Studies On Preparation And Properties Of The Ordered Molecular Assembly Based On Protic Ionic Liquids And Nitrogenous Heterocyclic Compounds

Ordered molecular assemblies, such as micelles,vesicles,lyotropic liquid crystal (LLC),and microemulsion,fabricated by amphiphilic molecules in suitable solvents are playing active roles in areas of materials,life, pharmaceutical, separation, dispersion, information,and energy. In respect of the self-assembly media, self-assemblies formed in traditional media such as water and various organic solvents might be limited in application because the system generally has poor stability, volatility, low conductivity and other shortcomings.Ionic liquids have special physical and chemical properties such as low volatility, wide electrochemical window, non-flammability, good thermal stability, etc.They are regarded as environmentally benign solvents and their application in molecular assemblies is of great interest. Recently, the development of protic ionic liquids (PILs),which can be used to build up a hydrogen-bonded network with the presence of proton-donor and-acceptor sites and easily purified, protic,is growing.The filed of self-assembly in PILs is especially active,which develop the self-assembly media and is useful when water is undesirable or proton is needed such as in the filed of proton conducting electrolyte in fuel cells, life, biocatalysis,and so on.On the aspect of amphiphiles, imidazolium amphiphilic compounds with long chain derivated from imidazolium ionic liquids have been widely used to construct micelles, microemulsions, lyotropic liquid crystal and gel ordered molecular aggregates,and further applied in the material preparation,and so on.In recent years,studies have shown that other long-chain heterocyclic compounds can exhibit excellent performance, and its application in fabricating ordered molecular aggregate has been paid attention, which can develop novel molecular aggregate system and provide potential applications.This dissertation is focused on the use of protic ionic liquids and nitrogenous heterocyclic compounds in ordered molecular assemblies.The main purpose is to construct novel LLC systems with protic ionic liquids as solvents and investigate their structure and properties, to synthesis and characterize nitrogenous heterocyclic compounds and investigate their properties and applications in ordered molecular assemblies.The outline and contents of this dissertation are as follows:In the first section,the research background of this work including the history and recent progress of surfactants and ionic liquids is summarized.The protic ionic liquids, nitrogenous heterocyclic compounds and their application in ordered molecular assemblies are briefly introduced.The research ideas, content, and significance of this dissertation are also pointed out at the end of this part.In the second section,aggregation behavior of Brij 97 (C18∶1EO10) in protic ionic liquids and their rheological and electric behaviors were investigated.Several polyoxyethylene amphiphiles, like Brij 97,Brij 30,Triton X-100,and NP-10,all of which can form LLC in water,,but only Brij 97 can be used to fabricate LLC in EAN. The T-X phase behavior and self-assembly behavior were characterized by several techniques such as small angle X-ray scattering (SAXS), polarized optical microscopy (POM), and differential scanning calorimetry (DSC).It is found that The scattering factor (q) values of Bragg peaks of the LLC system are correlated with the relative positions of 1:√3:2:√7, which is characteristic for a hexagonal liquid crystalline phase (H1).It could be concluded that the hexagonal LLC is self-organized well in the binary system and its ordering in the middle LLC range is better than that near the boundaries between micellar solutions based on the numbers and strength of the Bragg peaks.From the lattice spacing, it can be concluded that the Brij 97 molecules in H1 phase are not fully extended and conformational isomerization of the alkyl chains exists in the liquid crystalline phase. EAN molecules distribute mainly among PEO blocks and form network with them by H-bonding of types like N-H…O(CH2)2,N-H…O-NO2, N-H-N-H, N-H…O-H, O-H…O-NO2, and O-H…O(CH2)2.Temperature elevation mainly weakens the hydrogen bonds between PEO blocks and EAN and results in the decreasing of the cylindrical ordering, but the distance between the cylinders is less affected.To investigate the solvent effect, a degraded ability to produce the ordered self-assembly of Brij 97 from H2O to EAN to [Bmim][PF6],[Bmim][BF4],[Pyrr][NO3],and EAB is found and analyzed based on the molecular packing and Gordon parameters, and also hydrogen-bonding or solvophobic interactions.Rheological measurements show that these unflowable samples on the top of inverse tubes exhibit high apparent viscosity at low shear rate, and the shear-thinning phenomenon is observed.Rheograms of the oscillatory shear were also compared.A crossover frequency is found at lower Brij 97 concentration. Before it, the loss modulus (G")is higher than the storage modulus(G') showing a viscous behavior, and at higher frequencies,G' becomes larger than G" where the elastic response dominates.At higher Brij 97 concentrations, the crossover frequency disappears and G'>G" exists in all the frequency range.This system also shows good conductivity compare with that in water.In the third section,the aggregation behavior, phase transformation,effect factors, and rheological behavior of triblock copolymer Pluronic P123 (EO20PO70EO20) in a protic ionic liquid,pyrrolidinium