Polymer Synthesis CHEM 421 Methods for Polyester Synthesis Direct reaction Acid halide / hydroxyl...
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Polymer Synthesis CHEM 421 Methods for Polyester Synthesis •Direct reaction •Acid halide / hydroxyl •Transesterification •Melt acidolysis
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Transcript of Polymer Synthesis CHEM 421 Methods for Polyester Synthesis Direct reaction Acid halide / hydroxyl...
Polymer SynthesisCHEM 421
Methods for Polyester Synthesis
• Direct reaction
• Acid halide / hydroxyl
• Transesterification
• Melt acidolysis
Polymer SynthesisCHEM 421
Direct Reaction
C
O
OH
+H
+
H2O
C
O
HO
HO CH2CH2 OH
C
O
C
O
O CH2CH2 On
• Self-catalyzed
Rp [OH] [COOH] [COOH]
• Catalyzed by added acid ( [H+] = constant)
Rp [OH] [COOH] Faster
DacronTM, MylarTM
Polymer SynthesisCHEM 421
Terephthalic Acid Synthesis
C
O
OHC
O
HO
CH3H3C
O
C
O
OHH3CCH
O
C
O
HO
• Early catalysts not quantitative…
Polymer SynthesisCHEM 421
Transesterification
C
O
OCH3 +
+
C
O
H3CO HO CH2CH2 OH
O C
O
C
O
O CH2CH2 OH
200 0C, 1 atm
HO CH2CH2 H3C OH
HO CH2CH2 OH
280 0C, vacuum
O C
O
C
O
O CH2CH2 OHHO CH2CH2
n
Polymer SynthesisCHEM 421
Transesterification
O C
O
C
O
O CH2CH2 OHO CH2CH2 C
O
C
O
O CH2CH2 OH
HO CH2CH2 OH
O C
O
C
O
O CH2CH2 OH
200 0C, 1 atm
HO CH2CH2
O C
O
C
O
O CH2CH2 OHHO CH2CH2
Polymer SynthesisCHEM 421
Transesterification
O C
O
C
O
O R OHO Rn
H
Diol Tg (oC) Tm (oC)
80 265
HO CH2CH2 OH
Polymer SynthesisCHEM 421
Continuous Process
Polymer SynthesisCHEM 421
Primary Degradation Pathway
C
O
C
O
O CH2CH2 O C
O
C
O
C
O
C
O
OH O C
O
C
O
+ CH
H2C
C
O
C
O
O O C
O
C
O
CH
CH3
C
O
O
O C
O
C
O
CH2
CH
H
Polymer SynthesisCHEM 421
Primary Degradation Pathway
C
O
C
O
O O C
O
C
O
CH
CH3
H3C C
O
H
C
O
C
O
O C
O
C
O
Acetaldehyde< 3 ppm for taste
Anhydride intermediateHydrolytically unstable
Polymer SynthesisCHEM 421
Chip X-tallizesChip X-tallizesTTgg < T < T < T < Tmm
Solid State Polymerization
SPPSPP
• 12h Residence Time12h Residence Time
• Increased MWIncreased MW
• Minimizes AcetaldehydeMinimizes Acetaldehyde
EGEG
NN220.90.9
Polymer SynthesisCHEM 421
PET Recycling
•1997 – 13 million tons; 1.5 million tons for bottles1997 – 13 million tons; 1.5 million tons for bottlesInd. Eng. Chem. Res., Vol. 36, No. 4, 1997
•Methanolysis; catalyst – usually Zn(OAc)Methanolysis; catalyst – usually Zn(OAc)22
•Copolymers pose problems – no well-definedCopolymers pose problems – no well-defined decomposition Ex. branchingdecomposition Ex. branching
Polymer SynthesisCHEM 421
Acid Chlorides
•More reactive than acidMore reactive than acid•Use w/ less reactive diolsUse w/ less reactive diols•Solution or interfaciallySolution or interfacially•Drawbacks?Drawbacks?
O O
O
Me
Me
O
Cl
O O
Cl HO
Me
Me
OH
HCl
Polymer SynthesisCHEM 421
Melt Acidolysis
O
Me
Me
O
O O
O
Me
Me
O
O
Me
O
Me
Me
O O
Me
Melt Polym’zMelt Polym’zAcetic AcidAcetic Acid250 250 °C Vac°C Vac
•Avoids side rxnsAvoids side rxns•High tempsHigh temps•HeterogeneousHeterogeneous•LCP’sLCP’s
Polymer SynthesisCHEM 421
Polyamides
• Two major classes– Fibers
– Engineering resins
• Nylon– Invented in 1930s…stockings!
– 1940s (WWII) all production went to parachutes, airplane tire chords, glider tow rope, military apparel
– Today» Apparel
» Carpet
» Automotive
» Security (Kevlar,Nomex)
Polymer SynthesisCHEM 421
Polyamides
• Nylon 6, 6
# carbons indiamine
# carbons indiacid
N CH2CH2CH2CH2CH2CH2 N C
O
CH2CH2CH2CH2 C
O
HH n
Polymer SynthesisCHEM 421
Nylon 6,6:
• Nice balance of properties– Tm = 265 C– 50% crystalline (high) (solvent resistant)– Easily oriented (fibers)– High strength– Abrasion resistant– Dyeable– Resistant to alkaline solution
• Problem– Moisture pick-up– Not resistant to acid hydrolysis
Polymer SynthesisCHEM 421
Polyamides: Structure / Property Relationships
• X Y Name Tm
• 4 6 Nylon 4,8 278 C
• 4 7 Nylon 4,9 233 C
• 4 9 Nylon 4,11 223 C
• 6 4 Nylon 6, 6 265 C
• 6 6 Nylon 6, 8 250 C
• 6 9 Nylon 6, 11 205 C
N CH2 N C
O
CH2 C
O
HH nx y
Polymer SynthesisCHEM 421
Synthesis of Polyamides
• Direct amidation (“Nylon Salt”)
• Acid chlorides / Amines
• Phosphorylations
• (Ring opening)
Polymer SynthesisCHEM 421Direct “Nylon Salt” Route
H2N CH2CH2CH2CH2CH2CH2 NH2
HO CCH2CH2CH2CH2C OH
O O
Boiling methanol+H3N CH2CH2CH2CH2CH2CH2 NH3
O CCH2CH2CH2CH2C O
O O
ppt’d saltTm = 183 C
Dissolve in waterControl MW by addingcalculated amount of Acetic acid
220 C closed vessel
270 - 280 C for 2-3 hours
Vacuum
Melt processed under nitrogen blanket
Nylon 6, 6
Polymer SynthesisCHEM 421Acid Chloride / Amine Route
• Acid chlorides more reactive
• Expensive
• Less nucleophilicaromatic amines
• Interfacial route– Fast
– Does not require1:1 stoichiometry
– Rp is f(surface area)
• Solution route
Polymer SynthesisCHEM 421
Solution Acid Chloride Route
NH2H2N CC
O
Cl
O
Cl
Acid scavengerPolar, aprotic solvent (DMAc)LiCl
HN
HN
C
O
C
O
Polymer SynthesisCHEM 421
Phophorylation Route
H2N HOOCNH2 COOH
PyridineP(OPh)3 (triphenyl phosphite)LiClNMP
C CNH
O
NH
O
n
Motivation: Use cheaper diacid route instead of expensivediacid chloride route with less nucleophilic aromatic amines
