Hydroxypropyl lignin derivative block (HPL) was reacted with low DP cellulose triacetate block (CTA). The synthesis of this block copolymer involves the following steps. • Synthesis of an hydroxyl-terminated CTA oligomer through the depolymerization of high molecular weight cellulose triacetate under conditions that deacetylation is prevented. • Reaction of this block with 2,4 toluene diisocyanate (TDI) to form an isocyanate-capped CTA prepolymer under conditions that chain extension is limited and a sufficient NCO equivalent/mole is achieved (ie: 1 or 2). • Reaction in solution of this low DP CTA prepolymer with the HPL block. Films were directly obtained by solution casting of the mixture and cured. The parameters of investigation were HPL, or CTA block content and size of CTA block. Morphological characteristics and thermal analysis were investigated as a function of these parameters. Analysis of the results showed that all the films were brittle. They exhibited single T_g values and were crystalline even for short size cellulose blocks. Network structure was not the predominant factor influencing the properties as was expected from the multi-hydroxyl functionality of the HPL component but rather the crystalline character observed in the copolymers at all compositions. / M.S.