Ultra-High Molecular Weight Nonlinear Bisphenol A Polycarbonates by Solid State Polymerization in Micro-Layers
| dc.contributor.advisor | Choi, Kyu Yong | en_US |
| dc.contributor.author | Baick, In Hak | en_US |
| dc.contributor.department | Chemical Engineering | en_US |
| dc.contributor.publisher | Digital Repository at the University of Maryland | en_US |
| dc.contributor.publisher | University of Maryland (College Park, Md.) | en_US |
| dc.date.accessioned | 2014-06-26T05:31:38Z | |
| dc.date.available | 2014-06-26T05:31:38Z | |
| dc.date.issued | 2013 | en_US |
| dc.description.abstract | The solid-state polymerization of bisphenol A polycarbonate (BPAPC) has been studied in amorphous and partially crystallized micro-layers (SSP<sub>m</sub>) of low molecular weight prepolymers in presence of LiOH.H<sub>2</sub>O catalyst at a temperature between the glass transition temperature and the melting point. When the prepolymers (14,000 g/mol) in micro-layers of a thickness range from 5 μm to 35 μm were solid-state polymerized at 230 °C, the polymer molecular weight increased rapidly to above 100,000 g/mol, exceeding the highest molecular weight obtainable by the conventional solid-state polymerization in micro-particles. It has also been observed that the final molecular weight reached as high as 600,000 g/mol even in presence of significant stoichiometric imbalances of end group mole ratios when the prepolymer having 21,000 g/mol is used at 230°C under low pressure (10 mmHg). Most notably, amorphous prepolymer micro-layers showed significantly higher increase in molecular weight than partially crystallized prepolymer micro-layers. The chain branching and partially cross-linked structures in high molecular weight polycarbonates have been confirmed by <super>1</super>H-NMR spectroscopic analysis as well as pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). <super>13</super>C-NMR analysis and SSP theoretical model simulation have shown that conventional linear step-growth polymerization is not responsible for the additional increase in molecular weight beyond 50,000 g/mol of polycarbonate MW. The ultra-high molecular weight is contributed to the formation of branched and partially cross-linked structures via Fries or Kolbe-Schmitt rearrangement reactions and radical recombination reaction, respectively. Micro-radical polycarbonate species can be produced via chain scission reaction and hydrogen abstraction at the solid-state polymerization temperature. The formation of cross-linked polymers by radical recombination reactions was attributed to the near complete removal of phenol (i.e. radical scavenger) from the micro-layers during the solid state polymerization. Branched structure polycarbonate was also confirmed by atomic force microscopy (AFM). The presence of branched and cross-linked polymers contributed to the insolubility of the polymer in solvents such as chloroform, tetrahydrofuran (THF), and methlylene chloride. As SSP<sub>m</sub> process extends for a long reaction time at 230°C, about 95% of the polymer was insoluble with excellent transparency (90-93% light transmission). Properties of ultra-high molecular weight nonlinear polycarbonates (SSP<sub>m</sub> PCs) have been investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and rheometer. The development of Multi-Layer Deposit and Reaction (MLDR) technique has shown that the SSP<sub>m</sub> process is not limited to 5-35μm scale. The layer thickness can be expanded while keeping the merits (e.g. high transparency, good solvent resistance, and obtaining high molecular weight in short reaction time) of the SSP<sub>m</sub> technique developed in this study. | en_US |
| dc.identifier.uri | http://hdl.handle.net/1903/15432 | |
| dc.language.iso | en | en_US |
| dc.subject.pqcontrolled | Chemical engineering | en_US |
| dc.subject.pqcontrolled | Polymer chemistry | en_US |
| dc.subject.pquncontrolled | Amorphous state | en_US |
| dc.subject.pquncontrolled | Bisphenol A Polycarbonates | en_US |
| dc.subject.pquncontrolled | insoluble polycarbonates | en_US |
| dc.subject.pquncontrolled | micro-layers | en_US |
| dc.subject.pquncontrolled | partial cross-linking | en_US |
| dc.subject.pquncontrolled | step-growth polymerization | en_US |
| dc.title | Ultra-High Molecular Weight Nonlinear Bisphenol A Polycarbonates by Solid State Polymerization in Micro-Layers | en_US |
| dc.type | Dissertation | en_US |
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