PHMSCI 540: Unit 3 - Polymer Chemistry

Initial creation by Emily P. <3

Define polymer

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

categories of polymer

natural, synthetic, elastomers

define monomer

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

define oligomer

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

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

molecular architecture of polymers (4)

-linear polymer

-branched polymer

-network polymer

-ladder polymer

define copolymer

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

types of copolymers (4)

random, alternating, graft, block

general aspect of microscopic features of bulk polymers

microcrystalline: amorphous matrix containing crystallites r

define glass transition temperature (Tg)

transition temperature where rubbery or flexible solid becomes glass like.

define melting temperature (Tm)

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

necking

-whitening

-isotropic becomes anisotropic

addition polymers nomenclature

-poly + name of monomer

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

define polymers - elastomers

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

e.g. polyisoprene

define polymers - fibers

polymers that have a very high resistance to deformation

e.g. nylon 6

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

classification by synthesis

-step growth (condensation polymers)

-chain growth (usually addition polymers)

step growth polymerization

-linear chains

-network polymers

linear chains

synthesized from bifunctional monomers

network polymers

synthesized from monomers that have more than 2 functionalities

conversion (p) equation

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

DP

number of constitutional repeating units per molecule

important step growth polymers

• Nylon 6 6

• PET

three step synthesis of PET

1) trans-esterification reaction

2) prepolymerization step

3) polycondensation reaction

chain growth polymerization (4)

-radical addition

-coordination addition

-cationic additoin

-anionic addition

3 steps of chain growth polymerization

1. initiation

2. propagation

3. termination

define bulk polymerization

simple yet easy to control temperature

define homogenous solution

synthesis for relatively small molecular weight polymers

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

define emulsion polymerization

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

-requires water soluble initiator

-useful for rubber manufacturing

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

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