Colloidal Stable PIC Vesicles And Lamellae Enabled By Wavelength-Orthogonal Disulfide Exchange And Polyinerization-Induced Electrostatic Self-Asscmbly

Polymerization-induced self-assembly(PISA)represents a versatile method for the synthesis of block copolymer(BCP)nanoparticles of defined morphologies,sizes and surface chemistry.RAFT regulated aqueous solution dispersion PISA can form block copolymer nanoparticles with various morphologies,which can be used in the fields of sterilization,drug delivery and nanoreactor and other aspects.Over the past decade,scientists have extensively studied the ordered morphological transformation of BCP nanoparticles in response to the stimuli.However,strict morphological maintenance is necessary to protect the properties of morphology-dependent structures,such as drug delivery or nanoreactor carriers.Typically,stabilization can be achieved by in situ crosslinking,and post-polymerization crosslinking.Particularly,photo-crosslinking is appealing for the spatiotemporal control.Recently,we developed a polymerization-induced electrostatic self-assembly(PIESA)using the water-soluble ionic monomers,in which phase separation is driven by polyion complex(PIC).This method provides the new method for rapid and efficient preparation of nanostructured polyion complexes(PICs).In view of the stability of its nanostructures,a new method for the convenient and reliable synthesis of stabilized spheres,films and vesicles was established in this paper by using orthogonal ultraviolet wavelength induced disulfide bond exchange reaction and visible light induced PIESA.Firstly,hydrophilic PHPMA45 was used as macromolecular chain transfer agent,PAMPS95 was used as poly-anionic template,and water-soluble photo-initiator SPTP was added to expand the chain of cationic monomer CysMA with photoinitiated PIESA formulation.It is found that with the increase of the degree of polymerization,the PICs morphology has undergone a series of evolution processes from sphere,lamella,vesicle to vesicle aggregation,which shows that polymerization-induced electrostatic self-assembly based on cystamine derivatives has a significant chain length dependent effect.In addition,due to the hydrophobic stability of the main chain methyl and the side disulfide bond in the PCysMA growth chain,it aggregates at the shorter chain length(DP=10)to form a very small spheres.Polymerization of DP=50 was tracked,and it is found that with the further increase of conversion rate,its morphology experiences the same evolution trend as the above surface-neutralized PICs.However,because of the repulsion of the charge generated by surface-charged PICs,the morphological hysteresis effect is produced.Therefore,the disulfide functionalized surface-neutralized and surface-charged micrometer-sized vesicles can be predictably achievedSurface-neutralized vesicles as-synthesized above were selected as the reference,UV irradiation of the vesicles in ambient air induces very fast exchange reaction of locally confined/enriched disulfide motifs.The wavelength orthogonality is evident from the disabled PIESA synthesis under UV light and the ineffective post-polymerization functionalization under visible light.It was found that the PIC was still retained after cross-linking,and the morphological evolution had an opposite trend to that of the PIESA process.Then,the freezing stability of as-synthesized PIC vesicles and the cross-linked particles were investigated,and it was found that they had good freezing stability.After that,the PICs were dissolved in the mixture of water and ethanol,and morphology of the cross-linked PICs vesicles changed into vesicle clusters,spheres evolved into worms,rings,and membrane structures evolved into layer-by-layer stacking structures,all of which were hierarchical self-assembly.When ethanol was removed by dialysis,it was found that cross-linked PICs have reversible morphological transformation,while uncross-linked PICs cannot be recovered,so it can be known that the cross-linked PICs have better colloid stability,which is of great importance for the application of nanoreactor and drug carrier related biological materials.In summary,we present a method for convenient yet reliable synthesis of stabilized PIC spheres,lamellae and vesicles,taking advantage of wavelength orthogonality of the UV-induced disulfide exchange and the visible light-initiated PIESA.As such,surface-neutralized and surface-charged vesicles can be achieved.UV irradiation of the vesicles in ambient air induces very fast exchange reaction of locally confined/enriched disulfide motifs,leading to crosslinking,shape transition and cystamine salt release in 4 min.As such,crosslinked PIC spheres,lamellae and vesicles can be achieved,in one pot,from one single vesicle precursor.The wavelength orthogonality is evident from the disabled PIESA synthesis under UV light and ineffective post-polymerization functionalization under visible light.The crosslinked PIC spheres,lamellae and vesicles show the outstanding shape/size stability and high reversibility in solution-adaptive electrostatic hierarchical self-assembly and disassembly upon adding ethanol into aqueous dispersion and subsequent dialysis.