Living/controlled Radical Polymerization Of Fluorescent Polymers Containing 1, 8-naphthalimide Moieties

Presently, much attention has been devoted to polymeric materials with fluorescent and third-order nonlinear optical (NLO) properties for their great potential usages in optical and electro-optical applications. Such polymers not only remain good optical properties of small molecules, but also exhibit good mechanical properties and excellent processabilities. As one chromosphere that possessing outstanding optical properties, 1,8-naphthalimde derivatives have been promising materials in recent decades. Many endeavors have been done to design and synthesize polymers containing 1,8-naphthalimide groups. Atom transfer radical polymerization (ATRP) and Reverse addition-fragmentation transfer (RAFT) polymerization are two versatile tools to prepare functional polymers. By selecting functional initiators, RAFT regents or monomers, functional polymers with well-defined structure can be obtained.In this thesis, we focused on the design and synthesis of novel polymers containing 1,8-naphthalimide moieties for singal or composite fluorescent materials and third-order NLO materials. All polymers that have 1,8-naphthalimide groups in the end or side chain were prepared via ATRP and RAFT polymerization. The fluorescent and third-order NLO properties were studied. The work can be summarized as follows:(1)1,8-naphthalimide end functional polystyrene (NAPH-PSt) with green fluorescence were prepared via functional initiators of ATRP. We synthesized a novel 1,8-naphthalimide derivative NAPHCl as the initiator, which was used in the polymerization of styrene to obtain NAPH-PSt. The fluorescent properties of NAPHCl and NAPH-PSt were investigated. Results showed that both NAPHCl and NAPH-PSt have green emission, but the polymer has higher quantum yield and energy yield.(2) A series of polymers with blue and green di-color emission were prepared by the combination of functional initiator and monomer of ATRP. Two stilbene derivatives, 1-(4-methoxystyryl)-4-vinylbenzene (MEOVS) and 1-(4-vinylstyryl)naphthalene (NVS), were synthesized. Then, NAPHCl was selected to initiate the polymerization of MEOVS and NVS to prepare polymers NAPH-PMEOVS and NAPH-PNVS. Results show that the polymerization of MEOVS is uncontrolled and NVS is controlled. The fluorescent properties of NAPH-PNVS were investigated. Each of the obtained polymers with different molecular weight has a composite emission spectrum comprising a blue component originated from NVS and a green component originated from NAPHCl. The relative intensity of the blue and green emission bands can be easily tuned by changing the polymer chain length.(3) Based on the research of NAPH-PVS, we tried to change the method of end function of the polymer with a di-color emission prepared via ATRP. Here, a series of homopolymers, poly[(4-(benzoxazole-2-yl)phenyl)methyl methacrylate] (NAPH -PMABEs) with different molecular weight, containing benzoxazole side chains and 1,8-naphthalimide terminated end, were prepared by ATRP of (4-(benzoxazole -2-yl)phenyl) methyl methacrylate (MABE) and chemical modifications with 1,8-naphthalimide moieties. The optical properties of NAPH-PMABE were investigated. Results show that NAPH-PMABE also has a composite emission spectrum comprising an ultraviolet component originated from benzoxazole side chains and a green component originated from 1,8-naphthalimide end group both in solution and film. Besides, NAPH-PMABE has obviously third-order nonlinear optical (NLO) properties which was introduced by the end-functional moieties of 1,8-naphthalimide. The NLO properties were attributed to both nonlinear absorption and refraction.(4) A series of polymers containing 1,8-naphthalimide moieties in the side chains have been prepared via RAFT technique. Firstly, five styrene and two methyl acrylate based 1,8-naphthalimide monomers were synthesized and characterized. Then, carbazyl group terminated polystyrene (CA-PSt) was used as macromolecular RAFT agent. Thus, the well-defined copolymers (CA-NAPH-PSts) containing 1,8-naphthalimide side chains and carbazole end group were obtained only for those styrene based 1,8-naththalimide monomers. The fluorescent properties of monomers and copolymers were investigated. All monomers have strong orange emissions with the maximum wavelength at 558 nm in DMF solution. In solid films, the emission maximum wavelength of CA-NAPH-PSts is red-shifted to 572 nm. Besides, all monomers and copolymers have large third-order NLO properties. The third-order NLO coefficientχ(3) was attributed to dual contributions of nonlinear absorption and refraction of the molecules. Also, we investigated the third-order NLO properties of CA-NA6PH-PSt in film state.