Samples of poly(D, L-β-methyl β-propiolactone) (PMPL) were prepared and studied in several solvents by light scattering and viscometry. No differences between PMPL and its isotactic homolog, poly(D-β-hydroxybutyrate) (PHB) could be observed in either the molecualr dimensions or thermodynamic properties. The values of the radius-expansion factor α for PMPL and PHB in TFE at 25°C were calculated on the basis of the characteristic ratio 〈S〉/Mw estimated from [η] of PMPL in butyl chloride at 13°C, a theta solvent for the polymer. These values increased in proportion to Mw, in accord with the fifth-power theories for flexible linear polymers. In contrast to the prediction from the current two-parameter theory, the values of AMw/[η] for PMPL in THF as a function of α≡[η]/[η] showed a systematic deviation from literature data for α<5 and continuously ascended as α approached unity. © 1979 The Society of Polymer Science, Japan.
