8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
1/22
Polymer Synthesis
" I am inclined to think that thedevelopment of polymerizationis perhaps the biggest thing thatchemistry has done, where it hashad the biggest effect on everydaylife
Lord Todd, 1980
[ C H2 C H 2 ]nMagic ?
Ethylene PolyethyleneCH
2= CH
2
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
2/22
Polymer TypesCarothers: ..most polymerscould be classified according tothe mechanism of polymerization,
Condensation Addition
. or the kinetics of the reactions.
Step-growth Chain
.based on Synthesis .
Condensation reactions,Nylon (1938)
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
3/22
Types of Reactions
Condensation
Addition
Ring opening
Nylon 6,6
Polyethylene
Nylon 6
H 2 N (CH 2 )6 NH 2 + HO C (CH 2 )4 C OH
OO
CH 2 CH 2
N
CO
H
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
4/22
Condensation Reactions(Small molecules)
Acetic Acid Ethyl Alcohol
ReversibleReaction!
Ethyl Acetate
Ester linkage
CH 3 C OH + CH 3 CH 2 OH CH 3 C O CH 2 CH 3 + H 2 O
O O
Reactants with a functional groupMono-functionalStep-wise reaction.
H2O by-product.
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
5/22
....produce a more stable state.
HO CH 2 CH 3
Acetic Acid
Reaction intermediate
Ethyl Alcoholor Ethanol
CH 3 C OH
O
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
6/22
Reaction: cat. by acid and higher temps.
Heating to just over 100
C,-gets the reaction going, drives off water,
Step-wise reaction1st step: addition reaction (rev.)2nd step: product formed; water eliminated (rev.).
Why doesnt it form a polymer?
Acetic Acid Ethyl Alcohol
ReversibleReaction!
Ethyl Acetate
Ester linkage
CH 3 C OH + CH 3 CH 2 OH CH 3 C O CH 2 CH 3 + H 2 O
O O
Carboxylic acids react withalcohols to form esters
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
7/22
Producing a PolymerMono-functional molecules: undergo only one step;
produce small molecules
Bi-functional molecules: each product can react again;
produce linear chains;
The reaction proceeds step-wise!
+
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
8/22
First step towards a Polyester
Dimer?
Monomers
HO C (CH2)
n C OH + HO (CH
2)
m OH
O O
HO C (CH 2 ) C O (CH 2 )m OH + H 2 O
O O
Bi-functionality is retained through-out the polymerization;
This is the first repeat unit (AB). Is it a copolymer?
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
9/22
Step-Growth Reaction
H 2 O
Trimer M 1 + M 1 M 2 M 2 + M 1 M 3
M 2 + M 2 M 4
M 3 + M 1 M 4
M 4 + M 1 M 5
M 3 + M 2 M 5
M 5 + M 1 M 6Etc.
HO C (CH 2 )n C OHHO C (CH 2 )n C O (CH 2 )m OH +
O O O O
HO C (CH 2 )n C O (CH 2 )m O C (CH 2 )n C OH
O O O O
This is the ABA,or half-way tothe AB dimer.
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
10/22
Step-Growth Polymerization;Summary
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
11/22
First polyesters had low MWs, low MPs.(
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
12/22
Nylons (Polyamides)
Adipic Acid Hexamethylene Diamine
Amide Group
H 2 N (CH 2 )6 NH 2 + HO C (CH 2 )4 C OH
O O
H 2 N (CH 2 )6 N C (CH 2 )4 C OH + H 2 O H
O O
Condensation reaction: proceeds step-wise,rev. steps, elim. water.
Reactants: carboxylic acid plus amide.
AB with asymmetricreactive ends.
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
13/22
Nylon 6,6
n
6
Amide Group
6
O O
N (CH 2 )6 N C (CH 2 )4 C O
H
H
-Several nylons.-Structures vary by the number of
(CH 2) groups between the amide linkages;6,6; 4,6; etc.
- Basic repeat unit has two different mers.
Error: N not O
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
14/22
Ad. from N.Y. Herald Tribune,Oct. 30 1938
I am making theannouncement of a brandnew chemical textile fiber ---
derivable from coal, air andwater -- and characterized byextreme toughness andstrength --
Charles Stine V.P. forresearch, Du Pont, 1938
Biggest initial impact on products forthe military and stockings .
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
15/22
Post WWII stocking sale, San Francisco.
Find Waldo.
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
16/22
Stoichiometry Issue
The reaction requires equal molar amts of the monomers.. . . not an easy on an industrial scale.
Trick with nylon: pre-prep the acid:amine salt, precipitates as a 1:1 complex .
Nylon Salt
OOC (CH 2 )4 COO
+ NH 3 (CH 2 )6 NH 3 +
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
17/22
Nylons (Polyamides) From Diacyl Halides
Adipoyl Chloride Hexamethylene Diamine
Amide Group
Is a water molecule always eliminated?
H 2 N (CH 2 )6 NH 2 + Cl C (CH 2 )4 C Cl
O O
H 2 N (CH 2 )6 N C (CH 2 )4 C OH + HCl
O O
H
HCl is driven off, drives the reaction, makes it irrev.
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
18/22
Hexamethylene diaminein water
Adipoyl chloridein chloroform
Nylon 6,6 formedat the interface
Nylon "skin"
carefully drawn offto form fiber or rope
The Nylon Rope Trick
What about the stoichiometry in the reactor?
Forms amide bond;HCl byproduct
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
19/22
O C N (CH 2 )6 N C O + HO (CH 2 )2 OH
Polyurethanes-Bi-functional monomers-Addition reaction-No small molecule eliminated.
Hexamethylene Diisocyanate Ethylene Glycol
Urethane Linkage
O
H O C N (CH 2 )6 N C O (CH 2 )2 OH
R-N=C=O from the dehydration of R-NH-COOH .
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
20/22
Polyesters From Diesters
+ 2CH 3 OH
Dimethyl Terephthalate Ethylene Glycol
CH 3 O C C O CH 3 + 2(HO (CH 2 )2 OH)O O
C O CH 2 CH 2 OHHOCH 2 CH 2 O C
O O
COOH was converted (activated) to an ester group.Ester monomer produces ester polymerMethanol by product
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
21/22
+ HOCH 2 CH 2 OH
Polyesters from Trans-esterification
Transesterification
And so on
C O CH 2 CH 2 OHHOCH 2 CH 2 O C
O O
C O CH 2 CH 2 OHHOCH 2 CH 2 O C
O O
C O HOCH 2 CH 2 O C
O O
C O CH 2 CH 2 OHCH 2 CH 2 O C
O O
8/12/2019 Lect 4 Polymer Synthesis Ch 3 Pt1.2014 (1)
22/22
Summary of Polymerization Reactions
Addition Condensation*
Chain reaction Initiator Double bond present in
monomer Single monomer No by-products Few long chains; no
double bonds Branching possible
Step-wise reaction H+ Initiator Bifunctional monomers 2 different monomers 2 mer repeat unit By-products Oligomers Branching is unlikely
Top Related