Photo and thermal properties of cinnamoyl Pluronic F‐127

Abstract

Abstract 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 1 H NMR spectrum. The melting point (around 52 °C) of Cin‐Plu was somewhat less than that (around 55 °C) of Pluronic F‐127. Furthermore, the melting point of Cin‐Plu decreased to around 50 °C on UV irradiation. The micellization temperature of Pluronic F‐127 was around 15 °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 °C and Cin‐Plu solution (22% w/v) at around 39 °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 °C to 37 °C, possibly due to the coexistence of dimeric Cin‐Plu and monomeric Cin‐Plu. © 2013 Society of Chemical Industry