Synthesis,Self-Assembly And Application Of Carboxylate Gemini And Polymeric Surfactants

Gemini surfactant(GS),with two hydrophilic head groups and two hydrophobic tail chains connected by a spacer group,are amphiphilic compounds(member of oligomeric surfactants).Compared with traditional surfactants,GS have greater surface activity?lower critical micelle concentration(CMC)and better aggregation behaviors.GS have received widespread attension due to its one of the most important applications in morphology-controllable synthesis of nanomateials.Unlike GS,polymeric surfactants are amphiphilic macromolecules with thousands of molecular weight.This kind of amphiphiles,which possess both characteristics of polymer and surfactant,are termed as functional polymers.Polyurethane is one of the most important polymers with excellent comprehensive performance and wide application fields.It will be widely applied to the emulsion polymerization,biomedical materials and polymer-based nanocomposites after being endowed surface activity.This thesis mainly studied the synthsis,surface activities and aggregation behaviors of carboxylate GS and carboxylate polyurethane surfactants(PUS).Then carboxylate GS were uesed as soft template to synthesize Nano-La2O3,Nano-CeO2 and Nano-CuO.Finally,CuO nanowire was dispersed in the carboxylate PUS to prepare hydrophobic coatings.Similarly,Nano-SiO2 and polyvinyl alcohol(PVA)were dispersed in the carboxylate PUS to prepare electrostatic spinning solution.The specific contents are as follows:Chapter 1--In this chapter,we summarized anionic gemini surfactants and anionic polymeric surfactants,including the classification,synthesis methods,properties and applications.Chapter 2--A series of carboxylate gemini surfactants(CGS,Cn-?-Cn,n=12,14,16,18,? is the group of diphenyl ketone)with diphenyl ketone as spacer group were prepared with a simple and feasible synthetic method.These CGS exhibited excellent surface activity with extremely low CMC value(about 10-5 mol/L),good performance in reducing surface tension(??30 mN/m),and the ability of molecular self-assembly into different aggregate morphologies via adjusting the concentrations,which is attributed to the introduction of diphenyl ketone and carboxylic acid ammonium salt in the molecular structure.Moreover,the surface activity and aggregation behaviors of CGS were further optimized by tuning the length of tail chain.These excellent properties imply that CGS can be a soft template to prepare nanomaterials,especially in morphology-controllable synthesis.Through adjusting the aggregation morphologies of C12-?-C12,Nano-La2O3 particles with diverse morphologies were obtained,including spherical shape,bead-chain shape,rod shape,velvet-antler shape,cedar shape and bowknot shape.This work offers a vital insight into the rational design of template agents for the development of morphology-controllable nanomaterials.Chapter 3--A series of anionic gemini surfactants(AGS)were synthesized from N,N-dimethylaminoethanol(DMEA)and tetracarboxylic acid diester(TAD).TAD was derived from the reactant of 3,3',4,4'-biphenyl tetracarboxylic dianhydride with long alkyl alcohol.The surface properties and aggregation behaviors of these novel AGS were investigated.These AGS displayed super low CMC and excellent aggregation behaviors.Meanwhile,the thermodynamic parameters of surface area per molecule and surface excess adsorption were investigated respectively.Moreover,by changing solution concentration,surfactant molecules self-assemble into different micellar morphologies,including spherical micelles,threadlike micelles,dendritic micelles and vesicles.Tunable micellar morphology of AGS,which directed the orientated growth of nanocrystals,assisted fabricating Nano-CuO.Through reaction,diverse shapes(spherical,linear,branch and multilayer)of nano-CuO were obtained and confirmed.AGS-templated shape-controllable synthesis of Nano-CuO is energy-saving,environment friendly and highly effective.Chapter 4--A series of anionic gemini surfactants(BGS)were synthesized from the reactant of N,N-dimethylaminoethanol with dicarboxylic acid diester(PM-DADE),after the PM-DADE was synthesized from pyromellitic dianhydride(PMDA)and fatty alcohol.Through rational design,benzene ring was introduced into the molecular structure to work as spacer group;carboxylic acid ammonium salt with hydroxyl as functional hydrophilic head group,and double-alkyl chain performed as hydrophobic tail chains.Then,surface active properties and micellization behavior were investigated respectively.It is found that these novel molecular structure dramatically improved the surface active properties,including critical micelle concentration(CMC:10-3mol/L),surface tension(?min:26.5mN/m),conductivity and absorption at interface.Moreover,the thermodynamic parameters of surface excess concentration,surface area per molecule,Gibbs free energy of micellization(AG°m)and standard Gibbs energy of adsorption(AG°ads)were studied.Moreover,BGS were able to form intermolecular hydrogen bonds,which,together with rigid spacer group,greatly affected the micellization behavior in bulk solution.More importantly,the self-assembly of aggregation with different morphologies can be controlled via adjustment to solution concentration or tail chain length.Finally,BGS were applied in synthesis of Nano-CeO2,and CeO2 nanoparticles of diverse shapes were eventually obtained and verified,such as dorayaki shape(double-pancake shape),rod-cluster shape,lamellar shape,butterfly shape and dendrite shape.The results of the experiment showed that BGS could be used as soft templates for the shape-controllable synthesis of Nano-CeO2.Chapter 5--Precusor of carboxylate polyurethane surfactants(PUS)was synthesized from the reactant of 4,4'-dicyclohexyl methane diisocyanate(HMDI,hard segment),Polyether polyol(PTMEG2000,soft segment)and 2,2-dimethylolbutanoic acid(DMBA,functional monomer).Then,1,4-butanediol(BDO)was used as chain extender to react with the precusor,and N,N-dimethyl ethanolamine(DMEA)was used to neutralize the free carboxyl of precusor to form PUS.The obtained PUS solution is a light blue transparent colloidal dispersion,and the surface activity and aggregation morphology were studied respectively.Then,Nano-CuO was dispersed in PUS via ultrasonic,the uniform and good stability of polyurethane nanocomposite coatings system was obtained and coated on the glass surface.After being dried,the coatings surface was rough and uneven,the water contact angle was as large as 120°,the dust removal experiment showed that the surface was spotless where the water passes,which suggested that CuO nanowires were able to effectivly modify the surface of PUS and the coatings had good hydrophobic property.Similarly,Nano-SiO2 and PVA were dispersed in PUS via ultrasonic to prepare electrostatic spinning solution,which could be spinned nanofiber.As environment-friendly material,PUS can be used in many areas,such as hydrophobic coatings and polyurethane-based composites.