Synthesis and characterization of Eu(III) complexes of modified cellulose and poly(N-isopropylacrylamide)

A series of thermo-responsive copolymers of poly(N-isopropylacrylamide) (PNIPAM) and cellulose were synthesized via atom transfer radical polymerization (ATRP) using N-isopropylacrylamide as the monomer, cellulose acetate as the initiator, and CuCl/tris(2-dimethylaminoethyl)amine (Me6TREN) as a catalytic system. The resulting polymers had a narrow range of polydispersity indexes 1.27–1.37, and molecular weights of 8600–17,300 g mol−1. Novel functional complexes of cellulose-g-PNIPAM/Eu(III) with excellent thermosensitive and fluorescent properties were then formed by the chelation of copolymers and europium(III) ions. The maximum emission intensity of the complexes at 613 nm was enhanced by a factor of approximately 10 relative to that of the corresponding Eu(III) complexes. Additionally, the lower critical solution temperatures (LCSTs) of cellulose-g-PNIPAM/Eu(III) were slightly greater than those of the copolymers.