Relationship between interface chemistry and reinforcement in polybutadiene/cellulose nanocrystal nanocomposites

Abstract Interfacial interaction between matrix polymer and nanofiller greatly influences the mechanical properties of polymer nanocomposites. Herein, two kinds of functionalized polybutadienes containing carboxyl or hydroxyl groups, PB-COOH and PB-OH, were synthesized via thiol-ene reaction and utilized as matrices to investigate the reinforcing effect of CNCs. Homogeneous PB-COOH/CNC and PB-OH/CNC nanocomposites containing up to 30 wt% CNCs were successfully fabricated. The incorporation of CNCs into the polymers led to remarkably enhanced mechanical properties, while the reinforcing effect of CNCs was more pronounced for PB-COOH than that toward PB-OH. Transmission electron microscopy and theoretical modeling studies revealed that the mechanical enhancement is attributed to the formation of a CNC percolation network within the polymer matrix and the interfacial interaction between matrix and CNCs. Differential scanning calorimetry analysis demonstrated that the polymer-filler interaction in the PB-COOH nanocomposites was stronger than that in the PB-OH systems, which results in a larger amount of constrained polymers in the former system and consequently contributes an increase in storage modulus. Thus, the CNC-CNC and polymer-CNC reactions are both responsible to the mechanical enhancement of the resulting nanocomposites.