Fifty-four years after the Nobel Prize was awarded to KarlZiegler and Giulio Natta for the polymerization of olefins bycomplex organometallic catalysts, the field continues to elicitenormous interest, both from the academia and the industry.Furthermore, this chemistry and technology occupy ahigh ground in the annals of 20th-century science. The eleganceand simplicity of Ziegler’s chemistry continue to astoundresearchers even today, and the enormous impact thischemistry has had on the quality of our life is truly incredible.Polyethylene, produced using Ziegler’s chemistry hastouched every aspect of common man’s life, so much so that,today it is impossible to imagine life on this planet withoutpolyethylene. Equally fascinating is the story of how Zieglerstumbled on this most impactful discovery. Ziegler’s disciplineand rigor in systematically following every lead in thelaboratory, however trivial it seemed, and his penchant forunderstanding the basics of science culminated in 1954, witha simple reaction for converting ethylene to polyethylene, thequintessential carbon-carbon (C-C) bond forming reaction.His life and work hold many lessons for all scientists whodream of making their scientific quests useful and relevantto society. It is also relevant to the contemporary debate onbasic versus applied research.

The name of Natta is entwined inextricably with that of Ziegler,in the famous catalyst systems known by their names andused to make polyethylene and polypropylene. Unlike ethylene,which is achiral, propylene is a prochiral molecule andupon polymerization can lead to interesting stereochemicaland regiochemical enchainment sequences. Natta’s presciencein recognizing this unique feature of propylene led to the discoveryof crystalline isotactic polypropylene and the beginningof a new industry. The story of how Natta discoveredpolypropylene is an engrossing one – one of stiff competitionamongst contemporaries, Natta’s intimate relationship withthe Italian industries, and his unique scientific background.Natta’s identification of isotactic polypropylene as a righthandedthree fold ‘single helix’ in March 1954, in quick successionto the discovery of DNA ‘double helix’ by Watson,Crick, and Rosalind Franklin (March 1953), and the coiledcoilmotif of ‘triple helix’ of collagen by G N Ramachandran(August 1954), makes this period the ‘golden age of macromolecularcrystallography’.

This article focuses on the different components that makeup Ziegler–Natta olefin polymerization systems and showshow investigating the interactions between these componentsthrough computational approaches provide crucial informationabout the chemistry of these systems. Hence, the necessityof theory acting as a counterpoint to experiment is revealed,underlining the importance of computational chemistryin attacking important problems of the day.

Polymers have become indispensable in the 21st century, andtoday we cannot imagine life without them. However, tillaround the beginning of the last century, the science of polymerswas considered a very primitive discipline, and majorityof the scientific community did not believe that polymers evenexisted. Hermann Staudinger, among others, fought a longbattle to convince the scientific community that polymers arereal and that they are long chain molecular entities. Buildingon this rational bedrock of polymer science, Prof. KarlZiegler laid the foundation of ethylene polymerization. Asoutlined by Dr. Sivaram in his articles on Ziegler and Natta,careful observations and systematic analyses of serendipitousresults enabled Ziegler to develop the enormously significant

‘M¨ulheim atmospheric polyethylene process’. A decade later,Cossee and Arlman revealed the mechanism of this polymerizationreaction, which is called ‘insertion polymerization’.Insertion polymerization is popularly known as the ‘Ziegler–Natta polymerization’, in recognition of its founding fathers.Today, the world produces about 180 million tons of polyolefinsannually, and polyethylene or polythene has become ahousehold name.

In this article, I shall present an overview of Ziegler–Nattapolymerization. I will highlight the mechanism of this reaction,and outline the progress made in the last seven decadesusing some real-world examples. The last part of this article will take a stock of the unresolved challenges posed byZiegler–Natta polymerization, briefly discuss current solutions,and reiterate the enormous potential of this seventyyear-old reaction to meet contemporary challenges.

Conversion of sunlight to electricity with high conversion efficienciesat low cost is possible with emerging photovoltaictechnologies. Organic–inorganic halide perovskite, a newcomerin the solar cell industry has proved its potential forincreasing efficiency rapidly from 3.8% in 2009 to 22.1% in2016. High efficiency, flexibility, and cell architecture of theemerging hybrid halide perovskite have caught the attentionof researchers and technologists in the field. This article focuseson the emergence, properties, and current research statusof hybrid perovskite solar cells.

The instability of the interface separating a denser fluid froma lighter one below it has applications to the surroundings ofmassive stars – both when they are born and when they die.

In this series of articles, the authors discuss various phenomenain fluid dynamics, which may be investigated via tabletopexperiments using low-cost or home-made instruments. Theninth article in this series explores and demonstrates Rayleigh–Taylor instability.