Interaction Between Cyclodextrin And Alkyltrimethyl Ammonium Bromide & The Role In Dispersion Of Carbon Nanotubes And Preparation Of Calcium Carbonate

Cyclodextrin/surfactants mixtures have not only wide applications in cosmetic, pharmaceutics,and food products,etc.but also have the ability to simulate biological systems, which expedites the penetration of biological technology into chemical industry and medicine field.Therefore,the interest in the interaction between cyclodextrin and surfactant is very high for many years.The interaction between cyclodextrin and surfactant has been widely reported in literature, such as the interaction between CTAB,SDS,TX-100 and cyclodextrin,but less attention has been paid to the effect of additives on the interaction.The property of the surfactant solution, especially ionic surfactant,is affected greatly by the presence of additives,such as electrolyte and polar organic compounds.The addition of electrolyte must have some function on the interaction between alkyltrimethylammonium bromide(CnTAB),which is a kind of traditional cationic surfactant,and cyclodextrin.The interaction between modified cyclodextrin,which have improvements in the binding and selectivity,and CnTAB would be affected by the chain length of the substituent,the exact positions of the substituent,and the degree of substituent.In this dessertation,the influence of NaBr upon the interaction between TTAB/β-CD and CTAB/β-CD has been studied systematically.The effect of NaCl on the interaction between CTAB andβ-CD was studied as well to show the influence of counterion of the electrolyte.The interaction between modified cyclodextrin(2-HP-β-CD,6-HP-β-CD, 2-HB-β-CD,and 6-HB-β-CD) and CnTAB(TTAB and CTAB) was presented.The interfacial behavior of an amphiphilic cyclodextrin 2-O-(hydroxypropyl-N,N-dimethyl-N-dodecylammonio) -β-cyclodextrin(HPDMA-C₁₂-CD) was investigated using oscillating bubble rheometer and electrical conductivity method at different temperatures.The dispersion effect of naturalβ-CD and modified cyclodextrin to the CNTs was studied.The influence of dispersion effect of CnTAB to the CNTs by the presence ofβ-CD was investigated.This dissertation comprises of five parts.Chapter 1 gives an introduction to the interaction between surfactant and cyclodextrin. Chapter 2 involves three parts.The first part involves an examination of the effect of NaBr and NaCl on the interaction between CTAB andβ-CD.The stoichiometry,R,has been determined by the surface tension method.The ability to form complexes with CTAB:CD ratios of 1:1 and 1:2 are shown to depend on the concentration and counterion of electrolyte. It is found that R first decreases then increases as a function of electrolyte and NaBr increases R more efficiently.The results obtained from the oscillating barrier measurements at low dilational frequencies(0.005-0.1 Hz) reveal that the dilational modulus passes through a maxium value and a minimum value as the concentration ofβ-CD increses at a given concentration of CTAB.The addition of NaBr decreases the dilational modulus of CTAB/β-CD solution at a given concentration of both CTAB andβ-CD.The second part of Chapter 2 deal with the effects on the interaction between CnTAB (n=14 and 16) andβ-CD of NaBr to get an appreciation of the effect of hydrophobic chain length of surfactant.It is concluded from the surface tension data that the adsorption efficiency(pc₂₀) of CTAB are higher than those of TTAB,while the values of cmc^*,cmc/c₂₀ ratio andâ–³G°_mic are somewhat lower.These results demonstrate that the surface activity of CTAB is still higher than TTAB in the presence ofβ-CD.Although the hydrophobic chain of TTAB is shorter than that of CTAB,the TTAB/β-CD complexes can adsorb on the air/water interface as well.The presence of NaBr elongated the effective hydrophobic chain of CnTAB which increases the adsorption of the complexes at the air/water interface,thereforeγ_cmc decreases.As the concentration of NaBr increasing,the effect of the concentration ofβ-CD on theγ_cmc decreases.The adsorption of TTAB/β-CD complexes at the air/water interface decreases the effect of the consumption of TTAB forming complexes to the efficiency of adsorption.The increase in theγ_cmc of CTAB/β-CD in the presence of NaBr could be attributed to the close pack of CTAB at the air/water interface.The third part of Chapter 2 describes the interaction between CnTAB and modified cyclodextrin(6-HP-β-CD,6-HB-β-CD,2-HP-β-CD,and 2-HB-β-CD) using surface tension method.Modified cyclodextrin(MCD) can decrease the surface tension of water itself,and the surface tension of MCD decreases as the concentration of MCD increases.The surface tension isotherm of CnTAB/CD solution has two breaks for a given CD concentration.The surface tension value decreases before the first break,which means that the surface activity of CnTAB/CD complexes is comparable to the one of MCD.The surface activity of MCD varies according to the structure:long substituent,high degree of substituent and substitute on the secondary side of CD result in a high surface activity.The positions of the substituent on MCD affect the interaction between CnTAB and MCD,result in different influences on R, cmc^*,andγ_cmc.When the CnTAB interact withβ-CD and MCD which is modified at the C2-position,R in most complexes is 1:1,result in a higher cmc^*;and