Lignocresol was synthesized from Hinoki cypress (Chamaecyparis obtusa) through the phaseseparation system with pcresol and 72% sulfuric acid. Molecular responses of lignocresol for heating were observed at around 160C. These behaviors were caused by molecular rearrangement associated with the cleavages of benzyl aryl ether linkages. By the alkaline treatment under ordinary pressure at room temperature, benzyl aryl ether linkages with phenolic units are cleaved, and then low molecular lignin fractions are formed. After the alkaline treatment, thermal stability of lignocresol was improved. The glasstransition temperature (T g ) of lignocresol was shifted up by removing the low molecular weight units. The solidliquid transition temperature was also shifted. These results indicated that the low molecular weight fractions released from lignocresol work as plasticizer. Lignophenols are biobased thermo plastics, selfproviding plasticizer through molecular rearrangement under high energy condition.Key words: Lignin, Phaseseparation system, Lignophenol, Solidliquid transition
Lignin, accounting for approximately 2535% of lignocellulosics, is an aromatic network polymer. It is formed by the random radical coupling of phenylpropane type precursors, followed by the nucleophilic attack to the quinonemethides. Lignin is expected to serve as one of the alternatives to fossil resources. However, it has been difficult to utilize lignin as functional polymers, because lignin is highly sensitive to a given environment, and subjected to complicated molecular rearrangement during the isolation. Through the phaseseparation system, which was developed by Funaoka in 1988, both quantitative separation of components and selective control of the structures of lignin can be achieved [13]. Lignocellulosics are rapidly separated under ordinary pressure at room temperature: carbohydrates are swollen and partially hydrolyzed, giving watersoluble saccharides. At the same time, linkages and functional groups formed by the nucleophilic attack to the quinonemethides are selectively released, and phenol derivatives are grafted at benzyl positions in lignin. Separated lignin (lignophenol), which has 1,1bis (aryl) propane type structures, has the solidliquid transition, indicating that the structures are linear type compared with native lignins and conventional lignins.Thermal properties of biomaterials are important for utilization as industrial materials. Molecular response of lignocresol for high energy input was observed at around 160C. In the previous study, lignophenol treated with alkaline solution under ordinary pressure at room temperature showed higher thermal stability [4]. This improvement of thermal stability was probably caused by elimination of the low molecular weight lignin fractions linked at benzyl positions during alkaline treatment. Namely, it is indicated that the formation of low molecular weight units could be dominating molecular response for high energy input to give low thermal stability. In ...
