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

Basic organocatalysts of the guanidine (1,5,7‐triazabicyclo4.4.0]dec‐5‐ene, TBD), amidine (1,8‐diazabicyclo5.4.0]‐undec‐7‐ene, DBU), and phosphazene (2‐tert‐butylimino‐2‐diethylamino‐1,3‐dimethylperhydro‐1,3,2diazaphosphorine, BEMP) type do effectively polymerize β‐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 °C from bulk monomer, with up to 21 500 g mol⁻¹. The formation of α,ω‐guanidine/amidine/phosphazene,crotonate functionalized PHBs, as demonstrated by NMR, SEC, and MALDI–ToF mass spectrometry analyses, mechanistically suggests the formation of N‐acyl‐α,β‐unsaturated propagating species that originate from 1:1 guanidine/amidine/phosphazene:BL adducts.