Complex Effects of the Sweep Fluid on Solid-State Polymerization: Poly(bisphenol A carbonate) in Supercritical Carbon Dioxide
- Complex Effects of the Sweep Fluid on Solid-State Polymerization: Poly(bisphenol A carbonate) in Supercritical Carbon Dioxide
- 김재훈; L.B. Dong; D. J. Kiserow; G. W. Roberts
- Solid-State Polymerization; Poly(bisphenol A carbonate); Supercritical Carbon Dioxide
- Issue Date
- VOL 42, NO 7, 2472-2479
- The effects of the sweep fluid on solid-state polymerization (SSP) of poly(bisphenol A carbonate)
(BPA-PC) were investigated. Prepolymers with two different number-average molecular weights, PCP6C (Mn )
3800 g/mol) and PCP9C (Mn ) 2400 g/mol), were synthesized using melt transesterification. Solid-state
polymerization of these prepolymers was carried out at temperatures in the range of 150-190 °C with supercritical
carbon dioxide (scCO2) and N2 as the sweep fluids. It was found that scCO2 at 207 bar could either increase or
decrease the rate of SSP relative to the rate in atmospheric N2, depending on the prepolymer molecular weight.
At 190 °C, the molecular weights of the polymers synthesized from the higher-molecular-weight prepolymer
(PCP6C) were higher with scCO2 as the sweep fluid compared to those of the polymers synthesized with N2. In
contrast, at the same temperature of 190 °C, the molecular weights of the polymers synthesized from the lowermolecular-
weight prepolymer (PCP9C) were lower with scCO2 compared to those of the polymers synthesized
with N2. This apparently contradictory effect can be understood in terms of competition between rate-increasing
effects of scCO2, such as greater chain mobility and a higher byproduct diffusion coefficient caused by plasticizing
of the polymer by scCO2, and rate-diminishing effects associated with scCO2, such as lamellar thickening, higher
crystallinity, and perhaps increased occlusion of end groups in crystalline regions.
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