Poly(dodecamethylene terephthalamide) (PA-12,T) was synthesized by melt condensation polymerization of 12,T salt with 0, 1, 3, 5, or 10% molar excess of 1,12-diaminododecane (DA), terephthalic acid (TA), or benzoic acid (BA). Intrinsic viscosities (IV) (0.5 g/dL in 96% H2SO4 at 25 degrees C) were measured to determine relative molecular weight differences. IV was highest for reactions containing 1 and 3 mol % excess DA (1.36 and 1.31 dL/g, respectively), followed by the product of pure 1 : 1 salt (1.25 dL/g). For all concentrations of excess TA and BA, IV was decreased. C-13-NMR chemical shifts for DA, TA, and BA end groups were identified and their concentrations determined by comparison with the intensity of main chain polymer peaks. A log-log plot of IV versus number average molecular weight calculated from 13C-NMR data shows a linear trend with Mark-Houwink constants of K = 55.8 x 10(-5) dL/g and alpha = 0.81. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3388-3395, 2010