Chain configurational transitions have been studied in a selectively deuterated model membrane compound, decylammonium chloride, by means of deuterium NMR spectroscopy. The segmental order parameters of the chain near the head group and near its end are determined as a function of temperatures in the i, delta and alpha phases. There is no evidence of the nematic order parameter showing critical behaviour at the i-delta phase transition. The tilt angle of the decylammonium chain with respect to the normal of the chlorine layers has been determined as a function of temperature in the delta phase. (C) 2003 Elsevier Science B.V. All rights reserved.