Thermo-responsive behavior

In addition, all representatives are highly fluorescent in the solid state, but essentially nonfluorescent in solution at room temperature. Upon cooling the solutions of benzo[b][l,4]diazepines 51 cryo-fluorescence is observed, which can be attributed to a freezing of the ring interconversion and aggregation. This thermo responsive behavior of fluorophores as a consequence of restricted conformational... 

VA1 Van Diume, K., Rahier, H., and Van Mele, B., Influence of additives on the thermo-responsive behavior of polymers in aqueous solution. Macromolecules, 38, 10155, 2005. 

Thermo-responsive Behavior of Poly(DMAEMA) in Aqueous Solution... 

A-substituted acrylamides are an extensive class of thermo-responsive polymers that have attracted a lot of interest due to their unique thermo-responsive behavior in aqueous media. Among this class, poly(A -isopropylacrylamide) (PNIPAAm) is the most extensively studied polymer for structure activity relationships (Bae, Okano, Kim, 1990 Feil, Bae, Feijen, Kim, 1992) and potential thermo-responsive apphcations. 

The thermo-responsive behavior of PVCL has been extensively studied to elucidate the mechanism of its phase transition behavior. Smdies with PVCL in aqueous systems below its LCST have revealed that the seven-membered ring of the polymer attains a chair-like conformation, with the carbon backbone chain reconfiguring and attaining syndiotactic configuration (Kirsh, Yanul, Kalninsh, 1999 Sun Wu, 2011). 

The di-block copolymers of hydrophobic-hydrophiUc PLGA-PEG also showed thermo-responsive behavior with sol-to-gel transition on increase in temperature (Choi et al., 1999). These polymers formed micelles, with a core of hydrophobic PLGA and an outer shell composed of hydrophilic PEG blocks. There is formation of bridged micelles due to interactions between PEG chains of adjacent micelles. The bridge density increases with increase in temperature, leading to aggregation and gelation. 

Duan et alP also reported the synthesis of poly(A -isopropylacrylamide)-silica composite microspheres by using inverse Pickering suspension polymerization with various sizes of silica particles as stabilizers. Figure 1.14 shows examples of such microgels stabilized by silica particles with mean diameters of 53, 301, 500 and 962 nm. To generate these nanocomposite structures, droplets of an aqueous solution of 7V-isopropylacrylamide were first dispersed in toluene and then stabilized by silica particles. The monomer was subsequently polymerized to obtain polymer silica composite microspheres. It was also observed that the thermo-responsive behavior of the polymer was not affected in the presence of silica, as a lower critical solution temperature of 32 °C for the poly(A -isopropylacrylamide) was also observed in the polymer-silica microspheres. 

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