Synopsis R( +) and S( -) enantiomers of a-methyl 8-propiolactone (MPL) have been synthesized from the corresponding a-methyl 8-hydroxymethylpropionates and racemic MPL from methyl methacrylate. The optical purity and absolute configuration of these lactones were determined using 'H-NMR spectroscopy after complexation with a chiral compound: 2,2,2-trifluoro-1-(9-anthry1)-ethanol. Optical purities of 100% were obtained for both the S(-) ([ao]E5 = -10.4", c = 1.3 g/dL in CHC1,) and the R(+) ([ao]E5 = +10.5', c = 1.0 g/dL in CHCl,) enantiomers. The corresponding racemic and optically active polylactones [poly(MPL)] were prepared by anionic polymerization, in bulk and in solution, as well as poly(MPL)s of intermediate optical purities. The polymers thus obtained are optically active ([a0]i5 = 16.2" in CHCl, for the optically pure polymer, S configuration) and exhibit significant differences. For example, the racemic poly(MPL) is soluble in several organic solvents such as tetrahydrofuran, benzene, CCI,, CH,Cl,, hexafluoroisopropanol, and CHCl,, whereas the optically active poly(MPL)s are soluble in CHCl, and hexafluoroisopropanol only. Moreover, racemic poly(MPL) is amorphous whereas optically active poly(MPL)s are semicrystalline for optical purities larger than 51%. Melting temperatures and enthalpies of fusion of the semicrystalline polylactones vary with optical purity whereas glass transition temperatures remain invariant for all polymers, at about -28°C. The poly(MPL) of highest optical purity exhibits a melting temperature of 95°C and an enthalpy of fusion of 61 J/g.

The synthesis and optical resolution of α‐phenyl β‐amino‐ethylpropionate led to the preparation of optically active α‐phenyl β‐propiolactones (PhPL) of different optical purities. The enantiomeric excess of PhPL was determined using 200 MHz 1H‐NMR spectroscopy, after complexation with tris[3‐(trifluoromethyl hydroxymethylene)‐d‐camphorato]europium III. It was then polymerized, in bulk and in solution, using a potassium acetate/crown ether complex as initiator. The optically active poly(PhPL)s thus obtained are insoluble in most organic solvents, whereas atactic poly(PhPL)s are soluble in CCl4, CHCl3, and dichloroethane. Several differences are observed between the physical properties of optically active and atactic poly(PhPL)s. However, atactic poly(PhPL)s are semi‐crystalline polymers, similar to poly(α‐disubstituted β‐propiolactone)s, but in contrast with poly(α‐methyl β‐propiolactone). Melting (Tf) and glass transition temperatures, as well as enthalpy of fusion (ΔH), vary with the optical purity of the polymers. For example, atactic poly(PhPL) exhibits a Tf = 94°C and ΔH = 9 J/g as compared to Tf = 119°C and ΔH = 37 J/g for a poly(PhPL) having an enatiomeric excess of 50%.

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