| 초록 |
Polyisocyanates have a dynamic right- (P) or left-handed (M) helical conformation. Optically active polyisocyanates can be obtained by using chiral initiator, monomer, solvent, or terminator. When poly(n-hexyl isocyanate) (PHIC) is end capped at one end by chiral moiety, chirality can be induced in it up to ~36 monomer unit (i.e Mn = 5.0 k). Herein, we have synthesized chiral PHIC using bifunctional initiator sodium naphthalenilde (Na-Naph), additive NaBPh4 in tetrahydrofuran (THF) at -98 °C by living anionic polymerization. The polymerization is terminated at both ends by chiral acid chloride in presence of pyridine. We found helicity reversal due to chiral end capping at both ends against chiral end capping at one end. The obtained polymers were characterized by H1-NMR, SEC-LS and CD spectroscopy. We compared intensity of CD spectra for different molecular weight polymers and tried to explain reasons responsible for the differences. |
