Photo and thermal properties of cinnamoyl Pluronic F-127

Cinnamoyl chloride was covalently attached to the ends of Pluronic F-127 chains. The molar ratio of cinnamoyl groups to Pluronic F-127 of the cinnamoyl Pluronic F-127 (Cin-Plu) was calculated to be about 1:1 on a H-1 NMR spectrum. The melting point (around 52 degrees C) of Cin-Plu was somewhat less than that (around 55 degrees C) of Pluronic F-127. Furthermore, the melting point of Cin-Plu decreased to around 50 degrees C on UV irradiation. The micellization temperature of Pluronic F-127 was around 15 degrees C and it was affected neither by the covalent attachment of cinnamoyl chloride nor the UV irradiation. On the other hand, Pluronic F-127 solution (22% w/v) in distilled water became a gel at around 28 degrees C and Cin-Plu solution (22% w/v) at around 39 degrees C. The elevation in the gelation temperature is possibly because the cinnamoyl group interferes with the intermolecular hydrophobic interaction of propylene oxide blocks, a main cause for the gelation. Cin-Plu solution (22% w/v) which had been subjected to UV irradiation (365 nm, 400 W) for 3 h exhibited no gelation temperature but a gradual increase in viscosity when the solution temperature increased from 17 degrees C to 37 degrees C, possibly due to the coexistence of dimeric Cin-Plu and monomeric Cin-Plu. (c) 2013 Society of Chemical Industry