nitrate([Pyrr][NO3])have been investigated by the techniques of SAXS,POM, and rheological measurements.It is found that the samples are highly viscoelastic LLC gels.Firstly, the phase diagram of this binary system was constructed,P123 can form hexagonal and lamellar LLC in [Pyrr][NO3] in a wide concentration.Structural analysis of hexagonal LLC shows that the lattice spacing gradually decreased with the increased concentration and the ordered aggregates arranged more closely. Lamellar LLC has similar properties.Temperature effect is also investigated for the system.The results indicate that the ordering gradually reduced and the lattice parameter increased with the increased temperature for the hexagonal phase.The mixed phase has the trend to become lamellar LLC when the temperature is increased.For the lamellar LLC,the ordering changes a little at first and then reduced, and the lattice parameter increased with the increased temperature.Compare to the hexagonal phase,lamellar phase is more stable.But for the samples with high concentration like 95%, the LLC is easily destroyed by increased temperature.Rheological measurements show that these samples show high apparent viscosity at low shear rate,and it's increased with concentration.The shear-thinning phenomenon is also observed.In each phase region,the higher the concentration,the more stable the structure of the sample, and it's more difficult to shear thinning.Further characterization of their viscoelastic properties shows that most samples are G'>G" except the samples at low concentration in ecah phase region, and the complex viscosity has a linear decrease.These results indicate that most of the samples of the system are LLC gels with highly viscoelastic properties.In the fourth section,a series of protic tertiary pyrrolidinium surfactants, morpholinium compounds with long chain, amphiphilic molecules composed of N-methylimidazole or pyrrolidine with different fatty acids were prepared and characterized by several techniques such as 1H NMR and MS.Their thermal behaviour, phase transition,and self-assembly in water were further investigated by DSC,TGA,POM, and SAXS.The LLC behavior were analyzed in detail.Firstly, the protic pyrrolidinium surfactants have good thermal stability before 250℃and were less affected by chain length.DSC results show that T phase appeared during the thermal transition, which has also been further confirmed by POM. The longer chain length the compounds have, the higher temperature required for the formation of T phase.Through the conductivity of them in water, it can be concluded that their CMC decrease with chain length increased. Hexagonal LLC can be formed by further increase of concentration, but their stability is poor, and the longer the chain is, the more difficult it is to form LLC.Ordered linear structure was formed during holding. The reasons for the formation of this structure may be the growth, accumulation, and alignment of surfactants along the column of hexagonal LLC.Secondly, Six-membered morpholinium compounds with different chain length were systhesized and characterized.Their thermal stability is worse than that of similar pyrrolidinium compounds, which may be due to the oxygen atom of the morpholinium heterocycle. DSC results show that they are decomposed before melting and T phase was formed in the process.When lager anion were introduced in the compounds like [Mor1,12]BF4, its melting point could be reduced markedly below 100℃, and SmA phase could be formed in the heating process.Its thermal stability is also greatly increased,and it is not decomposed until 400℃.Therefore,anions play an important role for its phase transformation and performance.It is also found that the CMC of these compounds decreased with the increasing chain length, and it increased a little compare to that of similar five-membered pyrrolidinium compounds.Thirdly, amphiphile was constructed by N-methylimidazole with different fatty acids, and their aqueous aggregation behavior was further investigated by POM,SAXS techinques.It is concluded that this novel ternary system can exhibit La phase with its lamellar spacing changing regularly in a wide concentration range.The relationship between uptake of water and the lattice spacing reflects a typical one-dimensional swelling. The amphiphile fabricated by decanoic acid with a shorter carbon chain and N-methylimidazole also can form well ordered La phase.Three driving forces, hydrophobic interaction, H-bonding interaction,andπ-π. interactions can be considered to be mainly responsible for such an ordered assembly. Finally, the phase behaviour of non-covalent amphiphile constructed by pyrrolidine with lauric acid, myristic acid and palmitic acid in water was investigated.The results showed that all the three systems can form ordered lamellar phase in a wide concentration range.It is found that chain length and concentration play an important role on the structural parameters by SAXS analysis.The longer the chain length, the greater the spacing parameters at the same concentration.The greater the concentration, the smaller the layer spacing in the same system.For the system including myristic acid and palmitic acid, there are two sets of peaks for lamellar structure.This can be attributed to the formation of La phase with different structure by two kinds of amphiphiles, which is formed because of the partly decomposed complex with carboxylic acids having a longer chain length in higher concentration.Thanks for the supports from the National Natural Science Foundation of China (No.20573066,20773080 and 20973104).