Stabilization of Atactic-Polyacrylonitrile under Nitrogen and Air As Studied by Solid-State NMR

详细信息    查看全文

• 作者：Xiaoran Liu ; Wei Chen ; You-lee Hong ; Shichen Yuan ; Shigeki Kuroki ; Toshikazu Miyoshi
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：August 11, 2015
• 年：2015
• 卷：48
• 期：15
• 页码：5300-5309
• 全文大小：526K
• ISSN：1520-5835

文摘

Solid-state (ss) NMR spectroscopy was applied to study the stabilization process of 30 wt % ¹³C-labeled atactic-polyacrylonitrile (a-PAN) heat-treated at various temperatures (T_s) under nitrogen and air. Direct polarization magic-angle spinning (DP/MAS) ¹³C NMR spectra provided quantitative information about the functional groups of stabilized a-PAN. Two dimensional (2D) refocused ¹³C鈥?sup>13C INADEQUATE and ¹H鈥?sup>13C HETCOR NMR spectra gave through-bond and through-space correlations, respectively, of the complex intermediates and final structures of a-PAN stabilized at different T_s values. By comparing 1D and 2D NMR spectra, it was revealed that the stabilization process of a-PAN under nitrogen is initiated via cyclization, while the stabilization under air proceeds via dehydrogenation. Different initial processes lead to the isolated aromatic ring and ladder formation of the aromatic rings under nitrogen and air, respectively. Side reactions and intermediate structures are also discussed in detail. Through this work, the stabilization index (SI) was defined on the basis of the quantified C-1 and C-3 DP/MAS spectra. The former reached 0.87 at T_s = 370 掳C, and further higher T_s values did not affect SI; however, the latter continuously increased up to 0.66 at T_s = 450 掳C. All of the experimental results indicated that oxygen plays a vital role on the whole reaction process as well as the final products of stabilized a-PAN.