Topic_4.Polymers_and_surfactant_static_[1]

Nonionic and Anionic Emulsifiers, Copolymerizable Surfactants, Dispersing Agents and DefoamersExactly your chemistry.SurfactantsApplicationsfor Industrial Division Functional ChemicalsContents131313131314141415161616174699910101111111111111212121212121212123Surfactants from Clariant What we offer for industrial customers5Besides the existing range Clariant offers smaller sample amounts of non-commercial products for labora-tory investigations. These include nonionic emulsifiers based on alcohol ethoxylates, which are synthesized in our development laboratory. If requi-red, almost any alcohol can be reac-ted with the desired amount of ethylene oxide and a sample provided. Our production know-how permits rapid scale-up of new products from the laboratory to the production stage.Development products are thus rapidly available commercially. We will gladly advise you of what we can do for you.Nonionic Surfactants Product range(1)1 g in 100 cm3distilled water • (2)5 g in 25 cm325% aqueous BDG • (3)1 g in 100 cm310% aqueous NaCl solution • *relative to the active substance…Alkyl ethoxylates“ to be continued on page 87Nonionic Surfactants Product range(1)1 g in 100 cm3distilled water • (2)5 g in 25 cm325% aqueous BDG • (3)1 g in 100 cm310% aqueous NaCl solution • *relative to the active substanceNonionic Surfactants Product range(1)1 g in 100 cm3distilled water • (2)5 g in 25 cm325% aqueous BDG • (3)1 g in 100 cm310% aqueous NaCl solution • *relative to the active substance11Anionic Surfactants Product rangeCopolymerizable Emulsifiers & Speciality MonomersProduct rangeDispersing AgentsProduct range15Defoamers Product rangeSurfactants from Clariant Emulsifiers for emulsion polymerizationEmulsifiers are substances that becomeactive at interfaces. They perform anumber of tasks in the complex systemof emulsion polymerization. For examplethey enable the water-insoluble mono-mers to be distributed extremely finelyin the aqueous phase and stabilize thepolymer dispersion produced from it.Clariant emulsifiers are used to manu-facture a variety of polymer systems:s In the polymerization of vinyl acetateto homopolymers or co- and ter-Polymer Particlepolymers together with other vinylesters, acrylates, vinyl chlorideand ethylenes In the polymerization of pure acrylateand styrene-acrylate dispersionss In the manufacture of butadiene-styrene laticess In the manufacture of polyvinylchloride using the emulsion polymer-ization processs In the manufacture of butadiene-styrene rubbers In the manufacture of ABS plasticThe diagram beside shows a model ofthe complex interactions involved in thestabilization of the polymer particles.OH Groups17Surfactants from Clariant Emulsifiers for emulsion polymerization19Not only the constitution of the emul-sifier but also its concentration has an influence on the properties of the dispersion. The next four graphsillustrate this effect on the viscosity of the dispersion by means of the model formulation vinyl acetate/VeoVa 10.2)Determined by turbidity measurements, these values are not absolute but indicate a tendencySurfactants from Clariant Emulsifiers for emulsion polymerization21Surfactants from Clariant Emulsifiers for emulsion polymerization23This information is based on our present knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as guaranteeing specificproperties of the products described or their suitability for a particular appli-cation. Any existing industrial property rights must be observed. The quality of our products is guaranteed under our General Conditions of Sale. February 2004Our products are constantly upgraded on the basis of the latest research re-sults. Products may occasionally be deleted in the course of updating the sales range. Development products that have reached the production stage are not included in this list.。

tubular inner core is expected to yield to confine-effects similar to those existing inside the pores zeolites.23Diffusion of molecules inside wide pores similarly to waterflowing through a pipe.It conventionally takes place following the Poiseuillediffusion,where moleculeϪmolecule colli-much higher than moleculeϪwall collisions.the size of the pore or of the pipe decreases,the interaction of the molecules with the walls cannot be neglected anymore.24Theflow then follows the Knud-model.If the size of the pore is further decreased tothe dynamic diameter of molecules in the gasparticular effects due to confinement of the mol-the pore appear.25These effects are well-knowncase of zeolites which present cavities in the 1Ϫ10Å.They are extensively described in theof Derouane.23The existence of similar effects inpores,that is,in the nanometer range,was a mat-debate during several years.Recently,it was how-demonstrated that they also exist in organized me-soporous silicates like MCM-41and SBA-15that present few nanometers.26Similar effects are thus sus-to also exist inside CNTs.access this information and to be able to per-investigation of the catalytic properties of met-inside or outside CNTs,one has tofirst master the synthesis of metal nanoparticles selectively localized in-outside of carbon nanotubes.Several groups al-attempted such localized selective deposition.main synthesis routes were suggested:(1)Deposi-vature and the size of the inner cavity are changed, and hence no curvature/confinement effects can duced from the catalytic behavior.