title: Synthesis and characterization of functionally gradient materials obtained by frontal polymerization.
abstract: Functionally gradient materials (FGMs) with gradual and continuous changes of their properties in one or more dimensions are useful in a wide range of applications. However, obtaining such materials with accurate control of the gradient, especially when the gradient is nonlinear, is not easy. In this work, frontal polymerization (FP) was exploited to synthesize polymeric FGMs. We demonstrated that the use of ascending FP with continuous feeding of monomers with computer-controlled peristaltic pumps provided an excellent method for the preparation of functionally gradient materials with programmed gradients. To test the effectiveness of the method, copolymers made from triethylene glycol dimethacrylate/hexyl methacrylate with linear and hyperbolic gradient in composition were synthesized. Differential scanning calorimetry (DSC), Shore A hardness measurements, compression tests, and swelling studies were performed along the length of the materials to assess the relationship between the gradients and the material properties. Glass transition temperatures, determined by DSC, showed a linear dependence on the composition and were in agreement with theoretical values. The other properties showed different and specific behaviors as a function of the compositional gradient.
authors.affiliation: Dipartimento di Chimica e Farmacia, Università di Sassari , Local INSTM Unit, Via Vienna 2, 07100 Sassari, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Nuvoli
authors.forename: Valeria
authors.initials: V
authors.lastname: Alzari
authors.forename: John A
authors.initials: JA
authors.lastname: Pojman
authors.forename: Vanna
authors.initials: V
authors.lastname: Sanna
authors.forename: Andrea
authors.initials: A
authors.lastname: Ruiu
authors.forename: Davide
authors.initials: D
authors.lastname: Sanna
authors.forename: Giulio
authors.initials: G
authors.lastname: Malucelli
authors.forename: Alberto
authors.initials: A
authors.lastname: Mariani
keywords: copolymer; frontal polymerization; functionally gradient material; glass transition temperature; mechanical properties; polyacrylate; shore A hardness; swelling ratio