for the MCD modified at the C6-position,R in most complexes is 2:1.Theγ_cmc at the CnTAB/C6-position modified MCD and CnTAB/β-CD is lower than that of CnTAB/C2-position modified MCD at lower CD concentration.The interaction between TX-100 and MCD conform that it is the adsorption of complexes,due to the loose pack of CnTAB at the air/water interface,which decrease theγ_cmc of CnTAB/CD solution.The induced circular dichroism spectrum(ICD) shows that it is the interaction between the benzene ring of TX-100 and the hydrogen bond ring in the cavity of CD which produces the induced chirality.A high degree of substituent results in a weak induced chirality in the TX-100/C6-position modified MCD solution.Chapter 3 involves two parts.The first part involves the examination of the dispersion effect of five cyclodextrins,including 2-HP-β-CD,6-HP-β-CD,2-HB-β-CD,6-HB-β-CD, andβ-CD,on carbon nanotubes(CNTs).2-HB-β-CD is the most efficient dispersing agent.It is found that both the substituted position and the chain length of the substituted group were important for the dispersion of CNTs.The dispersing ability of CDs on the dispersion of CNTs was 2-HB-β-CD＞＞6-HP-β-CD＞β-CD＞6-HB-β-CD＞2-HP-β-CD.The interaction between the CDs and CNTs was studied by Fourier transform infrared spectroscopy(FTIR), Raman spectrum,and X-ray powder diffraction.The movement in the FTIR spectra of the asymmetric and symmetric stretching vibrations of O-H of the composites means that hydrogen bonding is an important factor on the dispersing ability of CDs.These results indicate that the type of interaction might be the combination of a weak interaction similar to the van der Waals and a hydrogen bonding mechanism.The second part of Chapter 3 deal with the effect of the interaction between CnTAB(n=12, 14,16) andβ-CD on the ability of dispersing CNTs of CnTAB by UV-vis-NIR and Raman spectra observations.Of the three surfactants,the ability of dispersing CNTs of DTAB is the smallest,while it is greatly enhanced in the TTAB and CTAB aqueous solution.The maximum amount of CNTs in TTAB and DTAB solution is similar to each other,but the concentration of CTAB solution to this amount is much lower than that in the TTAB solution. The DTAB solution does not have the ability to disperse CNTs,while the TTAB and CTAB solution could disperse CNTs when the concentration of surfactant is lower than the cmc.The presence ofβ-CD enables the DTAB solution to disperse CNTs even when the concentration is lower than the cmc.The type ofβ-CD self-aggregates affect the ability of dispersing CNTs of CnTAB,and the complexes of the monomer ofβ-CD and CnTAB result in the best dispersing ability before cmc^*.The stability of CnTAB/β-CD/CNTs suspended systems has an improvement probably due to the electrostatic repulsion between the ionic hydrophilic groups of CnTAB and steric hindrance ofβ-CD.Chapter 4 describes the interfacial behavior of HPDMA-C₁₂-CD by oscillating bubble rheometer and electrical conductivity method at different temperatures.The surface tension and interracial dilational viscoelasticiy of HPDMA-C₁₂-CD are provided.The results showed that HPDMA-C₁₂-CD could adsorb on the air/water interface which efficiently decreases the surface tension of water,cmc can be clearly defined from the surface tension isotherm,pc₂₀ andÏ€_cmc are derived from the surface tension isotherms as well.The thermodynamic parameters(â–³G°_m,â–³H°_m,-Tâ–³S°_m) derived from electrical conductivity indicate that the micellization of HPDMA-C₁₂-CD varies from entropy driven process to enthalpy driven process.The dilational modulus appeares to have a maximum value while the phase angle have two maximums as a function of the concentration of HPDMA-C₁₂-CD.Chapter 5 involves the effects on the crystallization of calcium carbonate ofβ-CD,which is conducted by an open vapor diffusion method(decomposition of(NH₄)₂CO₃),including the effect of the concentration ofβ-CD,diffusion time,and the type of CD.Flat concentric circles morphology was observed at the air side of the CaCO₃ particles in the absence ofβ-CD,which gives evidence to the layer-by-layer assembly mechanism.Circular cone morphology was obtained at the air side of the CaCO₃ particles in the presence ofβ-CD, while the morphology is similar to the one withoutβ-CD if the concentration ofβ-CD increases.β-CD accelerats the growth of"circle" particles.Both the prolonged diffusion time and the increasing of the mass of(NH₄)₂CO₃ increase the size of the particles.The time-dependent evolution was studied by SEM.The bulk side of the particles is composed of nanoparticles about 50 nm,and these nanoparticles aggregate to be thin layers which cover the inside particle.FTIR and XRD analysis show that the particles are calcite with only a little vaterite.However,β-CD might just transport Ca²⁺ to the interface rather than form inorganic-organic hybrid with CaCO₃,because the weight loss is not observed in the TG analysis.The particles observed in the bulk are nano-particles assembled center pop out disks. It dramatically decreases the size of the particles when the concentration ofβ-CD increases to 1 mmol·dm^-3.It is a mixture of calcite and vaterite.Calcite is the main component at short diffusion time,while vaterite is the main component at long diffusion time.Layer packed dlipsoid was Observed in the presence of 6-HP-β-CD and 6-HB-β-CD.