Abstract
We report here the synthesis of well-defined thermoresponsive diblock copolymer bearing amino acid diamide derivatives, poly(N-acryloyl-l-valine N′-methylamide)-b-poly(ethylene glycol) monomethylether, via click reaction using CuSO4/sodium ascorbate as catalyst in DMF/water mixed solvent. The effects of chain length and water volume fraction in DMF on coupling efficiency were investigated. For those reactions that both reacting polymers have short chain length, the reaction efficiency was less affected by water volume fraction and relatively high conversion was achieved. And the higher molecular weight of reactant polymer performed, the more impressive effects of water content on coupling efficiency appeared. Then, the thermoresponsive property in terms of the lower critical solution temperature (LCST) of the block copolymer was evaluated in aqueous solution by UV/vis spectroscopy. Optically active character was detected by circular dichroism instrument under temperature ranging from 1 to 30 °C, and the spectra undergo one drastic change at the temperature near LCST point.
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