Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
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Chapter 4<br />
The 1 H NMR <strong>and</strong> 13 C NMR measurements were performed on Bruker DMX300<br />
spectrometer with tetramethylsilane (TMS) as an internal reference. FTIR spectra were<br />
measured on a Bruker Vertex 70 Fourier Transform Infrared spectrometer using the KBr disk<br />
method. Atomic force microscopy (AFM) images were acquired in a commercial<br />
SPA300HV/SPI3800N Probe Station, Seiko Instruments, Japan, in tapping mode. A silicon<br />
microcantilever (spring constant 2 N/m <strong>and</strong> resonance frequency ~ 70 kHz, Olympus, Japan)<br />
with an etched conical tip was used for scan. Silicon wafers were cleaned by a 30 min dip in<br />
fresh 1:1 H2SO4 (concentrated)/H2O2 (30%) solution. Subsequently, the acids were removed<br />
by a thorough rinse in Millipore water. Polymer thin films were obtained by spin-coating a<br />
copolymer chlor<strong>of</strong>orm solution onto silicon wafers. Magnetization <strong>and</strong> magnetic<br />
susceptibility <strong>of</strong> the powder polymer sample were measured using a Quantum Design<br />
MPMS-7 SQUID (superconducting quantum interference device) magnetometer. The<br />
magnetic susceptibility was measured from 10 to 300 K under a 1.0 T field. Cyclic<br />
voltammetry was performed using a normal potentiostat system (BAS Inc. ALS660B) with a<br />
conventional three-electrode cell under a dry argon atmosphere. A platinum disk, coiled<br />
platinum wire, <strong>and</strong> Ag/AgCl were used as the working, auxiliary <strong>and</strong> reference electrode,<br />
respectively. The cyclic voltammogram was measured in a dichloromethane solution in the<br />
presence <strong>of</strong> 0.1 M tetrabutylammonium tetrafluoroborate as the supporting electrolyte. The<br />
film <strong>of</strong> copolymer was 100 nm in thickness. The formal potential <strong>of</strong> the<br />
ferrocene/ferrocenium redox couple was 0.45 V vs the Ag/AgCl reference electrode. The<br />
GPC analysis was performed using TOSOH HLC-8220 with 0.1 M LiCl DMF as solvent.<br />
<strong>Synthesis</strong> <strong>of</strong> PLA-HEMA<br />
PLA-HEMA was easily prepared by the ring-opening polymerization <strong>of</strong> L-lactide in the<br />
presence <strong>of</strong> HEMA <strong>and</strong> stannous octoate (Sn(Oct)2). First, 0.48 g HEMA, 5.0 g L-lactide, 8<br />
mg hydroquinone, <strong>and</strong> 5 mg Sn(Oct)2 were added into a dried glass reactor already<br />
flame-dried <strong>and</strong> nitrogen-purged three times. After injection <strong>of</strong> 35 mL toluene, the reactor<br />
was sealed <strong>and</strong> maintained at 120 o C for 24 h. The product was precipitated with an excess <strong>of</strong><br />
ethanol, purified by precipitating twice into ethanol from chlor<strong>of</strong>orm solution, to give a white<br />
product. Yield: 34%.<br />
<strong>Synthesis</strong> <strong>of</strong> PTAP-g-PLA<br />
Typically, 0.15 g PLA-HEMA <strong>and</strong> 0.35 g 2,2,6,6-tetrametylpiperidine-4-yl acrylamide<br />
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