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PART I
GIULIO NATTA: THE WORKS, THE
SCIENTIST, THE MAN
Biographical notes. University
career
Giulio Natta was born in Porto Maurizio (Imperia) on 26
February 1903, to Ligurian parents: Francesco Maria, an
eminent judge, and Elena Crespi. After gaining a diploma
from Colombo High School in Genoa he was admitted to Genoa
University, aged only 16 years, to study on the two-year
propedeutic mathematics course. In 1921 he enrolled on
practical courses in Industrial Engineering (Chemistry)
at the Polytechnic of Milan, graduating in 1924 at the
age of 21 with a degree in Industrial Engineering (Chemistry),
having also studied from 1922 at the Institute of General
Chemistry under the Directorship of Professor Giuseppe
Bruni, whose assistant Natta immediately became.
Giulio Natta lost no time in embarking on a university
career with Giuseppe Bruni and, after three years, was
appointed to the teaching staff in General Chemistry as
"libero docente".
In 1925 he was appointed to teach Analytical Chemistry,
a post which he held until 1932. Meanwhile, from 1929
to 1933, he also taught a course in Physical Chemistry
at the Faculty of Science of the Univer-sity of Milan.
In 1933 he was awarded the chair of General Chemistry
at the University of Pavia, where he remained until 1935,
and where he also taught Physical Chemistry. In 1935 he
was invited to take up the prestigious professorship in
Physical Chemistry at the University of Rome and, in 1937,
the chair in Industrial Chemistry at the Polytechnic of
Turin. In that period Mario Giacomo Levi was forced, due
to racial persecution, to leave the Directorship of the
Institute of Industrial Chemistry of the Polytechnic of
Milan and in 1938 Natta was appointed in his place. Natta
was to remain at the Polytechnic of Milan until 1973 as
Full Professor of Industrial Chemistry and Director of
the Institute of the same name.
The scientist
An examination of Natta's academic curriculum and of his
scientific works reveals that he did not have a proper
teacher as such, but that he was self-taught.
His passion for chemistry innate. While still a student,
he had set up and equipped a laboratory in his home in
Via Rugabella in Milan, where he would conduct experiments,
sometimes with hazardous consequences.
In the early 1920s, while doing his military service,
he conducted experiments at the Polytechnic of Milan on
mustard gas, a vesicant gas used in the First World War:
he tested the characteristics of his preparations on the
skin of his own wrist, for years marked by small scars.
To be nearer to his research he set up a camp bed in a
laboratory at the Institute of General Chemistry.
His first scientific work was published in the "Gazzetta
Chimica Italiana" 1923 (vol. 53, p. 532). But his
scientific activity ranged across various sectors, as
we describe later (see pdf document).
Studies in structural chemistry
Natta's research soon became oriented towards structural
chemistry, first by studying the application of X-rays
and then by tackling a subject that was ultra-modern at
that time: the diffraction of electron beams. These were
techniques that in Italy were being applied for the first
time - and in the centre which could then be considered
the most important in Italy for such studies - to the
resolution of problems in the field of chemistry.
In the study of compounds of metallic oxides and sulphides
he identified the relationship between the ionic radii
of the components which affect the formation of particular
structures. He went deeply into the study of the phenomena
of isomorphism and accomplished the preparation of solid
solutions with new methods, such as by precipitation.
He defined the structure of several hydroxides and hydrates
containing coordination water. With a special and ingenious
spectrograph for low temperatures, which he constructed
himself, he described the structure of gases that solidify
at low temperatures. In the case of halogenidric acids
which present the same structure as noble gases having
the same number of electrons, he arrived at a direct method
for the determination of the ionic radii in crystals.
He determined the structure of solid hydrogen sulphide
and other compounds of hydrogen.
It was these researches that aroused in Natta an interest
also in the issue of applications. His first industrial
patent dates back to 1927.
