polymer structure Flashcards
those derived from plants and animals
naturally occurring polymers
organic materials are__________________
hydrocarbon
composed of hydrogen and carbon
hydrocarbon
intermolecular bond of polymers
covalent
exists when each of the two bonding atoms contributes one electron
covalent
Molecules that have double and triple covalent bonds
unsaturated
weak hydrogen and van der Waals bonds exist between molecules, and thus these hydrocarbons have relatively low melting and boiling points
paraffine
hydrocarbon with the same composition by different atomic arrangement
isomers
physical properties of hydrocarbon are independent to its isomer state
false (depend)
they are referred to as, macromolecules
polymer molecules
it is the backbone of carbon chain polymer
carbon atoms
carbon chain polymer is composed of entities called _______________
repeat units
it is sometimes called mer
repeat units
originates from the Greek word meros, which means “part”
mer
small molecule from which a polymer is synthesized
Monomer
Have the trade name teflon, belong to the family of polymers called fluorocarbon
Polytetrafluoroethelyne
Slight variant of ethylene, in which one of the hydrogen atom is replaced by Cl
Vinyl chloride monomer
When all of the repeating units along a chain are of the same type
Homopolymer
Chains may be composed of two or more different repeat units
Copolymer
monomers have an active bond that may react to form two covalent bonds with other monomers forming a two-dimensional chainlike molecular structure
Bifunctional
number of bonds that a given monomer can form
Functionality
Molecular weight of is often express as
Number average
Weight average
obtained by dividing the chains into a series of size ranges and then determining the number fraction of chains within each size range
Number - average molecular weight
based on the weight fraction of molecules within the various size ranges
Weight - average molecular weight
alternate way of expressing average chain size of a polymer
Degree of polymerization
Single chain bonds are capable of rotating and bending in three dimensions
True
occur when the chains assume twisted, coiled, and kinked shapes or contours as a consequence of chain bond rotations
Molecular entanglements
Rotational flexibility is independent on repeat unit structure and chemistry
False (dependent)
introduction of a bulky or large side group of atoms restricts rotational movement
True
those in which the repeat units are joined together end to end in single chains
Linear polymers
Polymers may be synthesized in which side-branch chains are connected to the main ones
Branched polymers
adjacent linear chains are joined one to another at various positions by covalent bonds
Crosslinked chain
Multifunctional monomers forming three or more active covalent bonds make three-dimensional networks
Network polymers
situation in which atoms are linked together in the same order (head-to-tail) but differ in their spatial arrangement
Stereoisomerism
all of the R groups are situated on the same side of the chain
Isotactic configuration
R groups alternate sides of the chain
Syndiotactic configuration
random positioning of R group
Atactic configuration
chain configurations, or geometrical isomers, are not possible within repeat units having a double bond between chain carbon atoms
False (possible)
Trans-polyisoprene, sometimes called ____________, has properties that are distinctly different from natural rubber as a result of this configurational alteration
gutta percha
soften when heated (and eventually liquefy) and harden when cooled
Thermoplastics
results when a molten thermoplastic polymer is raised to too high a temperature
Irreversible degradation
are generally harder and stronger than thermoplastics and have better dimensional stability
Thermoset
two different units are randomly dispersed along the chain
Random copolymer
two repeat units alternate chain positions
Alternating copolymer
identical repeat units are clustered in blocks along the chain
Block copolymer
homopolymer side branches of one type may be grafted to homopolymer main chains that are composed of a different repeat unit
Graft copolymer
common random copolymer from which automobile tires are made
Styrene - butadiene rubber
composed of acrylonitrile and butadiene
Nitrile rubber
block copolymer that consists of alternating blocks of styrene and butadiene
Impact - modified polystyrene
packing of molecular chains to produce an ordered atomic array
Polymer crystallinity
Folds occuring at the faces
Chain-folded model
grow to be roughly spherical in shape
Spherulite
considered to be the polymer analogue of grains in polycrystalline metals and ceramics
Spherulite
expressed using a modified form of Fick’s first law
Permeation flow rate
