Nanostructurized polyurethanes of different structure and functionality were obtained and used for studying silver ions adsorption from aqueous medium. Formation of (Ag+)n-polymer complexes was confirmed by combination of UV-vis/FTIR spectroscopy. Silver ions capacity of polyurethanes obtained reaches 1.1-1.4•10-5 mol/g for polymers based on polyester (polyether), aromatic diisocyanate and aminefunctionalized chain extender (cross-linker). Presence of urea fragments in polymer macrochains increase Ag+ adsorption capacity of polyurethanes as well

Matyushov, V.F.

Slisenko, O.V.

Tolstov, A.L.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 4 No 2, 02NNSA09(3pp) (2015)   2304-1862/2015/4(2)02NNSA09(3) 02NNSA09-1  2015 Sumy State University Ag+ Adsorption/Complexation Behavior of Polyurethanes of Fifferent  Structure and Functionality  A.L. Tolstov*, O.V. Slisenko, V.F. Matyushov  Institute of Macromolecular Chemistry of the NAS of Ukraine, 48, Kharkivske Shose, 02160 Kyiv, Ukraine  (Received 31 May 2015; published online 27 August 2015)  Nanostructurized polyurethanes of different structure and functionality were obtained and used for studying silver ions adsorption from aqueous medium. Formation of (Ag+)n-polymer complexes was con-firmed by combination of UV-vis/FTIR spectroscopy. Silver ions capacity of polyurethanes obtained reaches 1.1-1.4•10-5 mol/g for polymers based on polyester (polyether), aromatic diisocyanate and amine-functionalized chain extender (cross-linker). Presence of urea fragments in polymer macrochains increase Ag+ adsorption capacity of polyurethanes as well.   Keywords: Polyurethanes, Silver, Composites, Thin Films, Chemical Structure, Complex.   PACS numbers: 81.05.Qk, 82.35.Np, 87.85.Rs                                                             * tolstov@nas.gov.ua 1. INTRODUCTION  Metal-containing polymer composite materials attract a great attention in science and industry. The main fields of their application are electronics, optics, medicine etc [1]. Using polyurethanes for preparation of metal-containing polymer materials is very popular because of their excellent technical and exploitation properties, high stability, biocompatibility [2]. Among variety of ap-proaches for producing of such materials the most appli-cable are introducing fine metal particles into polymer matrix or in situ formation of highly-dispersed metals in polymers [3]. According to the literature adsorption of metals in ionic form mainly uses for metals concentration or decontamination of waste water [4-5]. The very few researches report an application of adsorption technique for producing metal-containing polymer systems, mainly for medical uses [6]. At the same time the studies of structure-dependent Ag+ adsorption behavior of polyure-thanes and its effect on lyophilic properties of the metal-filled polymers were not conducted yet.  The aim of this work is determination of the features of Ag+ ions adsorption by polyurethane matrices of dif-ferent structure and functionality as well as an effect of Ag+ ions bonded by the matrix on lyophilic properties of metal-containing polyurethane.   2. EXPERIMENTAL SECTION  2.1 Materials  For preparation of polyurethanes as oligomeric diols poly(butylenes glycol adipate) (PBGA) of Mw = 800 and poly(propylene glycol) (PPG) of Mw = 1000 were used. As diisocyanate constituent the tolylene diisocyanate (TDI) (mixture of 2,4/2,6-isomers with weight ratio of 80/20) and isophorone diisocyanate (IPDI) were taken. 