The chemistry of carbon monoxide,
alcohols and formaldehyde (C1 chemistry)
The first scientific works on the synthesis of methanol
and higher alcohols (preceded and accompanied by several
patents, extended abroad) date from 1930. At that time
methanol was one of the most important industrial organic
derivative products, used for the preparation of various
organic compounds and as a solvent, and its synthesis
was the object of research at foreign companies and in
the most adavanced countries.
On the scientific front, Natta's work in this sector made
it possible, in particular, to relate catalytic activity
to the dimensions of individual crystals, to define reaction
mechanisms, to highlight the role of a number of promoters
and to propose some new catalysts.
On the applicative front, his work led to the construction
in 1930 of the first Italian methanol plant in Coghinas
(Sassari), followed by others, in Italy, Switzerland and
South America, with a capacity, notable for that time,
of over 10,000 t per year.
His work in this sector brought Natta international fame,
with the result that he was subsequently asked to write
two chapters for a renowned series of volumes: "Catalysis",
edited by P.H. Emmett [Synthesis of Methanol, in "Catalysis",
P.H. Emmett (editor), Reinhold Corp., New York 1955; Direct
Catalytic Synthesis of Higher Alcohols from Carbon Monoxide
and Hydrogen, ivi, 1957].
The 1930s also saw his studies on gasification with oxygen
at low temperatures of domestic fuels, carried out with
an experimental gas generator which he installed at the
Institute of Industrial Chemistry at the Polytechnic of
Milan. These researches, too, led to the construction
of a number of industrial gas generators, each one with
a potential of 50,000 m3 of gas per day, used (during
periods of economic self-sufficiency) for the preparation
of ammonia, nitrogen fertilizers, fuels and methanol.
Still in the early 1930s, Natta took up the study of the
preparation of formaldehyde (another important organic
derivative, used in the preparation of thermosetting resins
-phenol/formaldehyde resins (Bakelite), urea/formaldehyde
resins, adhesives, paints, explosives) by means of oxidative
dehydrogenation of methanol which, later on, was to lead
to the production of new catalysts applied on an industrial
scale.
First researches into high
polymers
The first work by Natta in the field of high polymers
dates from 1934, following a period spent in Germany,
in Freiburg (with a study grant awarded by the Volta Foundation
in 1932) at the Laboratory of Dr. Seeman, where Natta
met Prof. Hermann Staudinger, Nobel Laureate in Chemistry
in 1953 for his research into the properties and structure
of high polymers, both natural (cellulose, natural rubber,
gutta-percha) and synthetic.
Staudinger had already demonstrated in 1922 that these
substances were made up of large molecules rather than
aggregates, coining the term "macromolecules".
It was to substances of this kind, some of which he received
from Staudinger, that Natta applied for the first time
the technique of electron diffraction in order to characterize
their structure.
Hydrogenation of furfural and
carbohydrates
For some years more, however, he was to be concerned with
other problems of an applicative nature: the hydrogenation
of carbohydrates for the production of glycols and glycerol,
which was important for national self-sufficiency, the
hydrogenation of furfural, the synthesis of isooctane
(as fuel), and the production of hydrogen from methane.
Research into synthetic rubber
In 1938, under commission from the government and in close
collaboration with industry, Natta devoted himself to
research into the production of synthetic rubber in Italy,
working mainly on the separation - from l-butene - of
butadiene in a sufficiently pure state to permit its use
for the production of elastomers by means of copolymerization
with styrene (Buna S). This was an extraordinarily difficult
operation to conduct physically, owing to the extreme
closeness of the boiling points of the two compounds.
Natta brought about a new physical method of separation,
which he himself meticulously studied and perfected: fractionated
absorption.
