BEHAVIOR OF POLY(BETA-HYDROXYBUTYRIC ACID) IN DILUTE-SOLUTION

The refractive indices of poly(beta-hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (M(w) = 20.9 x 10(3)-929 x 10(3) g mol-1) in 2,2,2-trifuoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.