Diyne polycyclotrimerizations initiated by transition-metal catalysts afforded hyperbranched polyphenylenes, which exhibited low viscosity, outstanding thermal stability, and small optical dispersion. Under optimized reaction conditions, polycyclotrimerizations of 1,8-nonadiyne (1) and 1,9-decadiyne (2) catalyzed by TaCl₅-Ph₄Sn produced hyperbranched poly(1,2,4-benzenetriyl-1,5-pentanediyl) (3) and poly(1,2,4-benzenetriyl-1,6-hexanediyl) (4),^1-5 respectively, in high yields (up to 93%). The polymers were completely soluble and film-forming, and possessed high molecular weights (M_w up to ∼1.4 × 10⁶) but low intrinsic viscosities ([η] down to 0.13 dL/g). Their structures and properties were analyzed and evaluated by IR, UV, NMR, SEC, TGA, DSC, spectrofluorometry, light scattering, and spectroellipsometry. The structural characterizations confirmed the expected hyperbranched molecular architectures of 3 and 4 (comprising of 1,2,4-benzene rings and αω-alkyl spacers) and revealed the regioselective feature of the diyne polycyclotrimerizations. Polymers 3 and 4 underwent glass transitions at 43 and 23°C, respectively, and lost almost no weights when heated to ∼500°C. Polymer 3 emitted UV light upon excitation, whereas 4 was practically nonluminescent. The thin films of 3 were highly transparent (>99.5% transmittance) and displayed an optical dispersion as low as 0.009 in the visible spectral region, much superior to those of the commercially important "organic glasses" such as poly(methyl methacrylate) and polycarbonates.

Kaitian Xu;Han Peng;Qunhui Sun;Yuping Dong;Fouad Salhi;Jingdong Luo;军武 陈;一 黄;Dezhen Zhang;Zhongde Xu;本忠 唐

Macromolecules

2002-7-16

The detection of food spoilage is a major concern in food safety as large amounts of food are transported globally. Direct analysis of food samples is often time-consuming and requires expensive analytical instrumentation. A much simpler and more cost-effective method for monitoring food fermentation is to detect biogenic amines generated as a by-product during food decomposition. In this work, a series of 1,2-dihydroquinoxaline derivatives (DQs) with aggregation-induced emission (AIE) characteristics were synthesised and their protonated forms, that is, H⁺DQs, can be utilised for the sensitive detection of biogenic amines. For example, upon exposure to amine vapours, deprotonation occurs that converts the red-coloured, non-emissive H⁺DQ2 back to its yellow-coloured, fluorescent parent form. The bimodal absorption and emission changes endow the system with high sensitivity, capable of detecting ammonia vapour at a concentration of as low as 690 ppb. Taking advantage of this, H⁺DQ2 was successfully applied for the detection of food spoilage and was established as a robust and cost effective technique to monitor food safety.

Parvej Alam;Nelson L.C. Leung;Huifang Su;Zijie Qiu;Ryan T.K. Kwok;Jacky W.Y. Lam;本忠 唐

Chemistry - A European Journal

2017-10-20

A chiral tetraphenylethene derivative with two valine-containing attachments (TPE-DVAL), was synthesized by Cu(I)-catalyzed azide-alkyne click reaction. The optical properties and self-assembling behaviours of TPE-DVAL were investigated. The molecule is non-emissive and circular dichroism (CD)-silent in solution, but shows strong fluorescence and Cotton effects in the aggregation state, demonstrating aggregation-induced emission (AIE) and CD (AICD) characteristics. TPE-DVAL exhibits good circularly polarized luminescence (CPL) when depositing on the surface of quartz to allow the evaporation of its 1,2-dichloroethane solution. SEM and TEM images of the molecule show that the molecule readily self-assembles into right-handed helical nanofibers upon the evaporation of its solvent of DCE. The molecular alignments and interactions in assembling process are further explored through XRD analysis and computational simulation. The driving forces for the formation of the helical fibers were from the cooperative effects of intermolecular hydrogen bonding, €- € interactions and steric effect.

