UltraHigh Molecular Weight Nonlinear Polycarbonates Synthesized in Microlayers

Abstract

Ultrahigh molecular weight bisphenol A polycarbonate (BPAPC) with nonlinear chain structures has been synthesized by solid-state polymerization in microlayers at 230°C. It has been found that the molecular weights of the microlayers of low molecular weight prepolymers with thickness ranging from 5 to 35 μm increased rapidly to ultrahigh molecular weight (300,000−600,000 g/mol) without any discoloration. The amorphous prepolymers exhibited much higher reaction rate than the partially crystallized prepolymers. Although the reactive end group mole ratios of the prepolymers prepared by semibatch melt polycondensation deviated significantly from the stoichiometric value, branching and partial cross-linking reactions have been found to occur to rapidly increase the polymer molecular weight. These nonlinear chain structures observed were due to Fries rearrangement, Kolbe-Schmitt rearrangement reactions, and radical-induced scission/cross-linking reactions. The microstructures of the high molecular weight polymers have been analyzed by 13 C NMR, 1 H NMR, pyrolysis-gas chromatography mass spectrometry, and atomic force microscopy.

Decoupling Study of Melt Polycondensation of Polycarbonate: Experimental and Modeling of Reaction Kinetics and Mass Transfer in Thin Films Polycondensation Process

“…[10] The typical PC process is composed of a transesterification and a polycondensation stage. [11][12][13] In the transesterification stage, DPC and BPA monomers are initially polymerized to form a low molecular weight prepolymer with a basic catalyst in stirred reactor. Then, the prepolymer is further polymerized to obtain the high molecular weight PC at higher temperature (250-300 °C) during the finishing polymerization stage.…”

“…The typical PC process is composed of a transesterification and a polycondensation stage . In the transesterification stage, DPC and BPA monomers are initially polymerized to form a low molecular weight prepolymer with a basic catalyst in stirred reactor.…”

Antisolvent crystallization and solid‐state polymerization of bisphenol‐A polycarbonate

“…But the molecular weight decreased as the crystallinity increased above 39.5%. Higher crystallinity could decrease SSP rate by inhibiting the mobility of polymer chains in the amorphous phase and hindering the diffusion of by‐product throughout the polymer particles . As a result of crystallinity effect, BAPC prepolymer of 2 h crystallization time with crystallinity of 37.1% synthesized the highest molecular weight of 57,343 in SSP reaction.…”

Structure and properties of ultra‐high molecular weight bisphenol a polycarbonate synthesized by solid‐state polymerization in amorphous microlayers

“…In the solid‐state polymerization of BPAPC in amorphous micro‐layers (SSP m ), the reaction byproduct (phenol) can be removed more effectively than in micro‐particles and hence high molecular weight is obtained in short reaction time . A small amount of casting solvent left in the micro‐layer can also act as a plasticizer to facilitate the movement of chain segments at the reaction temperature.…”

“…Theoretical modeling of a single SSP particle used in such conventional SSP process has shown that significant diffusion resistance is present in the transport of phenol (byproduct of polycondensation of BPAPC) from the particle interior to the external surface of the particle . In our recent work, we have reported that when BPAPC is polymerized in thin micro‐layers under solid‐state polymerization conditions, very high molecular weight polycarbonate ( M w > 100,000 g mol −1 ) can be obtained in short reaction time …”