Ice Squeezing Induced Multicolor Fluorescence Emissions from Polyacrylamide Cryogels.

Being short of conventional chromophores, polyacrylamide is generally not regarded as a fluorescent material. Exactly the polymerization of dilute solutions of acrylamide and N,N'-methylenebisacrylamide led to thick liquids at 60 °C, showing no fluorescence. Things changed when the phase transition of water was involved. The squeezing effect of ice crystals not only created polymeric solids (cryogels) at - 20 °C, but also endowed them unexpected fluorescence emissions. The macroporous cryogels are mainly blue fluorescent polymers. However yellow and red fluorescence were also achieved by changing the ingredient ratios. A series of instrumental detections revealed that the multicolor fluorescence were based on exquisite amido stacking induced from ice squeezing. If people make good use of the squeezing effect of the heaven-sent molecule to manipulate the interactions of monomer functionalities, cryogenic polymerization can be a promising method to produce diverse polymeric materials.