Characterization of lactone oligomers isolated by preparative SFC

Oligomerization of epsilon-caprolactone and delta-valerolactone was performed by use of SmMe(C5Me5)(2)(THF)(2) initiator, and the 26-mer, 28-mar and 30-mer of epsilon-caprolactone were isolated in pure form by preparative SFC. The MALDI-TOF mass spectrum of the 28-mer indicates that the parent peak (3256.1) emerges as 28-mer + 2Na - H (3256.9). The ESI mass spectrum of the 28-mer indicates that the molecular weight (3211.7) is consistent with the calculated value (3211.9). In a similar manner, the 19-, 25- and 32-mers of delta-valerolactone were isolated. The MALDI-TOF mass spectrum of the 19-mer indicates that the parent peaks(1896.6 and 1879.9) emerge as 19-mer + Na + K + MeOH - 1-hexanol-5-one (1896.3) and 19-mer + 2Na + MeOH - 1-hexanol-5-one (1880.2). Glass transition and melting temperatures (T-g and T-m) of oligo-epsilon-caprolactones and oligo-delta-valerolactones increase with increasing degree of polymerization.