Photodegradation of polyfluorene and fluorene oligomers with alkyl and aromatic disubstitutions

The stability of fluorene-based compounds and polymers, especially at the bridged C-9 position under photoirradiation and thermal treatment, has claimed wide attention. We report the electronic, vibrational, and MALDI-TOF mass spectral combined studies for the fluorene oligomers with alkyl and aromatic substitutions under UV-light irradiation. The low-energy emission and the formation of ketonic defects after degradation highly depend on the proportion of alkyl substitution. The oligomer with fully aromatic substitution shows good stability, but when the proportion of alkyl substitution increases, their photostability rapidly decreases. The mass spectra show not only the mass of the fluorenone-fluorene trimer but also another new degradation product with a large mass (pristine oligomer plus 14) from alkyl oxidation, which testify to the assistance of alkyl side chain during degradation. We propose that the degradation of fluorene is a radical chain process propagated by alkyl side chains, and then the different stability between alkyl and aromatic substitution can be well explained.     

讲授高分子化学中缩聚反应的点滴体会

讨论了高分子化学课程教学过程中有关缩聚反应所涉及的反应程度、平均官能度的理解、缩聚物数均聚合度的计算以及它们之间的关系     

"Click" immobilization on alkylated silicon substrates: model for the study of surface bound antimicrobial peptides

We describe an effective approach for the covalent immobilization of antimicrobial peptides (AMPs) to bioinert substrates via Cu(I) -catalyzed azide-alkyne cycloaddition (CuAAC). The bioinert substrates were prepared by surface hydrosilylation of oligo(ethylene glycol) (OEG) terminated alkenes on hydrogen-terminated silicon surfaces. To render the OEG monolayers "clickable", mixed monolayers were prepared using OEG-alkenes with and without a terminal alkyne protected by a trimethylgermanyl (TMG) group. The mixed monolayers were characterized by X-ray photoelectron spectroscopy (XPS), elliposometry and contact angle measurement. The TMG protecting group can be readily removed to yield a free terminal alkyne by catalytic amounts of Cu(I) in an aqueous media. This step can then be combined with the subsequent CuAAC reaction. Thus, the immobilization of an azide modified AMP (N3-IG-25) was achieved in a one-pot deprotection/coupling reaction. Varying the ratio of the two alkenes in the deposition mixture allowed for control over the density of the alkynyl groups in the mixed monolayer, and subsequently the coverage of the AMPs on the monolayer. These samples allowed for study of the dependence of antimicrobial activities on the AMP density. The results show that a relative low coverage of AMPs (～1.6×10(13) molecule per cm(2)) is sufficient to significantly suppress the viability of Pseudomonas aeruginosa, while the surface presenting the highest density of AMPs (～2.8×10(13) molecule per cm(2)) is still cyto-compatible. The remarkable antibacterial activity is attributed to the long and flexible linker and the site-specific "click" immobilization, which may facilitate the covalently attached peptides to interact with and disrupt the bacterial membranes.     

Testing the quantum effects near the event horizon with respect to the black hole shadow

In recent years, the study of quantum effects near the event horizon of a black hole (BH) has attracted extensive attention. It has become one of the important methods to explore BH quantum properties using the related properties of a quantum deformed BH. In this work, we study the effect of a quantum deformed BH on the BH shadow in two-dimensional Dilaton gravity. In this model, quantum effects are reflected by the quantum correction parameter m. By calculation, we find that: (1) the shape of the shadow boundary of a rotating BH is determined by the BH spin a, the quantum correction parameter m, and the BH type parameter n; (2) when the spin \begin{document}$ a=0 $\end{document}, the shape of the BH shadow is a perfect circle; when \begin{document}$ a\neq 0 $\end{document}, the shape is distorted; if the quantum correction parameter \begin{document}$ m=0 $\end{document}, their shapes reduce to the cases of a Schwarzschild BH and Kerr BH, respectively; (3) the degree of distortion of the BH shadow is different for various quantum correction parameters m; with an increase in the parameter m, the boundary of the BH shadow expands; (4) the size of the BH shadow varies greatly with respect to various quantum deformed BHs (n), and the change in BH shadow shape caused by parameter n is similar to that caused by parameter m, which indicates that there is a "degenerate phenomenon" between the two parameters. Because the value of m in actual physics should be very small, the current observations of the event horizon telescope (EHT) cannot distinguish quantum effects from the BH shadow. In future BH shadow measurements, it will be possible to distinguish quantum deformed BHs, which will help to better understand the quantum effects of BHs.     

Dependence of solutions and eigenvalues of measure differential equations on measures

It is well known that solutions of ordinary differential equations are continuously dependent on finite-dimensional parameters in equations. In this paper we study the dependence of solutions and eigenvalues of second-order linear measure differential equations on measures as an infinitely dimensional parameter. We will provide two fundamental results, which are the continuity and continuous Fréchet differentiability in measures when the weak^? topology and the norm topology of total variations for measures are considered respectively. In some sense the continuity result obtained in this paper is the strongest one. As an application, we will give a natural, simple explanation to extremal problems of eigenvalues of Sturm–Liouville operators with integrable potentials.     

Lifetime measurements of the C1Π1 and B3Pi1 electronic states of InCl by laser induced fluorescence

The laser-induced fluorescence spectra of the InCl molecule over the range 266.5–287.0nm and 332.0–373.0nm are reported and assigned to C¹Π₁-X¹Σ⁺, B₃Π₁-X¹Σ⁺, or A³Π₀-X¹Σ⁺ transitions. It is the first time those radiative lifetimes of the C¹Π₁ and B³Π₁ states have been measured by laser-induced fluorescence. The collision-free fluorescence radiative lifetime τ₀ = 353(7)ns and a quenching rate constant k _Q = 1.985(0.010)x 10^-10 cm³ molecule^-1 s^-1 are proposed for B³Π₁ and τ₀ = 11(1)ns for C¹Π₁ states. From the radiative lifetime τ₀ and the Franck-Condon factors q_v″v′ for the v′ - v″ transitions, the electronic transition moments |R_e|² of the B³Π₁ and C¹Π₁ states have been obtained.     

亚铁离子对驱油聚合物溶液黏度的影响及其降黏机理

采用NaOH沉淀法去除胜坨油田T28区污水含有的亚铁离子(Fe2+),使配制的聚合物溶液黏度增加,通过红外光谱仪(IR)、荧光光谱仪及扫描电子显微镜(SEM)对Fe2+的降黏机理进行了分析。 结果表明,采用NaOH沉淀法处理Fe2+含量为5.9 mg/L的污水,控制pH=9,聚合物溶液的黏度可由19.17 mPa·s提高到92.50 mPa·s。 Fe2+使聚合物大分子发生断链,分子间的缔合作用减弱,破坏了分子链间形成的空间网络结构,导致溶液黏度显著降低;当用NaOH处理Fe2+后形成了Fe(OH)2沉淀而析出,同时使聚合物分子链间形成致密的空间网络结构。     

双准均衡合作对策\tau值的公理化

介绍了能准确刻画现实生活中每个参与者有三种选择的双合作对策,在此基础上研究了双合作对策的\tau值,并对双准均衡合作对策的\tau值进行了公理化,其中双合作对策的上向量、间隙函数、让步向量的构造是刻画其\tau值的基础.