The Interaction Of Water-soluble Polymers And Surfactants ~ 1h Nmr Study

In this paper, we studied water-soluble polymers (PVP and PVA)-three differentkinds of surfactants systems by relaxation time and self-diffusion coefficientmeasurements and 2D NOESY. Interactions between polymers and surfactants wereextensively discussed.In PVP/SDS system, T₂ arid self-diffusion coefficient of SDS protons decreaseapparently when the concentration of SDS reaches 2.5 mM. T₂ of PVP protons alsodecrease apparently when the concentration of SDS reaches 2.5 mM. In the 2DNOESY spectrum of the solution containing 2 g/L PVP and 2.5 mM SDS, theappearance of the cross peaks between remote SDS protons indicates the micellizationof SDS. The appearance of the cross peaks between PVP protons and SDS protonsindicates that polymer chains reside in the interior of the micelles. That is to say, theCMC of SDS decreases from 8.7 mM to 2.5 mM and PVP molecules are solubulizedinto SDS micelles.In PVP/TX-100 system, T₂～C_TX-100 curves of TX-100 protons have turningpoints at the concentration equal to 0.6 CMC. In the 2D NOESY spectrum of thesolution containing 2 g/L PVP and 0.6 CMC TX-100, the appearance of the crosspeaks between remote TX-100 protons indicates the micellization of TX-100. So thepresence of 2 g/L PVP causes the decrease of the CMC of TX-100. The measurementsof the relaxation times of water protons show that the adding of 2 g/L PVP to 10 CMCTX-100 solution causes the increase of T₁ of water protons and the decrease of T₂.This indicates that the presence of 2 g/L PVP makes the motion of water moleculesmore restricted, reflecting the contraction of the loose hydrophilic layer of the TX-100micelle. Calculated inter-proton distances from the intensities of the cross peaks in 2DNOESY spectrum support this conclusion.In PVP/CTAB system, the interaction is hardly detected. We can conclude thatPVP interacts with anionic surfactant strongly, while interactions of PVP withnonionic or cationic surfactants are weak or non-existent.PVA/SDS and PVA/TX-100 systems are also studied. The interaction is hardlydetected between PVA and the two kinds of surfactants. The mechanism ofinteractions between polymers and surfactants is considered to be hydrophobic effect.So the hydrophilic character of PVA prevents its binding to surfactant micelles.