Liu Dongsheng

A novel self-assembled NLO structurally controlled polymer film

Abstract A novel self-assembled NLO (Nonlinear Optical) polymer film constructed from a structurally controlled, cage-like crosslinking polymer (SCCP) and chromophore NPP((S)-(−)-1-(4)-Nitrophenyl-2-pyrro-lidinemethanol) embedded in SCCP has been prepared by “sol-gel process”. The cage size of SCCP was designed according to the molecular size of NPP so that each cage could trap one NPP molecule. The film is uniform and transparent when the molar ratio of chromophore/organosilicon spacer was 1:1 without any phase separation. Its χ(2) (coefficient of second harmonic generation) is 3.0×10−8e.s.u. measured by IR dichroism. The structure has been investigated by AFM (atomic force microscopy), IR, solubility test. The result indicated that the chromophore molecules NPP was largely trapped within the cages of the crosslinking polymers at molecular level.

MAGNETIC SUSCEPTIBILITY OF CHINESE LOESS AS A PALAEOCLIMATIC INDICATOR

Through the studies on low temperature susceptibility, frequency dependent susceptibility, isothermal remanent magnetization, low temperature magnetization and demagnetization for loess and palaeosols one can easily reveal some significant characters of rock magnetism for the magnetic minerals of ultrafine grain sizes, those are very difficult to identify by general geological methods. It is shown in the present study that both loess and palaeosols cover magnetic grain size from superparamagnetism, single domain to multidomain. Loess samples with relative high peramagnetic minerals are dominantly of thermally stable characteristics while palaeosols have relatively high percentage of superparamagnetic grain (0.01—0.03μm). The relative grain size of magnetite is always finer in palaeosol with higher susceptibility than in loess, indicating that many tiny ferri-ferromagnetic minerals formed during the process of soll formation, which has caused a higher susceptibility in palaeosols than in loess. The climatic history of Quaternary can therefore be understood in terms of the susceptibility based on Chinese loess/palaeosol sequences.