Cellulose nanofibril aerogels reinforcing polymethyl methacrylate with high optical transparency

An interpenetrating composite composed of cellulose nanofibrils (CNF) and polymethyl methacrylate (PMMA) with excellent optical transmittance and high mechanical strength was successfully fabricated via a novel approach. Firstly, a flaky CNF aerogel was prepared by lyophilizing the CNF gel. The obtained CNF aerogel was then impregnated in methyl methacrylate monomer. Through further thermal initiation polymerization, a CNF/PMMA composite with excellent mechanical and optical properties was obtained. The above strategy overcomes the problem that CNF is difficult to be integrated with hydrophobic polymers due to its hydrophilicity. The CNF aerogel provided a strong 3D skeleton for the composite, which can significantly enhance the tensile strength of PMMA from 8 to 32 MPa. The obtained CNF/PMMA composite maintained a light transmittance of 75-80% because the refractive index of cellulose is close to PMMA. Overall, this work demonstrated a facile and environment-friendly strategy to prepare CNF/PMMA composites, which eliminated the traditional time-consuming and environmentally harmful processes involved in the modification of CNF for achieving its uniform dispersion in PMMA matrix. The obtained composites can be used in the field of general-purpose materials, such as transparent packaging materials, electronic product touchpad, lightweight transparent materials for automotive lampshades, solar photovoltaic cells, window, optical lens, medical equipment, and so forth.