Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
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Chapter 3<br />
aluminum based complexes were totally inactive for the ROP <strong>of</strong> LacOCA.<br />
3.4 <strong>Characterization</strong> <strong>of</strong> the Obtained PLA<br />
Figure 3.3 Structures <strong>of</strong> aluminum based complexes.<br />
The 1 H NMR spectrum <strong>of</strong> the obtained PLA was shown in Figure 3.4. The doublet peaks<br />
at 1.73 ppm was assigned to CH3 resonance <strong>of</strong> the polymer chain. The quartet peaks at<br />
5.15 ppm was attributed to that <strong>of</strong> the CHCH3 <strong>of</strong> PLA. 13 C NMR spectrum <strong>of</strong> the PLA was<br />
displayed in Figure 3.5. The signals at 169.5, 69.0 <strong>and</strong> 16.6 ppm corresponded to the carbon<br />
resonances <strong>of</strong> carbonyl, methine, <strong>and</strong> methyl groups <strong>of</strong> the PLA chain, respectively. These<br />
results were consistent with the reported NMR spectra <strong>of</strong> PLA, 28 which demonstrated that<br />
PLA was formed by the polymerization <strong>of</strong> LacOCA. The carbonyldioxy group was<br />
eliminated from the polymerization system by the liberation <strong>of</strong> carbon dioxide.<br />
8 6 4 2 0<br />
ppm<br />
Figure 3.4 1 H NMR spectrum <strong>of</strong> poly(lactic acid) from LacOCA.<br />
The DSC thermogram <strong>of</strong> the obtained PLA was shown in Figure 3.6. The glass transition<br />
‐ 80 ‐