Potential of two‐dimensional near‐infrared correlation spectroscopy in studies of pre‐melting behavior of nylon 12
Potential of two‐dimensional near‐infrared correlation spectroscopy in studies of pre‐melting behavior of nylon 12
复制标题
二维近红外相关光谱在尼龙 12 预熔化行为研究中的潜力
DOI：
10.1002/masy.19971190106
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
I. Noda
中科院分区：
文献类型：
--
作者：
Y. Ozaki;Yongliang Liu;I. Noda
本文综述了广义二维（2D）近红外（NR）相关光谱在尼龙12预熔行为和氢键研究中的潜力。本文还综述了作为尼龙12模型化合物的n -甲基乙酰胺（NMA）解离和氢键的二维近红外研究。在30-150°C的温度范围内，测量了尼龙12在9000-5000 cm -1区域的傅里叶变换(FT)-近红外光谱，观察到分子间或分子内结合相互作用逐渐减弱，局部阶数降低，导致尼龙12晶体最终融合。二维相关分析为尼龙12的预熔行为提供了以下结论：(i)在不同的环境下，尼龙12在6800-6100 cm -1区域至少有8个可分配给自由和氢键的NH基团。上述区域的非同步二维相关谱图表明，随着温度的升高，首先出现游离羰基氧的酰胺基团，其次是未缔合的游离酰胺基团和含游离NH的酰胺基团。（ii） 6000-5500 cm -1区域的非同步光谱表明，在更多有序组分消失之前，大量无序或解离组分开始出现，而ch2拉伸模式的第一泛音预计会出现。它们似乎是预熔前体（甚至可能是间接原因），导致尼龙12在更高温度下熔化时有序组分的急剧减少。
This review paper discusses the potential of generalized two-dimensional (2D) near-infrared (NR) correlation spectroscopy in studies of pre-melting behavior and hydrogen bonds of nylon 12. A 2D NIR study on dissociation and hydrogen bonds of N-methylacetamide (NMA) is also reviewed here as a model compound study of nylon 12. Fourier transform (FT)-NIR spectra in the region of 9000-5000 cm -1 of nylon 12 were measured over a temperature range of 30-150°C where gradual weakening of inter- or intramolecular associative interactions and decrease of local order leading to the eventual fusion of nylon 12 crystals are observed. The 2D correlation analysis provided the following conclusions for the pre-melting behavior of nylon 12. (i) There are at least eight bands in the 6800-6100 cm -1 region assignable to free- and hydrogen-bonded NH groups of nylon 12 in various environments. The asynchronous 2D correlation spectrum in the above region indicates that the amide groups with free carbonyl oxygen appear first and then the unassociated free amide and amide groups with free NH follow as the temperature is increased. (ii) The asynchronous spectrum in the 6000-5500 cm -1 region, where the first overtones of the CH 2 stretching modes are expected to appear, indicates that substantial amount of disordered or dissociated components start appearing before the disappearance of more ordered components. It seems that they appear as the pre-melting precursors (or even possibly as the indirect cause) to the precipitous decrease of the ordered components associated with melting of nylon 12 occurring at a much higher temperature.