Chemically imaging the effects of the addition of nanofibrillated cellulose on the distribution of poly(acrylic acid) in poly(vinyl alcohol)

The distribution of poly(acrylic acid) (PAA) in model laminates of nanocellulose and poly(vinyl alcohol) (PVOH) was investigated by FTIR chemical imaging. The method was effective in spatially discerning the three components of the composite. PAA can potentially improve the performance of nanocellulose reinforced PVOH by not only crosslinking the PVOH matrix but also improving the adhesion between PVOH and nanocellulose by forming ester linkages with both of them. However, PAA was found to migrate out of the PVOH matrix and concentrate in the nanocellulose layer of the laminate. This led to a PAA-depleted region in the matrix near the nanocellulose layer, which would likely lead to a weak interphase and limited stress transfer between the fiber and matrix in the heat-treated composite. Methods for improving the distribution of the PAA need to be investigated to optimize performance. This is the first chemical imaging study of nanocellulose materials using synchrotron-based vibrational spectroscopy.