Stereoregular polyamides entirely based on tartaric acid

Two new stereoregular polyamides, namely PTA-LL and PTA-LD, derived from (2 S,3S)-(-)-2,3-dimethoxy-1,4-butanediamine and (2R,3R)-(+)- or (2S,3S)-(-)-2 ,3-dimethoxybutanedioic acid are described. The two diastereoisomeric polym ers contain two pairs of stereocenters in the main chain of the repeating u nit, one in the diamine and the other in the diacid counterpart. L and D re fer to the configuration of the tartaric acid unit from which they proceed. These polyamides were prepared by polycondensation in solution and were fu lly characterized by elemental analysis, DSC, and IR/NMR spectroscopies. Nu mber average molecular weights around 30,000 were estimated by GPC and visc osimetry. Both compounds are soluble in water and display large optical act ivity. CD and H-1-NMR measurements in chloroform solution suggested the pre sence of definite secondary structures in this solvent. Solid samples were found to crystallize upon annealing and the crystal structure of both polya mides was investigated by X-ray diffraction. PTA-LL crystallized in an orth orhombic lattice in the space group P22(1)2(1) whereas PTA-LD seemed to ado pt a P1 triclinic structure. In both cases the polymer chain appears to be in a folded conformation more contracted than in the common gamma-form of c onventional nylons. (C) 1999 John Wiley & Sons, Inc.