Presentation on theme: "Polymer Synthesis CHEM 421 Polycarbonates: Interfacial Polymerizations Commercially Important Commercially Important Brunelle, D. J. Am. Chem. Soc., 1990,"— Presentation transcript:
Polymer Synthesis CHEM 421 Polycarbonates: Interfacial Polymerizations Commercially Important Commercially Important Brunelle, D. J. Am. Chem. Soc., 1990, pg. 2399. Brunelle, D., Macromolecules, 1991, pg. 3035.
Polymer Synthesis CHEM 421 Step Growth Polymerization of Poly(bisphenol A carbonate)
Polymer Synthesis CHEM 421 Advantages High Molecular Weight Excellent Optical Clarity and color Disadvantages Phosgene based Uses H 2 O and CH 2 Cl 2 Advantages Solvent Free Potentially Phosgene Free Disadvantages Colored Product Intermediate Molecular Weight Interfacial Route Melt Condensation Traditional Routes
Polymer Synthesis CHEM 421 Swelling and Plasticization of a Polymer Melt Impact: Lower T processing CO 2 & Polymer Processing
Polymer Synthesis CHEM 421 Melt Phase Condensation Polymerization Viscosity ( ) increases with conversion High hinders mixing and removal of condensate, causing slower reaction rates Addition of supercritical CO 2 as a plasticizing agent decreases , increasing mobility Supercritical CO 2 extracts reaction byproducts, shifts equilibrium, increases DP CO 2 inlet CO 2 + byproduct outlet Swollen polymer melt
Polymer Synthesis CHEM 421 In a closed system, the polymer swelling correlates to CO 2 mass uptake by the polymer Swelling measurements allow for the determination of the diffusion coefficient of CO 2 in the polymer Swelling Measurements 0 psi2000 psi3000 psi4000 psi5000 psi
Polymer Synthesis CHEM 421 Solvent-Induced (CO 2 ) Crystallization of Polycarbonate Amorphous Polycarbonate Pellets Polycarbonate Pellets Crystallized with Supercritical CO 2
Polymer Synthesis CHEM 421 Solid State Polymerization Synthesize amorphous prepolymer Crystallize the prepolymer with supercritical CO 2 to eliminate the need for organic solvents Heat the semicrystalline prepolymer between T g and T m Flow sweep fluid past the surface of the polymer particle to remove condensation byproduct Investigate the use of supercritical CO 2 as a sweep fluid Amorphous region Crystalline region
Polymer Synthesis CHEM 421 Solvent induced crystallization presents a unique opportunity to study solid state polymerization PETPC -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 Synthesis CHEM 421 M w versus Time as a Function of Temperature: SSP of Polycarbonate Beads (3.6 mm) with N 2 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. N 2 flow rate 2 mL/min
Polymer Synthesis CHEM 421 Role of Phenol Diffusion Segment Radius Core = 0.0 to 0.4 mm Inter = 0.4 to 1.4 mm Shell = 1.4 to 1.8 mm Phenol must diffuse from the particle to increase polymer molecular weight. core intermediate shell The sample was separated into three regions for analysis... -molecular weight -percent crystallinity -melting point (T m ) What is the role of…. -phenol diffusivity -tortuosity -end group mobility
Polymer Synthesis CHEM 421 Macromolecules, 2000, 33, 40. PC Beads=3.6 mm N 2 Flow=2 mL/min MW as a Function of Diameter? 1 Xn2Xn2 [Condensate] ——
Polymer Synthesis CHEM 421 M w versus Time for the SSP of PC Powder (20 um) Using N 2 as the Sweep Fluid 180 ºC Variable Temperature N 2 flow rate 2 mL/min
Polymer Synthesis CHEM 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 Synthesis CHEM 421 Copolymers in Step Growth Polymerizations