The effect of delignification ratio on the PMMA occupation in poplar wood cell wall by the macro and micro comparative study

Abstract The polymer/wood functional products may not be true nanocomposites due to the poor permeability of non-polar monomers into the hydrophilic wood cell wall. In this paper, methyl methacrylate (MMA) chosen as the representative non-polar monomer was used to impregnate wood with different lignin removal and then polymerized in situ in delignified wood to obtain polymethyl methacrylate/delignified wood (PMMA/DW). The larger 10 nm mesopores reduction in PMMA/DW-29.9 and the disappearance of the smaller 3 nm mesopores of PMMA/DW-51.7 indicated that the removal of lignin was beneficial for the penetration of MMA in the wood cell wall. When the lignin removal reached between 29.9 and 51.7%, the dimensional stability of PMMA/DW was improved, and it could be speculated that the resin began to enter the wood cell wall at this stage. In addition, the indentation modulus and hardness of the PMMA/DW cell wall were significantly increased when the lignin removal reached 29.9%. This result was consistent with the conclusion of the pore size analysis, which further confirmed that the nanopores of the cell wall were filled with PMMA when the lignin removal was greater than 29.9%. The results of this paper indeed provide a basis for the design of biomass functional nanocomposites.