Unveiling causal relationship between non-covalent interactions and evaluated Young’s modulus within oligolignols-cellulose complexes

Linear correlation coefficients were calculated between the reported Young’s modulus (YM) values and non-covalent interactions within cellulose-oligolignol complexes, considering the composition of an efficient adhesive formulation previously reported. A paradigmatic relationship was observed. Molecular complexes of oligolignols with cellulose Iβ were modeled using hybrid quantum mechanics/molecular mechanics (QM/MM) computations to obtain wavefunctions at the interaction region. Subsequently, a study of non-covalent interactions (NCI) based on the atoms in molecules (AIM) theory was implemented, utilizing graphics processing units (GPUs) for calculations. Our findings indicate that non-covalent interactions control the forces associated to adhesive-cellulose contacts, primarily through X-H···O hydrogen bonds, which promote the adhesion of oligolignols on cellulose Iβ. Results indicate that the adhesion strength projected from larger YM values cannot be described solely by the number of stronger hydrogen bonds nor by the number of the weak interactions but by the entire contributions of specific interactions. Thus, significant linear correlations were observed between reported values of Young’s modulus and the molecular interactions observed, rendering the influence of oligolignol structure on the adhesion phenomenon in our cellulose Iβ crystallite model. These observations promote the NCI and AIM analysis in a new framework to design adhesive formulations.