Abstract
Photoinitiated ring-opening polymerization of l-lactide (L-LA) using a photobase generator (PBG) able to release 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is reported. Polymerization using the PBG with ketoprofenate counteranion (TBDH+.keto-) was studied in dichloromethane either in the presence or in the absence of 1-butanol as initiator. In both cases, full monomer conversion was reached at room temperature after 10 min of irradiation at 254 nm. In the presence of 1-butanol, linear poly(L-LA) chains (PLA) were obtained, as confirmed by 1H NMR and MALDI-TOF analyses. The polymerization was well controlled as attested by the production of polymers with low dispersity (Đ < 1.26) and by the linear evolution of molecular weights with the quantity of initiator. Without 1-butanol, although MALDI-TOF analyses revealed cyclic PLA chains (actually formed in situ during MALDI-TOF analysis), linear PLA chains were formed as proven by 1H NMR, viscosity measurement, and phosphitylation titration. This fast and "on demand" polymerization opens the way to biodegradable UV coatings.
Published Version
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