Alcohol induced gelation of TEMPO-oxidized cellulose nanofibril dispersions

Abstract

Alcohol-induced gelation of partially oxidised cellulose nanofibrils (OCNFs): nanoscale (SAXS) and macroscale (rheology) insights into OCNF self-assembly in aqueous-alcoholic mixtures.

Filler size effect in an attractive fibrillated network: a structural and rheological perspective

“…Since the lower threshold for the data fitting was q min = 0.06 À1 , using values of L ) 2p q min kept the fitting unchanged. The model yielded values of R min = 1.1 AE 0.1 nm, R maj = 4.7 AE 0.1 nm and b Kuhn = 21.4 AE 0.1 nm, in good agreement with previous SAXS measurements 9,19,27 and imaging analysis of OCNF. 9 Upon SiNp addition, the SANS patterns had a similar trend to that of the pure OCNF gel, indicating that, in the probed q range, neither of these fillers strongly alters the structure of the fibrillated network.…”

“…2a) contains information regarding the shape of the fibrils in the high-q and intermediate-q region, which probe the radius and the larger dimensions of the fibril, respectively. 9,19,27 The upturn in the low-q region has been instead associated with the attractive interfibrillar interactions as described by Schmitt et al 9 The data were fitted, in the q region where interfibrillar interactions are not detectable (high-q and intermediate-q range), to a model of non-interacting flexible cylinders with an elliptical cross-section from which the minor radius (R min ), major radius (R maj ) and the Kuhn length (b Kuhn ) were obtained, where b Kuhn is indicative of the OCNF mesh size. 9 The data fitting was carried out using a fixed and arbitrary contour length (L) of 500 nm as the average length was not accessible in the probed q range, as indicated by the lack of a plateau in the low-q region.…”

Impact of wormlike micelles on nano and macroscopic structure of TEMPO-oxidized cellulose nanofibril hydrogels

“…The resulting oxidized cellulose nanofibrils (OCNFs) are anionic nanoparticles capable of forming stable dispersions of individualized nanofibrils in water. OCNF dispersions can undergo gelation due to changes in the aqueous environment such as addition of alcohols, 12 surfactants, 13,14 salts, [15][16][17][18] or block copolymers, 19 and changes in pH [20][21][22] or temperature. 23 Surfactants are capable of selfassembling in solution to form supra-molecular aggregates that can adopt a myriad of forms.…”

Spin diffusion transfer difference (SDTD) NMR: An advanced method for the characterisation of water structuration within particle networks

“…The alcohol-induced gelation of OCNF was recently investigated by rheology and SAXS. 32 Methanol, ethanol and 2-propanol (in order of decreasing hydrophilicity) were tested in their ability to induce OCNF gelation in mixtures with water. Alcohol hydrophilicity/hydrophobicity on its own did not explain the observed macroscopic properties.…”

“…With the exception of methanol gels, the analysis of SAXS data showed an increase in the cross-section of the OCNF nanofibrils above the gelation and phase separation concentrations. 32 The authors proposed that, having Na + preference for water over ethanol and 2-propanol (similar solubility of NaCl in methanol and water), gel formation could be driven to some extent by the aggregation of OCNF fibrils due to the increased association of Na + ions onto the surface of OCNF fibrils at higher ethanol and 2-propanol concentrations. 32 In conclusion, our SDTD NMR approach highlights the essential role of water structuration on the gelation properties of OCNF gels prepared in water and low molecular weight alcohol mixtures.…”