Hongkun Li;Xiaoyan Zheng;Huimin Su;Jacky W.Y. Lam;Kam Sing Wong;Shan Xue;Xuejiao Huang;Xuhui Huang;Bing Shi Li;本忠 唐

Scientific Reports

2016-1-13

The visualization of microphase separation in immiscible polymer blends is of great academic and industrial significance as the phase-separated structures are directly associated with the properties and performances of the blend materials and ultimately influence the corresponding product quality. However, conventional techniques for detecting microphase separation are generally expensive and time-consuming with troublesome and even destructive sample preparation procedures. Complicated and highly material-dependent chemical reactions or interactions are often involved in some characterization approaches. In this work, we demonstrated a simple, fast, and powerful method for high-contrast visualization and differentiation of micrometer-sized phase separation in polymer blends using luminogens with aggregation-induced emission characteristics (AIEgens) as fluorescent probes. This method relies on the sensitive fluorescence response of AIEgens to the change of environmental rigidity and polarity and operates based on the mechanisms of "restriction of intramolecular motions" and "twisted intramolecular charge transfer". The working principle indicates that this visualization strategy is applicable to a wide scope of polymer blends comprised of components with different rigidities and/or polarities.

Ting Han;Chen Gui;Jacky W.Y. Lam;Meijuan Jiang;Ni Xie;Ryan T.K. Kwok;本忠 唐

Macromolecules

2017-8-8

Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation-induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far-red/near-infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three-pronged PDT.

Wenhan Xu;Michelle M.S. Lee;Jing Jun Nie;Zhihan Zhang;Ryan T.K. Kwok;Jacky W.Y. Lam;Fu Jian Xu;Dong Wang;本忠 唐

Angewandte Chemie - International Edition

2020-6-8

Polyhydroaminations for the synthesis of stable nitrogen-substituted conjugated polymers with well-defined structures remain a great challenge and the control of the regio- and stereochemistry of the enamine product of the hydroamination is non-trivial. Herein we report an efficient tandem polymerization of alkynes, carbonyl chlorides and primary amines to afford regio- and stereoregular conjugated poly(enaminone)s. The atom-economical one-pot sequential polycoupling-hydroamination polymerization catalyzed by Pd(PPh₃)₂Cl₂/CuI proceeded smoothly under mild conditions, furnishing nitrogen-substituted conjugated polymers with high molecular weights (up to 46100) and high regio-/stereoregularities (100%) in nearly quantitative yields (up to 99%). The single crystal structure of the model compound, together with the NMR spectra comparison of the model compound and polymers provided direct insight into the stereoselectivity of the polymerization, verifying the sole Z-vinylene isomer of the polymers. Through the exquisite structural design strategy of the intramolecular hydrogen bond of the resulting hydroamination product, the tautomerization between enamine and imine as well as E/Z isomerization was successfully avoided, providing products with high chemical stability and sole Z-vinylene isomers. The conjugated polymers display excellent solubility in common organic solvents, good film-forming ability, and high thermal stability. The hydrogen bond formation of the polymer helps to block the potential photo-induced electron transfer process and the polymer shows a unique aggregation-enhanced emission phenomenon: their solutions are weakly emissive, while their nanoaggregates or thin films are brightly emissive. Furthermore, thin films of the polymers enjoy high refractive indices (1.9103-1.6582) in a wide wavelength region of 400-1000 nm, which can be further modulated by UV irradiation. Meanwhile, well-resolved fluorescent photopatterns of the polymers can be fabricated through the UV irradiation of thin films via a copper photomask.

Haiqin Deng;Rongrong Hu;Anakin C.S. Leung;Engui Zhao;Jacky W.Y. Lam;本忠 唐

Polymer Chemistry

2015-6-28

We successfully synthesized hyperbranched poly(triazole)s by in situ click polymerization of diazides 1 and triyne 2 monomers on different metal surfaces (copper, iron, and aluminum) and characterized their adhesive properties. Optimizations were performed to obtain high adhesive strength at different temperatures by analyzing the effects of curing kinetics, annealing temperature and time, catalyst, monomer ratio, surface conditions, alkyl chain length of diazides 1, etc. The adhesive bonding strength with metal substrate is 2 orders of magnitude higher than similar hyperbranched poly(triazole)s made by click polymerization and clearly higher than some commercial adhesives at elevated temperatures. With the same conditions, adhesives prepared on aluminum and iron substrates have higher adhesive strength than those prepared on copper substrate, and an excess of triyne 2 monomer in synthesis has greater adhesive strength than an excess of diazide 1 monomer. Tof-SIMS experiment was employed to understand these phenomena, and the existence of an interphase between the polymer and metal surface was found to be critical for adhesive bonding with thicker interphase (excess of triyne 2 monomer) and the higher binding energy between polymer atoms and substrate atoms (e.g., aluminum substrate) generating the higher bonding strength. In addition, the light-emitting property of synthesized polymers under UV irradiation can be used to check the failure mode of adhesive bonding.

