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