1,1,1-trimethylol propane (TMP), tris-(2-hydroxyethyl)amine (TEA) and 4,4’-diaminodicyclohexylmethane (DDM) were used ans cross-lonkers/chain extenders. As catalyst a dibutyltin dilaurate (DTD) was used as received. Ethyl acetate, N,N-dimethylformamide, 1,4-dioxane and dis-tilled water were used as solvents. For preparation of metal-containing polyurethanes silver nitrate of chemi-cal grade has been used as silver source.   2.2 Sample Preparation   Polyurethanes (PU) have been prepared via conven-ient polyaddition process between polyether and diisocy-anate components followed by addition of chain extender (cross-linker) at appropriate conditions. Solutions of PU were casted onto Teflon plate and film-forming and cur-ing processes were continued under moisture-free condi-tions. Polymer films obtained have a thickness of 100-150 μm. After elimination of solvent the polymers were used for silver ion adsorption experiments.   Table 1 – Composition and Ag+ adsorption behavior of PU of different structure  Code Polymer Composition Chain Extender (Cross-linker) Catalyst Ag+ capacity (10-6 mol/g) Silver  content, wt% PU-1 PBGA/TDI TMP + 7.9 0.085 PU-1a PBGA/TDI TEA - 13.8 0.150 PU-2 PPG/TDI TMP + 6.8 0.073 PU-2a PPG/TDI TEA - 10.7 0.116 PU-3 PPG/IPDI TMP + 3.6 0.039 PU-3a PPG/IPDI TEA + 8.5 0.092 PU-4 PPG/IPDI DDM - 6.1 0.066   A.L. TOLSTOV, O.V. SLISENKO, V.F.MATYUSHOV PROC. NAP 4, 02NNSA09 (2015)   02NNSA09-2 Adsorption of Ag+ ions by polyurethane films was performed by immersing the polymer film into 0.01 M aqueous solution of AgNO3 until the equilibrium state (controlled by electrochemical potential measurements) reaches. Swelled polymer films were washed by distilled water followed by drying in the dark to prevent photo-chemical reduction of ionic silver into metallic form.   2.3 Characterization  FTIR spectral analysis was performed using Bruker Tensor 37 spectrometer in the spectral range of 4000-600 cm-1 and a resolution of 0.5 cm-1. UV-vis spectra were recorded using ULAB UV-108 spectrometer in spectral region of 250-500 nm. Silver content during adsorption experiments were determined by electro-chemical potential measurements using Ionomer EL-74 equipped with both Ag+-specified and comparative elec-trodes. Moisture sorption testing was carried out in isothermal condition at 20 oC and 100 % humidity.   3. RESULTS AND DISCUSSION  Fig.1 shows FTIUR spectra of typical polyurethane before and after adsorption of Ag+ ions. PU-4 polymer could be characterized by few typical absorption bands. There are stretching vibration bands of hydrogen-bonded (H-bonded) NH groups (νNH) centered at 3325 cm-1, stretching vibrations of free and H-bonded C=O of urethane groups (νC=Oureth) with maxima at 1749 and 1716 cm-1, vibration band of H-bonded C=O of urea groups (νC=Ourea) at 1635 cm-1, deformation vibration bands of NH groups (γNH) at 1552, 1536 and 1274 cm-1, stretching vibration band of C-N (νC-N) with maxima at 1461 and 1151 cm-1,  absorption band of conjugated O–C–N bonds (νO–C–N) at 1373 cm-1, vibration band of С–О–С bonds of ether fragments with maxima at 1099 and 1089 cm-1, complex vibration band νC–O/νC–N centered at 931 cm-1, deformation vibration band of C=O groups at 786 and 771 cm-1.   Fig. 1 – FTIR spectra of neat PU-4 (1) and Ag-containing PU-4 (2).   Complexation of Ag+ ions by electron donor groups of polymer matrix initiates corresponding changes of spec-tral positions and integral intensity of νNH, νС=Оureth, νС=Оurea δNH νС–О–С bands and appearance of new vibration modes of C=O groups. At the same time redis-tribution of H-bonding network of polymer matrix was determined as well.  