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).