Abstract: Compositions and methods of producing paper-based materials are disclosed. The techniques can utilize an amine-containing polymer, such as chitosan, to functionalize one or more components of a mixture used to form materials such as paper-based materials. Such components can include the fibers of a pulp and/or filler particles. Techniques and compositions are also described to further improve the qualities of a paper material by utilizing a complementary polymer which can couple with the amine-containing polymer. Other compositions and methods are directed to forming paper-based materials that are expandable.