EFFECT OF LATTICE DISTORTIONS ON CRYSTALLINE STRUCTURE OF CI CELLULOSES

Impact of lattice distortions on parameters and packing density of crystalline unit cell of various cellulose samples has been studied. It was disclosed that decrease of the degree of paracrystallinity leads to reduction of parameters “a”, “b” and specific volume of C1β unit cell. Parameter “c” tends to increase with decrease in the degree of paracrystallinity. Using the specific volume of undistorted equilibrium lattice of CI and specific volume of paracrystalline lattice, the degree of distortion of crystalline lattice of various cellulose samples was evaluated. The results showed that large crystallites of tunicate cellulose have a little distorted monoclinic crystalline structure, while monoclinic lattice of smaller crystallites of cotton linter, bast fibers and wood cellulose is more distorted. On the other hand, triclinic lattice of CIα celluloses was highly distorted. However, paracrystalline distortions in large crystallites of CIα celluloses are negligible, therefore a high imperfection of CIα lattice is caused by other types of defects such as vacancies, dislocations, etc. As a result of annealing of CIα celluloses, most of these defects disappear that leads to decrease in distortion degree and conversion of unstable triclinic into stable monoclinic lattice with a higher packing density.