Two-Dimensional Correlation Vibrational Spectroscopy Study on Intermolecular Interactions in Polymer Blends

用二维红外、拉曼、近红外(2D IR、2D喇曼、2D NIR)相关光谱和异2D相关光谱研究了无规聚苯乙烯(PS)和聚(2，6-二甲基-1，4-苯基醚)(PPE)等聚合物共混物的构象变化和特殊相互作用，发现二维振动相关谱能很好地探测一维光谱中难以识别的谱带。2D同步相关分析分离了PS和PPE的近红外光谱谱带，2D异步相关分析产生了指示共混物中特定相互作用或构象变化的交叉峰。二维相关分析表明，PS和PPE中的苯环以及PPE中的CH3基团对共混物的形成起着重要的作用。所研究的10种PMMA/PVPh共混物的PVPh含量从1%到10%不等。首先用2D异质关联光谱分离了少量PVPh的弱振动带和主PMMA的强振动带，然后检测了PMMA和PVPh之间的分子间相互作用。拉曼-近红外光谱异相关分析表明，PVPh氢键羟基在6764和4637 cm~(-1)处有两个谱带，PMMA氢键羰基在5052 cm_(-1)~(-1)处有一个谱带，所有这些谱带都不能从一维光谱中识别出来。

Two-dimensional infrared, Raman, near-infrared (2D IR, 2D Raman, 2D NIR) correlation spectroscopy and hetero 2D correlation spectroscopy have been applied to the studies of the conformational changes and specific interactions in various polymer blends such as those of atactic polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene ether)(PPE), It was found that 2D vibrational correlation spectroscopy is powerful in detecting bands which are not readily identified in onedimensional spectra. The 2D synchronous correlation analysis separates the NIR bands of PS from those of PPE.The 2D asynchronous correlation analysis produces cross peaks that are indicative of the specific interaction or the conformational change in the blends. It is concluded from the 2D correlation analysis that not only the phenyl rings of PS and PPE but also the CH_3 groups of PPE play important roles in the formation of the blends.The 2D Raman-NIR heterospectral correlation spectroscopy was employed to investigate intermolecular interactions in the blends of poly(methyl methacrylate) (PMMA) and poly(4-vinyiphenol) (PVPh). Ten blends of PMMA/PVPh studied contained small PVPh contents from 1 to10 weight percentages. 2D hetero correlation spectroscopy was first applied to separate the weak vibrational bands of the minority PVPh from the strong bands of the principal PMMA, and then to detect the intermolecular interactions between PMMA and PVPh. The Raman-NIR hetero-correlation analysis detects two bands at 6764 and 4637 cm_<-1> for the hydrogen-bonded hydroxyl group of PVPh, and one band at 5052 cm_<-1> for the hydrogen-bonded carbonyl group of PMMA.All these bands are not identifiable from the one-dimensional spectra.