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United States Department of Agriculture

Agricultural Research Service

Title: Infrared Spectroscopy Method Reveals Hydrogen Bonding and Intermolecular Interaction Between Components in Polymer Blends

Authors
item Gordon, Sherald
item Cao, Xingxiang - BRADLEY UNIVER. CHEM. DEP
item Mohamed, Abdellatif
item Willett, Julious

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2004
Publication Date: May 13, 2005
Citation: Gordon, S.H., Cao, X., Mohamed, A., Willett, J.L. 2005. Infrared spectroscopy method reveals hydrogen bonding and intermolecular interaction between components in polymer blends. Journal of Applied Polymer Science. 97(3):813-821.

Interpretive Summary: An infrared spectroscopy method was devised to uncover evidence of hydrogen bonding and intermolecular interaction between components in solid poly (lactic acid) (PLA) and poly (hydroxyester ether) (PHEE) blends. The method mathematically extracts fitted curves from infrared spectra of the polymer blends and compares them with similarly extracted spectra of mixtures of the physically separated polymers. Infrared spectra of polymer blends, where hydrogen bonding exists, differ from spectra of physical mixtures of the polymers. Curve fitting spectra of the blends into their underlying peaks revealed theoretically expected differences between hydrogen-bonded and non-hydrogen bonded components, and gave estimates of the extent of interaction between PLA and PHEE. The method is superior to conventional spectral subtraction and it should be applicable to intimate mixtures or solid solutions in general. This new method will enable researchers to obtain fundamental knowledge needed to tailor polymer blends for end-uses such as starch-based adhesives, films, and biodegradable composites for plastics applications.

Technical Abstract: An infrared spectroscopy method was devised to uncover evidence of hydrogen bonding and intermolecular interaction between components in solid poly(lactic acid) (PHA) and poly(hydroxyester ether) (PHEE) blends. The methods compares Gaussian/Lorentzian deconvoluted infrared spectra of the polymer blends with deconvoluted spectra of weight ratio-equivalent mixtures of the physically separated polymers. Infrared spectra of polymer blends, where hydrogen bonding exists, differ from spectra of physical mixtures of the polymers. Deconvoluting spectra of the blends into their underlying peaks revealed theoretically expected differences between hydrogen-bonded and non-hydrogen bonded components. The findings are supported by differential scanning calorimetry, scanning electron microscopy and mechanical rheometry studies. Comparative spectral deconvolution afforded a quantitative estimate of the extent of hydrogen bonding between PLA and PHEE, and could therefore be used to measure the degree of interaction between components in thermoplastic blends. This technique is superior to conventional spectral subtraction using Beer's law and it should be applicable to intimate mixtures or solid solutions in general.

Last Modified: 10/1/2014
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