Fourier Transform Infrared Study on the State of Water Sorbed to Poly(ethylene glycol) Films

Abstract

The state of sorbed water and sorption processes of water in poly(ethylene glycol) (PEG) films were studied by Fourier transform infrared. From the assignment and time evolution of the components of the O-H stretching band, the adsorption and penetration of water into the films are considered to proceed as follows: (1) At the polymer surface, a water molecule binds to the oxygen atoms of PEG with one of its hydrogen atoms ("binding water"). The same phenomenon more gradually occurs in the polymer matrix too. (2) The water binding to the oxygen atoms of PEG molecules with both of its hydrogen atoms ("bridging water") is formed from the binding water, while a dimeric water is gradually formed by the association of the free water molecule with the binding water. (3) The amount of monomeric species (both binding water and bridging water) is equilibrated. (4) The water dimer is further formed by the association of the free water molecule with the binding water, and finally the amount of the dimer is equilibrated. When the molecular weight of PEG was small, a new band at 3400 cm -1 gradually appeared. This band could be attributed to the O-H stretching of water molecules attaching to hydroxyl groups at the end of PEG molecules. An ab initio molecular orbital calculation and hybrid density functional method supported the assignment of the peaks. Experimental SectionMaterials. PEGs [viscosity-averaged molecular weight (Mv) ) 1.1 × 10 4 (11K), 1.5 × 10 4 (15K), 2.8 × 10 4 (28K), 4.9 × 10 4 (49K), and 6 × 10 4 (60K)] and PEG-DME [Mw ) 2.1 × 10 3 (2.1K)] from Aldrich, Milwaukee, WI, were purified by precipitation in ethanol-diethyl ether. Poly(methyl methacrylate) (PMMA; atactic, Mv ) 1.23 × 10 5 ) from Wako Pure Chemicals, Osaka, Japan, was used without further purification. Poly(2-hydroxyethyl methacrylate) (PHEMA; Mv ) 6.4 × 10 4 ) was prepared by the conventional radical polymerization of 2-hydroxyethyl methacrylate (HEMA; purified by distillation in vacuo) in methanol at 65 °C for 24 h using 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator (molar ratio of HEMA and AIBN, 100:1) and subsequent precipitation from diethyl ether. Polyethylene film (PE; low-density polyethylene; thickness, 10 µm) from Ohji Special Carton Co., Tokyo, Japan, was used without further purification. The Mv values of PEG, PMMA, and PHEMA were determined by using an Ubbelohde dilution-type viscometer (type 0B; Kusano,

In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films

“…To verify this idea, the PEG sample presented above is exposed to hydrogen gas in a vacuum chamber prior to optical SPR experiments. The hydrogen atoms form bonds with the ether oxygen atoms of the PEG chains [10]. Therefore, fewer ether oxygen atoms are available for the water molecules to make hydrogen bonding during the exposition of water vapour.…”

The interaction between poly(vinylpyrrolidone) and reversed micelles of water/AOT/ n -heptane

“…The hydroxyl of the water in the reversed micelle systems can be resolved by the FTIR spectrum [12,13,36,37].…”

The Structure of Water Sorbed to Polymethoxyethylacrylate Film as Examined by FT–IR Spectroscopy

“…However, only a limited number of 1 Presented at the 49th Polymer Symposium of the Society of Polymer Science, Japan, at Sendai, Japan, in October 2000. 2 To whom correspondence should be addressed. 3 Present address: Molecular Device Laboratory, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.…”

“…We have been studying the state of water sorbed to polyethylene glycol films by using the transmission and the attenuated total reflection (ATR) infrared spectroscopies (1,2). Moreover, using an in-situ difference IR spectroscopic method, sorbing processes of water to the PEG films at an early stage has been examined (1,2).…”