Figure 2 Changes in CD and UV-vis spectra of the CABu/PMMAzo-1
composite films (CABu/PMMAzo-1 = 2:1, w/w) (a) before annealing as
prepared films at room temperature and (b) after termal annealing at 80
°C for 10 min. (c) A comparison of g CD values at
the first Cotton band (350–400 nm) in three composite films prepared by
chloroform (red), dichloroethane (green), and tetrahydrofuran (blue)
before and after the annealing processes. (d) Possible supramolecular
stacking structure of PMMAzo.
Besides, the relative weight ratios of CABu to PMMAzo significantly
affect g CD values (entries 2, 5-7 in Table 1).
From Figure 3a, it is evident that all the polymer composite films
showed very strong Cotton effects at room temperature in the absorption
region of the trans -azobenzene group, demonstrating that the CABu
successfully induced the helical π-stacks of Azo building units in
polymer side-chains. Further annealing increased the CD amplitude by two
orders of magnitude (Figure 3b). The correspondingg CD values were summarized in Figure 3c, the
maximum g CD values of each polymer films
decreased gradually with the increase of CABu content. This may be
attributed to the fact that proper content of inducer helps to form a
more regular surface, because we found that more inducer would make the
film inhomogeneous (Figure 4d). Apparently, the preference for induced
supramolecular chirality can be tuned by changing the content of chiral
semi-synthetic biomaterials or the type of solvent.