Unprecedented Multicolor Photoluminescence from Hyperbranched Poly(amino ester)s

Aliphatic hyperbranched polyphosphate: a novel multicolor RTP material with AIE character

Long-lived photoluminescent probes are emerging as significant luminogens for biological imaging. However, currently, most long-lived luminescent materials contain expensive rare elements or cytotoxic bulky aromatic or conjugated units. Herein, a novel hyperbranched polyphosphate (HBPPE) was synthesized using triethyl phosphate (TEP) and ethylene glycol (EG) through a transesterification polycondensation reaction. The obtained HBPPE P1 can emit bright blue photoluminescence under UV light and show significant AIE character. Interestingly, the average photoluminescence lifetime of P1 is 12.82 μs. This suggests the first phosphorescent material without rare elements or aromatic structures attributed to the covalent-crystal-like structure. Besides, P1 shows an obvious red-shift along with the excitation wavelength, which emits blue, cyan, green, yellow and red photoluminescence, covering nearly all the visible light region. This study not only enriches the species of nonconventional multicolor AIE luminogens but also provides a concise method for the synthesis of HBPPE and demonstrates the possibility for phosphorescent materials without rare elements or bulky aromatic units.

Self-reporting and Biodegradable Thermosetting Solid Polymer Electrolyte

To date, significant efforts have been dedicated to improve their ionic conductivity, thermal stability, and mechanical strength of solid polymer electrolytes (SPEs). However, direct monitoring of physical and chemical changes in SPEs is still lacking. Moreover, existing thermosetting SPEs are hardly degradable. Herein, by overcoming the limitation predicted by Flory theory, self-reporting and biodegradable thermosetting hyperbranched poly(β-amino ester)-based SPEs (HPAE-SPEs) are reported. HPAE is successfully synthesized through a well-controlled "A2+B4" Michael addition strategy and then crosslinked it in situ to produce HPAE-SPEs. The multiple tertiary aliphatic amines at the branching sites confer multicolour luminescence to HPAE-SPEs, enabling direct observation of its physical and chemical damage. After use, HPAE-SPEs can be rapidly hydrolysed into non-hazardous β-amino acids and polyols via self-catalysis. Optimized HPAE-SPE exhibits an ionic conductivity of 1.3×10-4  S/cm at 60 °C, a Na+ transference number (t N a + ${{t}_{Na}^{+}}$ ) of 0.67, a highly stable sodium plating-stripping behaviour and a low overpotential of ≈190 mV. This study establishes a new paradigm for developing SPEs by engineering multifunctional polymers. The self-reporting and biodegradable properties would greatly expand the scope of applications for SPEs.

Citric Acid-Based Intrinsic Band-Shifting Photoluminescent Materials

Citric acid, an important metabolite with abundant reactive groups, has been demonstrated as a promising starting material to synthesize diverse photoluminescent materials including small molecules, polymers, and carbon dots. The unique citrate chemistry enables the development of a series of citric acid-based molecules and nanomaterials with intriguing intrinsic band-shifting behavior, where the emission wavelength shifts as the excitation wavelength increases, ideal for chromatic imaging and many other applications. In this review, we discuss the concept of "intrinsic band-shifting photoluminescent materials", introduce the recent advances in citric acid-based intrinsic band-shifting materials, and discuss their potential applications such as chromatic imaging and multimodal sensing. It is our hope that the insightful and forward-thinking discussion in this review will spur the innovation and applications of the unique band-shifting photoluminescent materials.

Clustering-enhanced, nonconventional photoluminescence from a silicone surfactant

By using the intrinsic nonconventional photoluminescence (n-PL) of organo-siloxane and the synergetic effect of the surfactant mixture, we report strong n-PL from aqueous colloids containing a nonionic silicone surfactant mixed with a traditional anionic surfactant, with an unprecedently high fluorescence quantum yield of up to 85.58%.

Improve Quantum Yield of Poly(Maleic Anhydride-Alt-Vinyl Acetate) via Good Solvents

In this study, the optical properties of poly(maleic anhydride-alt-vinyl acetate) (PMV) synthesized by different polymerization methods are studied systematically. Compared to self-stabilized precipitation polymerization (pPMV), solution polymerization produces PMV solids (sPMV) with an extraordinarily high quantum yield (QY) of 20.65%. Additionally, redissolving pPMV in good solvents (rPMV) will also help to increase QY. The rising QY of sPMV and rPMV supports the idea that good solvents will reduce the rigidity of polymer chains and promote cluster formation, which is confirmed by lower glass transition temperature (T_g ) and small angle X-ray scatterer (SAXS). The study also finds that PMV exhibits application potentials in white light-emitting diodes (WLEDs) and light conversion film.

