H NMR、2D NOESY NMR方法测定了PAA-α-CD与PAM-Azo间的主客体作用。结果表明
PAM-Azo侧链的
trans
-Azo基团能够被PAA-α-CD侧链的α-CD包结
而
cis
-Azo基团不能被α-CD包结。在一定浓度下
PAA-α-CD与PAM-Azo通过主客体间的识别能够形成超分子水凝胶
并且该凝胶具有光响应性。在365nm紫外光光照下
PAM-Azo侧链的
trans
-Azo转变为
cis
-Azo
不能被PAA-α-CD侧链的α-CD包结
超分子水凝胶转变为溶胶。而在430nm的可见光光照下
PAM-Azo侧链的
cis
-Azo转变为
trans
-Azo
重新被PAA-α-CD侧链的α-CD包结
又可得到超分子水凝胶。
Abstract
A α-cyclodextrin (α-CD) modified poly(acrylic acid) (PAA-α-CD) acting as the host-polymer and an azobenzene-branched polyacrylamide (PAM-Azo) acting as the guest-polymer were prepared. The interaction of PAA-α-CD with PAM-Azo was characterized by
1
H NMR and 2D NOESY NMR spectroscopy. The 2D NOESY NMR spectroscopy indicate that
trans-azobenzene
(
trans
-Azo) units are bounded strongly within the cavities of PAA-α-CD whereas the
cis-azobenzene
(
cis-Azo
) is not bound at all. A supramolecular inclusion complex
formed by PAA-α-CD and PAM-Azo
is accompanied by the formation of a light-responsive hydrogel. Upon photoirradiation with UV light of 365nm
the hydrogel is converted efficiently to the sol phase because the
trans
-Azo units are converted photochemically to their
cis
configuratons
where upon the resulting
cis
-Azo units dissociation from PAA-α-CD. The hydrogel can be recovered from the sol phase by photoirradiation with visible light of 430nm.