Polycarbonate

About: Polycarbonate is a research topic. Over the lifetime, 14032 publications have been published within this topic receiving 141740 citations. The topic is also known as: PC & Polycarbonate, PC.

Solution-processed nanostructured benzoporphyrin with polycarbonate binder for photovoltaics.

Abstract: Figure 1 . (a) Chemical transformation of BP precursor (CP) to benzoporphyrin (BP) during annealing; (b) standard BP OPV device; (c) TGA analysis of PC and CP; (d) schematic of processing method used to form fi lms of BP for morphology analysis. Organic photovoltaics (OPV) based on bulk heterojunctions (BHJs) have effi ciencies above 7% [ 1 , 2 ] and can be processed from solution at potentially low cost. [ 3 ] BHJs comprise a blend of an electron donor and an electron acceptor in a phase separated morphology that provides a large interfacial area for photogeneration of electron-hole pairs. [ 4 ] The highest performance OPVs currently comprise blends of semiconducting polymers and fullerenes, such as [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM). [ 4 ] Despite their performance in BHJs, semiconducting polymers often take many complicated steps to synthesize and may be diffi cult to purify. [ 5 , 6 ]

Effect of supercritical carbon dioxide on the crystallization and melting behavior of linear bisphenol A polycarbonate

Abstract: The crystallization and melting behavior of bisphenol A polycarbonate treated with supercritical carbon dioxide (CO2) has been investigated with differential scanning calorimetry Supercritical CO2 depresses the crystallization temperature (Tc) of polycarbonate (PC) The lower melting point of PC crystals increase nonlinearly with increasing treatment temperature This indicates that the depression of Tc is not a constant at the same pressure Tc decreases faster at a higher treatment temperature than at a lower temperature The leveling off of the depression in Tc at higher pressures is due to the antiplasticization effect of the hydrostatic pressure of CO2 The melting curves of PC show two melting endotherms The lower melting peak moves to a higher temperature with increasing treatment temperature, pressure, and time The higher temperature peak moves toward a higher temperature as the treatment temperature is increased, whereas this peak is independent of the treatment pressure, time, and heating rate The double melting peaks observed for PC can be attributed to the melting of crystals with different stability mechanisms © 2003 Wiley Periodicals, Inc J Polym Sci Part B: Polym Phys 42: 280–285, 2004

Epoxy−Polycarbonate Blends Catalyzed by a Tertiary Amine. 1. Mechanism of Transesterification and Cyclization

Abstract: In the Bisphenol A base polycarbonate−Bisphenol A base epoxy blend system, the carbonate group can react with epoxide in the presence of a tertiary amine. The transesterification reactions convert the original aromatic/aromatic carbonate of PC to aromatic/aliphatic and aliphatic/aliphatic carbonates. IR spectroscopy shows an unknown major structure formed during the later stages of the transesterification reaction. The unknown structure was investigated by a model reaction using diphenyl carbonate and phenyl glycidyl ether leading to the formation of 4-(phenoxymethyl)-1,3-dioxolan-2-one (PMD), which has been identified by IR, UV, 1H NMR, 13C NMR, and mass spectroscopy. The mechanism of forming the cyclic carbonate is proposed to proceed through a zwitterion and a nucleophile attack of the aromatic/aliphatic or the aliphatic/aliphatic carbonate group.

Effects of thermal history, crystallinity, and solvent on the transitions and relaxations in poly(bisphenol‐A carbonate)

Abstract: The following system of nomenclature for the transitions and relaxations in polycarbonate has been proposed: α = Tg = 150, β = 70, γ = −100, and δ = −220°C (frequency range of 10–50 Hz). The three component peaks of the γ relaxation are denoted by γ1, γ2, and γ3 relaxations correspond to phenylene, coupled phenylene-carbonate, and carbonate motions, respectively. Dynamic mechanical analysis of poly(bisphenol-A carbonate) using the DuPont 981–990 DMA system shows that the magnitude of the β relaxation depends upon the thermal history of the polycarbonate; annealing greatly reduces the intensity of the β relaxation. A relaxation map constructed for the β relaxation gives an activation energy of 46 kcal/mol. Exposure of polycarbonate to methylene chloride vapor for various times shows that after an induction period of about 5 min the intensity of the γ3 relaxation at −78°C decreases whereas the intensity of the γ1 relaxation of −30°C is unaffected and the ratio E″(γ1)/E″(γ3) increases linearly with the square root of time. This has been ascribed to the interaction of methylene chloride on the carbonate group in polycarbonate. Thermal crystallization of polycarbonate does not affect the positions of the γ relaxation and the glass transition peaks, but merely reduces their intensity. The glass transition peak intensity falls off sharply in comparison to the γ relaxation intensity. Both the γ3 and γ1 peaks in polycarbonate have been observed simultaneously for the first time by dynamic mechanical analysis. Impact strength measurements show that methylene chloride treatment of polycarbonate results in a change in mode of failure from ductile to brittle with a resultant 40-fold reduction in impact energy for fracture. Thermally crystallized polycarbonate exhibits brittle fracture with very low force and energy at break.

Method of polycarbonate preparation by solid state polymerization

Abstract: Solid state polymerization of partially crystalline polycarbonate oligomers bearing ester-substituted terminal groups occurs at useful reaction rates despite their high level of endcapping. Partially crystalline polycarbonate oligomers having ester substituted terminal groups may be obtained in a single step by reaction of an ester substituted diaryl carbonate such as bis-methyl salicyl carbonate with a dihydroxy aromatic compound such as bisphenol A in the presence of a transesterification catalyst such as sodium hydroxide. Alternatively, amorphous oligomeric polycarbonates incorporating ester-substituted end groups may be obtained through careful control of the melt reaction conditions. The amorphous oligomeric polycarbonates are crystallized upon exposure to solvent vapor and subsequently undergo solid state polymerization at synthetically useful reaction rates.