Giulio Natta discovered how to produce polymer chains with orderly spatial arrangements – i.e. stereoregular polymers. Such polymers can be customized to have different degrees of crystallinity and hence different physical properties, allowing them to be geared to different applications. For their discoveries in polymer chemistry, Giulio Natta and Karl Ziegler shared the 1963 Nobel Prize in Chemistry.
Beginnings
Giulio Natta was born on February 26, 1903 in the coastal city of Imperia, northern Italy, close to the French border.
His father was Francesco Maria, a magistrate. His mother was Elena Crespi, who dedicated herself to her son’s education – he could read at age three. Elena was a widow and Giulio had an elder half-sister, Pina.
When Giulio was still an infant, his father’s job required the family to move to the city of Genoa.
Education
From the time of his childhood, Giulio Natta wanted to be a scientist. He graduated from Christopher Columbus High School in 1919, age 16.
In 1921, age 18, he graduated from a two-year preparatory course in Mathematics at the University of Genoa.
Next he moved to the city of Milan, to the city’s Polytechnic, to study for a doctorate in Chemical Engineering. He obtained this in 1924, age 21. Impressed by his work, Professor Giuseppe Bruni, director of the Polytechnic’s Institute of Chemistry, appointed Natta as his research assistant.
Career Summary
In Bruni’s research group Natta learned X-ray crystallography. Pioneered by Lawrence Bragg and his father in 1912, X-ray crystallography used the diffraction of X-rays as a means of ‘seeing’ the positions of atoms in solids and hence determining atomic structures. Natta was so enthusiastic about his work that he slept in his laboratory on a camp bed.
In 1925, age 22, Natta began giving lectures in Analytical Chemistry at the Milan Polytechnic.
In 1929, he began also lecturing in Physical Chemistry at the University of Milan.
In 1933, age 30, he was appointed Professor of Chemistry at the University of Pavia.
In 1935, he was appointed Professor of Physical Chemistry at the University of Rome.
In 1937, he was appointed Chair of Industrial Chemistry at the Turin Polytechnic.
In 1938, he was appointed Chair of Industrial Chemistry at the Milan Polytechnic, where he remained until he retired in 1973. This was a controversial appointment because the previous chair, Mario Giacomo Levi, was fired as a result of anti-Jewish laws passed under Italy’s Fascist dictator Benito Mussolini.
Giulio Natta’s Polymer Discoveries
Macromolecules
In 1933, Natta traveled to Freiburg, Germany to discuss X-ray and electron diffraction methods with Dr. H. Seeman. There he met Hermann Staudinger, the founder of polymer and macromolecular chemistry – Staudinger would be awarded the 1953 Nobel Prize in Chemistry for his work.
The concept of giant molecules captured Natta’s imagination. Although many scientists refused to believe they existed, Natta decided he would investigate their atomic structures using X-ray and electron diffraction.
Synthetic Macromolecules
A macromolecule, also often known as a polymer molecule, is made by linking together molecules of smaller substances into a long, chemically bonded chain. For example, ethene molecules can react together to form polyethene, often called polythene or polyethylene. Similarly, styrene molecules can react together to form polystyrene, as shown below.
A Polymerization Reaction
Large numbers of individual styrene molecules on the left react together in a polymerization reaction to form giant molecules of polystyrene on the right.
No Macromolecules, No Life, No Information Age
A macromolecule:
- may be a natural molecule – for example DNA or protein. All life on Earth is based on natural macromolecules.
or
- may be a synthetic molecule – for example nylon or polypropylene. Without synthetic macromolecules there would be no laptops, smartphones, monitors, computers, televisions, speakers, credit cards, cars, clothes, etc. Our modern information age is possible only by virtue of synthetic macromolecules.
Ziegler and Natta
Natta worked as a consultant to the Italian chemical company Montecatini. As a result of this, in 1952, he was excited to learn about a discovery made by the German chemist Karl Ziegler. Ziegler had found that he could produce high molecular weight polyethylene at low pressures using a mixed catalyst consisting of TiCl4 and Al(C2H5)2Cl.
