The aggregation of triphenodioxazine reactive dyes in aqueous solution andon cellulosic and nylon substrates

Monomer-dimer equilibriums of triphenodioxazine (TPDO) reactive dyes with v inylsulfone anchors (PVS-TPDO) and monochlorotriazine anchors (MCT-TPDO) we re investigated in water, in aqueous organic solvent, and on a cellulosic s ubstrate. The aggregation tendency of PVS-TPDO in water was promoted by the addition of neutral electrolyte and suppressed by that of 1-methyl-2-pyrro lidone (MP). The dimerization constants, K, for PVS-TPDO were estimated in water and in aqueous sodium chloride solution; PVS-TPDO showed also aggrega tion on a cellulosic substrate. The apparent value of K on dry cellulose wa s two orders of magnitude smaller than that in water, and was increased by about ten times by water. The aggregation of PVS-TPDO in aqueous sodium chl oride solution was suppressed by the addition of both MP and poly(vinylpyrr olidone). Four TPDO dyes examined showed the same order of aggregation tend ency on cellulosic and nylon substrates as that in aqueous solution. (C) 20 00 Elsevier Science Ltd. All rights reserved.