| Nanosuspensions,nanoemulsions,and nanobubbles are typical nanodispersions,which have a nanoscale dimension and possess excellent physical and chemical properties,such as high specific surface area,high efficiency,etc.They have been widely used in the fields of medicine,petrochemicals,agrochemicals,food,daily chemicals,and mechanical manufacturing.However,the preparation and application of these nanodispersions face many challenges,such as poor particle size uniformity and time-consuming preparation.The flash nanoformation(FNF)technology based on confined impinging jets(CIJ)micromixer is a new technology for a rapid,large-scaled,and controllable preparation of nanodispersions,which has excellent application prospects.However,the formation mechanism of nanoparticles in this technology is still speculative,and there is limited exploration of the mechanism of flash formation of particles.Moreover,the FNF technology currently employs the single mixer,lacking modular design and its application scenarios.A minimun length of the tubling between the mixers,which is related to the input flow rates and the various characteristic times during the mixing,is not explored.This thesis aims to explore the formation mechanism of nanoparticles prepared by the FNF technology using a method of a molecular fluorescent probe,to obtain various characteristic times during the mixing and a minimum length of the tubling between mixers,and to expand applications by constructing modular devices with multiple mixers,e.g.,preparing a nanosuspension of core-shell pigment particles or a gel hand sanitizer(GHS)suspending antimicrobial nanoparticles by cascading multiple CIJ micromixers.Specifically,the work includes:1)a preparation of nanoparticles with an aggregation-induced emission(AIE)effect based on the FNP method,and an investigation of the competition between the relaxation time of either a polymer chain or a hydrophobic molecule,the aggregation of molecular clusters,and the characteristic time of mixing on the particle size,stability,and fluorescence intensity of the nanosuspension;2)an acquisition of the characteristic time for determining the tubling length and the flow rate between cascaded devices.By modularizing the CIJ micromixers,a core-shell structure protecting hydrophobic small molecules in the core is prepared,and the protective efficacy of the shell material and surfactant on hydrophobic small molecules is studied;3)an application of the cascading modularization concept to mixing medium-to-high viscous fluids.By setting up cascading modularization device,the preparation of a washing-free GHS suspending CMC/Zn(Ⅱ)/PAC nanoparticles is investigated,and its antimicrobial effect is evaluated.In Chapter 2 was to develop a quantitative method by using an AIE based molecular fluorescence probe and investigate the competitive relationship between the characteristic times of the molecular aggregation(τSM-agg and τBCP-agg),the molecular cluster aggregation(τMC-agg),and the mixing(τmix)during the formation of fluorescent nanoparticle(FNP).We revealed the mechanism of FNP formation and obtained the following findings:(1)by using block copolymers(BCPs)with different molecular weights and glass transition temperatures(Tg)and the hydrophobic small molecule tetraphenylethylene(TPE),we investigated the influence of polymer and small molecule relaxation time(τ)on the internal structure of the particles.The closer the relaxation time of the BCP(τBCP)is to that of the small molecule(τSM),the smaller and more stable the particles are.(2)By adjusting the flow rate of the mixer,we investigated the effects of molecular cluster coalescence and mixing time on the particles.The smaller the characteristic time of the mixer,the more compact the internal structure of the particles,and the particle size and fluorescence intensity tend to remain constant.(3)By measuring the characteristic viscosity[η]of the BCP and performing theoretical derivations,this chapter proposed a quantitative relationship between the characteristic viscosity of a BCP and the corresponding homopolymer of each block.This work provides a theoretical basis for determining the process parameters such as the pipeline length between the cascade CIJ mixers and the mixing flow rate for the subsequent chapter.Chapter 3 explores the modular cascading preparation of nano-pigment particles with a core-shell structure suspension to prevent the inner core pigment from a light catalyzed oxidation.The work in this chapter uses a hydrophobic compound of β-carotene as a model inner core molecule,and includes that(1)by cascading CIJ-D and CIJ-L micromixers and setting an appropriate length of tubling length between mixers based on τMC-agg and τmix obtained in Chapter 2,a preliminary and simple modular device is built.Compared with the nanoparticles precipitated by single CIJ-D mixer,cascading mixing can form nanoparticles with core-shell structure;(2)by using various homopolymers i.e.,PS,PLGA,PVDF,PMMA,as a shell ingredient,this chapter explores their influence on the color retention of core-shell nanoparticles.The results show that the color retention and the light transmittance of the nanosuspension are mainly affected by the difference of the solubility parameters of the homopolymer and β-carotene.The smaller the difference between their solubility parameters is,the better the color retention.(3)by adding an amphiphilic BCP,the light transmittance of nanosuspension can be improved(corresponding to a particle size reduction).Nanoparticles with a core-shell structure would have wide applications and an added high value,but there were fewer corresponding engineering production technologies.Based on the FNF technology,this work develops a cascading process and efficiently prepares pigment nanosuspensions with core-shell structure.The work demonstrates significance for the preparation of core-shell nanoparticles,the selection of shell layer formula,and the construction of modular device with CIJ micromixing.It would act as a base for building a modular cascading device for preparing the gel hand sanitizer containing nanoparticles in Chapter 4.In addition,the successful development of a cascading process and small-scale device would promote the modular development of the FNF technology to realize more engineering applications in various fields.Chapter 4 focuses on the CIJ mixing of medium-to-high viscous fluids and as an example explores the cascade and modularized preparation of a gel hand sanitizer containing antibacterial nanoparticles.(1)By evaluating the viscosity of thickener of carbomer with a rotational rheometer and using it for the preparation of a gel hand sanitizer,the micromixing device containing CIJ-D was used to prepare a gel hand sanitizer with an ethanol content of 68.4 vol%(theoretical value of 70.0 vol%),which is much higher than that prepared by stirring(63.8 vol%).(2)By optimizing the concentration of the antibacterial compounds proanthocyanidins(PAC),carboxymethyl chitosan(CMC),and zinc chloride,a CMC/Zn(Ⅱ)/PAC nanoparticle suspension with a particle size of about 100 nm is successfully prepared via the RFNP,which exhibits excellent inhibition against E.coli,S.aureus,and Penicillium italicum,(3)By modularizing the production units,the gel hand sanitizer containing antibacterial nanoparticles is successfully prepared,which has not only a rapid killing effect on microorganisms but also an efficient bacteriostatic effect.This work expands the application of the CIJ micromixer in medium-to-high viscous fluid mixing.In addition,the construction of the modularized CIJ device and the development of the cascading micromixing process are of great significance for promoting engineering applications of the FNF technology... |
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