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2D Correlation Analysis of Spin-Coated Films of Biodegradable P(HB-co-HHx)/PEG Blends
김민경,Isao Noda,류수연,정영미 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.11
We investigated thermal behavior of spin-coated films of P(HB-co-HHx)/PEG blends by using infraredreflection absorption (IRRAS) spectroscopy and 2D correlation spectroscopy. Based on 2D IRRAS correlation spectra, we could determine the sequence of spectral intensity changes with increasing temperature that PEG band changes first and then a band for crystalline component of P(HB-co-HHx) changes before a band for amorphous component. The intensities of bands for PEG and amorphous P(HB-co-HHx) were changed greatly as PEG weigh % of P(HB-co-HHx)/PEG blends increased. Transition temperatures of P(HB-co-HHx)/PEG blends were successfully determined by 2D gradient mapping method. The transition temperature of spincoated films of 98/2 and 90/10 P(HB-co-HHx)/PEG blends and 80/20 P(HB-co-HHx)/PEG blend determined by 2D gradient map are, respectively, about 137.5 and 132.5 ^oC. Furthermore, P(HB-co-HHx)/PEG blends show an additional transition temperature that have been interpreted in terms of different lamellar thicknesses in spin coated films.
Moving Window Principal Component Analysis for Detecting Positional Fluctuation of Spectral Changes
류수련,Isao Noda,정영미 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.7
In this study, we proposed a new promising idea of utilizing moving window principal component analysis (MWPCA) as a sensitive diagnostic tool to detect the presence of peak position shift. In this approach, the moving window is constructed from a small data segment along the wavenumber axis. For each window bound by a narrow wavenumber region, separate PCA analysis was applied. Simulated spectra with complex spectral feature variations were analyzed to explore the possibility of MWPCA technique. This MWPCA-based detection of the peak shift, potentially coupled with 2D correlation analysis to provide additional verification,may offer an attractive solution.
Relationship between Infrared Peak Maximum Position and Molecular Interactions
류수연,Isao Noda,정영미 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.11
We explored the interpretation of the well-accepted correlation between the apparent peak maximum position shift and extent of molecular interactions, like hydrogen bonding and dipole-dipole interactions, based on the overlapped multiple band model. The simulation of two overlapped Lorentzian bands was carried out to interpret how the maximum position of a composite peak relates to the relative contributions of two species representing the different levels of molecular interactions, i.e., free (or very weekly bound) vs. strongly bound. To demonstrate the validity of our interpretation of the origin of the peak position shift, the temperaturedependent IR spectra of ethylene glycol were also analyzed. It was found through the analysis of simulated and experimental spectra that the apparent peak shift in certain case can be safely interpreted as the measure of the strength of hydrogen bonding. The result of this study gives a new insight to interpret molecular interactions probed by vibrational spectroscopy.
Chen, Yujing,Noda, Isao,Jung, Young Mee Elsevier 2018 Journal of Molecular Structure Vol.1162 No.-
<P><B>Abstract</B></P> <P>The 3-hydroxyhexanoate (HHx) molar fraction has a great effect on the property of poly(3-hydroxybutyrate-<I>co</I>-3-hydroxyhexanoate) (PHBHx). In the present study, we investigated the influence of HHx comonomer molar fraction on the thermal property of PHBHx with 3.9 mol% (PHBHx3.9) and 13 mol% HHx (PHBHx13) comonomer content and their polyethylene glycol (PEG) blends in thin films by temperature-dependent infrared-reflection absorbance spectroscopy (IRRAS) and two-dimensional correlation (2D-COS) analysis. 2D-COS analysis demonstrated that there are two distinct amorphous bands of CO stretching of PHBHx13 during the heating process, respectively at 1752 and 1760 cm<SUP>−1</SUP>, while PHBHx3.9 only shows one amorphous band at 1756 cm<SUP>−1</SUP>. This is due to the increase of HHx content from 3.9 mol % to 13 mol % increases the amorphous state of PHBHx. Furthermore, with incorporation of 30 wt% PEG, an additional amorphous band at 1746 cm<SUP>−1</SUP> was observed in the case of 70/30 PHBHx3.9/PEG during the heating process, while this band was absent in the case of 70/30 PHBHx13/PEG, suggesting that the influence of PEG on PHBH3.9 is different from PHBHx13.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The influence of HHx content on the thermal behavior of PHBHx and its PEG blends in thin film were reported. </LI> <LI> 2DCOS analysis reveals the presence of two amorphous states in PHBHx13 while only one in PHBHx3.9. </LI> <LI> The PEG solvent effect on PHBHx3.9 is different from that on PHBHx13. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Study on melting and crystallization of PHBHx thin films using IR and 2D correlation spectroscopy
Kim Minkyoung,Noda Isao,박연주 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.1
The thermal behavior of poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHx) thin films having various molar fractions of hydroxyhexanoate (Hx) was investigated using IR, 2D gradient mapping, 2D correlation spectroscopy (2D-COS), and multivariate curve resolution (MCR) analysis. The melting and crystallization temperatures were determined using 2D gradient mapping. The 2D-COS combined with MCR analysis provided information on the unambiguous components that appeared in PHBHx thin films during the melting and crystallization processes.
