Insolubility in Cuprammonium Hydroxide as a Means of Detecting Crosslinking in Chemically Modified Cotton

Abstract

Native cellulose dissolves in cuprammonium hydroxide solution, but, when it is crosslinked, it becomes a space polymer and is insoluble in this reagent. A method of detecting alkali-stable crosslinks in cotton is presented—the sample to be tested is shaken with cuprammonium hy droxide solution for 17 hr. If it dissolves completely, cellulose chains are not crosslinked, but, if it is partially insoluble, crosslinking is indicated. Partially insoluble cellulosic material appears in the cuprammonium hydroxide as granules that are easily detected visually. Cellulose was reacted with compounds which contained one or more groups that are reactive toward cellulose. In all cases the cellulosic derivatives made from cellulose and compounds that could crosslink it were partially insoluble in cuprammonium hydroxide. The compounds that were not capable of crosslinking cellulose produced derivatives soluble in cuprammonium hydroxide. Cotton was made insoluble in cuprammonium hydroxide by reacting it with formaldehyde, glyoxal, chloroethylsulfuric acid, α,γ-glycerol dichlorohydrin, a mixture of α,β- and α,γ-glycerol dichlorohydrin, tetrakis (hydroxymethyl) phosphonium chloride, compounds containing two or more N-methylol groups, 1,4-disulfato-2-butyne, and potassium (disulfatoethyl) amine. Aminized cotton, which is soluble in cuprammonium hydroxide, was made insoluble by cross linking it with either formaldehyde or tetrakis (hydroxymethyl) phosphonium chloride.