Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
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Sample<br />
Table 1. Feed <strong>and</strong> result compositions <strong>of</strong> copolymers.<br />
CPAD-PLA-CPAD/Monomer<br />
(mol)<br />
Feed Result a<br />
‐ 105 ‐<br />
<strong>Synthesis</strong> <strong>of</strong> Triblock Copolymers <strong>of</strong> TEMPO‐Acrylamide<br />
<strong>and</strong> Lactate by RAFT Polymerization<br />
Yield<br />
(%)<br />
PDI b<br />
TLT1 1 : 100 1 : 70 81.0 1.40<br />
TLT2 1 : 200 1 : 180 90.0 1.42<br />
a Calculated from 1 H NMR; b Determined from GPC in DMF.<br />
The cyclic voltammogram (CV) <strong>of</strong> the copolymer at different scan rates were shown in<br />
Figure 3. The CV curves also confirmed the success <strong>of</strong> the oxidation.<br />
Figure 3. CV <strong>of</strong> the copolymer (TLT1) at different scan rates in acetonitrile solution <strong>of</strong> 0.1 M<br />
tetrabutylammonium perchlorate.<br />
5.3 Thermal Properties<br />
The typical DSC traces for PLA, TLT1, TLT2 <strong>and</strong> PTAm were collected in Figure 4A. The<br />
PLLA homopolymer has a Tm at 155.6 o C <strong>and</strong> a Tc at 97.4 o C, while TLT1 exhibits a Tm at<br />
160.0 o C <strong>and</strong> TLT2 exhibits no Tm or Tg in the test temperature range. These differences<br />
indicated that the physical properties <strong>of</strong> the PLA in the block copolymers were really<br />
different from those <strong>of</strong> homo-PLA. In the triblock copolymers, the PLA block was still<br />
crystalline, but its crystalline parameters changed much due to the restriction <strong>of</strong> the PTAm
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