Figure 1 . Changes in CD and UV-vis spectra of the composite films consisiting of CTA/PMMAzo-1 (1:1, w/w, red curves) and CABu/PMMAzo-1 (1:1, w/w, blue curves, entry 5 in Table 1) (a) before (as prepared films at room temperature) and (b) after termal annealing process at 80 °C for 10 min.
We therefore investigated the effect of annealing time on the induction of the chiral supramolecular structure of polymer films. As shown in Figure S4, a 10-minute annealing treatment of the polymer composite film is enough to obtain a 10-fold increase in maximum helicity over the pristine one (entries 1-4). Furthermore, the solvent used to dissolve the polymer is the key for aggregation processes and can strongly influence aggregation behavior via the specific interactions between solvent and solute. On the one hand, the basic features of solvents such as polarity, viscosity, and solubility for the polymers could affect the interaction tendencies between building blocks of supramolecular systems. According to our previous works,7, 29, 30 the types of solvents played an important role in the supramolecular assembly of azobenzene-containing polymers. For example, supramolecular chirality of azobenzene-containing polymers can be constructed in chloroform, dichloromethane and 1,2-dichloroethane, but cannot inN ,N -dimethylformamide.29 Furthermore, the chiral expression of supramolecular aggregates also differs in different solvents. On the other hand, supramolecular chirality is produced by nonsymmetric arrangement of building blocks through weaker noncovalent bond interaction, which can be easily influenced by external environmental factors such as solvents, which is generally dynamic, changing in response to external stimuli.31 Here, CABu and PMMAzo-1 were co-solved in chloroform (CHCl3), dichloroethane (CH2Cl2) and tetrahydrofuran (THF) with the mass concentration of 30 mg/mL, and solvent polarity is also an important factor determining the chiral expression of composite films. When the solvent for dissolving the mixture was changed from CHCl3 to CH2Cl2 and THF, there was a more significant increase in chiral expression regardless of the annealing treatment (Figures 2a and 2b). The g CD of the spin-coated film prepared by THF solvent is the largest among all series (Figure 2c). These results indicate that THF is the best solvent for dissolving polymers, and its appropriate polarity can effectively promote the cooperative interaction between polymer building blocks and chiral CABu semi-synthetic biomaterials (Figure 2d).