Poly-L-aspartic acid based nonconventional luminescent biomacromolecules with efficient emission in dilute solutions for Al3+ detection

Nonconventional luminescent macromolecules exhibiting bright fluorescence or phosphorescence emission at high concentrations and solid-state have attracted significant attention due to their promising application in different fields. However, most reported nonconventional luminescent macromolecules show weak or no emission in dilute solutions, limiting their large-scale applications. Herein, nonconventional luminescent biomacromolecules with hydrophobic rigid chains, hydrophilic flexibility and inter- or intra-molecular hydrogen bonding interactions were proposed to achieve effective luminescence in dilute solutions. Poly-L-aspartic acid (PASA) with a fluorescence quantum yield of 4.6 % in a dilute solution (0.8 mg/mL) was synthesized to validate this design strategy. The fluorescence intensity of PASA solution increased with the increase of the concentration, demonstrating a clustering-triggered emission (CTE) effect. Furthermore, the fluorescence intensity significantly enhanced when adding Al³⁺ into PASA aqueous solution via the Al³⁺ recognition effect. The detection limits for Al³⁺ (1.71 × 10^-6 mol/L) meet the World Health Organization (WHO) requirements for food detection. At last, PASA solid-state samples exhibit room temperature phosphorescence emission.

High-Efficiency Long-Wavelength Fluorescent Hyperbranched Polysiloxanes: Synthesis, Emission Mechanism, Information Encryption, and Film Preparation

Unconventional fluorescent polymers possess the advantages of excellent biocompatibility, environmental friendliness, and facile structural regulation; however, such polymers usually have low fluorescence intensity and quantum yields in the long-wavelength range. In this work, three kinds of high-efficiency long-wavelength emissive hyperbranched polysiloxanes are obtained by introducing aromatic amino acids. These functionalized hyperbranched polysiloxanes have high fluorescence intensity and quantum yields in green, yellow, and red emission regions. Experimental results and density functional theory calculations reveal that the long-wavelength emission comes from the enhanced electronic communication among the conjugated π bonds, electron-rich atoms, and -Si(O)₃ and other functional groups. Especially, the conjugated π bonds efficiently enlarge the spatial electronic delocalizations, resulting in the high-efficiency long-wavelength emission. Moreover, the prepared polymers show excellent applications in information encryption and film preparation. This work could serve as a guide to develop high-efficiency long-wavelength unconventional fluorescent polymers.

Construction of hyperbranched polysiloxane-based multifunctional fluorescent prodrug for preferential cellular uptake and dual-responsive drug release

Hyperbranched polymers hold great promise in nanomedicine for their controlled chemical structures, sizes, multiple terminal groups and enhanced stability than linear amphiphilic polymer assemblies. However, the rational design of hyperbranched polymer-based nanomedicine with low toxic materials, selective cellular uptake, controlled drug release, as well as real-time drug release tracking remains challenging. In this work, a hyperbranched multifunctional prodrug HBPSi-SS-HCPT is constructed basing on the nonconventional aggregation-induced emission (AIE) featured hyperbranched polysiloxanes (HBPSi). The HBPSi is a biocompatible AIE macromolecule devoid of conjugates, showing a high quantum yield of 17.88% and low cytotoxicity. By covalently grafting the anticancer drug, 10-hydroxycamptothecin (HCPT), to the HBPSi through 3,3'-dithiodipropionic acid, HBPSi-SS-HCPT is obtained. The HBPSis demonstrate obvious AIE features and it turned to aggregation-caused quenching (ACQ) after grafting HCPT owing to the FRET behavior between HBPSi and HCPT in HBPSi-SS-HCPT. In addition to on-demand HCPT release in response to changes in environmental pH and glutathione, a series of in vitro and in vivo studies revealed that HBPSi-SS-HCPT exhibits enhanced accumulation in tumor tissues through the enhanced permeation and retention (EPR) effect and preferential cancer cell uptake by charge reversal, thus resulting in apoptotic cell death subsequently. This newly developed multifunctional HBPSi-SS-HCPT prodrug provides a biocompatible strategy for controlled drug delivery, preferential cancer cell uptake, on-demand drug release and enhanced antitumor efficacy.

