of a 1.07 M solution in toluene; 2.0 X 10-5 mol of DoOH) and Sn(Oct)2 solution (0.25ml of a 0.24 M solution in toluene; 6.2 X 10-5 mol of Sn(Oct)2 ) were added into the cell. The cell was filled with liquid DME to ca. 50 bar at 50 oC by an air-driven gas compressor (Maximator Schmidt Kranz & Co. GMBH) and then gradually heated to 130 oC to achieve a pressure of 380-385 bar. Polymerization was allowed to proceed for 10 hrs. Polymer Characterization. Molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC). NMR spectra were recorded at 25 °C using Varian Unity Plus 300 MHz spectrometer in CDCl3 for 1H NMR. TMS used as an internal shift reference. |
| 저자 | 이항수1, 박현덕1, 김세윤1, 김병수2, 김수현1, 김영하1 |
| 소속 | 1한국과학기술(연), 2한양대 |
| 키워드 | supercritical; L-lactide |
