| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 가을 (10/13 ~ 10/14, 제주 ICC) |
| 권호 | 30권 2호 |
| 발표분야 | 고분자 합성 |
| 제목 | Ab Initio Calculations of Sodium Benzanilide to Elucidate the Mechanism of Polymerization of n-Hexyl Isocyanate |
| 초록 | Initiators for living anionic polymerization of isocyanates are associated with several limitations such as side reactions due to rapid initiation rates as well as backbiting by the growing chain. We have successfully prevented backbiting by using additives such as 15-crown-5 and sodium tetraphenylborate.1 These additives protect the amidate anion, such that the attack to the C=O group on the backbone is stereochemically hindered. Recently we found sodium benzanilide (Na-BA) as a very fascinating initiator for the polymerization of n-hexyl isocyanate (HIC) because it does the dual function of initiation as well as chain end protection. 2 The yield of the polymer is ~100% and there is a perfect control over MW and MWD. Further we found that the experimental molecular weight is five times the theoretical molecular weight. To explain this we proposed a structure for the initiator as a self-assembled cluster of five Na-BA molecules to form a weakly interacting pentameric macroring. It works out that of the total initiator 20% do the job of initiation whereas the rest 80% protect the chain end. As a proof in support of this mechanism, we carried out ab initio binding energy calculations of Na-BA monomer to hexamer macrorings using Gaussian at the B3LYP/6-31G* levels. At the B3LYP/6-31G* level the ground-state geometries have been optimized. We find that the pentameric macroring has the minimum energy, in close agreement with the proposed structure of the initiator. Results of ab initio calculation along with the optimized structure of the macroring will be presented. Na-BA5 Na-BA5-HIC References 1. (a) Lee, J.-S.; Ryu, S.-W. Macromolecules 1999, 32, 2085. (b) Shin, Y.-D.; Kim, S.-Y.; Ahn, J.-H.; Lee, J.-S. Macromolecules 2001, 34, 2408. 2. Ahn, J.-H.; Shin, Y.-D.; Yogendra Nath G.; Park, S.-Y.; Rahman, M. S.; Samal, S.; Lee, J.-S. J. Am. Chem. Soc. 2005, 127, 4132. |
| 저자 | 김재기, 이재석 |
| 소속 | 광주과학기술원 신소재 공학과 |
| 키워드 | sodium benzanilide; ab initio calculation; Isocyanate |
