Convenient characterization of polymers grafted on cellulose nanocrystals via SI-ATRP without chain cleavage

Abstract

Cleaving is usually required to characterize the molecular weight of grafted polymers on substrates. Here, we report on a technique to estimate the molecular weight of grafted polystyrene (PS) (Mngrafted PS) in PS-grafted cellulose nanocrystals (PS-g-CNCs) without chain cleavage. PS-g-CNCs were prepared from brominated CNC (CNC-Br) by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) in the presence of sacrificial initiators. Differential scanning calorimetry (DSC), dynamic light scattering (DLS), and thermogravimetric analysis (TGA) of PS-g-CNCs revealed that Mngrafted PS increased proportionally with monomer conversion. By comparing the mass of grafted PS, deduced from TGA curves, with initiating sites on CNC-Br, Mngrafted PS was calculated. The resultant Mngrafted PS was the same as Mn of free PS initiated by sacrificial initiators and matched theoretical values calculated according to monomer conversion. Therefore, grafting polymerization from CNC-Br and free polymerization were progressing in a controlled manner with the same propagating rates.