(2)Asymmetric tionalization.Thefirst asymmetric functionalization reported by Lee et al.who managed to graft different functional groups on each tip of the same CNT. similar concept was used by Jiang et al.to perform the asymmetric functionalization of the innerouter surface of opened CNTs.29Chen et ed dation with nitric acid to functionalize capedand,depending on the reaction conditions,tively open their ends.30Functionalization deeply modifies the surface properties of the CNTs.ever,none of these reports mentions effectsported metal nanoparticles.The characterization of the sample is not straightfor-ward with respect to the localization of the supported metal nanoparticles.Winter et al.,as well as Ersen demonstrated that metal nanoparticles supported CNTs are difficult to localize from conventionalview TEM images because of ambiguous estimates projection effects.31,32It is nearly impossible tomine the3D location in a2D image for particlespear to be in the center of the tube or next toner wall of the tube without tilting the specimen TEM.Electron tomography(3D TEM)appears to suitable technique that can clearly evidence the location of the particle with respect to the nanotube and further yields some statistics about the ratioticles inside and outside the CNTs.(A)SEM image of the pristine CNTs.Inset:HRTEM image of a CNT tip.(B)Statistical distribution of theirdiam-organic nanopar-in-CNTslocal-selectingtolo-from pH1.5to9.5.Deprotonation of the functional groups occurs whenever the HNO3-treated CNTs are in contact with water,thus leaving a negatively charged carbon surface.This surface charge improves signifi-cantly the interaction between the CNT and metal cat-ions of the precursors used during the subsequent im-pregnation.The functional groups attract the M xϩions and help their dispersion,thus leading to metal nano-particles evenly decorating the CNTs after calcination and reduction.Selective Deposition of Metal Nanoparticles Inside CNTs.In-cipient wetness impregnation is a well-known tech-nique used for catalyst preparation.35A solid catalyst support is brought in contact with a solution contain-ing the metal precursor.The volume of this solution is adjusted to the porous volume of the solid so that it to-Figure2.SEM images of the1wt%Ni/CNT sample prepared by incipient wet-ness impregnation.The same area was acquired in SE(left)and TE(right)mode.of the external surface and an image tubule.Figure2shows that many particles outside the CNT,in agreement with Ersen believe that during the incipient wetness impregna-process,the aqueous solution containingmainlyfills the inner channel.However,tension of water(72mN·mϪ1)is lowercritical surface tension of the CNTs(180mNof the CNT surface with the Ni precursor cannot be avoided.The external surface of also covered with solution,which leadsthe calcination and reduction of Ni nanoparti-the outer surface.based our new synthesis procedure onsurface of the CNTs.Hence,a higherexpected.Because of its low surface tension),the ethanolic solution wets the nanotubeandfills the inner channel,as describedLaplace equation.36In a second step,distilled water are then added.The functionaliza-with nitric acid created many oxygen-containing groups which decrease the hydrophobic of the CNT surface and allow its wetting organic and aqueous solvents(contactHowever,the intrinsic lipophilicity of theleads to lower liquid/solid interface energiessolvents than for aqueous ones.Thereforephase is expected to remain outsideand to displace the thinfilm of ethanolic located on the outer surface to the innersample is dried at room temperature overnight at323K for10h to remove any remainingThe sample isfinally calcined in air atreduced in pure hydrogen at673K forreference sample prepared by the incipientSchematic view of a longitudinal crossnanotube during the different steps for deposition of nanoparticles inside CNTs:(a)impregna-the ethanolic solution containing the metalimpregnation with distilled water to washthe outer surface from metal deposition;c) calcination,and reduction,metal particles are inner surface of the CNT with a high