私密直播全婐app免费大渔直播,国产av成人无码免费视频,男女同房做爰全过程高潮,国产精品自产拍在线观看

相關鏈接
聯系方式
  • 通信地址:杭州市 浙江大學玉泉校區高分子大樓421房間
  • 郵編:310027
  • 電話:0571-87953732
  • 傳真:0571-87953732
  • Email:xhzhang@zju.edu.cn
當前位置:> 首頁 > 論文著作 > 正文
An Investigation of the Selective Chain Scission at Centered Diels- Alder Mechanophore under Ultrasonication
作者:Han-Yi Duan, Yu-Xiang Wang, Li-Jun Wang, Yu-Qin Min, Xing-Hong Zhang,* and Bin-Yang Du*
關鍵字:Diels-Alder ,Mechanophore, Ultrasonication
論文來源:期刊
發表時間:2017年

ABSTRACT: It is a challenging topic to disconnect a linear polymer selectively at the mechanophore site by an external force in a “cold” fashion. In this work, the effect of the power output of ultrasonication on the selective cleavage at the centered urfuryl-maleimide Diels-Alder (DA) mechanophore of poly(methyl acrylate)s (DA-PMA-a and DA-PMA-b) were quantitatively investigated by comparative study on experimental and simulated chain scission kinetics as well as high-resolution 1H NMR spectroscopy (600 MHz). At low power output of the ultrasonication (2.10 W), DA-PMA-a with Mn of ca. 2Mlim (Mlim, below which no further chain scission was observed) presented a DI (degradation index)-t (sonication time) plot with a turnover point at ca. 1.0 and no clear variation of the molecular weight after the turnover, which met well with the calculated center cleavage mode. At 5.52 W, DA-PMA-a and a poly(methyl acrylate) that contained two centered ester bonds (ester-PMA) presented similar DI-t plots with turnover points less than 1.0 within same sonication times, while poly(methyl acrylate) with fully carbon-carbon chain (PMA) had a turnover at DI value of ca. 0.5. By way of contrast, high power output of the ultrasonication (5.52 W) caused a possible cleavage of ester bonds of DA-PMA-a, which would mask the selective cleavage at the DA site. High-resolution 1H NMR result of DA-PMA-b (115.8 kDa, Mn was slightly higher than 2Mlim) showed that DA conversions were up to 55% under 2.10 W and 38% under 5.52 W. The kinetics from GPC traces and 1H NMR results of DA-PMA-b as well as 1H NMR results of DA-PMA-c (68.4 kDa, Mn was slightly higher than Mlim) under sonication confirmed the observation that low power output favored selective chain scission at DA site. The turnover point in the DI-t plot might be used as characteristic parameter to gauge the selective chain scission at mechanophore site for single mechanophore-centered polymers.


主站蜘蛛池模板: 固原市| 株洲市| 浑源县| 左云县| 柳州市| 泽州县| 永泰县| 名山县| 辽中县| 万宁市| 萨嘎县| 连山| 黄浦区| 吉隆县| 安宁市| 定日县| 黔西县| 牟定县| 浪卡子县| 名山县| 信丰县| 河曲县| 湖州市| 正镶白旗| 房产| 独山县| 厦门市| 托里县| 大埔县| 大田县| 中卫市| 安福县| 内丘县| 梓潼县| 定远县| 崇礼县| 桂平市| 长海县| 彭州市| 蛟河市| 隆子县|