Polymer Classifications: Foreword.

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Polymer Classifications Foreword.

• This presentation is to be used with Chapter 2 of
  the Virtual Book. Students can complete their
  virtual book thusly
• Make simple sketches and write ideas during the
  class when this material is presented.
• Improve that by making better sketches and
  editing a downloaded copy of Chapter2.

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Linear polymers can be represented by a simple
sequence such as A-A-A-A-A .

• Polystyrene
• Styrene monomer

Nylon Two monomers make one repeating unit.
Nylon 6,6
There many different kinds of nylon.
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Polydispersity is the term we use to describe the
fact that not all macromolecules in a given
sample have the same repeat number x.
Polydisperse
Monodisperse
Paucidisperse

Even in a pure sample, not all molecules will be
the same. Nature often does better than people
do.
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Addition one monomer at a time Also called
chain growth.
Condensation anything goes! Also called step
growth.
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The molecular weight of condensation (step
growth) polymers is limited to fairly low values.

Why?

• Condensations usually
• Addition can be quite high
• (e.g., 46 x 106 for polystyrene)
• Convert that to tons/mol

Nature makes huge polycondensates, but they are
usually made in chain growth fashion!
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There are such things as inorganic polymers.
R used to be a secret. Not sure if it still is.
Others POSS, poly(phthalocyanines), many
colloids (colloids are close relatives of
polymers)
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Cascade polymers are also known as dendrimers.
This remains one of the hottest areas of
macromolecular science. Co-invented at LSU, it
is still practiced here. (McCarley, Warner,
Daly, Russo)
Newkome _at_ LSU
Tomalia _at_ Dow
Future Nobelists?
Tomalia now at MMI Newkome now at U. Akron
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Copolymers can be used to tailor functionality or
generate new phases and behaviors.
Block copolymer, example Poly(styrene)-block-pol
y(butadiene)
Random copolymer, example Poly(styrene-ran-butad
iene)
Graft copolymer, example Poly(styrene)-graft-pol
y(butadiene)
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Some chemists really care about nomenclature.
James TraynhamLSU, 2003
From the Chemistry at U. Missouri Rolla website
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Star polymers have the ability to act a little
bit like spheres and you can get higher Ms.
What does that mean?
A lot of the magic of polymers is just size.
Suppose each of the 4 arms is polydisperse.
Are such molecules more or less polydisperse
than their linear counterparts?
Each arm of this star is a random coil. Star
rods would be fun.
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Letter polymers are synthetically challenging and
useful for testing theories.
From the Mays website

• In Hartford, Hereford and Hampshire, Hs Hardly
  Happen
• In Knoxville, Tennessee (home of Jimmy Mays) they
  do.
• Matters in polyolefinsmakes for better
  processing? Regular letter
• polymers help manufacturers defend billion
  dollar patents.

Adapted from the musical, My Fair Lady
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Combs, brushes and ladders give you ways to
stiffen a polymer.
Think bottle brush
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Rodlike polymers are used for very high strength,
liquid crystals, photonics, efficient
viscosification and control of phase relations.
Rodlike because of linear backbone
Used in stealth bomber? Maybe.
Rodlike because of helix
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Polyelectrolytes strange things happen when you
try to separate charges by a few Angstroms.
Do they still tell you about Angstroms?
Strong polyelectrolytes (e.g., salts of
strong polyacids or polybases) Sodium
polystyrene sulfonate fully charged, yet
behavior depends on added salt Weak
polyelectrolytes (e.g., weak polyacids or
polybases) Poly(acrylic acid) Behavior depends on
added salt and pH
Monomer
CH2CH-COOH
Monomer
One of the hottest areas of fundamental polymer
research involves polyelectrolytes.
Concentration of charge along a backbone, with
charged groups closely separated, produces some
weird distortions in the moleculesand in the
surrounding solution. Opposites may repel!
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You are made of biopolymers.

• R group varies one unit to the next

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Proteins can do almost anything.

• Proteins are the most amazing molecules on Earth,
  large or small. They have 4 levels of structure,
  which can confer enormously high function. In
  particular, they make excellent catalystsyou are
  all burning fuel nowat 37oC.efficiently
  compared to most human-designed combustion
  devices! Its the proteins that do this. They
  also give structure and strength and resilience.
  They can change their shapethe original smart
  molecule.

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The 4 levels of structure

• Primary the sequence of the amino acids
• Secondary helix, coil or random sheet (and a
  few others)
• Tertiary folding of the unit, including
  S-S- bridges
• Quaternary how the blobs assemble

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Structure FunctionMore Structure More
Function
http//www.sciencecollege.co.uk/SC/biochemicals/bs
heet.gif
Alpha helix
Beta sheet
http//www.search.com/reference/Alpha_helix
http//www.biosci.ohio-state.edu/prg/protein1.gif
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There are 20 common, naturally occurring amino
acids.
http//www.genome.iastate.edu/edu/gene/genetic-cod
e.htmlAmino Acids
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Another type of biopolymer, nucleic acids,
contains the information needed to make proteins.
Borrowed from Natural Toxins Research Center
Webpage http//ntri.tamuk.edu/cell/nucleic.html
An interesting sub-section of the nanotech
community tries to use nucleic acids as
structural materials.
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Biopolymers Nucleic Acids
DNA
RNA
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Nucleic acids code proteins, a molecular build
sheet

• Nucleic acids are how we get (or code)
  proteins. There are 4 bases (called A,T,G,C).
  Three of these in a row gives a "codon" which
  tells the cellular machinery to add a particular
  amino acid. Nucleic acids are much less
  prevalent than proteins, in the same sense that
  auto factories are less prevalent than
  automobiles. They make interesting model
  polymers for a variety of studiesfrom better
  understanding of polymer flexibility to liquid
  crystal behavior.
• You can get a list of the codons for the various
  amino acids at
• http//www.genome.iastate.edu/edu/gene/genetic-co
  de.htmlAmino Acids

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Networks (Gels) combine the properties of liquids
and solids.

• Keep on branching. The ultimate molecule M ??

http//www.kraftfoods.com/jello/ CLICK IT!
It only takes a little polymer to turn the water
to a nominal solid, and the polymers are held by
noncovalent forces.
Making the network for a tire involves
significantly more polymer and covalent forces
are involved.
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Thermoplastic/Thermoset is another big
distinction.

• Macromolecular chemistry involves chemists,
  biologists, physicists, and various engineers.
  The engineers, just like average citizens, have
  very little use for a molecular point of view.
  They tend to divide the polymer world into
  thermoplastic and thermoset resins.
• Thermoplastic when you heat it, it flows (e.g.,
  polyethylene, polystyrene)
• Thermoset when you heat it, it sets up into a
  solid (e.g., epoxy glue, styrene monomer)

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Polymers can be amorphous, crystalline, or a bit
of bothcorresponding to brittle, gooey and tough
(oversimplified!).

• Polymers can be solid without crystalline
  structures. These are called glasses.
• Polymers can be crystalline (amazing).
• Most useful polymers a little bit of bothregions
  in the material have crystalline inclusions and
  other regions are amorphous. These materials are
  often toughthe amorphous regions absorb shock.

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Transitions

• We deal with this later, but even from the outset
  you should know a little bit.
• Glass transition is the temperature BELOW which
  the amorphous regions of a sample start to act
  like solids.
• Melting transition is the temperature ABOVE which
  the crystalline regions of a sample start to act
  like fluids.
• Either way, these are oversimplificationsbig
  molecules have a number of transitions that
  describe the chain mobility.
• These molecular transitions, in turn, impact the
  physical propertiesfrom feel to stickiness
  (tack) to elongation and breakage.