PROBING THE MACROMOLECULAR STRUCTURE OF WOOD AND PULPS WITH PROTON SPIN-LATTICE RELAXATION-TIME MEASUREMENTS IN THE SOLID-STATE

By measuring the proton spin-lattice relaxation times (T-1) in the sol id state, for a series of progressively sulphonated and methylated bla ck spruce pulps, the molecular mobilities of carbohydrates and lignin have been evaluated as a function of chemical treatment. These measure ments were made possible only after the paramagnetic metal ion impurit ies were removed from the samples. For untreated wood the proton T-1 v alues of carbohydrates and lignin were virtually undistinguishable, ir respective of the applied magnetic field strength. The introduction of sodium salts of carboxylic and sulphonic acid groups in softwood pulp s and the introduction of methoxyl groups, seem to very significantly increase the molecular mobilities of carbohydrates and lignin. The opp osite was true when calcium were the counterions of the acidic groups. These observations have been attributed to the disruption of associat ive lignin-carbohydrate hydrogen bonding interactions otherwise operat ing within untreated wood.