Ryu, Soo Ryeon,Noda, Isao,Jung, Young Mee SAGE Publications 2010 APPLIED SPECTROSCOPY Vol.64 No.9
<P>We investigated what is really meant by so-called positional or frequency fluctuation of spectral features. To show the difference between the true frequency shift of a single band and apparent peak maximum shift caused by relative intensity changes of overlapped adjacent bands, we analyzed infrared (IR) spectra of the OH stretching band of ethylene glycol during the heating process and the C=O stretching band of acetone in a mixed solvent CHCl(3)/CCl(4) with varying solvent compositions. These spectra are well-known examples of so-called 'band shift' phenomena often interpreted as the manifestation of gradual changes in the IR frequency associated with a specific chemical bond under the influence of molecular interactions. Analyses of IR spectra showed that the apparent positional shifts of peak maxima in these systems are actually due to relative contribution changes of two overlapped bands, instead of the gradual frequency shift of a single band induced by the change in the strength of molecular interactions. To further clarify our interpretation of 'peak maximum shifts', we also analyzed simulated spectral datasets, comparing the true band frequency shift and change in the relative contributions of overlapped bands. It was found that principal component analysis (PCA) is a surprisingly sensitive tool to distinguish the two possible mechanisms of peak maximum shift. The new insight revealed by this study should help the interpretation of molecular interactions probed by vibrational spectroscopy.</P>
Ryu, Soo Ryeon,Noda, Isao,Lee, Chang-Hee,Lee, Phil Ho,Hwang, Hyonseok,Jung, Young Mee SAGE Publications 2011 APPLIED SPECTROSCOPY Vol.65 No.4
<P>In this study, we demonstrate the potentials and pitfalls of using various waterfall plots, such as conventional waterfall plots, two-dimensional (2D) gradient maps, moving window two-dimensional analysis (MW2D), perturbation-correlation moving window two-dimensional analysis (PCMW2D), and moving window principal component analysis twodimensional correlation analysis (MWPCA2D), in the detection of the existence of band position shifts. Waterfall plots of the simulated spectral datasets are compared with conventional 2D correlation spectra. Different waterfall plots give different features in differentiating the behaviors of frequency shift versus two overlapped bands. Two-dimensional correlation spectra clearly show the very characteristic cluster pattern for both band position shifts and two overlapped bands. The vivid pattern differences are readily detectable in various waterfalls plots. Various types of waterfall plots of temperature-dependent infrared (IR) spectra of ethylene glycol, which does not have the actual band shift but only two overlapped bands, and of Fourier transform infrared (FT-IR) spectra of 2 wt% acetone in a mixed solvent of CHCl(3)/CCl(4) demonstrate that waterfall plots are not able to unambiguously detect the difference between real band shift and two overlapped bands. Thus, the presence or lack of the asynchronous 2D butterfly pattern seems like the most effective diagnostic tool for band shift detection.</P>
Relationship between Infrared Peak Maximum Position and Molecular Interactions
Ryu, Soo-Ryeon,Noda, Isao,Jung, Young-Mee Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.11
We explored the interpretation of the well-accepted correlation between the apparent peak maximum position shift and extent of molecular interactions, like hydrogen bonding and dipole-dipole interactions, based on the overlapped multiple band model. The simulation of two overlapped Lorentzian bands was carried out to interpret how the maximum position of a composite peak relates to the relative contributions of two species representing the different levels of molecular interactions, i.e., free (or very weekly bound) vs. strongly bound. To demonstrate the validity of our interpretation of the origin of the peak position shift, the temperaturedependent IR spectra of ethylene glycol were also analyzed. It was found through the analysis of simulated and experimental spectra that the apparent peak shift in certain case can be safely interpreted as the measure of the strength of hydrogen bonding. The result of this study gives a new insight to interpret molecular interactions probed by vibrational spectroscopy.