We successfully controlled birefringence and its wavelength dispersion of cellulose esters by choosing different ester substitution groups and sites, controlling the orientation of the crystal, adding low-mass molecules, and forming microscale porous structures. The substitution of two ester groups could provide extraordinary wavelength dispersion of birefringence, which is important for wide-range retardation films. The low-mass additives enhance birefringence values due to the intermolecular orientation correlation with matrix cellulose esters. The anisotropic microporous structure produced by thermoinduced phase separation generates form birefringence, which improves the total birefringence of cellulose esters.
