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Period: to
Pre-synthetic polymers
The investigation of the nature of materials and the creation of polymers is just beginning and is unknown to the inventors. They are not aware of the structure of the materials that they are manipulating -
Karl Nageli uses the term molecule
Karl Nageli was a Swiss botanist who claimed starches were made of 'molecules'. This term had not yet been popularized so there was confusion as to what it meant in the science community. Scientists like Cannizzaro and Avogadro had differing definitions.
NOS: community, evolving, tentative
(Olby, 1970, p. 168) -
Karlsruhe Conference defines molecule; Negali retracts
At the Karlsruhe Conference, scientists establish a meaning to the term molecule after being persuaded by the research of Avogadro and Cannizzaro. This defintion is essentially the same today.
NOS: community, collaboration, self-correcting Negali's usage did not correspond to the new usage so he changed his term to micelle. This term was defined as an association of molecules that formed a crystalline array. Picture shows Mendeleyev and a young Kekule.
(Olby, 1970, p. 168) -
Kekule proposes fairly accurate model
Kekule proposes that molecules are like 'net or sponge-like masses formed by the union of many univalent molecules with polyvalent atoms acting as centers of attachment". He did not introduce the idea of chains of atoms, but it did explain molecular masses. This concept was not accepted and micellar theory was used to explain colloid condtions by proposing that the molecules had associations and formed ring-like structures.
NOS: coherence, tentative, self-correcting
(Olby, 1970, p. 169) -
New methods for determing molecular weight
Previously there were not any quantitative methods used to determine molecular weight. In 1882, Raoult's Law was introduced as a method of obtaining molecular weights by freezing and in 1886, van't Hoff instroduced a method of obtaining molecular weights by osmotic pressure. Both methods produced variable answers and it was deemed that these equations didn't work for colloidal solutions. The error of the methods for macromolecules produced errors greater than the measurement
(Olby, 1970, 169) -
Partial Valencies by Thiele
As scientists questoned the data of more and more large molecular weight species as being impractical especially for cellular applications, the aggregate or partial valency hypothessis became popular which said that the molecules did not have to have full valences to form molecules and that these collections of molecules made the large structures.
NOS: evolving, explanatory power, fecundity
Picture of Johannes Thiele
(Olby, 1970, p. 169) -
Aggregate theory is introduced
The concept that the odd behavior of synthetic and natural molecules is attributed to the nature of the molecules forming primary and secondary forces with each other and forming larger structures. The idea is that is the molecules were separated into their base molecules by breaking these forces then the properties could be accounted for in traditional ways.
Werner was an advocate for aggregate theory.
Picture shows Alfred Werner.
NOS: parsimony (Olby, 1970, p. 170) -
Period: to
Early Synthetic Polymers
Rapid development of eary polymers -
Period: to
World War I
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Staudinger's Heated Discussion
After a lecture in Zurich where he disputed the 'secondary forces of association' and proposed the concept of macromolecules, he received much criticism and the debate was very hectic. His final words of the discussion were "Here I stand, I cannot do otherwise" (quote from Luther). NOS: skepticism, collaboration, communication, tentative
(Olby, 1970, p. 171) -
Staudinger Receives Advice
Staudinger received the following advice in a letter after the discussion: "Dear Colleague, Leave the concept of large molecules well alone; organic molecules with a molecular weight above 5000 do not exist. Purify your products, such as rubber, then they will crystallize and prove to be lower molecular substances. Organic molecules of more than 40 carbon units do not exist. Molecules can not be larger than the crystallographic unit cell, so there can be no such thing as a macromolecule." -
Molecular mass estimates renewed
Svedberg and Adair both estimate hemoglobin molecular weight to be around 66,000. Collaboration begins and the theory of aggregate molecules is to be cast aside for macromolecules.
NOS: emperical, testable, repeatable
Picture shows Theodore Svedberg (Olby, 1970, p. 171) -
Tiselius shows mass to charge is constant
This showed that partial valence theory was not likely as described by Werner and that the end groups must have normal valance structures. NOS: emperical, testable, repeatable, self-correcting, parsimony, logical coherence, skepticism -
X-ray used to determine molecular structure
Mark and Meyer use X-rays to determine cellulose and rubber cyrstalline forms. This refuted the idea that the molecule had to be a small molecules built through association. NOS: emperical, testable, self-correcting, explanatory power, skepticism. Picture of Herman Mark.
(Seymour et al., 1981, p. 4) -
Carothers synthesizes polyester/ polyamides
Carothers synthesized polyesters and then polyamides (nylon) and shows wool and silk are also polyamides.
NOS: emperical, testable, repeatable
(Seymour et al., 1981, p. 4) -
Period: to
Production of natural materials synthetically
Development of many polymer substitutes -
Period: to
World War II
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Tiselius receives Nobel Prize for Chemistry
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Period: to
Catalyst-based Polymers emerge
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Staudinger receives Nobel Prize for Chemistry
He won the prize for his work on determing that macromolecules exist. -
Period: to
Conductive Polymers emerge
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Period: to
Protein Chemistry and Genetic Engineering are potential futures