Oxo-synthesis
In the immediate post-war period Natta tackled a new subject
of great topical interest at that time: "oxo-synthesis",
a synthesis discovered in Germany, which made it possible
to obtain aldehydes (and alcohols) by means of catalytic
addition of CO and H2 to olefins. Natta's contributions
in this sector made it possible to clarify reaction mechanisms
and better define operating conditions, and they were
then applied in the construction of the first oxo-synthesis
plants in Ferrara, within the first major petrochemicals
complex in Italy.
Stereospecific polymerization
However, the work for which Natta is most famous and which
led to his being awarded the Nobel prize, together with
Karl Ziegler of the Max Planck Institute in Mülheim,
concerns stereospecific polymerization, which he discovered
- thanks partly to a series of lucky circumstances - and
studied exhaustively.
In 1952, while attending a conference given by Karl Ziegler
in Frankfurt, he was struck by the fact that ethylene
polyaddition took place in the presence of organometallic
compounds, producing oligomers of low molecular weight,
but perfectly linear; and that, in the dimerization of
the ?-olefin, a single dimer was produced, but with a
clearly defined structure, unlike the complex mixes produced
by normal cationic catalysts. Natta invited Ziegler to
hold a conference at the Polytechnic of Milan and suggested
that Montecatini should draw up a contract with Ziegler
to grant the company the use of any results, past and
future, obtained by Ziegler in the field of organometallic
compounds and their application.
In the meantime, Natta set up at the Polytechnic an advanced
course in organic aliphatic industrial chemistry for trainee
graduates, employed by Montecatini but selected by Natta,
who was thus able to have at his disposal in his laboratories
an exclusive group of skilled researchers, with whom he
began the study of ethylene polyaddition and the polymerization
of other olefins with organometallic compounds.
In 1953 Ziegler filed his first patent on the polymerization
of ethylene to high polymers, obtained at low pressure
in the presence of catalysts consisting of metallo-alkyls
of metals from the 1st and 3rd groups of the periodic
system and compounds of transition metals from the 4th
to the 8th group. These studies by Ziegler, though of
great importance, were limited to ethylene polymerization,
which was already being obtained at that period in great
steam cracking plants, together with substantial quantities
of propylene - which at the time had limited uses - into
which Natta directed his own research.
In the first months of 1954, using Ziegler's catalysts,
Natta obtained the first partly crystalline polypropylene
and on 11 March noted in his diary, "Made polypropylene".
He at once recognized that the crystallinity of the polymer
thus obtained was due to a particular type of steric regularity,
which he defined as "isotactic".
Before Natta's discovery, the succession of the monomeric
units along the polymeric chains in synthetic polymers
derived from vinyl-type monomers had been disordered,
particularly from the steric point of view. Stereospecifìc
polymerization made it possible for the first time to
synthesize polymers that were ordered, both chemically
and sterically, starting from vinylic or in any case unsaturated
monomers.
Prior to this, polymers of this type had only been found
in nature (for example natural rubber and gutta-percha).
The type of regularity involved in the concatenation of
the monomeric units in the macromolecules of polymeric
products is a determining factor governing the properties
of the polymer itself. On this subject, it is worth recalling
the differences between natural rubber and gutta-percha
(both are isoprene polymers: the former is a 1,4-cis polyisoprene
and the latter a 1,4-trans polyisoprene). Moreover, the
significant differences in mechanical, physical and organoleptic
properties observable between cellulose and starch are
due to the difference in the types of steric regularity
with which monomeric units that are identical (glucose)
succeed one another along polymeric chains.
The stereoregular polypropylene defined by Natta as "isotactic"
is a crystalline powder with a density lower than that
of water and a melting point of 170° C, from which
products with a tensile stress of 3-4 kg/mm2 can be made;
whereas non-stereoregular polypropylene (atactic) is an
oily substance.
The first work on this discovery was presented at the
National Lyncean Academy in 1955 [G. Natta, A new class
of polymers of alpha-olefin having exceptional regularity
of structure, in "Atti Acc. Naz. Lincei", Mem.
4 (8), 61 (1955)].
