Synthesis and Characterization of Poly(chiral methylpropargyl ester)s Carrying Azobenzene Moieties

Novel chiral methylpropargyl esters bearing azobenzene groups, namely, 4‐[4′‐(benzyloxy)phenylazophenyl]‐ carbonyl‐( S )‐1‐methylpropargyl ester ( e ), 4‐[4′‐( n ‐butyloxy)phenylazophenyl]carbonyl‐( S )‐1‐methylpropargyl ester ( f ), 4‐[4′‐( n ‐hexyloxy)phenylazophenyl]carbonyl‐( S )‐1‐methylpropargyl ester ( g ), and 4‐[4′‐( n ‐octyloxy)phenylazo‐ phenyl]carbonyl‐( S )‐1‐methylpropargyl ester ( h ) were synthesized and polymerized with Rh + (nbd)[ η 6 ‐C 6 H 5 B − ‐ (C 6 H 5 ) 3 ] (nbd=norbornadiene) catalyst to give the corresponding polymers with moderate molecular weights ( M n =8.4×10 3 –15.7×10 3 ) in good yields (76%? –?91%). The structures of polymers were illustrated by IR and NMR spectroscopies. Polymers were soluble in comment organic solvents including toluene, CHCl 3 CH 2 Cl 2 , THF, and DMSO, while insoluble in diethyl ether, n ‐hexane and methanol. Large optical rotations of polymer solutions demonstrated that all the polymers take a helical structure with a predominantly one‐handed screw sense in organic solvents.