Hanyang Univ. Hanyang Univ. Spring 2007 Classification by Mechanism Step – Growth Chain – Growth Classification by Type Condensation Addition Classification by Bond Radical Ion Chap 8. Polycondensation Reactions For further details, Click next homepage. http://www.pslc.ws/mactest/ synth.htm Surfing to the internet
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Hanyang Univ. Spring 2007 Classification by Mechanism Step – Growth Chain – Growth Classification by Type Condensation Addition Classification.
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Hanyang Univ.Hanyang Univ.
Spring 2007
Classification by Mechanism
Step – Growth
Chain – Growth
Classification by Type
Condensation
Addition
Classification by Bond
Radical
Ion
Chap 8. Polycondensation Reactions
For further details,
Click next homepage.
http://www.pslc.ws/mactest/synth.htm
Surfing to the internet
Hanyang Univ.Hanyang Univ.
Spring 2007
Step Growth Polymerization
•The growing chains react with each other.
•Polymers frwo to high Mw at a slow rate.
•High Mw is formed at the end of polymerization.
•Long reaction time is needed to obtain high Mw and high conversion
Chain Growth Polymerization
•Monomer molecules add on to a growing polymer chain one at a time.
•Polymers grow to high Mw at a very fast rate
•High Mw is formed at the early stage.
•Monomer adds on the growing polymer chain via reactive active center.
What are differences between step and chain growth polymerizatoin?
Hanyang Univ.Hanyang Univ.
Spring 2007
Addition versus Condensation polymerisation
• Condensation polymers (C): fewer atoms in the backbone because of formation of by-products
• Addition polymers (A): the repeating unit contains the same atoms as the monomer
OH OH
O O
2NH2 NH2
6 * N N *
O O
H Hn
4 6+
**
OO
n
**
n
OO
Hanyang Univ.Hanyang Univ.
Spring 2007Characteristics of Step-Growth
Step-growth polymerization principle was used by Carothers in 1929.
HO C
O
CH2CH3OH CH2CH3 CH3 CH2 C
O
O CH2CH3
Synthesis of Ester
Carothers thought about following reaction.
OH C
O
R C
O
OH R' OHOHMany scientists were sure that one would get a ring-like moleculeO
R'O
RO O
But, if more acid and alcohol were used, ring would not form because of unstability of ring-shaped molecules more than six atom.
It seemed to him more likely that one would get long chainlike macromolecules like this
Hanyang Univ.Hanyang Univ.
Spring 2007
JACS (Journal of American Chemical Society, 51, P. 2548 (1929))
“Polyintermolecular condensation requires as starting materials
compounds in which at least two functional groups are present
in the same molecule”
Characteristics of Step-Growth
OH C
O
R C
O
OH R' OHOH
Hanyang Univ.Hanyang Univ.
Spring 2007
Extended by Flory
The reactivity of functional group is not correlated with complexity and size of molecule with
functional group.
HO R OH + HOOC R' COOH (complexity)
HO R OH (size)
HO R OH
This concept is useful to polycondensation type polymerization.
ex) OCNRNCO + H2NR`NH2 polyurea
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
This concept also can be applied to Chain-growth polymerization.
Olefins
Vinyl monomers
Unsaturated monomers
So, double bond in vinyl monomer is considered as bifunctional.
Equal Functional Group Reactivity Concept
C C
H
H
H
H
C C OR
H
H
H
H
OR C C OR
H
H
H
H
CCC
H
H
H
H
H
H
C C
H
H
H
H
Hanyang Univ.Hanyang Univ.
Spring 2007
I. Thermodynamic Approach
“In order to for a polymerization to be thermodynamically feasible, the
Gibbs-Free Energy change must be negative, that is, ΔGp < 0.”
G = HTS
GP = HPTSP : this equation is the basic of understanding about polymerization,
depolymerzation equilibrium
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
GP = Gpolymer Gmonomer
= (HP – Hm) – T(SP – Sm)
= HP – TSP
Where HP : enthalpy change per monomer unit
SP : entropy change per monomer unit
GP < 0 Polymerization is spontaneous
GP > 0 Polymerization is not possible
GP = 0 monomer polymer
at this temperature is ceiling temperature.
(for both step and chain growth)
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
II.Kinetic Approach
“A negative GP does not necessarily mean that polymerization occurs under
a particular set of reaction conditions and reaction sites”
e.g) should have
functional group
proper initiator
temperature etc.
Equal Functional Group Reactivity Concept
Hanyang Univ.Hanyang Univ.
Spring 2007
Stage 1
Consumptionof monomer
n n
Stage 2
Combinationof small fragments
Stage 3
Reaction of oligomers to give high molecular weight polymer
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
1. Polyesterification by esterinterchange
2. Polyesterification and polyamidation by Schotten-Baumann Reaction
O
C Cl+
NH2
OH
O
x
OO
R" (OCR' C O R ) OH + (2 x 1)R" OH
O
x HO R OH + xR"OCR' C O R"
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
3. Amidation by thermal dehydration of ammonium salt
4. Reaction of OCNRNCO + HOR’OH polyurethane
H2NR’NH2 polyurea
n46H NH (CH2) NH CO (CH2) CO OH + (2n 1) H2O
++
6 H3N(CH2) NH3
4OOC(CH2) COO
n
46n H2N(CH2) NH2 + n HOOC(CH2) COOH
Step Growth Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Well-studied, well characterized rexns
Well-understood rexns at least on an empirical basis.
brittleness, softness depends on X-linking densityh.
Applications: bowling ball, helmet, auto part, air con
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
C
O
ClCl+ OH OH
O* O C
O
*n + HCl
Lexan from GE
Tm = 270°C, Tg=150°C
high impact resistance, transparency, packaging, phone dial ring,
process similar to polyester synthesis
2stage,
①vaccum at 200°C
②300°C
I. Polycarbonate
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
HO(CH2)nOH O C N (CH2)6N C O
OCN
CH2 NCO
NCO
NCO
CH3
+
diol HMDI (hexamethylene diisocyanate)
diol
+
4,4'-diphenylmethane diisocyanate
or
+
TDI (tolylene diisocyanate)
diol
J. Poly urethane
Example of condensation polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
diamine in water
Polymer film forming at the interface
diacid chloride in organic solvent
O
CR C
O
ClCl + HOR'OHnn
O
CR C
O
R'O ** n + 2n ClH
O
CR C
O
ClCl + H2NR'NH2nn
O
CR C
O
* N R'NH H
*n 2n ClH+
Interfacial Polymerization
Hanyang Univ.Hanyang Univ.
Spring 2007
Cl Cl
O O
4H2N NH24
Adipoyl chloride 1,6-Diaminohexane
Cl NH
NH
H
O O
4 4
NaOH
HO NH
NH
H
O O
4 4n
6 carbondiacid
6 carbondiamine
Nylon-6,6Diamine, NaOH, in H2O
Adipoyl chloridein hexane
Nylon 6,6
Nylon-6,6
Hanyang Univ.Hanyang Univ.
Spring 2007
Diamine, NaOH, in H2O
Adipoyl chloridein hexane
Nylon 6,6
Since the reactants are in different phases, they can only react at the phase boundary. Once a layer of polymer forms, no more reaction occurs. Removing the polymer allows more reaction to occur.