Catalytic Synthesis and Characterization of Biodegradable ...

5.2 Synthesis of Triblock Copolymer
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Synthesis of Triblock Copolymers of TEMPO‐Acrylamide
and Lactate by RAFT Polymerization
The schematic procedures of the synthesis of the PTAm-b-PLA-b-PTAm copolymer were
shown in Scheme 1. The first step was to prepare PLA bearing two hydroxyl groups at each
chain end. The molecular weight of the HO-PLA-OH can be determined from 1 H NMR as
1.0×10 4 (Figure 1A). Then the CPAD, used as a chain transfer agent, was coupled onto the
PLA chain ends via condensation reaction in the presence of DCC and DMAP. The 1 H NMR
spectra of CPAD-PLA-CPAD showed signals at 7.4 – 7.9 ppm, corresponded to the resonance
of the protons from the phenyl in the CPAD (Figure 1B). The PTAP-b-PLA-b-PTAP was
synthesized by RAFT polymerization using CPAD-PLA-CPAD as macro-RAFT agent. The
monomer, TAP, is not suitable for ATRP polymerization due to its pendant imine group,
which may competitively complex with the copper and form species with lower catalytic
activity. Therefore, we synthesized the block copolymer via RAFT polymerization. Finally,
the PTAm-b-PLA-b-PTAm was obtained after the oxidation of PTAP-b-PLA-b-PTAP.
Scheme 1. Synthetic route of PTAm-b-PLA-b-PTAm.