Chiral

This paper summarizes research work related to materials with zero, or negative Poisson's ratio, materials which are also referred to as auxetic materials. This review puts an emphasis on computations and aspects of their mechanics. It also considers diverse examples: from large structural, to biomedical applications. It is concluded that auxetic materials are technologically and theoretically important. While the development of the research has been dominated by periodic/ordered microstructures, the author predicts that future research will be in the direction of disordered microstructures utilizing the homogenization method.

Two fully fluorinated polymers, poly(tetrafluoroethylene) (PTFE) membranes and poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films, were modified by graft copolymerization with monoacryloxyethyl phosphate (MAEP) in an aqueous solution at ambient temperature using gamma irradiation. The modified membranes were characterized by XPS, FTIR, and phosphate analysis. A correlation between peak heights in the FTIR PAS spectra and the overall grafting yield was found. Neither the surface coverage (as obtained from XPS multiplex scans) nor the overall grafting yield (as obtained from phosphate analysis) showed simple correlations on the monomer concentrations (20–40%) or the irradiation doses (25–150 kGy) within the ranges investigated. Similar surface coverage was achieved on the PTFE membranes and on the FEP films. In contrast, the overall grafting yields were significantly higher for the PTFE membranes than for the FEP films. The high porosity of the PTFE membranes is the most likely explanation for these differences in grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2550–2556, 2002

Abstract A series of “Y-shaped” chromophores containing two chiral prolinol-substituted furans or thiophenes as the donor segment, and one pyran derivative with different electron-withdrawing groups as the acceptor moiety has been synthesized. The high hyperpolarizabilities ( μβ , μβ 0 ) and decomposition temperatures ( T d ) of these chromophores have also been demonstrated.