Recent trends and developments in pyrolysis-gas chromatography: review

Pyrolysis-gas chromatography (Py-GC) has become well established as a simple, quick and reliable analytical technique for a range of applications including the analysis of polymeric materials. Recent developments in Py-GC technology and instrumentation include laser pyrolysis and non-discriminating pyrolysis. Progress has also been made in the detection of low level polymer additives with the use of novel Py-GC devices. Furthermore, it has been predicted that future advances in separation technology such as the use of comprehensive two-dimensional gas chromatography will further enhance the analytical scope of Py-GC

Energy absorption of variable stiffness composite thin-walled tubes on axial impacting

In order to realize the engineering application of automated fiber placement for composite laminates, a method of the variable angle fiber placement was proposed to design the tube structures of variable stiffness composites based on the quadratic Bezier curve. The axial crushing responses were simulated to investigate the energy absorption characteristics of composite tubes. The results showed that the method of the variable angle fiber placement contributed to the improvement of the energy absorption effects. The maximum crushing force efficiency of the variable stiffness composite thin-walled tubes designed by the method was 49.04% which was 106.48% higher than the constant stiffness composite tube. The results could be helpful for the process of automated fiber placement and the design of the energy absorption for composite thin-walled structures

Solid-State Self-Assembly of Heteroditopic Copillar[5]arenes

Self-assembly is a fundamental bottom-up tool for the construction of living or synthetic materials. Owing to the specific, definite, and directional host–guest interactions, heteroditopic monomers has become one of the classic models as building blocks in self-assembly investigation. Driven by the unique multiple CH···π interactions between the pillar[5]arene cavity and the linear n-alkyl group, copillar[5]arenes have become one of the simplest and optimal models for the construction of heteroditopic monomers in recent years. Here, by comparison of the reported crystal structures of heteroditopic copillar[5]arenes with six new ones (P6Br, P8Br, P6Im, P10Im, P4 ⊃ acetonnitrile, and P8Br ⊃ succinonitrile), we found that their self-assembly manner in the solid state was primarily decided by the competition of the pillar[5]arene cavity between the threading guest moiety and the solvent molecules (or external competitors). When the competitor had much higher affinity to the pillar[5]arene cavity, a traditional host–guest complex would be formed in the solid state. When the threading guest moiety showed much higher affinity, [cn]daisy chains (normally [c2]) would be formed. It was further found that only when they had similar bonding abilities with the pillar[5]arene cavity, [an]daisy chains could be formed in the solid state