Ionic complex of a rhodamine dye with aggregation-induced emission properties.

An AIE-active rhodamine based luminogen was prepared via a complexation reaction between non-emissive rhodamine hydrazide (RdH) and bulky camphorsulfonic acid (CSA). Besides acting to open the spirolactam ring of RdH, CSA also imposes a rotational restriction on the resultant ionic complex, RdH(CSA)x. Without CSA, the analogous complex RdH(HCl)3 is a luminogen with aggregation-caused quenching (ACQ) properties. The ionic bonds of RdH(CSA)3 are sensitive to several external stimuli and therefore it is a luminescent sensor for metal ions, organic amines and the blood protein bovine serum albumin (BSA). Besides being a sensor for BSA, the ionic RdH(CSA)3 is also a denaturant capable of uncoiling the peptide chain of BSA.

Complexation of fluorescent tetraphenylthiophene-derived ammonium chloride to poly(N-isopropylacrylamide) with sulfonate terminal: aggregation-induced emission, critical micelle concentration, and lower critical solution temperature.

Amphiphilic polymers with hydrophilic poly(N-isopropylacylamide) (PNIPAM) shell connecting hydrophobic tetraphenylthiophene (TP) core, which has the novel aggregation-induced emission (AIE) property, by ionic bonds were prepared to explore the AIE-operative emission responses toward critical micelle concentration (CMC) and lower critical solution temperature (LCST). To exercise the idea, ammonium-functionalized TP2NH(3)(+) and sulfonate-terminated PNIPAM were separately prepared and mixed in different molar ratios to yield three amphiphilic TP-PNIPAMn complexes for the evaluations of CMC and LCST by fluorescence responses. The nonemissive dilute aqueous solutions of TP-PNIPAMn became fluorescent when increasing concentrations above CMC. Heating micelles solution to temperatures above LCSTs causes further enhancement on the emission intensity. The fluorescence responses are explained by the extent of aggregation in the micelles and in the globules formed at room temperature and at high temperatures, respectively.

Micro- and Mesoporous Carbons Derived from KOH Activations of Polycyanurates with High Adsorptions for CO2 and Iodine.

The adsorption ability of porous carbons toward contaminants is closely related to the porous structures and the working functional groups. In this aspect, two porous carbons, with the potential use as adsorbents for CO2 and iodine, were prepared from polycyclotrimerizations (PCTs) of flexible bisphenyl A dicyanate (BPAC) and rigid binaphthalenyl dicyanate (BNC) cyanate ester monomers. Primarily, PCT reactions of BPAC and BNC generated the respective nonporous c-BPAC and c-BNC precursors, which contain high amounts of nitrogen and oxygen heteroatoms. Further KOH activations of c-BPAC and c-BNC produced the respective porous a-BPAC and a-BNC carbons, which mainly contain oxygen heteroatoms. The a-BNC derived from rigid BNC contains both micro- and mesopores and is high in adsorbing both CO2 (6.3 mmol/g) and iodine; in contrast, the microporous a-BPAC is lower in adsorbing CO2 (3.9 mmol/g) and iodine. The effects of molecular flexibility of the starting cyanate ester on the micro- and mesopore distribution as well as the CO2 and iodine adsorption behaviors of the porous carbons are therefore probed in this study.

Pyrene-Terminated, Amphiphilic Polypeptide and Its Hydrogen-Bonded Interpolymer Complex as Delivery Systems of Doxorubicin.

The intensity ratio between the first (373 nm) and the third (383 nm) vibronic peaks [I 1/I 3, as the pyrene (Py) scale] of fluorescent Py was used to monitor the critical concentration, drug-loading, and -releasing behaviors of a Py-terminated, amphiphilic polypeptide PPM and its hydrogen-bonded interpolymer complex (HIPC) with poly(acrylic acid) (PAA). Primarily, an amphiphilic PPM with a hydrophobic Py terminal and hydrophilic methoxy-bis(ethylene oxide) pendant groups was synthesized through multiple preparative steps, and the resultant PPM was thoroughly mixed with PAA through a preferable hydrogen bond (H bond) interaction to form HIPC. The emission study suggested that the I 1/I 3 ratio and the quantum yield (ΦF) are effective in determining the critical concentrations of the aqueous PPM and PPM/PAA solutions. Moreover, the I 1/I 3 ratio and ΦF were found to be convenient measures for determining the amounts of doxorubicin drugs loaded by and released from the aqueous PPM and PPM/PAA solutions.

Highly Stretchable, Self-Healable Elastomers from Hydrogen-Bonded Interpolymer Complex (HIPC) and Their Use as Sensitive, Stable Electric Skin.

