A surface science perspective on TiO2 photocatalysis

A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties

Hydrogels are macromolecular networks able to absorb and release water solutions in a reversible manner, in response to specific environmental stimuli. Such stimuli-sensitive behaviour makes hydrogels appealing for the design of ‘smart’ devices, applicable in a variety of technological fields. In particular, in cases where either ecological or biocompatibility issues are concerned, the biodegradability of the hydrogel network, together with the control of the degradation rate, may provide additional value to the developed device. This review surveys the design and the applications of cellulose-based hydrogels, which are extensively investigated due to the large availability of cellulose in nature, the intrinsic degradability of cellulose and the smart behaviour displayed by some cellulose derivatives. Keywords: Hydrogels; cellulose; biodegradation. 1. Introduction Hydrophilic polymers can swell and absorb water without dissolving, provided that chemical or physical crosslinks exist among the macromolecular chains. The polymer network resulting from the crosslinks swells in the aqueous solvent, until the thermodynamic force of swelling is totally counterbalanced by the elastic, retractive force exerted by the crosslinks. This ‘solid-like solution’ of polymer and water resulting at equilibrium is known as a hydrogel. The amount of water retained by

Biodegradable Cellulose-based Hydrogels: Design and Applications

This work is focused on the preparation of new environmentally friendly hydrogels derived from cellulose and hence originating from renewable resources and characterized by biodegradable properties. Two cellulose derivatives, sodium carboxymethylcellulose (CMCNa) and hydroxyethylcellulose (HEC), were used for superabsorbent hydrogel preparation. Citric acid (CA), a crosslinking agent able to overcome toxicity and costs associated with other crosslinking reagents, was selected in a heat activated reaction. Differential scanning calorimeter (DSC), fourier transform infrared spectroscopy (FTIR), and swelling measurements were performed during the reaction progress to investigate the CA reactivity with each of the polymers. Also, CMCNa/HEC polymer mixtures (3/1 w/w) crosslinked with CA were investigated and compared with previous results. Finally, a possible reaction mechanism was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Novel superabsorbent cellulose-based hydrogels crosslinked with citric acid

Past, present and future prospects of cotton cross-linking: New insight into nano particles

Four different carboxylic acids (1,2,3,4-butane tetracarboxylic acid (BTCA), maleic acid (MA), succinic acid (SUA), and citric acid (CA)) were used as crosslinking agents for finished cotton fabrics in the presence of nanometer titanium dioxide catalyst under the irradiation of ultraviolet (UV) light and/or an electronic field (EF). We find that the dry crease recovery angle, wet crease recovery angle, and softness improvement percentages of the treated fabrics for all the crosslinking agents are gradually increased with the increasing of irradiation time period, but the TSR values decreased in all cases. The crease recovery and softness properties for the various crosslinking agents are ranked as BTCA > MA > CA > SUA at a given UV irradiation time period. The addition of EF treatment on the UV-irradiated fabrics improves the catalytic effects significantly. The spectra of Fourier transform infrared spectrophotometry reveal the crosslinking reaction between the carboxylic acid group of citric acid and the hydroxyl group of methylcellulose; this reaction could form ester and ether groups in the presence of nanometer TiO 2 catalyst under UV irradiation and UV irradiation and EF treatment. The pictures of scanning electron microscopy and the electron spectroscopy for chemical analysis survey spectra show the surface deposition of acid crosslinking agents on the finished fibers and the crosslinking reaction between citric acid and cellulose molecule catalyzed with nanometer titanium dioxide under the irradiation of UV only and under the irradiation of UV and the treatment of EF separately.

Chyung-Chyung Wang

Papers

Physical properties of the crosslinked cellulose catalyzed with nanotitanium dioxide under UV irradiation and electronic field