A multilevel factorial design of 23 with 12 experiments was developed for the preparation of cellulose nanocrystals (CNC) from Agave tequilana Weber var. Azul bagasse, an agro-industrial waste from tequila production. The studied parameters were acid type (H2SO4 and HCl), acid concentration (60 and 65 wt% for H2SO4, 2 and 8N for HCl) temperature (40 and 60 °C for H2SO4, 50 and 90 °C for HCl), and hydrolysis time (40, 55 and 70 min for H2SO4; and 30, 115 and 200 min for HCl). The obtained CNC were physical and chemically characterized using dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XDR) techniques. The maximum CNC yield was 90 and 96% for HCL and H2SO4, respectively, and the crystallinity values ranged from 88–91%. The size and morphology of A. tequilana CNC strongly depends on the acid type and hydrolysis time. The shortest CNC obtained with H2SO4 (65 wt%, 40 °C, and 70 min) had a length of 137 ± 68 nm, width 33 ± 7 nm, and height 9.1 nm, whereas the shortest CNC obtained with HCl (2 N, 50 °C and 30 min) had a length of 216 ± 73 nm, width 69 ± 17 nm, and height 8.9 nm. In general, the obtained CNC had an ellipsoidal shape, whereas CNC prepared from H2SO4 were shorter and thinner than those obtained with HCl. The total sulfate group content of CNC obtained with H2SO4 increased with time, temperature, and acid concentration, exhibiting an exponential behavior of .

This paper reports the use of polysaccharides extracted from seed of Persea americana var. Hass in the synthesis of acrylic hydrogels. The effects of the chemical composition (acrylamide/acrylic acid), the concentration of crosslinking agent (glycerol diacrylate) and the type of initiation (redox, photoinitiation) of the hydrogels were evaluated with and without polysaccharides. Xerogels were characterized by FTIR spectroscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), while for the swollen hydrogels the swelling kinetic and mechanical properties were evaluated. The kinetic parameters were obtained using the second order equation proposed by Schott, where it is reported that by increasing the concentration of the crosslinking agent, the degree of swelling is reduced because of the greater structural level. The increase of the amount of acrylamide and the amount of polysaccharides causes also a decrease in the swelling degree. The type of initiation also affected the hydrogels swelling kinetic, the photoinitiated hydrogels were the ones that captured less water. Moreover, the increasing of the glass transition temperature and the compression modulus with the crosslinking agent concentration and molar ratio AAm/AAc are observed for hydrogels with and without polysaccharides. The results demonstrate a successful incorporation of polysaccharides into the polymeric network.

The interactions of proteins and other molecules and their adsorption onto substrates is a fascinating topic that has been applied to surface technologies, biosensors, corrosion studies, biotechnologies, and other fields. The success of these applications requires a previous characterization using some analytical techniques that, ordinarily, are not electrochemical. This work proposes analyzing the variation of the double-layer capacitance obtained through impedance electrochemical spectroscopy as an alternative strategy to show evidence of the interactions between proteins and triblock copolymers. The proposal is supported through the study of the interaction and adsorption of bovine serum albumin (BSA) and a commercial triblock copolymer (P103) in phosphate buffer on a gold electrode. The double-layer capacitance and the apparent interface thickness vs polarization potential curves as well as the potential of zero charge for pure P103 (0.6 wt %, corresponding to 6 g L –1 ), pure BSA (3 mg mL –1 ), and P103-BSA solutions (0.6 wt % and 3 mg mL –1 , respectively) are sensitive enough to show not only the interaction and the adsorption of the species but also the polarization potential where these interactions are taking place. A qualitative and quantitative analysis concerning the double-layer capacitance behavior is given. The significance and impact of this work is also presented.

Nanocrystalline cellulose (NCC) was prepared from Agave tequilana Weber blue variety via acid hydrolysis. The NCC was used in forming acrylic acid/acrylamide hydrogels (AA/AM), (80/20 w/w), crosslinked with N-N-methylene bisacrylamide (MBA) at addition levels of 1, 2, 4, and 8 wt% of the monomeric phase. The NCC was dosed at 0.1, 0.5, and 1.0 wt%. Two synthesis routes were used. In the first route, polymerization was performed immediately after mixing the components. In the second route, the mixture of the components was kept at 2 °C ± 1 °C for 24 h before the polymerization (thermal treatment). All the hydrogels were characterized by nuclear magnetic resonance (NMR), water absorption tests, scanning electron microscope (SEM) analysis, and rheology tests. The NCC particles had a diameter of approximately 75 nm. The hydrogels that were subjected to the thermal treatment reached the equilibrium after approximately 72 h. The un-treated hydrogels reached the equilibrium after approximately 58 h. The thermally treated samples had a lower swelling degree and the swelling degree decreased as the crosslinking degree and the NCC concentration increased. The swelling kinetics followed the Schott´s pseudo-second-order.

No abstract