DESTABILIZATION OF COLLAGEN IN HIDE AND LEATHER BY ANIONIC SURFACTANTS - II - CALORIMETRY OF THE REACTION OF COLLAGEN WITH SULFATES

Leather, a textile based on collagen, usually requires the addition of sulfated oils that have been recently found to cause instability when heated in critical manufacturing processes. Here reactions between co llagen and sodium dodecyl sulfate (SDS), sulfated castor oil, or a syn thetic sulfated oil are studied calorimetrically. Sodium lauryl sulfat e below its critical micelle concentration (cmc) displayed an immediat e exotherm due to equilibrium binding of the reagents with stoichiomet ry n = 12.6 +/- 0.2, K = (2.02 +/- 0.8) x 10(7) M-1, and enthalpy Delt a H = 62 +/- 2 Kcal/mol; and a delayed endotherm due to denaturation o f collagen. The endotherms accompanying the reactions with sulfated oi ls with longer chains were smaller, with no apparent denaturation of c ollagen. The micellar nature of these surfactants was apparent from ve ry large n for sulfated castor oil, 4082 +/- 11 and a very small value of Delta H, 0.77 +/- 0.01 cal/mol. The binding of sulfated castor oil at the polar bands of collagen crystallites, comprising extended mole cules arranged side-by-side, was shown directly by electron microscopy . (C) 1998 John Wiley & Sons, Inc.