The solubility of N-2, in poly(alpha-n-hexyl-beta,L-aspartate), a stereoregular poly(beta-peptide), was investigated with atomistic Monte Carlo simulations. The structure of this material is intermediate between that of polymers able to form a three-dimensional crystal lattice and that of liquid-crystalline polymers with a biphasic distribution. The dependence of the calculated solubility coefficients on both the parameters of the force field and the temperature was examined. The results are compared with recently reported experimental data. Furthermore, the motion of the penetrant molecules within the polymer matrix was analyzed. (C) 2003 Wiley Periodicals, Inc.