I've performed surface treatment on PVDF membrane and made it hydrophilic successfully. Now, i am looking for the effect of surfactant on its surface. While comparing FTIR of treated and untreated PVDF membrane, only one extra peak (weak intensity) is observed at around 2870cm-1. In the IR chart, it corresponds to -OH of carboxylic acid, but i am wondering, there are no other extra peaks observed. How can i confirm it?
Please show me your data and plot to me in physical metallurgy lab in mse iitk. after that I will conclude things accordingly. Mostly -OH peak of carboxylic group should be very broad in IR spectra.
Mr. Mehta,
Generally, there is possible to observe nOH of -COOH in the discussed region, even up to 2380 cm-1 such as, for example, the shown as attachment solid-state IR-spectrum of citric acid. However for COOH, in solid-state we are speaking about nOH, in a context of Fermi resonance multiple broad band, which is an effect of interaction of n(C=O)OH...O=C(OH) and d(C=O)OH...O=C(OH). So that such as frequency is a sub-maximum, in fact, not isolated nOH mode. Because of free nOH is usually observed about 3600 cm-1, while hydrogen bonded (but not in COOH) about 3300 cm-1.
In this respect if you have such as sub-maximum, this would means that you have just adsorbed dimers of COOH onto your surface, not acid/surface interactions. On the other hand you have mentioned, that you have not any other IR-modes, but those modes are usually low intensive ones, so that there is a low probability your band to originate of OH motion.
Particularly, evidencing of nOH could be obtain, conducting an isotope exchange experiment (OH/OD).
What about region 1800-1450 cm-1 region? How many IR-bands you have and where as region/s? Additional question: is your acid is mono-, di- or multiprotic?
In my opinion nu(OH) appear at higher frequency than 2870cm-1, specialy for water hydrates. But in in certain circumstances it shifts to lower wavenumbers under the H-bond formation. It is important to know what kind of substances do you have. Inorganic or organic and also to see the spectrum.
Actually i am looking for how does a surfactant (Triton X-100) make a PVDF membrane hydrophilic. Contact angle measurements have confirmed the hydrophilic behaviour of PVDF membrane after treatment. Now i want to know, what exactly is going on surface of PVDF. I was expecting it to be attachment of hydroxyl groups. But there is no broad peak observed in the range of 3000-3500 cm-1 in FTIR. and there is one extra peak (of small intensity) observed at 2870 along with peaks of symmetric and asymmetric stretching of CH2 at 3022 and 2981 cm-1. what can be the reason for this?i am also attaching here FTIR spectra.
Or suggest if there is any other way to characterize such surface treatment?
In the range 2800-2900cm-1 appear -CH2 and CH groups and other association by H -bond,but no OH group.
This peak of 2870 is also observed in my sample but I m not able to identify it
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