Polymer–water interactions. Origin of perturbed infrared intensities of water in polymeric systems (original) (raw)
Related papers
2006
ATR FTIR and Raman spectra of polymers containing amide groups in the main chain and in the side chain and of the amide low-molecularweight model compounds in water media were measured. The hydrophobic and hydrophilic interactions of the dissolved compounds with the neighboring water molecules are reflected in the wavenumbers of the CH 3 stretching and of the Amide I and II vibrations. The possibility of the existence of b-sheet-like structures in polypeptides surrounded by water molecules is also discussed.
Water Interactions with Crystalline Polymers with Large Dipoles
Zeitschrift für Physikalische Chemie, 2008
We compare the interactions of water with the ferroelectric copolymer poly(vinylidene fluoride (PVDF)trifluoroethylene (TrFE)) and poly(methylvinylidenecyanide) (PMCV), a strongly dipole ordered polymer. At the microscopic scale, dipole interactions matter and affect the surface chemistry at these polymer surfaces, as does lattice strain caused by water absorption. Light polarization dependent photo-assisted thermal desorption helps demonstrate that water desorption from surface and bulk can be influenced by the formation of electronic metastable states. Changes in local dipole orientation and the formation of long lived metastable states affect the strength of the coupling between the dipoles of water molecules and the dipoles of the copolymer poly(vinylidene fluoridetrifluoroethylene) but these effects were not observed for poly(methylvinylidenecyanide).
The Journal of Physical Chemistry B, 1998
We report a systematic FTIR study of the perturbation of water "sorbed" into the polymers PET and PVC as a function of crystallinity (PET) or plasticizer content (PVC). Band shapes of the composite ν(OH) band of H 2 O obtained by the ATR technique have been fitted to individual components,corresponding to those recently found for pure water itself. A detailed quantitative analysis of the frequency shifts and relative intensties has led to conclusion that these component bands show direct evidence for the breaking of the water network in the polymer matrix and that this process depends on the polymer chemical and/or physical properties. Evidence is also found for interactions of water with the polymer at the lower end of the hydrogen bond interaction scale. The component band relative intensities (compared with those of pure water) have been used to compute an intensity enhancement parameter, P, which is a measure of the perturbation of a particular water distribution due to dissolution in the polymer matrix. For PET, P varies systematically with density, reflecting the ability of water to penetrate the polymer microstructure. For PVC the plasticizer content (and hence T g) has a considerable influence on the sorption (and swelling) process and on the equilibrium content and state of water. Thus, ATR-FTIR has been used for the first time to demonstrate,via intensity enhancement, the extent of electronic perturbation at a polymer/water interface.
Chemical Physics Letters, 2001
We used infrared-visible sum-frequency generation spectroscopy to investigate the vibrational properties of the water/poly(ethylene glycol) interface in the 2800±3800 cm À1 spectral range. The vibrational ®ngerprint of the interface diers signi®cantly from the one associated with the air/poly(ethylene glycol) interface. It is shown that the poly(ethylene glycol) molecular arrangement, originally relatively well-ordered, becomes disorganised in the presence of water. Moreover, a new OH band is identi®ed demonstrating the strong interaction of water with the polymer. Ó
Water--Polymer Interaction during Water Uptake
Macromolecules, 2011
Water uptake by multilayer films plays an important role in their performance. Individual layers may consist of different polymeric phases. Understanding the water uptake in such systems requires knowledge of the water distribution, its state in the polymer, and influence on the polymeric phases. This study illustrates the application of high-resolution NMR and relaxometry for measuring water distributions and evaluating waterÀpolymer interactions. We studied water uptake in a two-layered base coat/top coat system, where the base coat consisted of acrylic, polyurethane, pigment particles, and a polymeric dispersant. Water and the polymer phases in the base coat were identified with NMR relaxometry. The water diffusivity in the base coat was determined. At high water contents water is highly mobile and is loosely bonded to the polymer. Reversible plasticization of the dispersant was observed. The polymeric dispersant seems to play a key role in the sorption of water by the coating.
Controlling wettability by light: illuminating the molecular mechanism
European Physical Journal E, 2003
The functionalisation of a surface with an organic monolayer containing photoactive moieties such as the azobenzene chromophore opens an elegant route for controlling its wettability by light. In this paper we investigate the microscopic origin of the macroscopic change in wettability upon photoinduced cis-trans isomerization of a copolymeric diphenyl-diazene Langmuir-Blodgett monolayer. Polarised UV-Vis and FTIR spectroscopy have been used to monitor the orientational order of various functional groups, Atomic Force Microscopy and Imaging Ellipsometry is employed for the quantification of the surface roughness and morphology, contact angle and surface potential measurements are carried out for a characterisation of the polar ordering. The data analysis is further supported by semi-empirical and ab-initio calculations of the molecular dipole moments and the normal IR-modes of the fluorinated chromophore. The combination of all these techniques provides a detailed molecular picture. The data suggest that changes in the projection of the dipole moment onto the surface normal caused by isomerization of the azobenzene are responsible for the observed changes in the surface energy. This knowledge allowed us to predict guidelines for the synthesis of molecules in order to maximize the wetting contrast upon photo-irradiation.
