title: Inverse temperature-dependent pathway of cellulose decrystallization in trifluoroacetic acid.
abstract: An unusual inverse temperature-dependent pathway was observed during cellulose decrystallization in trifluoroacetic acid (TFA). Decreasing the TFA treatment temperature accelerated the cellulose decrystallization process. It took only 100 min to completely decrystallize cellulose at 0 degrees C in TFA, a result not achieved in 48 h at 25 degrees C in the same medium. There was neither cellulose esterification nor a change of cellulose macrofibril morphology by TFA treatment at 0 degrees C. Our IR data suggest that TFA molecules are present as cyclic dimers when they penetrate into crystalline cellulose regions, transforming crystalline cellulose to amorphous cellulose. On the other hand, the rate of TFA penetration into the cellulose matrix was greatly retarded at higher temperatures where monomeric TFA prevails. At elevated temperatures, esterification of TFA monomers on the external surface of crystalline cellulose, agglomeration of cellulose macrofibrils, as well as water released from the esterification reaction, inhibit the diffusion rate of TFA into the cellulose crystalline region and decrease the TFA swelling capability.
authors: Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352, USA.
authors: Haibo
authors: H
authors: Zhao
authors: Johnathan E
authors: JE
authors: Holladay
authors: Ja Hun
authors: JH
authors: Kwak
authors: Z Conrad
authors: ZC
authors: Zhang
mesh_terms: D002482:Cellulose / Q000737:chemistry* / Q000648:ultrastructure; D008757:Methylglucosides / Q000737:chemistry; D013696:Temperature; D014269:Trifluoroacetic Acid / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D008757:Methylglucosides; C027020:methylglucoside; D002482:Cellulose; D014269:Trifluoroacetic Acid