Controlled ROP of β-Butyrolactone Simply Mediated by Amidine, Guanidine, and Phosphazene Organocatalysts

Basic organocatalysts of the guanidine (1,5,7-triazabicyclo[4.4.0]dec-5-ene, TBD), amidine (1,8-diazabicyclo[5.4.0]-undec-7-ene, DBU), and phosphazene (2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2diazaphosphorine, BEMP) type do effectively polymerize beta-butyrolactone (BL). Poly(3-hydroxybutyrate)s (PHBs) with controlled molecular features, that is, controlled molar masses, narrow molar mass distributions, and well-defined functional end groups are thus formed at 60 degrees C from bulk monomer, with $ \overline{M}_{\rm n,NMR}$ up to 21 500 g mol-1. The formation of a,?-guanidine/amidine/phosphazene,crotonate functionalized PHBs, as demonstrated by NMR, SEC, and MALDIToF mass spectrometry analyses, mechanistically suggests the formation of N-acyl-a,beta-unsaturated propagating species that originate from 1:1 guanidine/amidine/phosphazene:BL adducts.