Chapter 14 Flashcards
hydrocarbons
composed of hydrogen and carbon
unsaturated
molecules that have double and triple covalent bonds
saturated
all bonds are single ones and no new atoms may be joined without the removal of others that are already bonded
isomerism
hydrocarbon compounds with the same composition may have different atomic arrangements
macromolecules
gigantic in comparison to the hydrocarbon molecules
repeat units
long molecules that are successively repeated along the chain
monomer
small molecule from which a polymer is synthesized
polymer
many units
homopolymer
when all of the repeating units along a chain are of the same type
copolymers
chains composed of two or more different repeat units
bifunctional
monomers that have an active bond that may react to form two covalent bonds with other monomers forming a two-dimensional chainlike molecular structure
functionality
number of bonds that a given monomer can form
trifunctional
three active bonds, from which a three-dimensional molecular network structure results
linear polymers
those in which the repeat units are joined together end to end in single chains
branched polymers
polymers synthesized in which side-branch chains are connected to the main ones
crosslinked polymers
adjacent linear chains are joined one to another at various positions by covalent bonds
network polymers
multifunctional monomers forming three or more active covalent bonds make 3D networks
stereoisomerism
situation in which atoms are linked together in the same order (head-to-tail) but differ in their spatial arrangement
isotactic configuration
all of the R groups are situated on the same side of the chain
syndiotactic configuration
R groups alternate sides of the chain
atactic configuration
random positioning
cis structure
-for polymers, a prefix denoting a type of molecular structure
-for some unsaturated carbon chain atoms within a
repeat unit, a side atom or group may be situated on one side of the double bond or directly opposite at a 180 degree rotation position.
-in a cis structure, two such side groups within the same repeat unit reside on the same side
trans structure
for polymers, a prefix denoting a type of molecular
structure
-for some unsaturated carbon chain atoms within a repeat unit, a single side atom or group may be situated on one side of the double bond, or directly opposite at a 180 degree rotation position
-in a trans structure, two such side groups within the same repeat unit reside on opposite sides
thermoplastics
- soften when heated (and eventually liquefy) and harden when cooled—processes that are totally reversible and may be repeated
- most linear polymers and those having some branched structures with flexible chains
thermosets
- network polymers
- become permanently hard during their formation and do not soften upon heating
random copolymer
two different units are randomly dispersed along the chain
alternating copolymer
two repeat units alternate chain positions
block copolymer
identical repeat units are clustered in blocks along the chain
graft copolymer
homopolymer side branches of one type may be grafted to homopolymer main chains that are composed of a different repeat unit
polymer crystallinity
packing of molecular chains to produce an ordered atomic array
ceramics and polymers
- ceramics = all crystalline except for glass because its amorphous
- polymers = semi crystalline
amorphous
no crystalline structure
crystallite
a region within a crystalline polymer in which all the
molecular chains are ordered and aligned
chain-folded model
for crystalline polymers, a model that
describes the structure of platelet crystallites. Molecular
alignment is accomplished by chain folding that occurs at the crystallite faces
spherulite
an aggregate of ribbon-like polymer crystallites
(lamellae) radiating from a common central nucleation site; the crystallites are separated by amorphous regions
