Synthesis and Secondary Structure of Poly(1-methylpropargyl-N-alkylcarbamate)s

Abstract

A series of novel 1-methylpropargyl-N-alkylcarbamates, HC≡C-(R)-CH(CH3)OCONHCH2CO2CH2CH2CH3 [(R)-1], HC≡C-(S)-CH(CH3)OCONHCH2CO2CH2CH2CH3 [(S)-1], HC≡C-(S)-CH(CH3)OCONH-(R)-CH(CH3)CH2CH2CH2CH2CH3 [(S),(R)′-2], HC≡C-(S)-CH(CH3)OCONH-(R)-CH(CH3)CO2CH2CH2CH3 [(S),(R)′-3], HC≡CCH2OCONH-(R)-CH(CH3)CO2CH2CH2CH3 [(R)′-4], HC≡CCH2OCONH-(S)-CH(CH3)CO2CH2CH2CH3 [(S)′-4], and HC≡CCH2OCONHCH2CO2CH2CH2CH3 (5) were synthesized and polymerized using (nbd)Rh+[η6-C6H5B−(C6H5)3] (nbd = 2,5-norbornadiene) as a catalyst. Substituted cis-stereoregular polyacetylenes with moderate molecular weights were obtained in good yields. Poly[(R)-1], poly[(S)-1], poly[(S),(R)′-2], and poly[(S),(R)′-3] exhibited large optical rotations (|[α]D| = 344°−508°), clear CD signals (Δe = 4.8−7.0 M−1 cm−1) in CHCl3, and high viscosity indices (0.82−0.87), demonstrating the formation of helical structures with predominantly one-handed screw sense, which were stable up to 55 °C in the solvent. The solution state IR measurement confirmed the presenc...