Chapter 3
Conferring Smart Behavior to Polyolefins through Blending with Organic Dyes and Metal Derivatives 1,2
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Andrea Pucci , Vincenzo Liuzzo , Giacomo Ruggeri , and Francesco Ciardelli Downloaded by MONASH UNIV on June 17, 2013 | http://pubs.acs.org Publication Date: September 29, 2005 | doi: 10.1021/bk-2005-0916.ch003
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Department of Chemistry and Industrial Chemistry, University of Pisa, Via Risorgimento 35, 56126 Pisa, Italy INSTM, Pisa Research Unit, Via Risorgimento 35, 56126 Pisa, Italy INFM, Pisa Research Unit, Via Risorgimento 35, 56126 Pisa, Italy 2
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Bis(salicylaldiminate) M(II) complexes of Nickel, Copper and Cobalt have been prepared and mixed with ultra high molecular weight polyethylene (UHMWPE) in order to prepare new composite materials with interesting dispersion and optical properties by profiting of the presence of long and linear alkyl chains connected to the ligand structure. The phase dispersion behaviour of the binary polyethylene films has been studied by scanning electron microscopy (SEM) and x-ray microanalysis, whereas the optical properties of the oriented samples have been evaluated by UV-Vis spectroscopy in linearly polarized light and discussed in terms of the anisotropy induced by the mechanical orientation of the polymer matrix. The dichroism of the d π* electronic transition of the oriented complexes can be modulated by changing the nature of the metal centre according to the different strength of the transition dipole moment.
18 In New Polymeric Materials; Korugic-Karasz, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.
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Downloaded by MONASH UNIV on June 17, 2013 | http://pubs.acs.org Publication Date: September 29, 2005 | doi: 10.1021/bk-2005-0916.ch003
Introduction Polymeric films for linear polarizer applications were generally prepared by incorporating into oriented polymer matrices highly conjugated low molecular weight organic molecules (1-9). In this contest, terthiophene based chromophores properly fiinctionalized with push-pull organic derivatives and long alkyl lateral chains were extensively studied for the formulation of new highly oriented ultra high molecular weight polyethylene (UHMWPE) binary films (10,11). The modulation of the chromophore structure by introducing linear or branched alkyl chains thus providing molecules with lower degree of crystallinity and the use of polyethylene matrices with different molecular weight and density, with the possibility to take advantages from different preparation routes, allowed to reduce or even eliminate the distinct phase separation between the components (12-14). Actually, the formation of chromophore aggregates as a consequence of their separated crystallization from the polymer matrix strongly limits their alignment along the macromolecular chains providing oriented films with poor dichroism (13, 15, 16). Analogously, the efficient strategy based on coupling the optical and dispersion properties of the organic moiety and the metal properties of the inorganic core with extremely high dispersion in polymer matrices suggested the preparation of different metal complexes from ligands bearing alkyl chains with different length, in order to provide the metal with a hydrophobic shell thus allowing a favourite dispersion into polyethylene matrix (17). Nickel and Copper molecular Schiff-Base complexes (Figure la) were prepared and then mixed in the polyethylene matrix providing materials characterized by a great level of homogeneity even, in some cases, at high complex concentration (-12 wt.%)(17). In this work new Bis(salicylaldiminate) metal(II) complexes with similar structure but increased conjugation of the ligand moiety have been prepared and dispersed into polyethylene in small concentration (3 wt.%). The results are discussed in terms of the effect of the molecular structure of the metal complexes on their dispersion into UHMWPE and on their anisotropic absorption properties induced by polymer orientation.
Experimental Apparatus and methods FT-IR spectra were recorded by a Perkin-Elmer Spectrum One spectrophotometer on dispersions in KBr. ^ - N M R spectra were recorded with the help of a Varian-Gemini 200 on 5-10% CDC1 (Aldrich, 100.0 atom % D) 3
In New Polymeric Materials; Korugic-Karasz, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.
20 solutions. NMR spectra were registered at 20°C and the chemical shifts were assigned in ppm using the solvent signal as reference. The melting points were accomplished by a Reichert Polyvar optical microscope with crossed polarizers, equipped with a programmable Mettler FP 52 hot stage. Elementary analyses were made by microanalysis laboratory at the Faculty of Pharmacy, University of Pisa. The Scanning Electron Microscopy (SEM) analysis was performed with a Jeol 5600-LV microscope, equipped with Oxford X-rays EDS microprobe, instrument at the Chemical Engineering Department of Pisa University. Optical absorption studies were carried out in dilute (5* 10' M) solutions with a Jasco 7850 UV-Vis spectrophotometer or on polymer films in polarized light with the same instrument, fitted with Sterling Optics U V linear polarizer. The films roughness was diminished, using ultrapure silicon oil (Poly(methylphenylsiloxane), 710® fluid, Aldrich) to reduce surface scattering between the polymeric films and the quartz slides used to keep them planar. In the analysis of the absorption and emission data, the scattering contribution was corrected by the use of appropriate baselines. The fitting procedure was performed by using Origin 5.0, software by Microcal Origin®.
Downloaded by MONASH UNIV on June 17, 2013 | http://pubs.acs.org Publication Date: September 29, 2005 | doi: 10.1021/bk-2005-0916.ch003
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Materials 2,4-dihydroxybenzaldehyde, Nickel(II) acetate tetrahydrate monohydrate (Cu(0 Ac) Ή 0 ) (Co(OAc) 4H 0) (Aldrich) were 2
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1 -bromooctadecane, o-Phenylene-diamine, (Ni(OAe) 4H 0), Copper (II) acetate and Cobalt(II) acetate tetrahydrate used as received. Ultra High Molecular 2
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Weight Polyethylene (UHMWPE), M w = 3.6· 10 , density: 0.928 g/cm (Stamylan UH210, DSM, The Netherlands) was used as polymer matrix.
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2-Hydroxy-4-(n-octadecyloxy)benzaldehyde 3.7 g (0.026 mol) of 2,4- dihydroxybenzaldehyde, 9 g (0.026 mol) of 1bromooctadecane, 3.1 g (0.03 mol) di K H C 0 and 0.2 g (0.001 mol) of ΚΙ, were refluxed for 24 h in 100 mL of acetonitrile. After cooling, the obtained precipitate was filtered off and recrystallized from heptane (7.1 g, yield 70 %); m.p: 60 °C - IR (KBr): 3444 cm"' (v . ); 1671 c m (v =o) - Ή-NMR (CDC1 ): 0.9-1.8 (m, 35 H), 4 (t, 2 H, 0-CH ), 6.4 (s, 1H, Ar), 6.5 (d, 1H, Ar), 7.4 (d, 1H, Ar), 9.7 (s, 1H, CHO), 11.5 (s, 1H, OH) ppm. 3
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0
H
c
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N,N'~Bis[4~(n-octade
