Thermodegradable polycarbonates: Effect of substituents on the degradation temperature

Abstract

Abstract:The thermal degradation process of some new polycarbonates is investigated from an experimental and theoretical point of view, in order to obtain insight into the microscopic aspects that influence the reaction mechanism and the process of thermolysis. In particular, attention is focussed on the influence of the type of substituents in the polymer chain on the degradation temperature. A series of novel polycarbonates were designed differing from each other by the groups attached at the α and β carbon atoms. Thermal behavior was characterized by thermogravimetrical analyses. The polymers undergo rapid and complete thermolysis at different degradation temperatures depending on the structure. The degradation products were separated by gas chromatography and analyzed by mass spectroscopy. The ratio of formed dienes in the product distribution depends on the heating rate. Furthermore, density functional theory calculations were performed on a series of model compound systems for the polycarbonates under study, in particular carbonate systems differing by the groups attached at the α and β carbons. The study proves that the thermal degradation route can be controlled by tailoring the polymer backbone structure. Moreover, ab initio calculations provide further insight into the microscopic ingredients that govern the degradation process and associated reaction rates.

Polymerization mechanism of trimethylene carbonate carried out with zinc(II) acetylacetonate monohydrate

“…6), a slight effect of decrease in molecular weight was found with a simultaneous increase in mass dispersion from the M w / M n value equal to 1.2 to about 1.8. This effect was most likely related to the known phenomenon of thermal degradation of aliphatic polycarbonates in the presence of more amount of active OH groups 24, 25…”

Ab Initio and Experimental Study on Thermally Degradable Polycarbonates: The Effect of Substituents on the Reaction Rates

“…A detailed description of the synthesis of the polycarbonates is reported elsewhere. 38 Three commercially available 1,4-diols were used for the polycondensation reaction (Figure 8) in order to obtain poly-carbonates with a structure similar to those of the model compounds (Figure 2). The polycarbonates are analyzed by thermogravimetric analysis (TGA).…”

Ab Initio Studies of Thermal Syn-Elimination Reactions in Carbonates: Effect of Structure on Reactivity

“…As a result of the thermal elimination reaction, monomethyl carbonate is formed in addition with an olefinic species. Experimentally, it is observed that the first product is not stable at the elevated temperature encountered during the thermolysis reaction. , At low temperatures, monomethyl carbonate will reside in a stable minimum; however, at more elevated temperatures (600−700 K), at which the product is formed, it dissociated further into methanol and carbon dioxide. It cannot be excluded that intermolecular processes occur as well.…”