selectivity.Representative TEM image of the sampleprepared by2-step impregnation.Most of nanoparticles seem to be inside the tubule.boiling for organic corre-nano-solvents is order to pro-In atheaqueous solution containing the Ni precursor.Finally,all samples were dried,calcined,and reduced in the same conditions as previously.The SEM investigation at low accelerating voltage shows that small nanoparti-cles are homogeneously decorating the outer surface of the CNTs (Figure 4).The choice of the solvent A af-fected neither the Ni particle dispersion on the CNT sup-port nor the particle size distribution.TEM investiga-tion confirmed that particles with diameters ranging from 3to 10nm are homogeneously decorating the whole external surface of the CNTs (Figure 5).Conse-quently,it appears that the physical properties of sol-vent A do not have a significant impact on the final ma-terial when synthesized under our conditions.Usedthe point (K)Figure 4.SEM images of 1wt %Ni/CNT samples “metal outside”prepared with solvents of various boiling point and solubility in water (A,benzene;B,ethanol;C,octane;D,N ,N -dimethylformamide).The nature of the solvent affects neither the dispersion nor the average particle size.Figure 5.TEM images obtained for the samples “metal outside”prepared with different organic solvents:ethylene glycol (left),tetrahydrofuran (right).The nature of the solvent affects neither the dispersion nor the particle size.Additional experiments that are not reported here show that the boiling point of solvent A has the initial drying step is done at higher tempera-example,at a temperature close to or higher the boiling point of the solvent.In this case,evaporates and therefore no longer protects channel.The aqueous solution containing goes into the nanotube by capillarity,thus of selectivity.From Table 1,it is also worth other parameters,like the polaritiy of solvent not seem to play a role during the synthesis.dispersion and size distribution of the Ni for all samples make us conclude that the neither chemically modifies the external Figure 6.TEM tilt series obtained by tilting the sample “metal outside”prepared with octane from ؊35°to ؉40°.Figure 7.(A)Typical 2D-TEM image of the sample “metal inside”,used to reconstruct its volume.(B)Longitudinal section through the reconstructed volume.(C)Modeling of the reconstructed volume:(pink)carbon nanotube,(red)Ni particles inside the tube,(blue)Ni particles on the external surface).2.Schematic view of a longitudinal cross section nanotube during the different steps for the deposition of nanoparticles outside CNTs:(a)impregna-with the organic solvent to protect the inner tubule metal deposition;(b)impregnation with the aqueous containing the metal precursor;(c)after drying,and reduction,metal particles are decorating surface of the CNT with a high selectivity.Figure8.(A)One of the2D-TEM images from the tilts series used for 3D-TEM analysis of the sample“metal outside”prepared with ben-zene.(B)Transeversal and a longitudinal sections through the vol-ume obtained by reconstruction.erentially outside decoration of the tube.A typical pro-jection of the object and several sections through the volume as obtained from the reconstruction are pre-sented in Figure8.By extracting the nanoparticles and nanotube contributions from the total volume,we ob-tained the exact position of the nanoparticles with re-spect to the outer surface and estimated thus the ratioinside/outside in the case of the two-step impregnation process proposed here.For this sample,the selectivityof particles deposited on the outer surface is ratherhigh,close to85%.The higher selectivity for the exter-nal deposition was attributed to the fact that the aque-ous solution evaporation on the outer surface was moreefficient,as all the solution is in direct contact with air.The evaporation of the organic solvent is much sloweras itfills the tubule and it is in contact with air only atthe tube tips.For both types of samples,“metal inside”and“metal outside”,the particle size ranges from3to7nm for the particles inside and4to9nm for the par-ticles outside.These values are inline with the SEM andTEM observations(Figures3Ϫ6)and confirm that thenature of the solvent affects neither the dispersion northe average particle size.CONCLUSIONSelective,localized deposition of metal nanoparti-cles on carbon nanotubes is possible by using a combi-nation of organic and aqueous solvents.By testing dif-ferent solvents we demonstrated that other parameterslike the miscibility with water and the boiling pointhave no crucial effect in our synthesis conditions.The difference in the liquid/solid interface energies of both solvents with the CNT surface is a crucial parameter.This method allows the avoidance of any additional。