Optical Properties of Nd^3＋ in Nd（DBM）3Phen-doped Poly（methyl methacrylate）

Nd（DBM）3Phen-doped （DBM is dibenzoylmethane and Phen is phenanthroline） polymethyl methacrylate （PMMA） is prepared. Optical absorption, excitation and emission spectra were analyzed for Nd^3＋ in Nd（DBM）3Phen-doped PMMA. Using the Judd-Ofelt theory, the absorption spectrum was analyzed. The Judd-Ofelt（J-O） intensity parameters of Nd（DBM）3Phen-doped polymethyl methacrylate were calculated to be Ω2 = 20.97 × 10^-20 cm^2, Ω4= 3.42 × 10^-20 cm^2, Ω6 = 2.90 × 10^-20 cm^2. The radiative lifetime （631 μs） of the excited 4F3/2 level is given. The stimulated emission cross-sections and the fluorescence branch ratios for the ^4F3/2 →^4Ij′ transitions are also evaluated. Analysis reveals that Nd（DBM）3Phen-doped PMMA is promising for application in polymer optical fibers and planar waveguides.

Near-Field Scattering Enhancement of Perylene Based Aggregates for Random Lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes(POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N′-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide(DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

Photo-induced Alignment Behavior of Azobenzene-containing Polymer Films with Different Cross-linking Degree

Three series of amorphous copolymers containing azobenzene groups with various substituents and certain amounts of crosslinkable acrylic groups were prepared. The cross-linked polymer films were obtained by thermal polymerization of the acrylic groups in the copolymers, during which, by controlling the time of cross-linking reaction, the films can be made with different cross-linking degree （from 0 to 32%, which was monitored by FT-IR spectra measurement）. Photo-induced alignment process of the films was performed under irradiation with linearly polarized light at 442 nm, and the effect of cross-linking degree on the photo-induced alignment rate was investigated. The dynamics of the photo-induced alignment was analyzed with biexponential curve fitting. The photo-induced alignment rate and the maximum transmittance of the films decreased because of the cross-linking. Furthermore, for the cross-linked samples, it was found that their saturated value of transmittances keep constant after repeated ＂writing＂ and ＂erasing＂ cycles. The findings reveal that the cross-linking of the film can effectively restrain the phototactic mass transport of azopolymer during irradiation by polarized light. The relationship between the cross-linking degree and the photo-induced alignment behavior of azopolymer is discussed in detail.

Formation of [3]Pseudorotaxanes from β-cyclodextrin and a Series of Dicarboxylic Acids with Their Corresponding α,ω-alkanedicarboxylate Anions

Inclusion complexes between β-cyclodextrin （β-CD） and a series of dicarboxylic acids （DAn, n=11-15） were prepared by co-grinding and co-precipitation methods and the [3]pseudorotaxane structure of them was elucidated by FTIR, DTA and XRD characterizations. Inclusion complexes of β-CD and α,ω-alkanedicarboxylate anions （DAn^2-） were acquired by neutralizing β-CD/DAn different inclusion complexes with sodium hydroxide and the structure was also proved to be a pseudorotaxane structure by ^1H-NMR spectra and NOESY spectrum. Both the inclusion complexes of β-CD/DAn and β-CD/DAn^2- adopt the [3]pseudorotaxane structure with β-CD arranged in dimers threaded onto one aliphatic chain and the binding mode of 1：1 inclusion complex was excluded based on the consideration of chain conformations.

Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores

Three novel nonlinear chromophores with symmetric D-π-D molecular structure and extended conjugated length were synthesized. Solvatochromism analysis shows great symmetric intramolecular charge transfer occurring in chromophores by the enhancement in the dipole moment between the ground and excited states. The properties of optical power limiting induced by three-photon absorption （3PA） are demonstrated. Large 3PA coefficients and the corresponding molecular cross sections as high as 10^-74 cm^6s^2 were obtained for nanosecond laser pulses at 1.06μm from nonlinear transmission measurements.

Coordinate Bond Breaking Induced by Collapse of Poly(N-isopropyl acrylamide) as Ligands of a Rare Earth Complex

A novel water-soluble luminescent complex consisting of Eu(ally-dbm)3-2Tppo and poly(N-isopropyl acrylamide)(PNIPAM)is synthesized through a series of chemical reactions.The structure of the complex is characterized by TGA,GPC,HNMR,and the thermal-responsive uorescence of the complex in aqueous solution is investigated.It is found that PNIPAM collapse above the lower critical solution temperature causes the coordination bond breaking,leading to weakening of the uorescence from Eu3+and enhancing of the uorescence from the ligands.When temperature decreases,the uorescence from Eu3+is found to boost up and the uorescence from ligands weakens accordingly.It is deduced from this phenomenon that the ligands recoordinate with europium ions again along with the temperature decreasing,which is further confirmed by IR measurements.This thermal-responsive uorescence is of reversibility,which can be used as molecular probes for biological imaging and collapse studying of PNIPAM.

Photoinduced Reversible Solid-to-Liquid Transitions and Directional Photofluidization of Azobenzene-containing Polymers

Photoinduced reversible liquefaction and solidification of polymers enable processing and healing of polymers with light.Some azobenzene-containing polymers(azopolymers)exhibit two types of photoinduced liquefaction properties:photoinduced reversible solid-to-liquid transition and directional photofluidization.For the first type,light switches the glass transition temperature(T_(g))values of azopolymers and induces reversible solid-to-liquid transitions.For the second type,polarized light guides solid azopolymers to flow along the polarization direction.Here,we compare the two types of photoliquefaction and discuss their mechanisms.Recent progresses and applications based on photoliquefaction of azopolymers are also highlighted.