Poster, Bayreuth Polymer Symposium (BPS) 2013, Bayreuth: 15.09.2013 - 17.09.2013
The transfer of biological principles opens up pathways for the development of new materials. For example, marine mussels use their appendage, the so-called mussel byssus, to attach themselves onto rocks. The byssus consists of a longitudinal compositional gradient, creating a mechanical gradient along the thread and mediating the mussel’s soft interior to the hard rock surface. Similar to natural gradients, synthetic gradient materials offer advantages such as smooth stress distribution, reduced stress concentration, improved bonding strength, and increased fracture toughness. In this context, we report on a straightforward and reproducible method of fabricating longitudinal polymer gradient materials (PGMs) on a macroscopic centimeter scale. The longitudinal gradients were confirmed optically by UV/Vis spectroscopy with the aid of a dissolved dye and also mechanically by compressive modulus testing. The preparation of bulk polymer gradient materials is realized with a specially designed syringe pump setup. Two components (A, B) are fed via the syringe pump system through a static mixer into a mold on a moving platform. The gradients can be generated by continuously changing the ratio A:B, and are fixed by polyaddition reactions. SYRINGE PUMPS MIXER Flow Rate Time A B hard soft 0 GRADIENT MATERIAL This approach was utilized for the preparation of poly(dimethyl siloxane) (PDMS)-based PGMs with soft-hard and even more complex gradient structures. In addition, other thermally and photochemically curing polymer systems were used that cover a much larger modulus range than PDMS-based systems. Tensile testing of longitudinal PGMs revealed an improvement of the mechanical properties in dependency on the gradient structure. Furthermore, biocompatible protein gradient films were prepared with potential for biomedical applications.