It is impossible to outline in just a few pages the breadth
and importance of the contributions made by Natta and
his School in this field; we provide here a simple list
of the subjects that the Institute of Industrial Chemistry
of the Polytechnic of Milan tackled in the period from
1953 to 1971 (in the following years, up to 1979, the
publications bearing Natta's name were collections, essays
and educational texts), and which were developed in very
nearly one thousand scientific publications (see also
Appendix A, where the subjects are subdivided according
to topics and periods, with the indication of the main
collaborators):
- synthesis, characterization of the structure in the
crystalline state and determination of a number of physicochemical,
mechanical and physical properties of several new types
of polymers;
- preparation, study and characterization of catalytic
systems formed from a transition element compound and
an organometallic compound (Ziegler-Natta catalysts) or
from organometallic compounds alone;
- studies on the mechanisms and kinetics of various polymerizations;
- synthesis of polytactic polymers;
- asymmetric syntheses;
- synthesis of polyolefin copolymers with statistical
distribution and their application for the preparation
of saturated elastomers;
- synthesis of alternating crystalline copolymers;
- preparation and characterization of saturated and unsaturated
elastomers and fibres;
- grafted polymers;
- stereoregular polymers obtained from inclusion compounds;
- use of polymers in the field of pharmacology;
- application of spectroscopic (IR, NMR, ESR, Raman),
radiochemical and various analytical techniques to the
study of polymers, monomers, catalytic systems and their
components and various complexes.
The importance of these researches on a more strictly
scientific level is not limited to the fact that stereospecific
polymerization permitted for the first time the synthesis
of stereoregular polymers obtained from monomers of various
kinds. Just as fundamental was the work on the discovery
of various catalytic systems and on their behaviour, and
the work on the determination of the structure of polymeric
substances, on the relationship between properties and
structure, and on asymmetrical syntheses: indeed, with
this type of synthesis a link was established between
a class of phenomena occurring in nature and reactions
achievable for the first time in the laboratory. In the
Presentation Speech made by Professor A. Fredga, Member
of the Nobel Committee for Chemistry at the Royal Swedish
Academy of Sciences, on the occasion of the awarding of
the Nobel Prize we read: "Nature synthesizes many
stereoregular polymers, for example cellulose and rubber.
This ability has so far been thought to be a monopoly
of Nature, operating with biocatalysts known as enzymes.
But now Professor Natta has broken this monopoly".
Paul Flory, one of the greatest scientists in the field
of polymers, himself awarded the Nobel Prize in Chemistry
in 1974, in 1955 described Natta's discovery as "a
revolution in the field of macromolecular chemistry".
This "revolution" subsequently affected the
entire scientific and industrial world in this specialist
sector, so that very soon after 1954-1955 most university
and industry research laboratories involved in macromolecular
chemistry in various parts of the world ended up focusing,
to a greater or lesser extent, on activities concerned
with the new technique of stereospecific polymerization.
And for several years these laboratories were essentially
inspired by the work of Natta and his School, which meant
that for the most part they were doing follow-up research.
It would not be wide of the mark to state that most of
the significant results achieved in the field of stereospecific
polymerization, broadly speaking, for several years after
1954 continued to come out of Natta's laboratories.
In the June 1961 issue of the J. of Polymer Science, dedicated
to Natta as "The Father of Stereoregular Polymers"
we read:
"Seldom has a scientific contribution aroused such
a profound fundamental interest and been followed by such
a rapid technical development as the series of publications
by Professor Giulio Natta and his co-workers on the stereospecific
polymerization of olefins, which started to appear in
the Italian journals several years ago and have continued
ever since. Many prominent scientists in many large research
laboratories have become interested in the new technique
and have focused their interests and efforts on its promotion.
Yet Professor Natta has succeeded in maintaining undisputed
leadership in this field of polymer chemistry and continues
to surprise his colleagues by new and unexpected discoveries
along the general principles of stereoregulation."
