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【期刊论文】Variable Temperature FTIR Study of Poly(ethylene-co-vinyl alcohol)-graft-poly(є-caprolactone)
武培怡, Hongjin Jiang, Peiyi Wu, * and Yuliang Yang
Biomacromolecules, Vol. 4, No.5, 2003,-0001,():
-1年11月30日
A recently developed technique, i.e., two-dimensional infrared (2D IR) correlation spectroscopy, is used to study the thermal behavior of poly(ethylene-co-vinyl alcohol)-graft-poly(-caprolactone), a new synthesized highly grafted copolymer. The use of the 2D IR approach to analyze temperature-dependent spectra collected in situ during the temperature elevation process effectively enhanced the spectral resolution and revealed details on the hydrogen bonding and conformational change which are not easily detected in the traditional one-dimensional spectra. The sequence of the spectral changes of different OH and CH2 fundamental vibrations during heating the polymer was inferred from the signs of the asynchronous peaks. Evidence that the conformational changes of the methylene groups precede the loosening of hydrogen bonds is provided.
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武培怡, Kanyi Shen, †, ‡, Xiaohui Tian, *, Juhua Zhong, §, Jiaping Lin, Yi Shen, ‡ and Peiyi Wu*
Organometallics, Vol. 24, No.1, 2005,-0001,():
-1年11月30日
Chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring (1) or the unsubstituted aryl ring (2) have been synthesized and their UV-visible absorption spectra determined. In comparison to 2, 1 causes a subtle blue shift in the metal-to-ligand charge-transfer band along with spectral shape changes due to electron transfer from the NH2 substituent to the Cr(CO)3 center.
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武培怡, Yun Peng, Peiyi Wu, a) and Yuliang Yang
J. Chem. Phys., Vol. 119, No.15, 15 October 2003,-0001,():
-1年11月30日
In this study, the diffusion process of water molecules in poly(є-caprolactone) (PCL) has been investigated using in-situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. In our system, the original broad water OH bands in 1D IR spectra can be effectively differentiated into four bands, located at 3641, 3593, 3410, and 3203cm-1, respectively, using 2D correlation analysis. The bands at 3641cm-1 (antisymmetric) and 3593cm-1 (symmetric) are assigned to the OH stretching vibration of water partially hydrogen bonded with hydrophilic carbonyl group (CvO) of PCL, while the other band pair at 3410cm-1 (antisymmetric) and 3203cm-1 (symmetric) could be attributed to the stretching vibration of water fully hydrogen bonded with another water molecule. According to the result of the asynchronous correlation, it was concluded that the water molecules at first diffuse into free volume (microvoids) or are molecularly dispersed into the PCL matrix and then form hydrogen bond with the CvO group of the polymer during the process of water diffusion. In addition, the diffusion coefficient was estimated using nonlinear curve fitting of OH band areas in the range of 3800-3000cm-1.
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武培怡, Yi Shen and Peiyi Wu*
J. Phys. Chem. B, Vol. 107, No.18, 2003,-0001,():
-1年11月30日
Two-dimensional (2D) correlation ATR-FTIR spectroscopy was used to study the dynamic diffusion behavior and state of water in syndiotactic polypropylene (S-PP). The 2D asynchronous spectra of water bending band clearly reveal that there are three separate bands in the 1800-1500cm-1 region. These three bands at 1676, 1645, and 1592cm-1 are assigned, respectively, to the aggregated water with strong hydrogen bond, the aggregated water with moderate strong hydrogen bond, and the "free water". On the basis of this approach, the following mechanism for the diffusion process of water in S-PP has been proposed: the aggregated water molecules first diffuse into the polymer during the diffusion process. The water molecules with strong hydrogen bond will diffuse slower than water with moderate strong hydrogen bond because of their large size. In the late stage of the diffusion process, some aggregated water molecules in the PP matrix are forced to dissolve into the "free water" form.
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武培怡, Yi Shen, Feng'en Chen, Peiyi Wu a), Gaoquan Shi b)
J. Chem. Phys., Vol. 119, No.21, 1 December 2003,-0001,():
-1年11月30日
Raman spectra of a polythiophene film measured over a temperature range 298-98K were analyzed using generalized two-dimensional correlation spectroscopy. In the 1600-1250cm-1 region, the asynchronicity of the bands indicates the existence of different species in the investigated polythiophene sample. At least four distinct bands at 1485, 1454, 1418, and 1360cm-1 were identified. Among them, the band at 1454cm-1, attributed to the neutral species of PTh, is found to be sensitive to the temperature-induced structural changes of the polythiophene film, while the bands of the oxidized species are less sensitive to the temperature change during the cooling process.
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