Local Structure and Dynamics of Water Absorbed in Poly(ether imide): A Hydrogen Bonding Anatomy
The journal of physical chemistry. B, 2017
Hydrogen bonding (HB) interactions play a major role in determining the behavior of macromolecular systems absorbing water. In fact, functional and structural properties of polymer-water mixtures are affected by the amount and type of these interactions. This contribution aims at a molecular level understanding of the interactional scenario for the technologically relevant case of the poly(ether imide)-water system. The problem has been tackled by combining different experimental and theoretical approaches which, taken together, provide a comprehensive physical picture. Relevant experimental data were gathered by in situ FTIR spectroscopy, while molecular dynamics (MD) and statistical thermodynamics approaches were used as modeling theoretical tools. It was found that, among the possible configurations, some are strongly prevailing. In particular, water molecules preferentially establish water bridges with two carbonyl groups of the same PEI repeating unit. Water self-interactions w...
Effects of water adsorption in hydrophilic polymers
The origin of the adsorption-induced phenomena in hydrophilic polymers, such as cellulose, lies at the atomistic scale. We use molecular dynamic simulations to investigate the mechanisms by which the adsorbing polymers change their properties upon water adsorption. Despite of their limited spacial and temporal capabilities MD simulations are able to reproduce the hygroscopic swelling and moisture softening effects in several natural polymeric systems, such as crystalline and amorphous cellulose, hemicellulose, or lignin. The revealed picture of adsorption shows a complex dependency between system porosity, water concentration, chemical potential and number of hydrogen bonds. Clear correlation between the number of hydrogen bonds, porosity and mechanical moduli implies that the dynamics of hydrogen bonds is an underlying mechanism of the adsorption process in hydrophilic polymers. The adsorbed water molecules, attracted by sorption sites tend to break the hydrogen bonds between the polymer residues that are responsible for the mechanical stability of the system. As a result, the number of hydrogen bonds decreases with water concentration which causes a substantial decrease in elastic modulus. This plasticization effect causes the polymer matrix to yield under swelling pressure exerted by the water molecules clustered in the nanopores under higher-than-bulk density. Thus, as the adsorbed amount increases, the pore structure of the polymer evolves in such a way that the average pore size increases and the pores merge. The evolution of the pores topology makes that the diffusion of water changes non-linearly with water content. Highlighting the central role of hydrogen bonds in adsorption process helps understanding the concept of hydrophilicity in polymers and enables further research in a more application-oriented direction, e.g. wood industry, moisture sensors/actuators.
Vibrational spectroscopy of liquid polymer films adsorbed on gold surfaces under UHV
Journal of Electron Spectroscopy and Related Phenomena, 1986
The vibrational properties of liquid perfluorinated polyethers on gold surfaces have been studied by polarization modulated Fourier transform infrared reflection-absorption spectroscopy under UHV down to the glass transition at ca. 180 K. The dependence of ihe IR spectra on temperature and sample thickness yielded information about the mobility and distribution of these very large molecules on flat and lithographically patterned surfaces. The influence of surface morphology on liquid film thickness, surface diffusion, and molecular configurations is discussed.
Preferential adsorption in polymer/solvent-1 /solvent-2 solutions by infrared spectroscopy
British Polymer Journal, 1990
IR spectroscopy is shown to be a suitable technique for preferential adsorption studies in the following solvent-I/solvent-2/polynier systems: poly( Nvinylcarbazole) and polyacenaphthene in nitrobenzene/dioxane, nitrobenzene/ tetrahydrofuran, and nitrobenzene/cyclohexanone. Values of the prcfercntial adsorption parameters derived from the Schultz-Flory theory agree with those from IR when both solvents in the ternary system are considered to be good solvents for the polymer. In the systems studied, the relative adsorptions of solvent-1 and solvent-2 by the polymer depend on the solvent mixture composition. The number of adsorbed molecules and their performance are correlated with the ternary interaction parameters, x , ,~, and the Mark-Houwink-Sakurada exponent, a'. The adsorption changes observed are greater in those systems in which tetrahydrofuran was present.