The extent and significance of the new fields of research
activity originating from Natta's work can also be seen
from the fact that, even today, over 50 years on from
his discovery, stereospecific polymerization continues
to be the object of numerous intense studies, both scientific
and applicative.
On the applicative front such researches have led to the
discovery of new types of polymers of great industrial
interest, such as isotactic polypropylene, used in the
production of plastics, synthetic fibres and transparent
sheets, ethylene-propylene copolymers and 1,4-cis polybutadiene,
two important synthetic elastomers.
To highlight the importance in the area of applications
of these discoveries we may quote what was published in
the November 1963 issue of "La Chimica e l'Industria",
in the editorial dedicated to Natta, following the awarding
of the Nobel Prize: "... the field of industrial
chemistry has been 'ploughed' so deeply that it is unlikely
to hold the surprise of any discoveries as significant
as this". Over 50 years after the discovery made
by Giulio Natta, this statement has still not been invalidated.
The importance in commercial terms of isotactic polypropylene,
elastomers based on ethylene and propylene and 1,4-cis
polybutadiene is shown by the fact that polypropylene
is ranked in third place, in terms of commercial value,
among all chemical products produced on an industrial
scale, outdoing styrene polymers, polyamides, and vinyl
chloride polymers and copolymers, while 1,4-cis polybutadiene
and copolymers based on ethylene and propylene occupy
second and third positions respectively in the ranking
of synthetic rubbers.
One might now ask oneself how it was possible to achieve
such significant results in such a short time. The crucial
factor must indubitably be sought in the personality of
Giulio Natta, in his thorough preparation in various branches
of chemistry and in his gifted intuitions. But intuition
and scientific preparation are not sufficient to develop
research in a completely new field and on various substances
that had not existed before then, even taking into account
the fact that this research was characterized by a broad
interdisciplinary approach and that it required methodologies
and investigative techniques of numerous kinds. First
and foremost it required means and a "School".
In the matter of the provision of economic means and equipment,
we must acknowledge the credit to the company known then
as Montecatini, in the person of the CEO in that period,
Piero Giustiniani. The collection of equipment made available
for carrying out the research was of a remarkable standard:
from various pieces of apparatus for spectroscopic, analytical
and physicochemical analyses, to the apparatus in the
Plastics testing Laboratory (set up in 1952 with financial
contributions from various companies); this Laboratory,
in addition to conducting tests on behalf of third parties,
contributed to characterizing several of the new polymers,
in particular polypropylene and ethylene-propylene rubbers.
The "School", which in 1954-1955 originally
consisted of some fifteen researchers, both assistant
lecturers and Montecatini graduates - for the most part
very young - later expanded into the Polytechnic itself
with other Montecatini researchers and to other universities
and CNR (National Research Council) centres, eventually
turning out scientists who today hold, or held in the
past, prestigious posts in Italian and foreign universities,
in the most important national chemicals companies and
in CNR research Centres and Institutes, which emerged
with the creation of the National Centre for Macromolecular
Chemistry and with the National Institute for Macromolecular
Chemistry.
Giulio Natta's scientific personality,
intuitions and dedication to research
The determining factor which made the accomplishment of
such notable results possible, especially in the field
of stereospecific polymerization, in a relatively short
period of time, is to be discovered in Natta's personality,
in his exhaustive preparation in various branches of chemistry,
in his brilliant intuitions and in his extremely clear
and thorough knowledge of the frontiers reached by technology
and by chemical science, taken in the broadest sense:
unlike the majority of other Nobel Laureates he was not
a specialist. For Natta chemical science was one complete
whole, from the study of molecules in the laboratory to
the industrial plant.
His intuitions can best be illustrated with a few stories.
