Synthesis And Characteristic Of Luminescent Rare Earth Chiral Liquid Crystalline Polymers

Chiral liquid crystalline polymers (CLCPs) have attracted considerable interest because of the outstanding optical properties such as selective reflection and transmission of light, circular dichroism, and thermochromism. In addition, heat resistance, good elasticity and film-forming properties increase the potential application of side-chain CLCPs, such as flat-panel displays, organic pigments and full color thermal imaging. The structure of side-chain CLCPs mainly contains the polymer backbone, the flexible spacer length and the rigidity of the mesogenic units. At present, polysiloxane, cyclosiloxane, polyacrylates, polymethacrylates and polyvinylethers are usually used as polymer backbone for CLCPs. To obtain the lower Tg and mesomorphic properties at moderate temperature, the polysiloxane backbone is usually used. Rare earth luminescent materials are applied in many optical devices, such as displays, tunable lasers and amplifiers for optical communication. Many rare earth complexes have been investigated extensively, owing to their especially efficient strong narrow-width emission band in the visible region. By incorporating rare earth complexes into liquid crystalline polymers to obtain rare earth-containing LCPs materials can overcomehe the drawbacks of high transition temperatures, unworkability and low thermal stability. In addition rare earth-containing LCPs materials improved the promising applications in many fields such as optics, electronics, mechanics, displays, luminescent dye, and so forth.In this dissertation, cholesteric monomers M1～Mg, chiral crosslinking agent M10 and nematic monomer M11 are synthesized; six series of small molecule rare earth complexes L1-Ln-L6-Ln (Ln=Eu, Tb, Dy, Sm) were synthesized with Ln3+(Ln=Eu, Tb, Dy, Sm) as the center; dibenzoylmethane, thenoyl trifluoroacetone as the first ligand and acrylic acid, allyloxy undecen acid and undecylenic acid as the second ligand; Two series of comb-like rare earth liquid crystalline polymers, two series of rare earth liquid crystal elastomers and two series of mesh rare earth liquid crystal polymer was prepared by a one-step hydrosilylation reaction, in which mesogenic monomer, chiral crosslinking agent and complexes were grafted to the main chain of PMHS. Moreover, the mesogenic monomers M3-M9、M11 and the polymers are novel. The structures and properties of the obtained liquid crystalline monomers, crosslinking agents, polymers are investigated by FT-IR spectroscopy,1H-NMR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), polarizing optical microscopy (POM), and X-ray measurement.Their structure-property relationships are discussed in detail:(1) M1～M9 exhibite enantiotropic oily-streak texture and focal-conic texture of the cholesteric phase during the heating and cooling cycles. M2 displays typical nematic threaded texture on heating cycles and schlieren texture, Silky texture and droplet texture on cooling cycles.(2) All of the polymers showed similar cholesteric Grandjean textures. Forpolymers Eu-Pi and Eu-P2 series, when the concentration of europium complexes unit increased from Omol% to 1.5mol%, Tg of Eu-P1 and Eu-P2 series increase, but Ti decrease. Eu-P1 and Eu-P2 series display wide mesophase temperature ranges (ΔT?110℃). AT values decreased with increasing the content of europiumcomplex, The 5% weight loss of all the polymers took place at the temperatures above 270℃; For polymers Eu-P3 and Eu-P4 series, when the concentrationof crosslinking units increased from 3mol% to 10.5mol%, Tg of Eu-P3 and Eu-P4 series increase, but Ti decrease. Eu-P3 and Eu-P4 series display wide mesophasetemperature ranges (ΔT>120℃). AT values decreased with increasing the content of crosslinking units, The 5% weight loss of all the polymers took place at the temperatures above 270℃; For polymers Eu-P6 and Eu-P7 series, when theconcentration of lanthanide ions increased from 1 mol% to 3.5mol%, Tg of Eu-P6and Eu-P7 series is substantially not affected, but Ti decrease. Eu-P6 and Eu-P7 series display wide mesophasetemperature ranges (Δ7>120℃).AT values decreased with increasing the content of crosslinking units, The 5% weight loss of all the polymers took place at the temperatures above 300℃.(3) Complexes L1-Eu-L6-Eu can emit characteristic fluorescence of Eu3+,The maxima of these bands were sourced from 5D0→7F2 transitions at 612 nm, Showed red; Complexes L1-sm-L6-sm can emit characteristic fluorescence of Sm3+, The maxima of these bands were sourced from 4G5/2→6H9/2 transitions at 647 nm, Showed pink; Complexes L2-Tb and L5-Tb can emit characteristic fluorescence of Tb3+, The maxima of these bands were sourced from 5D4→7F5 transitions at 545 nm, Showed green;(4) Polymers Eu-P1 and Eu-P2 series can emit characteristic fluorescence of Eu3+, when Eu3+ ion content increases the luminescent intensity of the polymers gradually increases accordingly. At Eu3+(mol%)=1.5%, polymers still did not show fluorescence quenching; Polymers Eu-P3 and Sm-P4 series can emit characteristic fluorescence of Eu3+ and Sm3+, the fluorescence intensity and fluorescent lifetime of Eu-P3 and Sm-P4 series decreased monotonically with the increasing temperature in the studied range; Polymers Eu-P6 and Tb-P7 series can emit characteristic fluorescence of Eu+ and Tb+, the fluorescence intensity decreased monotonically with the increasing temperature in the studied range.