Polymer-polymer blends of rigid-rod and random-coil macromolecules are obtained by ionomer blend formation. The molecular dispersion of the rod molecules in the matrix polymer is achieved by acid-base interactions. The reinforcement effect in terms of the Young's modulus is discussed as a function of the degree of polymerization of the rods. By treating the reinforcer molecule as a fuzzy cylinder the reinforcement effect can be correlated to the reinforcers' size and shape. (c) 2005 Elsevier Ltd. All rights reserved.