化學

化學

來源出版物：Chinese Journal of Chemistry，2014，32（12）: 1245-1250聯(lián)系郵箱：Qiang Liu，Liuqiang@lzu.edu.cn

封面介紹：Polymer brushes on flat surfaces are known for their excellent self-lubricating and tribological properties，however，there is a lack of detailed information about the polymer chain conformation changes during sliding，and a comprehensive understanding of the correlation between the chain conformation and the lubrication behavior，the related problems will be addressed in this paper.

Correlation between Conformation Change of Polyelectrolyte Brushes and Lubrication

Bin Li，Bo Yu，Xiao-long Wang，et al.

Abstract： We directly monitor the absolute separation profiles that function as film thickness between a single glass disk and the charged polyelectrolyte brushes decorated steel slider in water using a home-made slider-on-disk apparatus，which reflects the structural conformation variations and interactions of polymer brushes under externally applied pressure，in addition to probing the relative variation of friction forces under different applied loads and sliding velocities. We find that the polyelectrolyte brushes modified surfaces can sustain high pressure and have extremely low friction coefficients（around 0.006 at pressures of 0.13 MPa； 0.5-0.6 without brushes）. The water-lubrication characteristics are correlated to the structural conformation changes of the polyelectrolyte brushes that are mainly governed by electrostatic interactions and the osmotic pressure of counterions inside the polymer chains，which can be used to support and distribute the normal pressure. The apparent thickness of the brush decreases with the increase of loading forces，an increase in the ionic strength causes the polymer chains collapse，and the friction forces increase. This fundamental research is of great importance to understand the mechanical and structural properties of polyelectrolyte brushes and their influences on the tribological behaviors，and helps to design friction/lubrication-controlled surface/interface by taking advantage of polyelectrolyte brushes.

Keywords： Polyelectrolyte brush； Lubrication； Conformation； Electrolyte；

來源出版物：Chinese Journal of Polymer Science，2015，33（1）: 163-172聯(lián)系郵箱：Bo Yu，yubo@licp.cas.cn

封面介紹：The cover picture shows an impression of industrial preparation of aromatized Nimodipine by sunlight and air on the arid lands. Visible light is most strongly emitted in the solar spectrum on the surface of the earth. Now Qiang Liu and co-workers develop a metal-free and visible-light driven aerobic aromatization catalyzed by organic dye eosin Y bis（tetrabutyl ammonium salt）（TBA-eosinY）. With the aid of K2CO3，the aerobic catalytic system converts 1，4-dihydropyridines such as Nimodipine to their corresponding pyridine derivatives efficiently under visible light irradiation at room temperature. More details are discussed in the article by Liu et al. on page 1245-1250.

Metal-Free-Mediated Oxidation Aromatization of 1,4-Dihydropyridines to Pyridines Using Visible Light and Air

Xiaojing Wei，Lin Wang，Wenliang Jia，et al.

A metal-free and environmentally friendly aerobic aromatization photosensitized by organic dye eosin Y bis（tetrabutyl ammonium salt）（TBA-eosinY）has been developed. With the aid of K2CO3，the aerobic catalytic system converts 1，4-dihydropyridines to their corresponding pyridine derivatives efficiently under visible light irradiation（λ=450 nm）at room temperature.

visible light irradiation； eosin Y； molecular oxygen； aromatization； photooxidation