Montecatini bought the commercial rights to Ziegler’s catalyst in Italy and Natta was given full access to Ziegler’s research work.
Ziegler and Natta became good friends, but later fell out because of disagreements over patents. In a meeting, without revealing that he had already successfully made polypropylene (see below), Natta induced Ziegler to say that he had not succeeded in doing this. Natta revealed nothing, because he wanted to patent the process and was worried that by telling Ziegler of his success he would endanger the prospects of creating a watertight patent.
Tacticity
Natta began his own experiments and produced the world’s first isotactic polypropylene using a catalyst consisting of crystalline α-TiCl3 mixed with Al(C2H5)3.
Polymer Tacticity
The spatial arrangement – i.e. the stereochemistry – of polymer chains is crucial in determining the physical properties of a polymer. Highly crystalline polymers tend to form rigid plastics while those with little crystallinity form more flexible materials.
When Natta explained his work to his wife Rosita, who was an expert in languages, she used Greek roots to coin the words we now use to describe the stereochemistry of polymer chains:
Isotactic: This is a stereoregular polymer – all the substituents are located on the same side of the polymer chain:
Syndiotactic: This is a stereoregular polymer – the substituents are located at regular alternate positions on opposite sides of the polymer chain:
Atactic: This is not a stereoregular polymer – the substituents are placed randomly along the chain:
“…we attribute to the new crystalline polymers a structure in which at least for long portions of the principal chain… all the R groups must be placed on the same side of the plane of the principal chain.”
The Helix
In March 1954, Natta established that the chain in isotactic polypropylene is arranged as a single helix. The helix was becoming a noticeably common feature in macromolecules: in 1951, Linus Pauling and colleagues established the alpha-helix structure in proteins; and in 1953, work by Francis Crick, Rosalind Franklin, James Watson, and Maurice Wilkins established that DNA is a double helix.
A Wide Range of New, Stereoregular Polymers
The polymerization catalyst mixtures used by Ziegler and Natta became known as Ziegler-Natta catalysts.
After making isotactic polypropylene Natta deployed 100 research workers on a program with three objectives:
- Producing new plastics.
- Producing new fibers.
- Producing new rubbers.
Natta and his teams produced a range of new stereoregular polymers from starting materials such as 1-butene, butadiene, styrene, and 4-methyl-1-pentene. In all cases, they were able to determine the dimensions of the crystalline unit cell and to precisely determine the structure and spatial arrangement of the polymer chains.
Nobel Prize and Lomonosov Gold Medal
In 1963, Natta and Ziegler were awarded the Nobel Prize in Chemistry for:
“their discoveries in the field of the chemistry and technology of high polymers.”
In 1969, Natta was awarded the Lomonosov Gold Medal, the USSR Academy of Sciences’ highest award, for
outstanding achievements in the chemistry of polymers.
Family and the End
In 1935, age 33, Natta married Rosita Beati, a language scholar and professor of literature at the University of Milan. They had a son and a daughter: Giuseppe and Franca.
In 1956, Natta was diagnosed with Parkinson’s disease. Stoically, with the help and care of his wife Rosita, he carried on working. In 1963, age 60, he gave his Nobel Lecture in Stockholm assisted by his son Giuseppe and academic colleagues.
Rosita died in 1968. Their daughter Franca, now married, took over from her mother, ensuring her father was cared for.
Giulio Natta died, age 76, on May 2, 1979 in Bergamo, Italy.
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Further Reading
Frank M. McMillan
The Chain Straighteners: Fruitful Innovation : the Discovery of Linear and Stereoregular Synthetic Polymers
Springer, June 1979
F.B. Seymour
Pioneers in Polymer Science
Springer Science & Business Media, Dec 2012
Francesco Ciardelli, Paolo Giusti
Structural Order in Polymers: Lectures Presented at the International Symposium on Macromolecules, Florence, Italy, 7-12 September 1980
Elsevier, October 2013