Micromechanical and positron annihilation lifetime study of new cellulose esters with different topological structures.

•Position of CH3 and CF3 groups in cellulose esters influences the molecular packing.•Inverse relationship between the hardness and modulus vs. o-Ps intensity was found.•The lowest modulus and highest o-Ps intensity when −CH3 or -CF3 are in m-position.•Scheme of the structural feature of the investigated cellulose esters was proposed.