Youhong Tang;Cathy K.W. Jim;Yang Liu;Lin Ye;Anjun Qin;Jacky W.Y. Lam;Chengbi Zhao;本忠 唐

ACS applied materials & interfaces

2010-2-24

Azide-alkyne click polymerization has become a powerful and popular technique for the preparation of polytriazoles with diverse topological structures and versatile properties. However, the synthesis of post-functionalizable 1,4,5-trisubstituted polytriazoles (1,4,5-PTAs) is still a challenge. In this work, a metal-free polycycloaddition of aldehyde-activated internal diynes and diazides is developed, and a series of soluble and thermally stable poly(formyl-1,2,3-triazole)s (formyl-PTAs) with high weight-average molecular weights (Mw, up to 54 550) are facilely produced in high yields (up to 93%). The tetraphenylethene moiety containing formyl-PTAs exhibit unique aggregation-induced emission features. Moreover, the aldehyde groups at the C-5/C-4 positions of triazole rings in the formyl-PTA enable it to be a highly selective chemosensor for hydrazine detection and to serve as a useful platform for further post-functionalization, enriching the properties of proto-polytriazole as desired. Thus, this work combines a metal-free approach toward 1,4,5-PTAs with a post-functionalization strategy to pave a way for the development of a multitude of functional polytriazole-based materials.

Baixue Li;Anjun Qin;本忠 唐;Ben Zhong Tang

Polymer Chemistry

2020-5-7

Nanocomposites reinforced with hybrid fillers of carbon nanotubes (CNTs) and carbon black (CB) are developed, aiming at enhancing the electrical conductivity of composites with balanced mechanical properties while lowering the cost of the final product. Epoxy-based nanocomposites were prepared with varying combinations of CNTs and CB as conducting fillers, and their electrical and mechanical properties were evaluated. It was shown that the addition of CNTs in CB composites enhanced the electrical conductivity of composites: a low percolation threshold was achieved with 0.2 wt % CNTs and 0.2 wt % CB particles. The CB particles also enhanced the ductility and fracture toughness of nanocomposites, confirming the synergistic effect of CB as a multifunctional filler. The novelty of this work lies in the synergy arising from the combination of two conducting fillers with unique geometric shapes and aspect ratios as well as different dispersion characteristics, which have not been specifically considered previously.

鹏程 马;Ming Yang Liu;Hao Zhang;Sheng Qi Wang;Rui Wang;Kai Wang;Yiu Kei Wong;本忠 唐;Soon Hyung Hong;Kyung Wook Paik;Jang Kyo Kim

ACS applied materials & interfaces

2009-5-27

Molecular science entails the study of structures and properties of materials at the level of single molecules or small interacting complexes of molecules. Moving beyond single molecules and well-defined complexes, aggregates (i.e., irregular clusters of many molecules) serve as a particularly useful form of materials that often display modified or wholly new properties compared to their molecular components. Some unique structures and phenomena such as polymorphic aggregates, aggregation-induced symmetry breaking, and cluster excitons are only identified in aggregates, as a few examples of their exotic features. Here, by virtue of the flourishing research on aggregation-induced emission, the concept of “aggregate science” is put forward to fill the gaps between molecules and aggregates. Structures and properties on the aggregate scale are also systematically summarized. The structure–property relationships established for aggregates are expected to contribute to new materials and technological development. Ultimately, aggregate science may become an interdisciplinary research field and serves as a general platform for academic research.

Haoke Zhang;Zheng Zhao;Andrew T. Turley;Lin Wang;Paul R. McGonigal;Yujie Tu;Yuanyuan Li;Zhaoyu Wang;Ryan T.K. Kwok;Jacky W.Y. Lam;本忠 唐

Advanced Materials

2020-9-1