ma8b00153_si_001.pdf (1.6 MB)
Block Copolymers of Macrolactones/Small Lactones by a “Catalyst-Switch” Organocatalytic Strategy. Thermal Properties and Phase Behavior
journal contribution
posted on 2018-03-16, 19:49 authored by Viko Ladelta, Joey D. Kim, Panayiotis Bilalis, Yves Gnanou, Nikos HadjichristidisPoly(macrolactones)
(PMLs) can be considered as biodegradable
alternatives of polyethylene; however, controlling the ring-opening
polymerization (ROP) of macrolactone (ML) monomers remains a challenge
due to their low ring strain. To overcome this problem, phosphazene
(t-BuP4), a strong superbase, has to be
used as catalyst. Unfortunately, the one-pot sequential block copolymerization
of MLs with small lactones (SLs) is impossible since the high basicity
of t-BuP4 promotes both intra- and intermolecular
transesterification reactions, thus leading to random copolymers.
By using ROP and the “catalyst-switch” strategy [benzyl
alcohol, t-BuP4/neutralization with diphenyl
phosphate/(t-BuP2)], we were able to synthesize
different well-defined PML-b-PSL block copolymers
(MLs: dodecalactone, ω-pentadecalactone, and ω-hexadecalactone;
SLs: δ-valerolactone and ε-caprolactone). The thermal
properties and the phase behavior of these block copolymers were studied
by differential scanning calorimetry and X-ray diffraction spectroscopy.
This study shows that the thermal properties and phase behavior of
PMLs-b-PSLs are largely influenced by the PMLs block
if PMLs components constitute the majority of the block copolymers.