Construction Of Polymer Nano-Objects With Tunable Fluorescence And Phosphorescence Emission Via Polymerization-Induced Self-Assembly

Fluorescent and phosphorescent polymer nanoparticles are widely applied in many fields such as fluorescent analysis and information anti-counterfeiting,among which polymer nanoparticles with adjustable luminescence are the main research direction in practical applications.Currently,chemical modification and noncovalent bonding are the common methods to regulate the luminescence of nanoparticles.But there are some shortcomings such as complex synthesis process and tedious experimental operation,it is of great importance to develop a more efficient and simple method to achieve the luminescence regulation of nanoparticles.Polymerization-induced self-assembly(PISA)is an efficient method to fabricate polymer nano-objects with various morphologies at high concentrations.During PISA,polymerization and self-assembly process are completed in one pot,which greatly simplifies the preparation of polymer nanoparticles.Besides,the morphologies of polymer nano-objects could be regulated through controlling the degree of polymerization of block copolymers in PISA.In this dissertation,PISA method is applied to the construction of fluorescent and phosphorescent polymer nano-objects,and the luminescence of polymer nanoparticles could be regulated by the morphological transformations during PISA.In different PISA systems,we realized the constructions of polymer nano-objects with color-tunable fluorescence,tunable phosphorescent intensity and clusterization-triggered emission(CTE)intensity,respectively.The relationships between the morphologies and luminescence properties of nanoparticles are emphatically analyzed.The primary results are listed as follows:1.Polymer nano-objects with color-tunable fluorescence emission were prepared via PISA method,and the morphologies of nanoparticles could be identified by smartphone application.Pyrene labeled fluorescent monomer(PyAMA)was prepared,and polymer nano-objects with different morphologies were obtained through reversible addition-fragmentation chain transfer(RAFT)dispersion copolymerization of benzyl methacrylate(BzMA)and PyAMA using PEO-PETTC as macro-RAFT agent.With the morphologies of PEO45-b-P(BzMA-co-PyAMA)x nanoparticles changing from micelles to vesicles,the fluorescent colors of the polymer nano-objects varied from blue to green,which gave an index to the morphological transformation process in PISA.A smartphone app morphology master was further designed to provide instantaneous and reliable prediction of the morphologies of copolymer nanoparticles.This app converts the fluorescence colors of the nanoparticles into digital information,which can quickly provide preliminary recognition results of the morphologies of polymer nanoparticles after comparing with existing standard information.This method can quickly analyze the morphologies of polymer nano-objects through the changes of fluorescence colors during PISA and provides a novel strategy for the preparation of multicolor fluorescent polymer nanoparticles.2.The polymer nano-objects with color-tunable fluorescent emission were obtained through the regulation of the fluorescent intensity ratio of two fluorescent groups by morphological evolutions during PISA.Two fluorescent monomers(2naphthylimide)ethyl methacrylate(M1)and(2-(4-bromonaphthylimide)ethyl methacrylate(M2)were synthesized,and the fluorescent colors of monomers Ml and M2 under 365 nm UV light were blue and red,respectively.Using PEO-PETTC as macro-RAFT agent,polymer nanoparticles with different morphologies were obtained by RAFT dispersion copolymerization of Ml,M2 and BzMA with appropriate ratio.The fluorescent colors of polymer nanoparticles changed from blue to red with the morphologies transforming from micelles to higher order morphologies.This work realized the construction of polymer nano-objects with color-tunable fluorescent emission in PISA system by controlling the fluorescent intensity ratio of two fluorescent groups,which enriched the strategy for preparing polymer nanoparticles with variable fluorescence colors in PISA system.3.Core-cross-linked nanoparticles with tunable room-temperature phosphorescence(RTP)intensity were fabricated by PISA method.The crosslinker(CL)containing phosphorescent group 4-bromobenzaldehyde was synthesized.Corecross-linked polymer nanoparticles with different morphologies were obtained through the RAFT dispersion copolymerization of CL and BzMA.It was found that the polymer nanoparticles showed room-temperature phosphorescence and the intensity enhanced gradually following the order of morphological evolutions:micelles<nanowires<vesicles.Furthermore,the application of polymer nanoobjects prepared by PISA method in information encryption was realized based on the oxygen-sensitive phosphorescence of polymer assemblies.This work provides an efficient approach toward regulating the phosphorescent emissions of polymer-based materials,and expands the application of PISA method in the construction of information encryption materials.4.Non-conjugated polymer nano-objects with tunable clusterization-triggered emission(CTE)intensity were obtained by PISA method.Poly(lauryl methacrylate)b-poly(methyl methacrylate)(PLMA-b-PMMA)and poly(lauryl methacrylate)-bpoly(N-isopropyl acrylamide)(PLMA-b-PNIPAM)nano-objects with different morphologies were obtained by RAFT dispersion polymerization of MMA and NIPAM in n-heptane,using PLMA-PETTC as macro-RAFT agent.The luminescence intensity of the polymer nano-objects increased gradually with the morphologies changing from micelles to nanowires.This work realized the regulation of the CTE intensity of polymer nano-objects via PISA method,which has a certain significance for the study of polymers with tunable clusterization-triggered emission.