Physicochemical design of the morphology and ultrastructure of cellulose beads

Cellulose was dissolved in NaOH-urea-water and beads were prepared by coagulation into nitric acid as well as saline solution. Morphology and ultrastructure of the beads were modified by controlling the molarity of the acid (0-10 M) and temperature (5-50 degrees C) of the coagulation media and the cellulose concentration (3-7%). The beads were characterized by optical image analysis (shape, volume, and size distribution) and weight (total porosity). Cross-sections of CO2 critical point dried beads were studied by field emission scanning electron microscopy (FE-SEM) and specific surface areas of 336-470 m(2) g(-1) were determined from nitrogen adsorption isoterms. Pore size distribution was analyzed using solute exclusion technique. Our results demonstrate that the ultrastructure can be controlled by alteration of the coagulation conditions. Changes in size, shape and surface area were substential. Also generation of micro- (<= 2 angstrom), meso-, or macropores (>= 50 A) can be favored. (C) 2012 Elsevier Ltd. All rights reserved.