polycarbonates: interfacial polymerizations
DESCRIPTION
Polycarbonates: Interfacial Polymerizations. Commercially Important Brunelle, D. J. Am. Chem. Soc., 1990, pg. 2399. Brunelle, D., Macromolecules , 1991, pg. 3035. Step Growth Polymerization of Poly(bisphenol A carbonate). Traditional Routes. Interfacial Route. Advantages - PowerPoint PPT PresentationTRANSCRIPT
Polymer SynthesisCHEM 421
Polycarbonates:Interfacial Polymerizations
• Commercially ImportantCommercially ImportantBrunelle, D. Brunelle, D. J. Am. Chem. Soc., J. Am. Chem. Soc., 1990, pg. 2399.1990, pg. 2399.Brunelle, D., Brunelle, D., MacromoleculesMacromolecules, 1991, pg. 3035., 1991, pg. 3035.
Polymer SynthesisCHEM 421
OHHO
O C O
OOH
O C O
O
O C O
O
n
n
+
Polycarbonate Oligomers
+
(2n-1)
181-300 oC
Polycarbonate Oligomers
OH
HO O C
O
O OH
O C
O
O O C
O
O
m
m
m
LiOH
Step Growth Polymerization of Poly(bisphenol A carbonate)
Polymer SynthesisCHEM 421
Advantages
•High Molecular Weight
•Excellent Optical Clarity
and color
Disadvantages
•Phosgene based
•Uses H2O and CH2Cl2
Advantages
•Solvent Free
•Potentially Phosgene Free
Disadvantages
•Colored Product
•Intermediate Molecular Weight
Interfacial Route
HO OH
+
O C O
O
Melt Condensation
O C O
O
)n(
O O- + PhaseTransferCatalyst
+ H2O
CCl Cl
O
+ CH2Cl2
Traditional Routes
Polymer SynthesisCHEM 421
Swelling and Plasticization of a Polymer Melt
Impact:Lower T
processing
CO2 & Polymer Processing
Polymer SynthesisCHEM 421
Melt Phase Condensation Polymerization
• Viscosity () increases with conversion• High hinders mixing and removal of condensate, causing slower reaction rates• Addition of supercritical CO2 as a plasticizing agent decreases , increasing mobility• Supercritical CO2 extracts reaction byproducts, shifts equilibrium, increases DP
CO2 inlet
CO2 + byproductoutlet
Swollen polymermelt
Polymer SynthesisCHEM 421
• In a closed system, the polymer swelling correlates to CO2 mass uptake by the polymer
• Swelling measurements allow for the determination of the diffusion coefficient of CO2 in the polymer
Swelling Measurements
0 psi 2000 psi 3000 psi 4000 psi 5000 psi
Polymer SynthesisCHEM 421
Polymer SynthesisCHEM 421
Solvent-Induced (CO2) Crystallization of Polycarbonate
AmorphousPolycarbonate
Pellets
Polycarbonate Pellets
Crystallizedwith
SupercriticalCO2
Polymer SynthesisCHEM 421Solid State Polymerization
Synthesize amorphous prepolymerCrystallize the prepolymer with supercritical CO2 to
eliminate the need for organic solventsHeat the semicrystalline prepolymer between Tg and Tm
Flow sweep fluid past the surface of the polymer particle to remove condensation byproduct Investigate the use of supercritical CO2 as a sweep fluid
Amorphous region
Crystalline region
Polymer SynthesisCHEM 421
Solvent induced crystallization presents a unique opportunity to study solid
state polymerization
PET PC -Thermally crystallizes -Does not readily thermally crystallize -Fixed level of crystallinity -Can control crystallinity -Uniform crystallinity -Can control morphology
Solid State Polymerization: Solvent Induced Crystallization
Solvent front
Polymer SynthesisCHEM 421
Mw versus Time as a Function of Temperature:SSP of Polycarbonate Beads (3.6 mm)
with N2 as the Sweep Fluid
Variable Temperature Profile: Hours 0-2: 180 °C Hours 4-6: 230 °C Hours 2-4: 205 °C Hours 6-12: 240 °C
Macromolecules, 1999, 32, 3167. N2 flow rate 2 mL/min
Polymer SynthesisCHEM 421Role of Phenol Diffusion
Segment RadiusCore = 0.0 to 0.4 mmInter = 0.4 to 1.4 mmShell = 1.4 to 1.8 mm
Phenol must diffuse from the particle to increase polymer molecular weight.
core
intermediate
shell
The sample was separated intothree regions for analysis...
-molecular weight-percent crystallinity-melting point (Tm)
What is the role of….-phenol diffusivity-tortuosity-end group mobility
Polymer SynthesisCHEM 421
Macromolecules, 2000, 33, 40.PC Beads=3.6 mmN2 Flow=2 mL/min
MW as a Function of Diameter?
1
Xn2
[Condensate] ——
Polymer SynthesisCHEM 421
Mw versus Time for the SSP of PC Powder(20 um) Using N2 as the Sweep Fluid
180 ºC
Variable Temperature
N2 flow rate 2 mL/min
Polymer SynthesisCHEM 421
PDI versus Time for the SSP of PC Beads (d =3.6 mm) and PC powder (20 um) at a variable temperature program
PDI of Bead
PDI of Powder
Significant molecular weight distribution broadening observed in larger polymer particles.
Polymer SynthesisCHEM 421
Copolymers in Step Growth Polymerizations
COCH3
CH3
O C
O
O CCH3
CH3
O C
O
C
O
n