Week 2: Polymers Flashcards
Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule
polymer
smallest repeating molecule in polymer chain
monomer
reaction of monomers to synthesize/form
polymers
polymerization
elimination/release of a smaller molecule while forming covalent bonding between monomers (e.g., water, ethanol, etc)
condensation polymerization
polymerization in which free radicals (unpaired electron) form to react with vinyl compounds to form the polymer.
addition polymerization
hard rigid glass polymer
acrylic resin
forms an adhesive water-soluble polymer
acrylic acid
polymer aspects
- length
- temp
- alignment
- disentanglement
the number of repeating units in a polymer, the number of monomer units joined together
degree of polymerization
degree of polymerization multiplied by the molecular weight of the repeating units; “average mass of molecules”
molecular weight
the _____ the molecular weight, the ____ the strength and the rigidity because it is more difficult to _____/____
higher, higher, uncoil/disentangle
3 physical states of polymers
elastomers
hard amorphous polymers
hard semicrystalline
effects of cross-linking on properties
- more purely elastic, less viscous
- may have higher Tg
- hard and more brittle
types of hard synthetic polymers
- condensation polymers
- free radical addition polymers (mostly linear)
- free radicals addition polymers (cross-linked)
flexible synthetic polymers
- elastomers
- plasticized methacrylates
a polymeric material is made out of polymeric _____
molecules
polymeric molecules are composed of ____
monomers
three steps needed for addition polymerization
- generation of radicals
- propagation of reaction
- termination of reaction
generation of radicals is accomplished when ______/(____) works on the ______(___) of reaction
activator (energy), initiator (molecule)
examples of activators; which is most important in dentistry?
heat, light, chemical; light is most important
intramolecular forces in polymeric molecules are ___ because covalent bonds are formed while polymer ____
strong, polymerizes
intermolecular forces between polymeric molecules to form a polymeric material can be _________ due to…
less to more strong; entanglement/friction, van der Waals forces, covalent bonds
small molecules that act reducing friction between polymeric molecules and thus soften the polymer to make it more flexible/visoelastic
plasticizers
example of a typical plasticizer
water
cross-linker polymers are usually more ____________ because mobility of molecules is limited
more rigid/harder/stronger, less viscoelastic (more purely elastic)
viscous material refers to…
- breaking of intermolecular bonds
- disentanglement of molecules
addition polymerization reaction
- generation of free radicals
- propagation of reaction
- termination of propagation
