Phase Behaviors and Photoresponsive Thin Films of Syndiotactic Side-Chain Liquid Crystalline Polymers with High Densely Substituted Azobenzene Mesogens

Azobenzene-containing polymers (azopolymers) are a kind of fascinating stimuli-responsive materials with broad and versatile applications. In this work, a series of syndiotactic C1 type azopolymers of Pm-Azo-Cn with side-chain azobenzene mesogens of varied length alkoxy tails (n=1, 4, 8, 10) and different length alkyl spacers (m=6, 10) have been prepared via Rh-catalyzed carbene polymerization. The thermal properties and ordered assembly structures of thus synthesized side chain liquid crystalline polymers (SCLCPs) have been systematically investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM) and variable-temperature small/wide-angle X-ray scattering (SAXS/WAXS) analyses. P10-Azo-C1 and P10-Azo-C4 with shorter alkoxy tails exhibited hierarchical structures SmB/Colob and transformed into SmA/Colob at a higher temperature, while P10-Azo-C8 and P10-Azo-C10 with longer alkoxy tails only displayed side group dominated layered SmB phase and transformed into SmA phase at higher temperatures. For P6-Azo-C4 with a shorter spacer only showed a less ordered SmA phase owing to interference by partly coupling between the side chain azobenzene mesogens and the helical backbone. More importantly, the series high densely substituted syndiotactic C1 azopolymer thin films, exhibited evidently and smoothly reversible photoresponsive properties, which demonstrated promising photoresponsive device applications.

Quasi-Chromophores Segregated by Single-Chain Nanoparticles of Fluorinated Zwitterionic Random Copolymers Showing Remarkably Enhanced Fluorescence Emission Capable of Fluorescent Cell Imaging

Organic and polymer fluorescent nanomaterials are a frontier research focus. Here in this work, a series of fluorinated zwitterionic random copolymers end-attached with a quasi-chromophoric group of pyrene or tetraphenylethylene (TPE) are well synthesized via atom transfer radical polymerization with activators regenerated by electron transfer (ARGET ATRP). Those random copolymers with total degree of polymerization 100 or 200 are able to produce fluorescent single-chain nanoparticles (SCNPs) through intra-chain self-folding assembly with quite uniform diameters in the range of 10-20 nm as characterized by dynamic light scattering and transmission electron microscopy. By virtue of the segregation or confinement effect, both SCNPs functionalized with pyrene or TPE group are capable of emitting fluorescence, with pyrene tethered SCNPs exhibiting stronger fluorescence emission reaching the highest quantum yield ≈20%. Moreover, such kind of fluorescent SCNPs manifest low cytotoxicity and good cell imaging performance for Hela cells. The creation of fluorescent SCNPs through covalently attached one quasi-chromophore to the end of one fluorinated zwitterionic random copolymer provides an alternative strategy for preparing polymeric luminescence nanomaterials, promisingly serving as a new type of fluorescent nanoprobes for biological imaging applications.

Synthesis and Characterization of Pyridine-Grafted Copolymers of Acrylic Acid-Styrene Derivatives for Antimicrobial and Fluorescence Applications

The goal of the present study was to copolymerize 3-(4-acetylphenylcarbamoyl) acrylic acid and styrene using azo-bis-isobutyronitrile (AIBN) as a catalyst. The resulting copolymers exhibited number average molecular weights (Mn) of 3.73-5.23 × 104 g/mol with a variable polydispersity (PDI = 2.3-3.8). The amide group of the PMA/PSA polymer was used for grafting poly (-styrene-maleic acid substituted aromatic 2-aminopyridine) by the Hantzsch reaction using a substituted aromatic aldehyde, malononitrile, and ammonium acetate. The polymer can emit strong blue fluorescence (λ = 510 nm) and its thermal stability and solubility were enhanced by polymer grafting. Moreover, the polymer showed the fluorescence spectra of the copolymer had a strong, broad emission band between 300 to 550 nm (maximum wavelength 538 nm) under excitation at 293 nm. The Hantzsch reaction yields an interesting class of nitrogen-based heterocycles that combine with a synthetic strategy for synthesis of grafted co-polymer pyridine-styrene derivatives. The as-prepared pyridine-based polymer compounds were screened against Gram-positive and Gram-negative bacteria, where a maximum inhibition zone toward all four types of bacteria was observed, including specific antifungal activity. Herein, a series of pyridine compounds were synthesized that showed enhanced fluorescent properties and antimicrobial properties due to their unique structure and ability to form polymer assemblies.

Dinuclear complexes of Mn, Co, Zn and Cd assembled with 1,4-cyclohexanedicarboxylate: synthesis, crystal structures and acetonitrile fluorescence sensing properties

Selective and reversible fluorescence sensing of acetonitrile in water by [Cd₂(H₂O)₂(chdc)₂(bipy)₂]·H₂O with a detection limit of 1.1 × 10⁻⁶ M.

Effects of solvents, additives, and π-allyl ligand structures on the polymerization behavior of diazoacetates initiated by π-allylPd complexes

We have revealed that the quality of control of the polymerization was improved by adding some compounds and polymer tacticity was dependent on the structures of π-allyl ligands.