Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Morgado, Daniella Lury; Martins, Virgínia da Conceição Amaro; Plepis, Ana Maria de Guzzi; Frollini, Elisabete

doi:10.1590/s0104-14282011005000019

Cited by 5 publications

(10 citation statements)

References 14 publications

(21 reference statements)

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“…The effects of alkali treatment on linter cellulose were discussed in a previous paper [44]; it led to a decrease in DP (from 408 to 358) as determined by viscometry,

\overset{D P}{true} v

, and in Ic% (from 79% to 73%) as determined by X-ray diffraction. The alkali treatment also increased the α-cellulose content (from 91% to 95%).…”

Section: Resultsmentioning

confidence: 99%

“…In a prior study [44], the solution behavior of mercerized linter and Ac0.8 in LiCl/DMAc was evaluated. In the viscometric study, the solutions were prepared at a range of very low concentrations (0.002–0.007 g mL −1 ) to suppress chain aggregation; k H values were calculated for cellulose and Ac0.8 were 1.8 and 0.3, respectively [44].…”

Section: Resultsmentioning

confidence: 99%

“…In the viscometric study, the solutions were prepared at a range of very low concentrations (0.002–0.007 g mL −1 ) to suppress chain aggregation; k H values were calculated for cellulose and Ac0.8 were 1.8 and 0.3, respectively [44]. These results indicated that, even at low concentration, the cellulose chains have a high tendency towards aggregation because k H >> 0.55 and that this tendency is considerably higher than that of the acetate chains (k H 0.3).…”

Section: Resultsmentioning

confidence: 99%

“…The introduction of acetate groups in the cellulose chains can lead to two opposing effects: (i) the expansion of chains due to steric repulsion between acetate groups, which, in principle, would increase the polymer/solvent interactions (LiCl/DMAc); (ii) a decrease of the polymer/solvent interactions because the replacement of hydroxyl by an acetate group decreases the interactions cel–OH - - - Cl − (from LiCl), which are important in the dissolution of cellulose in LiCl/DMAc and also most likely for their derivatives, such as acetates [44]. One of these effects can outweigh the other, depending on the conditions under consideration.…”

Section: Resultsmentioning

confidence: 99%

“…These were prepared from LiCl/DMAc solutions of neat cellulose acetates or cellulose and from mixed cellulose acetate/cellulose solutions [17]. In this prior study, the formation of chain aggregates during the dissolution of cellulose in LiCl/DMAc, which was detected in other studies [26,44], was considered a positive aspect, because of the possibility of generating supramolecular structures on the nanoscale directly in the process of film preparation, and the possible action of these supramolecular structures as a reinforcement of acetate-based matrices. …”

Section: Introductionmentioning

confidence: 99%

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Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties

et al. 2013

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This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS 0.8–2.9) mixed with linter cellulose (5, 10 and 15 wt %). Detailed characterization of the films revealed the following: (i) they exhibited fibrous structures on their surfaces. The strong tendency of the linter cellulose chains to aggregate in LiCl/DMAc suggests that these fibrous elements consist of cellulose chains, as can be deduced from SEM images of the film of cellulose proper; (ii) the cellulose acetate films obtained from samples with DS 2.1 and 2.9 exhibited microspheres on the surface, whose formation seems to be favored for acetates with higher DS; (iii) AFM analysis showed that, in general, the presence of cellulose increased both the asperity thickness and the surface roughness of the analyzed films, indicating that cellulose chains are at least partially organized in domains and not molecularly dispersed between acetate chains; and (iv) the films prepared from cellulose and acetates exhibited lower hygroscopicity than the acetate films, also suggesting that the cellulose chains are organized into domains, probably due to strong intermolecular interactions. The linter and sisal acetates (the latter from a prior study), and their respective films, were prepared using the same processes; however, the two sets of films presented more differences (as in humidity absorption, optical, and tensile properties) than similarities (as in some morphological aspects), most likely due to the different properties of the starting materials. Potential applications of the films prepared in tissue engineering scaffold coatings and/or drug delivery are mentioned.

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“…The effects of alkali treatment on linter cellulose were discussed in a previous paper [44]; it led to a decrease in DP (from 408 to 358) as determined by viscometry,

\overset{D P}{true} v

, and in Ic% (from 79% to 73%) as determined by X-ray diffraction. The alkali treatment also increased the α-cellulose content (from 91% to 95%).…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties

et al. 2013

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Ultrathin and nanofibers via room temperature electrospinning from trifluoroacetic acid solutions of untreated lignocellulosic sisal fiber or sisal pulp

Rodrigues

Ramires

Santos

et al. 2015

J of Applied Polymer Sci

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Lignocellulosic sisal fiber (LSF) and sisal pulp (SP) were electrospun at room temperature from solutions in trifluoroacetic acid (TFA) prepared at concentrations of 2 3 10 22 g mL 21 and 3 3 10 22 g mL 21 , respectively. Scanning electron microscopy images of the electrospun LSF showed fibers with diameters ranging from 120 to 510 nm. The presence of defects decreased along with increasing the flow rate of the SP solution, which generated nanofibers and ultrathin fibers with diameters in the range of 40-60 (at 5.5 mL min 21 ) up to 90-200 nm (at 65.5 mL min 21 ). Despite the known ability of TFA to esterify the hydroxyl groups present in the starting materials, the Fourier transform infrared spectra indicated the absence of trifluoroacetyl groups in the electrospun samples. The thermal stability of the final materials proved suitable for many applications even though some differences were observed relative to the starting materials. This study demonstrated a feasible novel approach for producing nano/ultrathin fibers from lignocellulosic biomass or its main component, which allows for a wide range of applications for these materials.

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Layer-by-layer hybrid films of phosphate cellulose and electroactive polymer as chromium (VI) sensors

Teixeira

Marreiro

Farias

et al. 2015

J Solid State Electrochem

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Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Cited by 5 publications

References 14 publications

Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties

Bio-based Films from Linter Cellulose and Its Acetates: Formation and Properties

Ultrathin and nanofibers via room temperature electrospinning from trifluoroacetic acid solutions of untreated lignocellulosic sisal fiber or sisal pulp

Layer-by-layer hybrid films of phosphate cellulose and electroactive polymer as chromium (VI) sensors

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