Shortly after the discovery of the stereospecific polymerization
of propylene he remarked, during a conversation with his
assistants, that it would be possible to obtain elastomers
by disturbing the tendency of polyethylene to crystallize,
by means of the introduction of some irregularities into
its chain, which was achievable with the copolymerization
of ethylene with propylene. A few days later, the first
ethylene-propylene copolymer was made in the laboratory,
and its elastomeric properties were confirmed.
On another occasion Natta wanted to "find" -
for reasons of patent protection - a crystalline polypropylene
that was different from isotactic polypropylene, in other
words syndiotactic polypropylene, whose existence had
only been conjectured. In this case also, after a few
days, the new polymer was identified and separated and
its crystalline structure defined. A few months later
a catalyst was produced which was highly syndiospecific
in the polymerization of propylene.
Other episodes highlight Natta's profound dedication to
research. In 1957 he was invited to give the keynote address
at the 16th International Congress of Pure and Applied
Chemistry (IUPAC) in Paris. Unfortunately he fell ill
(it was his first symptoms of Parkinson's disease) and
he was confined to his bed for several weeks. The lecture
was prepared in lengthy sessions at his bedside. Some
years later he underwent his first brain surgery: the
very day of the operation, immediately after the surgery
had been completed, he telephoned his assistant from the
hospital to find out the result of an experiment that
he was particularly interested in. He was an indefatigable
worker. He would work until late at night, even on public
holidays or during vacations, often accompanied by one
of his assistants, who would take turns at his desk in
Via Mario Pagano in Milano or at the houses where he stayed
during vacations, a habit which Natta kept up even after
he was seriously afflicted by Parkinson's disease, from
which he suffered for some 20 years.
Natta was not only a great scientist, he was a great teacher.
In the years preceding his work on stereospecific polymerization
he had already trained scholars who were subsequently
called on to take up prestigious university professorships.
In addition to the Nobel prize, Natta received innumerable
national and international awards.
The professor
As well as his scientific activity, we should remember
Natta's work as a teacher. He had a profound love of school
and of teaching, and considered such activities to be
among the most important and worthy. He would prepare
every one of his lessons with great care, though rather
than lessons it was more often a question of conferences,
in which he would communicate the wealth of his experiments,
expounding on subjects which he had been able to investigate
at first hand.
As long as his state of health allowed it he was determined
to continue to examine each of his students personally.
The generations of chemical engineering students who had
the privilege of attending his course, or of preparing
their graduation thesis with him, will never forget his
commitment to the role of "Professor".
His colleagues always recognised his great merit in having
succeeded in modernizing the teaching of industrial chemistry,
modelling it along rational and deductive lines which
differed radically from the traditional approach.
The man
As a person, Giulio Natta was shy and reserved, although
as a student he threw himself readily into undergraduate
life and took part in student events. He had sincere human
relationships with everyone, even if this was masked by
an apparent detachment that was clearly due to his shyness.
He could inspire respect, without ever raising his voice:
he gave no orders either to his assistants or to his students,
but only advice and suggestions. However, he managed to
coordinate with kindness and tenacity the activity of
various groups of researchers, each with its own specialist
expertise, accepting the diverse personalities of each
one.
His family life and his relations with various Italian
and foreign scientists were looked after by his wife Rosita
Beati, whom he married in 1935, a Humanities graduate
and a woman of enormous culture, great sensitivity and
vivacity, whose affection was also invaluable to the Professor.
Rosita died before him, in 1968, to the profound grief
of her children Franca and Giuseppe and everyone who had
known her.
Ever since he was a student, Natta loved the outdoor life,
with excursions to the mountains and skiing trips, and
always retained his love of nature, the quiet restfulness
of fishing, and long walks in the woods hunting for mushrooms.
He was a great connoisseur of minerals, mushrooms and
plants: when he had to travel to a foreign country he
would read up on the types of trees he would find there.
And it was in the tranquillity of one of his houses, on
the hills of Bergamo, with his daughter Franca by his
side, that on 2 May 1979 he passed away after years of
physical suffering endured with great strength of spirit.
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