Study of the electric properties of cellulose derivatives

Hydroxyethyl cellulose Acetate (HECA) was prepared starting from hydroxyethyl cellulose (HEC), acetic anhydride and perchloric acid which was used as catalyst. The synthesized product was characterized by FTIR, 13 C NMR, and 1 H NMR. Substitution degree (DS) of HECA was determined using FTIR spectra taking a classical titration method as reference. The 1 H NMR spectroscopy was also used to confirm the results obtained by FTIR. The DS is substantially affected by the temperature, the time of reaction and especially the equivalent number (eq. nb.) of the acetic anhydride added. We have studied and discussed in the context of usage in modification reactions, the solubility of the HECA samples by varying their DS. This investigation was based on the determination of the Flory-Huggins interaction parameters (v SP ) using the partial Hansen solubility parameters (HSP). HSP of HEC and the HECA samples were calculated from the Van-Krevlen-Hoftyze (VKH) method and the T. Lindvig approximation. We have focused our work on predicting and controlling family solvents of HECA with various DS, to facilitate and to optimize the homogenous modification reaction conditions. From results on a range of HECA samples, it is conclude that their prediction solubility taking the value of DS into account is possible, and then the surface modification can relatively be easily realized. The thermal analysis study shows some differences in T g and thermal degradation between HEC and HECA, moreover these thermal temperatures are influenced by DS values.

Section: Resultsmentioning

confidence: 92%

Synthesis and characterization of the new cellulose derivative films based on the hydroxyethyl cellulose prepared from “Stipa Tenacissima” cellulose of Eastern Morocco. I. Solubility study

Elidrissi

Barkany

Amhamdi³

et al. 2011

Characterization and electrical properties of methyl‐2‐hydroxyethyl cellulose doped with erbium nitrate salt

El‐Kader

Said

El-Naggar

et al. 2006

X-ray diffraction, infrared (IR), and electrical properties for pure and Er (NO 3 ) 3 -doped methyl-2-hydroxyethyl cellulose (MHEC) with concentrations of 0.5, 1, 2, 5, 7, and 10 wt % were studied. X-ray analysis indicates that the addition of Er (NO 3 ) 3 , which is a crystalline material, to MHEC at concentrations 10 and 13 wt % leads to the formation of crystalline phases in the amorphous polymeric matrix. The appearance of the bending mode n 2 and the combination mode (n 1 þ n 4 ) of Er (NO 3 ) 3 in the IR spectra of composite samples indicates the coordination of nitro group in the chains of MHEC. From the I-V characteristics, it was found that the charge transport mechanism in MHEC appears to be essentially space charge limited conduction, while the predominant mechanism in the composite samples is Poole-Frenkel. Values of both drift mobility (m) and the charge carrier density (n) has been reported. The temperature dependence conductivity data has been analyzed in terms of the Arrhenius and Mott's variable range hopping models. Different Mott's parameters such as the density of states, N(E F ), hopping distance (R), and average hopping energy (W) have been evaluated.

Synthesis and characterization of the new cellulose derivative films based on the hydroxyethyl cellulose prepared from esparto “stipa tenacissima” cellulose of Eastern Morocco. II. Esterification with acyl chlorides in a homogeneous medium

Idrissi

Barkany²,

Amhamdi³

et al. 2012

Esparto “Stipa tenacissima” cellulose esters derivatives: HECA‐COOC4H8COOC2H5, HECA‐COOC8H16COOC2H5, and HECA‐COOC6H4COOC2H5 were successfully prepared in Tetrahydrofuran (THF)/triethylamine system with a degree of substitution (DS), respectively, DSAD‐Et=0.32, DSSB‐Et=0.22, and DSTRP‐Et=0.50 using hydroxyethyl cellulose acetate (HECA; DSAC=0.50) as intermediate product, and we avoided the drawbacks of cellulose solubility. The structural modifications were investigated using Fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance (1H‐NMR), Carbon‐13 nuclear magnetic resonance (13C‐NMR), and Distortionless Enhancement by Polarization Transfer 135° (DEPT‐135). The results from these analyses revealed the presence of the characteristic groups indicating that the grafting reaction was successful. The crystallinity and the structure order changes during the esterification reactions were recorded by X‐ray diffraction (XRD), it is found that the crystallinity degree decrease from 63.1% for Esparto “Stipa tenacissima” cellulose to 27.74% for HECA. The thermal stability of the esterified and unmodified cellulose samples was studied by thermogravimetric analysis (TGA)‐differential thermal analysis (DTA); the modified HECA exhibits a decrease in thermal stability relatively to the unmodified HECA, and this may be related to the groups grafted. The resulted cellulose esters HECA‐Px (x = 1, 2, or 3) were soluble in THF and present an amorphous structure justified by XRD spectra. It was noted by TGA‐DTA analysis that the cellulose esters with low melting range were proved as thermoplastic polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013