Effect of aromatic groups on localization of high energy in cellulose

Arthur, Jett C.; Stanonis, David J.; Mares, Trinidad; Hinojosa, Oscar

doi:10.1002/app.1967.070110711

Cited by 25 publications

(2 citation statements)

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“…air oxidation. They were subsequently reacted with benzoyl, cinnamoyl, or a-naphthoyl chlorides in the presence of pyridine, following the general methods of preparing esters by Malm and Hiatt [8], as modified by the method of Arthur, Stanonis, Mares, and Hinojosa [2]. Microscopical Methods ' Staining-Calco Identification Stain #2 [6] with distilled water until the water was clear and then allowed to dry.…”

Section: Introductionmentioning

confidence: 99%

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Cannizzaro

Goynes

Rollins

et al. 1968

Textile Research Journal

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The effects on cotton of esterification to low degrees of substitution have been investigated by light and electron microscopy. Observations were made on partially esterified celluloses which included esters of acetic, palmitic, stearic, 12-hydroxystearic, linoleic, and ricinoleic acids and of the aromatic benzoic, cinnamic, naphthoic, and pkenylundecanoic acids.The uniformity of the esterification of cellulose was followed by dyeing and swelling techniques. Refractive index measurements were used to follow changes in optical anisotropy which accompanied the chemical modification. The average refractive indices of cellulose esters containing aromatic groups were greater than those of the esters with aliphatic substituents, the greatest difference being between indices measured perpendicular to the fiber axis.The normal fibrillate texture of the scoured surface appeared to become smooth upon esterification.Fragmentation of the esters in water in a laboratory blendor produced long strands of fibrillate material intermingled with clumps of spongy or amorphous material. On de-esterification of the fragments with an alcoholic base, the structure of the material reverted to that of unesterified cotton—fibrils became distinct and, in some cases, saponification proceeded to a stage where hydrocellulose-like particles were formed. , Many of the esterified fibers of low degrees of substitution swelled in the conventional methacrylate embedding technique. The swelling caused the cell wall to separate into layers, and the internal structure could then be studied by examination of thin sections of these fibers with the electron microscope. By use of an alternative embedding medium, aqueous polyvinyl alcohol, in the preparation of thin sections, compact unlayered structures of the esterified cottons were obtained. This permitted observations of the undisturbed structure of the modified cottons. Both types of observations were used in the microscopical evaluation of cotton fibers esterified to low degree of substitution to demonstrate structural changes brought about by the esterification reaction.

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Section: Introductionmentioning

confidence: 99%

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Cannizzaro

Goynes

Rollins

et al. 1968

Textile Research Journal

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Some Properties of Phenyl-Carbamylated Cotton

Sarkar

Arthur

George

1968

Textile Research Journal

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We have reported the substitution of aromatic groups and of substituted aromatic groups of glutosides [2,[9][10][11][12][13] and fibrous cellulose [2][3][4]6] to yield products which were resistant to degradation on exposure to high-energy, radiation. Phenyl-carbamylated glucosides were resistant to radiation-initiated degradation [11][12][13]. Also, solutions of phenyl-carbamylated glucosides exhibited fluorescent spectra with wavelengths slightly longer than those of their excitation spectra [12]. This indicated that most of the energy absorbed on excitation was emitted during fluorescence. These results suggested that cotton cellulose, reacted with phenyl isocyanate, would be resistant to radiation-initiated degradation.Cotton cellulose (about 4 g of purified Deltapine cotton [7] spun into 7s/3 yarn) was dried in '11 forceddraft oven for 1 hr at 110°C. A solution of dry pyridine containing 15 wt. % of phenyl isocyanate (about 100 g) was placed in a round-bottom flask fitted with a reflux condenser from which moisture was excluded by means of ~a CaCl2 tube. After the solution had been heated to reflux (about 130°C) the dried yarn was immersed in the solution under reflux conditions for the length of time required to give the desired degree of substitution (DS) on the cellulose. On completion of the reaction, the phenyl-carbamylated cotton yarns were washed three times with methanol at 50-60°C [8]. In one procedure, the yarns were left in the slack condition during the washing with methanol. In another procedure, the yarns were restretched to about 80% of their original length and then washed with methanol. Finally, the yarns were washed with distilled water and air-dried.The DS was calculated from the increase in weight of the original yarn. Textile tests were done according to ASTM methods [1], and other tests were done as previously described [5].The mechanical properties of phenyl-carbamylated cotton yarns (restretched before drying) are shown in Table I. If the substituted yarns were not restretched before drying, the values for the properties were decreased to values lower than those shown in Table I.

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ESR study of reactions of cellulose with ·OH generated by Fe⁺²/H₂O₂

Arthur

Hinojosa

Bains

1968

J of Applied Polymer Sci

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SynopsisIt was demonstrated by ESR spectroscopy that the Fe+2/Hz0z syst,em gave a reactive species which generated an ESR triplet spectrum or sorbitol similar to that generated by hydroxyl radicals from the Ti+3/Ha03 system. An ESR spectrum was obtained for the hydroxyl radicals generated by the latter system. However, the lifetime of hydroxyl radicals, generated by the Fe+2/Hz0z system, was apparently very short, and an ESR spectrum for the hydroxyl radicals, generated by this system, was not observed. The Fe+z/HzOz system also generated triplet spectra with cotton cellulose I, cotton cellulose 11, and microcrystalline cellulose, suggesting that a hydrogen at.om had been abstracted from the hydroxyl group on carbon C , or possibly the hydrogen atom on carbon Cg.The ESR spectrum generated on microcrystalline cellulose was less intense than those generat,ed on cellulose I and 11. On initiation of graft polymerization of the activated celluloses with acrylonitrile, the triplet spectrum disappeared and was replaced by two strong singlet spectra. One of the singlet spectra was likely generated on carbon C1 or C, on depolymerization of the cellulose molecule, and the other was probably generated on the end of the growing polyacrylonitrile molecular chain. The absence of a triplet spectrum gave direct evidence for the order in which the acrylonitrile monomer was being grafted onto the cellulose molecule. The mechanisms proposed by Haber and Weiss for the reactions generated in the Fe + 2 / H~0 z system were generally supported.

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Effect of aromatic groups on localization of high energy in cellulose

Cited by 25 publications

References 10 publications

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Some Properties of Phenyl-Carbamylated Cotton

ESR study of reactions of cellulose with ·OH generated by Fe⁺²/H₂O₂

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Effect of aromatic groups on localization of high energy in cellulose

Cited by 25 publications

References 10 publications

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Microscopical Evaluation of Cellulose Esters with Low Degrees of Substitution

Some Properties of Phenyl-Carbamylated Cotton

ESR study of reactions of cellulose with ·OH generated by Fe+2/H2O2

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ESR study of reactions of cellulose with ·OH generated by Fe⁺²/H₂O₂