Photoinduced morphology switching of polymer nanoaggregates in aqueous solution.
A novel photosensitive C-PNIPAAm comprising hydrophilic PNIPAAm conjugated with a relatively short but very hydrophobic coumarin part was designed and prepared using a coumarin-containing disulfide derivative (C-S-S-C) as transfer agent in the presence of Bu(3)P and water. It was found that C-PNIPAAm can form polymer micelles in aqueous solution. And the micellar morphology in aqueous solution can be photoswitched into hollow spheres according to the photodimerization of coumarin end groups upon 365 nm irradiation and reform the micellar morphology after the subsequent photoscission of dimers upon 254 nm. This instant morphology changing phenomenon was successfully monitored by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. TEM observations showed the small spherical shape of micelles with diameter at 30-50 nm before photo-cross-linking, the big vesicles with diameter at 200-350 nm after photo-cross-linking, and the small micelles with diameter at 30-50 nm after the subsequent photo-de-cross-linking in the first irradiation cycle. The reason for this significant morphology switching can be attributed to the reversible photoinduced amphiphilic structure transformation between the telechelic "hydrophobic end-hydrophilic chain" structure and the ABA type of "hydrophilic chain-hydrophobic center-hydrophilic chain" one upon alternating irradiation.
Jiang
Jinqiang
J
School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu, China 214122. jiangjq@jiangnan.edu.cn
Shu
Qiaozhen
Q
Chen
Xin
X
Yang
Yiqun
Y
Yi
Chenglin
C
Song
Xiaoqing
X
Liu
Xiaoya
X
Chen
Mingqing
M
D000178:Acrylamides / Q000138:chemical synthesis* / Q000737:chemistry; D000180:Acrylic Resins; D004220:Disulfides / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D010777:Photochemistry; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D012996:Solutions; D014867:Water / Q000737:chemistry
D000178:Acrylamides; D000180:Acrylic Resins; D004220:Disulfides; D011108:Polymers; D012996:Solutions; D014867:Water; C052970:poly-N-isopropylacrylamide