ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
From the results of initial acid-catalyzed hydrolysis of cellulose, and from certain data in the literature it is concluded that (1) native cellulose possesses an indefinitely high molecular weight; (2) as a consequence of common procedure adhered to by most investigators, native cellulose is unintentionally degraded to about DP 3000; (3) mild, initial acidic degradation, intentional or accidental, causes further decrease in the DP values down to the probable limiting value of 128 or 256, with complete loss of the tensile strength of the cellulose fiber; and (4) the few covalent bonds (about 0.3%) which become cleaved during these mild reactions are equally spaced, acid-sensitive, and entirely different from the regular 1,4-glycosidic bonds which are responsible for the random hydrolysis of cellulose in strongly acidic media. It is suggested that these acid-sensitive linkages represent hemiacetal or acetal bonds which originate from openchain glucose anhydride residues of “limit hydrocellulose” units and connect the latter along the a and b axes of the fiber. The length of the “limit hydrocellulose” is supposed to correspond to that of 27 = 128 glucose anhydride residues - that is, 660 Å., or twice these figures. Extension of this concept to starch leads to the postulate of a three-dimensional network of glucose anhydride units of indefinite number. The latter are held together by regular 1,4-α-glucopyranosidic bonds and, at short intervals, probably by acetal bonds of open-chain glucose anhydride residues. On mild, acid-catalyzed hy-drolysis these acid-sensitive linkages rupture rapidly and completely, giving rise to a material which consists of linear molecules only, containing 1,4-, 1,6-, and possibly 1,3-, glycosidic bonds between two adjacent glucose anhydride residues.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1947.120020602
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