Preparation, characterization, and porperties of optically active poly(α‐methyl‐α‐ethyl‐β‐propiolactones)

Abstract

S(−) and R(+) enantiomers of α‐methyl‐α‐ethyl‐β‐propiolactone (MEEPL) were prepared in an eight‐step synthesis with respective optical purities of 99 and 97% determined by 1H‐NMR (250 MHz) spectroscopy. Polymers (PMEPL) of different enatiomeric compositions were prepared with an anionic‐type initiator. Substantial differences in physical properties were observed between the racemic and optically pure polymers; for example, the melting point of the latter is 42°C higher than that of the former. Chiroptical properties of PMEPLs are reported. The 13C‐NMR (100.62 MHz) spectra of the polymers indicated that the distribution of configurational units in the macromolecular chain is random.

Optically Active Polyethers. 1. Studies of the Crystallization in Blends of the Enantiomers and the Stereoblock Form of Poly(epichlorohydrin)

“…The stereocomplex melted at a temperature 50 degrees higher than that of the a-form. Similar behavior has been reported by Prud'homme et al [1][2][3][4][5][6] for the optically active forms of poly(a-methyl-a-ethyl-/3-propiolactone).…”

“…Table 1 contains the estimates of the parameters Go, U*, Kgt and ooe that result from the best fit of the data to the growth rate equation (1) by the procedures described previously.39 The pre-exponential parameter, Go, may be the most poorly defined parameter of the growth rate equation, mainly due to a general lack of growth rate data for polymers at large undercoolings. The observed differences in the estimates of Go reported in Table 1 are relatively small, as might be expected for similar polymers.…”

Stereocomplex formation between enantiomeric poly(α‐methyl‐α‐ethyl‐β‐propiolactones): Effect of molecular weight

“…This discrepancy can be attributed to the difference between the hydrodynamic volumes of the polymers and the polystyrene standards. However, the M n values determined by NMR spectroscopy and by Maldi‐TOF spectrometry are in very good agreement with the corresponding theoretical values, confirming the “living” character of these polymerizations 19…”

Synthesis and polymerization of racemic and optically active substituted β‐propiolactones. VI. α‐Phenyl β‐propiolactone

“…Figure 4 shows the X-ray patterns of the atactic (#R1, left picture) and optically active (#05, right picture) poly (PhPL) samples. The same crystalline peaks (or rings) are seen in both cases at 2 8 = 8.6 (vs), 16.9 (vs), 20.7 ( m ) , 22.9 (m), and 26.8 (w) [vs = very strong, m = medium, and w = weak intensity] although the intensity is clearly larger (for a similar irradiated volume) for the optically active sample, in agreement with the DSC results. piolactone) 2,5,10, [14][15][16][17]28…”