SCHEDULED MAINTENANCE
Thermo-responsive and fluorescent cellulose nanocrystals grafted with polymer brushes†
Abstract
Cellulose nanocrystals (CNCs) grafted with fluorescent and thermo-responsive poly(N-isopropylacrylamide) (PNIPAAM) brushes were prepared via surface-initiated activators generated by electron transfer for atom transfer radical polymerization (SI-AGET-ATRP) in the CH3OH–H2O mixing solvent with different volume ratios. The successful grafting was supported by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) measurements. Gravimetric analysis plus 1H NMR and gel permeation chromatography (GPC) measurements showed that there was an increase in the monomer conversion and molecular weight of polymer brushes with increasing H2O proportion of the solvent system. The variation trend of graft length was further evidenced by the gradual change of decomposition and glass transition temperatures of the surface-grafted CNCs. A large scale of chain transfer occurred on the surface of CNCs in view of the minute quantity of free polymers generated by a sacrificial initiator. Free polymers cannot be used as a substitute to characterize grafted polymers in terms of the big difference between their molecular weights. The obtained surface-grafted CNCs showed thermo-enhanced fluorescence owing to the thermal-driven chain dehydration of the grafted PNIPAAM brushes.
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