The objective of this work is to characterize and understand the structure-to-thermomechanical property relationship in thiol-ene and thiol-ene/acrylate copolymers in order to complement the existing studies on the kinetics of this polymerization reaction. Forty-one distinct three- and four-part mixtures were created with systematically varied functionality, chemical structure, type and concentration of crosslinker. The resulting polymers were subjected to dynamic mechanical analysis and tensile testing at their respective glass transition temperature, T-g, to quantify and understand their thermomechanical properties. The copolymer systems exhibited a broad range of T-g, rubbery modulus - E-r and failure strain. The addition of a difunctional high-T-g acrylate to several three-part systems increased the resultant T-g and E-r. Higher crosslink densities generally resulted in higher stress and lower strain at failure. The tunability of the thermomechanical properties of these copolymer systems is discussed in terms of inherent advantages and limitations in light of pure acrylate systems. (C) 2009 Elsevier Ltd. All rights reserved.