2.3. Preparation of photothermal membranes by solvent-induced
recrystallization
The first step is the recrystallization of PDMS and photothermal
particles dispersion. CS and MWCNTs were mixed at a mass ratio of 1:1,
dispersed in tetrahydrofuran and stirred, followed by the addition of
PDMS and ultrasonication. The content ratio of substances was CS:
MWCNTs: PDMS: tetrahydrofuran=0.1g: 0.1g: 3g: 100ml, and the mass ratio
of PDMS to curing agent was 3:1. The PLLA fiber membrane was fixed on a
metal frame, immersed into the above mixing solution with continuous
ultrasonication for 20 seconds.
The second step is the recrystallization of PLLA. The membrane treated
by tetrahydrofuran are quickly taken out and immersed into acetone for 5
minutes, and finally removed and dried at room temperature to obtain the
double-sided heterochromatic photothermal membrane. The volume of
tetrahydrofuran was changed to 200 ml and 400 ml and the experiment was
repeated. For easy differentiation, in the Results and Discussion
section, we named the PDMS-containing solvent-treated PLLA as APLLA.
Other solvent-induced recrystallization were also explored. Method 1:
Acetone treatment, drying and then treated with tetrahydrofuran
containing PDMS and CS/MWCNTs. Method 2: Treated by the solvent of
tetrahydrofuran containing PDMS and CS/MWCNTs. Method 3: Treatment with
tetrahydrofuran containing PDMS and CS/MWCNTs, drying and then acetone
treatment. Method 4: Acetone treatment and then treatment with
tetrahydrofuran containing PDMS and CS/MWCNTs. Method 5: Treated by the
solvent of acetone containing PDMS and CS/MWCNTs (Little amounts of
tetrahydrofuran were used to dissolve PDMS in acetone).