A two-step initiation and polymerization process was developed for the preparation of two series of hydrogel-cellulose composites with distinctively different morphologies and swelling behaviors. Hydroentangled cotton cellulose fibers were optimally initiated in 20 mM aqueous ammonium cerium(IV) nitrate for 15 min and then polymerized in aqueous solutions of N-isopropylacrylamide (NIPAAm) monomer and NN'-methylene bisacrylamide (BisA) crosslinker. The extents of hydrogels on the cellulose solids could be controlled by variations in the concentrations of the monomer and crosslinker as well as the NIPAAm/ BisA solution-to-solid ratios. The two series of hydrogel-cellulose composites formed were hydrogel-covered/filled cellulose (I) and cellulose-reinforced hydrogel (II) composites. Series I composites were synthesized with NIPAAm/ BisA solutions below the liquid saturation level of the cellulose; this led to pore structures (size and porosity) that depended on both the extent and swelling of the grafted hydrogels. Series II composites were polymerized in the presence of excessive NIPAAm/BisA solutions to produce cellulose solids completely encapsulated in the hydrogels. All the cellulose-supported hydrogels exhibited lower extents of phase transition over a wider temperature range (28 -40degreesC) than the free poly(N-isopropylacrylamide) hydrogels (32degreesC). These findings demonstrate that hydrogels can be used to control the pore structure of cellulose and can be supported with cellulose fibers. (C) 2003 Wiley Periodicals, Inc.