Hyperbranched Conjugated Polysiloles: Synthesis, Structure, Aggregation-Enhanced Emission, Multicolor Fluorescent Photopatterning, and Superamplified Detection of Explosives

• Published in: Macromolecules Vol. 43; no. 11; pp. 4921 - 4936
• Main Authors: Liu, Jianzhao, Zhong, Yongchun, Lam, Jacky W. Y, Lu, Ping, Hong, Yuning, Yu, Yong, Yue, Yanan, Faisal, Mahtab, Sung, Herman H. Y, Williams, Ian D, Wong, Kam Sing, Tang, Ben Zhong
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 08.06.2010
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Five membered ring; Silicon heterocycle; Molecular structure; Photoluminescence; Fluorescence; Curing (plastics); Silicon copolymer; Optical properties; Luminescence quenching; Hyperbranched copolymer; Aromatic copolymer; Picric acid; Phenylene copolymer; Photolithography; Chemical reactivity; Fluorescence detector; Cyclopolymerization; Heterocyclic copolymer; Particle suspension; Branched copolymer; Experimental study; Absorption spectrum; Thermosetting resin; Luminescence decay; Organic solution; Conjugated copolymer; Cyclopolymer; Preparation; Soluble compound; Light sensitive copolymer; Explosives; Diynic compound
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma902432m

Hyperbranched poly(2,5-silole)s [hb-P1(m), m = 1, 6] are synthesized for the first time in this work. 1,1-Dialkyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsiloles [1(m)] were polymerized by TaBr5, affording hb-P1(m) with high molecular weights (M w up to 2.5 × 105) in high yields (up to 98%). The structures of hb-P1(m) were characterized by spectroscopic methods and the degree of branching of hb-P1(6) was determined to be 0.55. The hyperbranched polymers are soluble and stable, with no changes in solubility observed after they have been stored under ambient conditions for more than two years. Absorption and emission spectra of hb-P1(m) are red-shifted from those of 1(m), indicating that the polymers are more conjugated than the monomers. Both 1(m) and hb-P1(m) are nonemissive or weekly fluorescent when dissolved in their good solvents but become highly emissive when aggregated in their poor solvents or fabricated into thin solid films, showing unusual phenomena of aggregation-induced (AIE) and -enhanced emissions (AEE). Restriction of intramolecular rotations in the aggregate state is rationalized to be the main cause for the AIE and AEE effects. Photoluminescence (PL) of 1(m) and hb-P1(m) is tunable by varying their concentrations and morphologies. The polymers are readily cured when heated to high temperatures or upon photoirradiation, furnishing cross-linked networks with novel excitation wavelength-dependent emissions in the red spectral region. Photolithography of hb-P1(m) generates fluorescent photopatterns, with the exposed and unexposed areas emitting lights with different colors. The polymers function as sensitive fluorescent chemosensors for the detection of explosives, with a superamplification effect observed in the emission quenching of the polymer nanoaggregates by picric acid.