At the beginning of the 21st century, humanity is facing a series of challenges due to overpopulation, urban living, aging societies, environmental pollution, malnutrition, climate change, and an unrestrained consumption of limited resources. Polymers to a large extent help in meeting these challenges as they can easily be prepared on a large scale from cheap starting materials; possess low densities, easy processability, and high availability; and are resistant to corrosion. Accordingly, our modern consumer-based societies rely on such smart, resource-saving, and environmentally friendly synthetic materials.
Growth in plastic production during the early 20th century was driven by commodity polymers and their polymerization methods (i.e. step or chain polymerization). The expansion of macromolecular chemistry in the second half of the 20th century then was largely determined by the emergence of highly active Ziegler-Natta catalysts for the polymerization of ethylene, propylene, and other α-olefins. At the beginning of the 21st century, new materials are needed for specific applications to address the change from structural materials to complex system polymers. Materials of the future, in combination with nanotechnology, medicine, or materials science, offer solutions to these challenges. Furthermore, utilization and development of precision polymers will affect fields such as tissue engineering, membranes, stimuli responsive materials, mobility, energy storage, or even more effective engineering materials. The development of new materials as well as an improvement in existing materials and processing techniques, hence, is essential.
Living polymerizations techniques, which have rapidly been developed over the past two decades, are the most promising candidates for precision polymer synthesis needed to add specific functionalities to new materials. For most cases, the living characteristics result from low radical concentrations delivering rather low propagation rates and/or conversions. However, for feasible applications, methods with high precision of the macromolecular parameters in combination with rapid reaction velocities are required. Catalytic reaction sequences ideally fulfill these requirements for which in most cases transition metal-based organic complexes having been developed with combinatorial methods are being used. But of course, no single polymerization method or catalytic system can meet all requirements, demands, and needs.
Diverse developments like in-situ composites and new nano-structured materials; the catalytic conversion of CO2 into polymer building blocks; the unconventional use of renewable resources like lignin, carbon hydrates, and proteins; and new additive concepts stemming from the realms of e.g. supramolecular or liquid crystal chemistry contribute to the overall picture and altogether open huge potentials for future polymer applications.