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To understand the modifications of lignin in the steam explosion process (209°C, 7 min), lignin samples in native poplar (LP), steam explosion solid residue (LS) and steam explosion liquid (LL) were separated and studied. The lignin samples (LP, LS and LL) were characterized and analyzed by size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance [carbon 13 numclear magnetic resonance (13C-NMR) and heteronuclear single quantum coherence or heteronuclear single quantum correlation experiment NMR (HSQC) NMR] analysis. The results revealed that the pretreatment induced reductions in amounts of β-O-4′, β-β′, and spirodienone structure, and increases in the syringyl/guaiacyl (S/G) ratio from 1.14 (LP) to 1.70 (LS) and 1.86 (LL). The HSQC NMR spectra also gave more information about the predominance of G and S units, and only small amounts of p-hydroxyphenyl (H) units. Moreover, SEC demonstrated the depolymerization and repolymerization of lignin, which were the main reasons for the increase in the average molecular weight of LS and the decrease in average molecular weight of LL, respectively. In brief, after steam explosion treatment, the lignin structure changed, but the backbone structure was not noticeably modified.

In this paper, the different discharge and polymerizing characteristics of Ar and He atmospheric pressure plasma jets (APPJs) were studied. The as-deposited polymer of acrylic acid (PAA) on silk fibroin film (SFF) by APPJs with Ar/O 2 and He/O 2 gases is investigated with AFM, FESEM and XPS. Optical emission spectroscopy (OES) measurements indicated that various reactive radicals, such as OH and O as well as some acrylic acid (AA) particles existed in the plasma jets. AFM images showed that the He/O 2 plasma-deposited films had the most homogeneous characteristics and good water resistance properties. The cross-sections of silicon substrates obtained by FESEM showed that the deposition rates of PAA were 50 nm Á min À1 and 15 nm Á min À1 for Ar/O 2 and He/O 2 plasmas, respectively. Also, according to XPS analysis, He/O 2 plasma created a higher concentration of carboxyl groups on the deposited film than when Ar/O 2 plasma was used.

Three different low-temperature plasma-based methods for hydrophilicity improvement of polyethylene films at atmospheric pressure * Chen Guang-Liang(陈光良) a) † , Zheng Xu(郑 旭) a) , Huang Jun(黄 俊) a) , Si Xiao-Lei(司晓蕾) a) , Chen Zhi-Li(陈致力) a) , Xue Fei(薛 飞) a) , and Sylvain Massey b) a)

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