BIOM-polymers

Question 1

what are the 2 types of polymerization reactions?

Answer 1

condensation and addition

Question 2

what happens in condensation reactions

Answer 2

elimination of a smaller molecule when monomers react to form covalent bonds - example: AA’s , nylon (flexible dentures - water by-product), polysulfides (impression materials - salt by product), silicones (impression and wax - water byproduct)

Question 3

what happens in addition polymerization

Answer 3

free radicals form to react with vinyl compounds to form the polymer. vinyl compounds [CH2=CH-]. ex: ethylene to polyethylene

Question 4

acrylic resin vs acrylic acid

Answer 4

hard rigid glass polymer (splints/dentures/cements) vs. adhesive water soluble polymer (bonding)

Question 5

what are the 3 (4) steps needed for addition polymerization?

Answer 5

1) generation of radicals (activation and initiation) 2) propagation of reaction 3) termination (no more radicals available to react)

Question 6

how is generation of radicals accomplished

Answer 6

when energy (activator) works on the initiator molecule - can be heat, light, or chemical

Question 7

material structure affects….

Answer 7

material properties

Question 8

intrAmolecular forces in polymeric molecules

Answer 8

covalent bonds - strong

Question 9

intErmolecular forcesbtw polymeric molecules to form a polymeric molecules can be less to more strong. give examples

Answer 9

entanglement/friction, van der waals, covalent (crosslinking)

Question 10

degree of polymerization vs molecular weight

Answer 10

average length of molecules (# of repeating units) vs. average mass of the molecules (Degree of polymerization multiplied by the molecular weight of the repeating units.

Question 11

true/false: the higher the molecular, the higher the strength and rigidity of the polymer

Answer 11

true b/c more difficult to uncoil and disentangle

Question 12

elastomers have a glass transition temperature that is __________ (above or below) room temp

Answer 12

below

Question 13

hard polymers have a glass transition temperature that is ________ (above or below) room temperature

Answer 13

above

Question 14

polymers can be viscoelastic. the elastic component depends on:

Answer 14

the uncoiling and stretching of the molecules

Question 15

polymers can be viscoelastic. the viscous/plastic component depends on:

Answer 15

the disentanglement of the molecules and the breakage of intermolecular bonds

Question 16

if the polymer can not disentangle its molecules then the polymer will not have a ________ component

Answer 16

viscous: therefore, the polymer will not be viscoelastic it will be purely elastic

Question 17

small molecules that act to reduce friction

Answer 17

plasticizers - soften the polymer and make it more flexible (water is a common example) - lower the modulous of elasticity???

Question 18

cross-linked polymers

Answer 18

more purely elastic (less viscoelastic) - they are more rigid, harder, stronger bc the mobility of the molecules is limited due to the strong covalent bonds that they have btw molecules - untangling is more difficult (or impossible)

Question 19

how are co-polymers obtained

Answer 19

by combining different monomers in different sequential arrangements…. bcif we change strx then we change fx

Question 20

true/false: composition by itself does not define the properties of a material

Answer 20

true

Question 21

example of condensation polymers

Answer 21

nylon (dentures)

Question 22

ex of free radical addition polymers that are very linear

Answer 22

PMMA (denture base and repair)

Question 23

ex free radical addition polymer that is extensively crossed linked

Answer 23

composites, sealants, adhesive cements

Question 24

what are the components of resin composites

Answer 24

polymer + inorganic fillers

Question 25

examples of flexible synthetic polymers

Answer 25

elastomers (imp material and silicones) and plasticized methacrylates (resilient liners and tissue conditioners??)

Question 26

examples of water soluble synthetic polymers

Answer 26

polyacrylic acid and other acids used for adhesion to tooth tissues by ionic attraction.