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