There is a growing interest in developing stretchable strain sensors to quantify the large mechanical deformation and strain associated with the activities for a wide range of species. Herein, we constructed elastomeric, healable hydrogen-bonded interpolymer complex (HIPC) rubberlike film by complexation of hydrogen-bond (H-bond)-donating poly(acrylic acid) (PAA) and H-bond-accepting poly(ethylene oxide) (PEO) (or poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (F108)). All HIPC elastomers prepared from varied PAA/PEO (or PAA/F108) ratios are healable elastomers with high extensibility (with the highest strain of 1400%). Recovery of all films can automatically occur or be accelerated by externally added water droplet. The stress- and strain healing efficiencies (ησ and ηε) of the water-assisting healed PAA/F108 blends are as high as 99%. Furthermore, stretchable and healable conductor films were fabricated from silver nanowire-printed (Ag-p) and the single-walled carbon nanotube-blended (SW-b) conductor films, respectively. The healable Ag-p conductor film is an ultrasensitive strain sensor, exhibiting large electric resistance variation when stretched. In contrast, the healable SW-b film is an ultrastable strain sensor with reversible resistance strain response over 200 stretching release cycles within a high strain range of 500%. Therefore, this study provides a new and flexible HIPC strategy for the fabrication of stretchable, ultrasensitive, and stable self-healing electrode materials.

Light-Up of Rhodamine Hydrazide to Generate Emissive Initiator for Polymerization and to Afford Photochromic Polypeptide Metal Complex.

Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG⁻NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG⁻NCA to R-C, the spirolactam ring of R-C was opened by PLG⁻NCA, rendering emissive, ring-open R-O to initiate ROP of PLG⁻NCA. The emissive R-O moiety therefore produced fluorescent R⁻PLG with aggregation-induced emission (AIE) properties. Moreover, R⁻PLG was found to exhibit photochromic properties with good fatigue resistance and long lifetime when forming metal complexes with Sn(II) and Fe(III). In the dark, irradiated metal complexes slowly (~50 min) restored to the initial state. This research provides foundation for the development of new photochromic materials with long lifetime.

Protein quantitation by complexation of fluorescent tetraphenylthiophene cation to anion-terminated poly(N-isopropylacrylamide): aggregation-enhanced emission and electrostatic interaction.

A fluorescent biological sensor utilizing aggregation-enhanced emission (AEE) property was developed in our laboratory. First, the AEE-active fluorescent tetraphenylthiophene (TP) unit was synthetically connected to poly(N-isopropylacrylamide) by covalent and ionic bonds, resulting in the respective c- and i-TP-PNIPAM for the detection and quantification of the bovine serum albumin (BSA) model protein. When bind to BSA, the ionic i-TP-PNIPAM shows much better fluorescence (FL) sensitivity compared to c-PNIPAM. The fluorescence (FL) intensity of i-TP-PNIAPM displays a good linear dependence on concentration of BSA (0-1 mg/mL), indicating quantitative fluorimetric protein detection can be achieved. Further addition of anionic surfactant of sodium dodecylsulfate (SDS) considerably raised the FL intensity of the complex solution. All the FL response was discussed in term of conformational freedom of the TP unit under different environmental constraints.

Self-Scrolling Nanotubular Structure of Amorphous Vinyl Polymer Containing Tetraphenylthiophene-quinoline Pendant Groups.

In this communication, we report a scroll-like nanotubular structure found in an amorphous vinyl polymer of PS-Qu containing fluorescent tetraphenyl-quinoline (TP-Qu) pendant groups. By spin-casting dilute solution of PS-Qu, long nanoribbons with heights in correlated to the molecular width of TP-Qu pendant groups formed. On the contrast, single-, double-, and multiple-walled nanoscrolls are the major structures existing in the products from the slow-evaporation process. Presumably, scrolling of nanoribbons result in the scroll-like nanotubular structures with the resolved layer thickness in dimension close to molecular width of the TP-Qu pendant. Computer simulation on the single PS-Qu chain suggests the existence of a straight-chain backbone, with most of the vicinal 1,3-disubstituted TP-Qu groups positioned in near face-to-face arrangements. Intermolecular distances evaluated from the SAEDs were approached by the molecular dynamic of two straight-chain polymer backbones. Favorable π-π interactions among the vicinal 1,3-disubstitued TP-Qu groups are suggested to be a major factor leading to the straight-chain backbone and the observed nanoribbons and nanoscrolls.

Aggregation-induced emission in tetraphenylthiophene-derived organic molecules and vinyl polymer.

In this study, organic molecules of tetraphenylthiophene (TP) and the derived model compound of TP-Qu and vinyl polymer of PS-Qu with the pendant group of TP-Qu were prepared and characterized to identify their photoluminescent (PL) responses toward the effect of aggregation-induced emission (AIE). During aggregate formation by adding the nonsolvent water to the THF solvent, the corresponding TP solutions greatly gained the emission intensity. In contrast, TP-Qu and PS-Qu in THF/water solution mixtures emitted strongly with nearly the same emission intensity despite the composition differences on the applied THF/water mixtures. Restricted intramolecular rotation (RIR) is the key factor deciding the AIE effect in different media. With four small phenyl rotors around the central thiophene stator, the RIR of the TP molecules in dilute solution is low but increases upon aggregate formations. In contrast, the bulky C-2 quinoline rotor of the TP-Qu molecule enhances the RIR effect and its PL emissions in the aggregate and in the solution states are essentially the same (irrespective of the aggregate formation by adding nonsolvent water). With the inherent TP-Qu pendant groups, the vinyl polymer PS-Qu behaves similarly to the TP-Qu molecule; that is, solutions of PS-Qu have similar emission spectra in different solution mixtures. Several methods including PL excitation (PLE), low-temperature PL emission study, and computer simulation were used in this study to estimate the relative extents of RIR and therefore, the resulting AIE effect in all the TP-derived materials.