The remarkable progress in olefin polymerization catalysis and polyolefin technology contributes to sustainable development in manifold ways and helps to meet the urgent demand of the growing world population for cost-, resource-, and energy-efficient as well as environmentally benign materials with a low carbon footprint and facile recycling. Today, polyolefins such as polypropylene and polyethylene are the clear leaders in both world-scale polymer production and life-cycle assessment, far ahead of biobased plastics. Produced in highly efficient, solvent-free catalytic processes, polyolefins are hydrocarbon materials that preserve an oil-like high-energy content and are readily recycled by remelting or by thermal cleavage to recover oil and gas feedstocks (“renewable oil”) in essentially quantitative yield. Because of exceptionally high catalyst activities and precise control of polyolefin molecular architectures, no byproducts need to be removed. The minute amounts of nontoxic catalyst residues are left in the polyolefin. Moreover, morphology control by fragmentation of catalyst particles during polymerization enables the formation of spherical polyolefin granules in the reactor, thus eliminating pelletizing extrusion and saving energy. Modern polyolefin production can now meet the demands of green chemistry. Without any doubt, polyolefin chemistry is the most efficient way of utilizing resources, preserving them for future generations. Despite the great achievements in polyolefin research during the past 60 years, there are many challenges left to be met. Polyolefin chemistry and technology are still far away from maturity. In the past, the focus of catalyst research has been placed on improving catalyst activities and stereocontrol, aiming at controlling molecular architectures. In the future, as illustrated in, the new focus will be designing functional hierarchic architectures without impairing cost-efficacy of polyolefins.

The development of multisite catalyst and reactor blend technology will continue to play a prominent role. During the 20th century, in the premetallocene age, many attempts toward multisite and tandem catalysis were commercial failures due to poor process control, which frequently led to the formation of rather ill-defined product mixtures. Today, at the beginning of the 21st century, considerably more robust catalyst systems are at hand combining different single-site catalysts in a “single” multisite catalyst. Now it is possible to coimmobilize independent sites, thus preserving their single-site nature, to produce reactor blends in which immiscible polymers are blended together and uniformly dispersed on the nanometer scale. Blend composition and properties are primarily governed by the site mixing ratios and the properties of the individual catalyst components. Furthermore, interaction of sites via chain shuttling or molecular switching of sites enables the formation of a wide variety of segmented polyolefins. High-throughput screening enables identification of complementary single-site catalysts with matched compatibilities and polymerization kinetics. The multisite technologies presented in this Review create a new catalyst toolbox for tailoring advanced polyolefin materials by combining the performance of different single-site catalysts. Instead of designing reactor cascades, it is now possible to develop microreactors, embedded in the catalyst, to create a virtual nanometer-scale cascade within the catalyst and the polyolefin particles. Envisioned applications of multisite catalysis include segmented polyolefins and tailored reactor blends ranging from thermoplastic elastomers and thinner flexible packaging materials to new generations of highly damage-tolerant lightweight engineering plastics such as all-polyolefin composites, which are much easier to recycle than conventional composites. The progress of multisite olefin polymerization catalysis greatly improves the performance of polyolefin materials without impairing their attractive combination of cost efficiency and high sustainability. Advanced polyolefin materials and tailored reactor blends, exhibiting low carbon footprint and leading position in life cycle assessment, offer great prospects for sustainable development ranging from lightweight engineering to safe transport of food, water, and energy.

The authors declare no competing financial interest.