PHMSCI 540: Unit 3 - Polymer Chemistry

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Define polymer

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32 Terms

1

Define polymer

a large molecule constructed from smaller structural units called monomers, covalently bonded together in any conceivable pattern

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2

categories of polymer

natural, synthetic, elastomers

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3

define monomer

molecule which combines with other molecules of the same or different type to form a polymer

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4

define oligomer

low molecular weight polymer that should have at least two monomers.

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5

What distinguishes oligomers from polymers?

In oligomer: by addition or removal of 1 repeating unit, the physical properties of the oligomer changes. This is not observed in polymers

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6

molecular architecture of polymers (4)

-linear polymer

-branched polymer

-network polymer

-ladder polymer

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7

define copolymer

-macromolecule which contains structural units of two or more different precursors

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8

types of copolymers (4)

random, alternating, graft, block

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9

general aspect of microscopic features of bulk polymers

microcrystalline: amorphous matrix containing crystallites r

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10

define glass transition temperature (Tg)

transition temperature where rubbery or flexible solid becomes glass like.

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11

define melting temperature (Tm)

highest temperature at which any solid material can exist within an otherwise molten polymer

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12

necking

-whitening

-isotropic becomes anisotropic

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13

addition polymers nomenclature

-poly + name of monomer

-when the monomer has a multi worded name or has a substituted parent name: enclosed in parenthesis

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14

define polymers - elastomers

a group of polymers which can undergo very large, reversible elongations at relatively low stresses

e.g. polyisoprene

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15

define polymers - fibers

polymers that have a very high resistance to deformation

e.g. nylon 6

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16

define polymers - plastics

a polymer capable of changing its shape on teh application of a force and retaining its shape on removal of this force

e.g. polyethylene

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classification by synthesis

-step growth (condensation polymers)

-chain growth (usually addition polymers)

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18

step growth polymerization

-linear chains

-network polymers

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19

linear chains

synthesized from bifunctional monomers

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20

network polymers

synthesized from monomers that have more than 2 functionalities

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21

conversion (p) equation

conversion (p) = (# of reacted functional gropus)/(# of initial functional groups)

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22

DP

number of constitutional repeating units per molecule

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23

important step growth polymers

  • Nylon 6 6

  • PET

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three step synthesis of PET

1) trans-esterification reaction

2) prepolymerization step

3) polycondensation reaction

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25

chain growth polymerization (4)

-radical addition

-coordination addition

-cationic additoin

-anionic addition

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3 steps of chain growth polymerization

1. initiation

2. propagation

3. termination

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27

define bulk polymerization

simple yet easy to control temperature

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28

define homogenous solution

synthesis for relatively small molecular weight polymers

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29

define suspension polymersization

-for water insoluble monomers: suspended in a form of oil droplets

-particle size controlled by stirring speed

-easy control over polymerization heat

-suitable for PST, PAN, PMMA

-not suitable for rubbery, sticky materials

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30

define emulsion polymerization

-for water insoluble monomers: suspended in a form of micelles

-requires water soluble initiator

-useful for rubber manufacturing

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31

define emulsion polymerization process

-reaction starts upon entry of initators into micelles

-monomers diffuse into the micelles fom the droplet

-large droplet almost disappears at a yield

-at final stage of polymerization, all monomers are in the polymer micelles and swell the polymers

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32

Molecular Weights

JUST KNOW: Mz>Mw>Mn

  • Number average mol wt: M n = ΣN iMi/Σni Ÿ

  • Weight average mol wt: Mw = ΣNiMi2/ΣNiMi Ÿ

  • z average mol wt: Mz = ΣNiMi3/ΣNiMi2

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