Fig. 2 demonstrates UV-vis spectrum of poly(urethane-urea) (PU-4) after Ag+ adsorption. Earlier studies have shown complex ionic structure of ionic sil-ver in aqueous solution [7-8]. For such systems a pres-ence of complex ionic aggregates with adsorption in UV region (Ag42+ with λ1-max at ~280 nm, Ag3+ with λ2-max at 302 nm and Ag2+ with λ3-max at 313 nm) [8]. When the adsorption process is carried out an intensity of λ1-max drops down followed by an appearance of new multi-modal band at about 350 nm. The spectral position of this band and their asymmetric structure evidences of overlapping few band attributed to metal-polymer com-plex with Ag+ coordinated by C=O groups of PU-4 (favor-ably by urea due to its high coordination activity) (λ4-max ~310 nm), ionic aggregates and clusters with atoms hav-ing different electronic state (λ5-max and λ6-max at 337 and 342 nm, correspondingly). The band of surface-initiated plasmonic resonance of larger silver nanostructures at λ > 380 nm was not observed during experiments.     Fig. 2 – UV-vis spectrum of Ag+-filled PU-4.  Analysis of complexation behavior of polyurethanes (Table 1) shown high dependence of adsorption capacity and final silver content of the polymers from their chemical structure. Introducing amine constituent into polyurethane structure increases Ag+ capacity up to 2.5 times. Moreover aromatic structure of hard domains of polyurethanes increases adsorption capacity as well. Otherwise a presence of urea fragments with high co-ordination ability to Ag+ ions in the polymer chains increases silver adsorption compared to polymer with pure urethane functionality.   4. CONCLUSION  Polyurethanes of different chemical structure (amine-/urea functionalized, linear/cross-linked) have been synthesized and applied for studying an adsorption of silver ions from aqueous medium. It was shown that    AG+ ADSORPTION/COMPLEXATION BEHAVIOR OF POLYURETHANES … PROC. NAP 4, 02NNSA09 (2015)   02NNSA09-3 urea functional fragments in a structure of polyurethane could bond Ag+ ions into metal-polymer complex that was confirmed by UV-vis and FTIR spectral data. The results of Ag+ adsorption experiments evidence of great effect of polymer functionality on silver ions capacity of polyurethane films studied. Maximum of Ag+ capacity is peculiar to polyurethanes obtained from prepolymer based on polyester (polyether) and aromatic diisocya-nate, and extended (cross-linked) by amine-containing polyol. Thus, structurization of polymers, namely polyu-rethanes at nanolevel allows to substantially increase their metal adsorption properties.   AKNOWLEDGEMENTS  The authors kindly thank colleagues of the Center for Collective Use of Instruments at the Institute of Macromolecular Chemistry of the National Academy of Sciences of Ukraine for their assistance in research.    REFERENCES  1. Metal nanoparticles: Synthesis, Characterization and Ap-plications (Eds. D.L.Feldheim, C.A. Foss) (New York: Marcel Dekker Inc.: 2002). 2. Polyurethanes: Coatings, adhesives and sealants  (Ed. U. Meier-Westhues) (Hannover: Vincentz Network GmbH & Co KG: 2007). 3. A.L. Tolstov, Theoret. Experim. Chem. 49, 347 (2013). 4. E.A. Moawed, M.A.A. Zaid, M.F. El-Shahat, Anal. Lett. 36, 405 (2003). 5. A.B. Farag, M.H. Soliman, O.S. Abdel-Rasoul, M.S. El-Shahawi, Anal. Chim. Acta 601, 218 (2007). 6. M.S. El-Shahawi, M.A. El-Sonbati, Talanta 67, 806 (2005). 7. Y. Xia, Y. Xiong, B. Lim, S.E. Skrabalak, Angew. Chem. Int. Ed. 48, 60 (2009).  8. T. Linnert, P. Mulvaney, A. Henglein, H. Weller, J. Am. Chem. Soc. 112 No12, 4657 (1990).   

Ag+ Adsorption/Complexation Behavior of Polyurethanes of Fifferent Structure and Functionality

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