Lecture 1 Flashcards
Intro to polymers, Classification of polymers based upon molecular structure, polymer materials
polymer definition
large molecule composed of repeating structural units
how are subunits in polymers usually connected?
covalent chemical bonds
covalent bonding
two nuclei share electrons between them
ionic bonding
two nuclei have electrostatic attraction
electronegativity
the ability of an atom to attract electrons when the atom is in a compound
energy of covalent bonds
-lower total energy
-directional
energy of ionic bonds
in solid state, interact through coulomb potential
energy of van der waals
individual bonds can readily break and form at room temp
energy of hydrogen bonds
requires H bond to NOF, enhances polymer toughness
pi bond
double/triple bonds
sigma
single bonds
Cis double bond
two largest R groups are on same side of double bond
Trans double bond
two largest R groups are on opposite side of double bond
bonding in a polymer with other molecules on the same chain
intramolecular interaction
bonding in polymers with other polymer chains
intermolecular interaction
synthetic polymers
-will always have dispersity in MW
-not broad
-radical, condensation reactions
-polydisperse
natural polymers
-precise through sequences
-structure is identical
-polymerization through a template
-monodisperse
-narrow distribution
Carother’s definition for synthetic polymers
substance whose MW exceeds 5KDa and whose structure can be represented by -R-R-R- are not capable of independent existence
Types of synthetic polymers
thermoplastics, thermosets, and elastomers
Thermoplastics
linear, non-crosslinked, recyclable
ex of a high performing thermoplastic
PEEK
ex of thermoplastics
polyolefins(PE, PP, LDPE, HDPE), PS, PVC, PMMA
thermosets
permanently crosslinked, polymer networks, non recyclable
ex of thermosets
epoxies, polyesters, formaldehyde based resins
elastomers
flexible polymer chain, low crosslinking, can be thermoset or thermoplastic
ex elastomers
natural rubber, vulcanized rubber, thermoplastic rubber
vinyl polymers
polymers that are derided from monomers containing C-C bonds (PP, PVC)
Molecular parameters that determine properties of polymers
- chemical composition
- chemistry of chain ends
- chain architecture
- chain configuration
- MW and MW distributions
homochain
polymers with a single type of backbone
heterochain
polymers with more than one atom type in the backbone
homopolymers
same monomer
copolymers
different monomers
telechelic polymers
polymers with reactive end groups
chain ends determine
adhesion, friction, and wear
in the case of LDPE, branching occurs through
backbiting
polyfunctional monomer
can react with more than 2 other molecules under polymerization conditions (creates branching)
high network density in a polymers makes it
brittle and rigid
long, flexible networks that are loosely connected make polymers
rubbery and elastic
