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Biomaterials Exam 1 > Polymers > Flashcards

Polymers Flashcards

1
Q

Definition of a polymer

A

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

aka long chain molecules with many repeating units

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2
Q

monomer

A

smallest repeating unit (molecule) in polymer chain

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3
Q

polymerization

A

rxn of monomers to synthesize/form polymers

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4
Q

condensation polymerization

A

elimination/release of a smaller molecule (water, ethanol) while forming covalent bonding between monomers

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5
Q

addition polymerization

A

polymerization without the elimination of a smaller molecule

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6
Q

Dental examples of condensation polymerization

A

flexible dentures - nylon
impressions - polysulfides, silicones
wax - silicones

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7
Q

Free radical addition polymerization

A

free radical is a reactive chemical species with an unpaired electron

Can react with vinyl compounds (like acrylic resin - dentures, splints, cements)

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8
Q

What is the difference between acrylic resin and acrylic acid? What are each used for in dentistry?

A

acrylic resin: hard rigid glass polymer - splints, dentures, cements

acrylic acid: adhesive water-soluble polymer - adhesives

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9
Q

What are the stages of polymerization of vinyl compounds (addition polymerization)

A
  1. Generation of free radicals (activation, initiation)
  2. propagation of the rxn
  3. termination of the rxn
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10
Q

What is the difference between polymer molecules and polymeric materials?

A

Polymer molecules: composed of millions of repeated units (monomers)

Polymeric material: made up of polymeric molecules; natural and synthetic

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11
Q

What INTRAmolecular forces are employed by polymer molecules?

A

covalent bonds

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12
Q

What INTERmolecular forces are employed by polymeric materials?

A

Molecule entanglement - friction between mols
Secondary bonds - Van der Waals
Covalent bonds - crosslinking

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13
Q

Degree of polymerization (DP)

A

number of repeating units in a polymer - the # of monomer units joined together

Avg length of the molecules

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14
Q

Molecular weight of polymers

A

degree of polymerization x the molecule weight of the repeating units

avg mass of the mols

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15
Q

The higher the molecular weight, the higher the _______ and _________

A

strength

rigidity

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16
Q

higher degrees of polymerization provide ________ in dental polymeric materials

A

higher strength

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17
Q

What are the three types of physical states of polymers?

A 
Elastomers (rubbers)
Hard amorphous (glasses - transparent)
Hard semicrystalline (partially crystalline - translucent)
18
Q

What is the difference between flexible polymers (elastomers/rubbers) and rigid polymers?

A

Molecular flexibility depends on temp
Higher temps - more flexible, easier disentanglement
Lower temps - more rigid

19
Q

Glass transition temperature (Tg)

A

Each polymer has a temp range at which it changes from rigid to flexible (heating)/flexible to rigid (cooling)

20
Q

A polymer with a comparatively high Tg (78 degrees C) will be ______ at mouth temp

A

rigid

ex: denture base material

21
Q

a polymer with relatively low Tg (-22 degrees C) will be _______ at mouth temperature

A

flexible

Ex: impressions, denture linings

22
Q

Elastomers or rubbers have a ______ Tg, and work at temperatures ____ Tg

A

Have a low Tg

Work at temperatures above Tg

23
Q

Hard polymers have a ______ Tg and work at temperatures _____ Tg

A

high Tg

Work at temps below Tg

24
Q

Polymers show a combination of _____ and ____ behavior

A

elastic

viscous

25
Q

Viscous behavior in polymers

A

breaking of intermolecular bonds and disentanglement of molecules

26
Q

Elastic behavior in polymers

A

Uncoiling and stretching of molecules

27
Q

Plasticizers

A

Liquids that are able to penetrate between the randomly oriented chains of a polymer (eg. water)
Reduce frictional forces between mols
Result in a softened polymer
Polymer may be more flexible (lower Tg)

28
Q

How do plasticizers change polymers?

A

Soften them

May be more flexible (lower Tg)

29
Q

Resin composites are a _______ polymer

A

cross linked

30
Q

Cross linked polymers

A

More purely elastic, less viscous because mobility of mols is limited
May have higher Tg
Harder, more brittle
More resistant to action of solvents/plasticizers
Uncoiling/disentanglement harder/impossible

31
Q

co-polymers

A

Same composition but different arrangement = different properties

32
Q

Hydrocolloids such as agar and alginate are _______ polymers

A

naturally occurring polymers

33
Q

Gutta percha, an isomer of rubber, is a __________ polymer

A

natural rubbers

34
Q

Nylon (sometimes used in dentures) is what kind of polymer?

A

Hard synthetic, condensation

35
Q

Poly(methyl methacrylate) (PMMA), used for dentures, is what kind of polymer?

A

hard synthetic

free radical addition (mostly linear structures)

36
Q

Dental composites, fissure sealants and some adhesive cements are what kind of polymer?

A

hard synthetic

Free radical addition (extensively cross linked)

37
Q

resin composites consist of polymer and ________ and are used in:

A

polymer and inorganic fillers

pit and fissure sealants, luting cements, resin composite filling materials

38
Q

Impression materials (polysulfides, silicones, polyethers) and denture liners (silicone) are examples of…

A

flexible synthetic polymers

elastomers

39
Q

Resilient linings and tissue conditioners are examples of what kind of polymer?

A

Plasticized methacrylates

flexible synthetic polymers

40
Q

Poly(acrylic acid) and other acids (itaconic, aleic) are adhesive to tooth tissues by ionic attraction and are examples of what kinds of polymers?

A

water soluble synthetic polymers

Biomaterials Exam 1 (7 decks)

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