Ultrastretchable, Adhesive, Fast Self-Healable, and Three-Dimensional Printable Photoluminescent Ionic Skin Based on Hybrid Network Ionogels

Developing multifunctional stretchable ionic skin (I-Skin) to mimic the sensations of the human skin is of great interest and shows promising potential in wearable sensors and human-machine interfaces (HMIs). However, common ionogels prepared with small-molecule cross-linkers and single networks can hardly satisfy the requirements of adjustable mechanical properties, strong adhesion, fast self-healability, and good stability in extreme environments. Herein, an ultrastretchable (>10,000%), ultrastrong adhesive (>6.8 MPa), ultrafast self-healable (10 s), high thermally stable (-60 to 250 °C), and three-dimensional (3D)-printable photoluminescent ionogel with shape memory properties has been designed. The ionogel consists of hyperbranched polymer covalent-cross-linked poly(zwitterionic ionic liquid)-co-poly(acrylic acid) and multiple dynamic bonding cross-linked networks. The excellent performance of the ionogel-based high-stretchable strain sensor and the triboelectric nanogenerator (TENG)-based self-powered touch sensor is further demonstrated over a wide temperature range (-40 to 150 °C). More importantly, ionogel-based I-Skin can work as an HMI for human gesture recognition and real-time wireless control of robots under extreme vacuum conditions and can also self-heal immediately along with function recovery after mechanical damage.

Truly Multicolor Emissive Hyperbranched Polysiloxane: Synthesis, Mechanism Study, and Visualization of Controlled Drug Release

Unconventional fluorescent polymers have attracted increasing attention due to their facile synthesis, excellent biocompatibility, and novel photophysical properties. In this work, a truly multicolor emissive hyperbranched polysiloxane (HBPSi-β-CD) is obtained through adjusting the distribution of electron-rich atoms and grafting β-cyclodextrin; the quantum yields of HBPSi-β-CD after being excited by 360, 420, 450, and 550 nm are 19.36, 31.46, 46.14 and 44.84%, respectively. The density functional theory calculations reveal that the truly multicolor emission is derived from the formed electron delocalization among the hydroxyl, amine, ether, and -Si(O)₃ groups due to the strong intermolecular interaction, high density of electron-rich atoms, and low steric hindrance among functional groups. The prepared polymers could serve as a multisensitivity sensor in detecting Fe³⁺, Cu²⁺, and Co²⁺. The HBPSi-β-CD shows low cytotoxicity and excellent cellular imaging capability. The self-assembly of HBPSi-β-CD also possesses high drug loading capacity and pH-controlled drug release, especially, the drug delivery system could be applied in the visualization of controlled drug delivery.

Steric Hindrance Drives the Boron-Initiated Polymerization of Dienyltriphenylarsonium Ylides to Photoluminescent C5-Polymers

A series of alkyl-subsituted dienyltriphenylarsonium ylides were synthesized and used as monomers in borane-initiated polymerization to obtain practically pure C5-polymers (main-chain grows by five carbon atoms at a time). The impact of triethylborane (Et3 B), tributylborane (Bu3 B), tri-sec-butylborane (s-Bu3 B), and triphenylborane (Ph3 B) initiators on C5 polymerization was studied. Based on NMR and SEC results, we have shown that all synthesized polymers have C5 units with a unique unsaturated backbone where two conjugated double bonds are separated by one methylene. The synthesized C5-polymers possess predictable molecular weights and narrow molecular weight distributions (Mn,NMR =2.8 -11.9 kg mol-1 , Ð=1.04-1.24). It has been found that increasing the steric hindrance of both the monomer and the initiator can facilitate the formation of more C5 repeating units, thus driving the polymerization to almost pure C5-polymer (up to 95.8 %). The polymerization mechanism was studied by 11 B NMR and confirmed by DFT calculations. The synthesized C5-polymers are amorphous with tunable glass-transition temperatures by adjusting the substituents of monomers, ranging from +30.1 °C to -38.4 °C. Furthermore, they possess blue photoluminescence that changes to yellow illuminating the polymers for 5 days with UV radiation of 365 nm (IIE, isomerization induced emission).

Effective Internal and External Modulation of Nontraditional Intrinsic Luminescence

The rational modulation of the nontraditional intrinsic luminescence (NTIL) of nonconventional luminophores remains difficult, on account of the limited understanding on the structure-property relationships and emission mechanisms. Herein, the effective modulation of NTIL is demonstrated based on a group of nonaromatic anhydrides and imides. Mutual bridging of isolated subgroups effectively promotes intramolecular through-space conjugation (TSC), leading to red-shifted emission, enhanced efficiency, and prolonged persistent room-temperature phosphorescence (p-RTP). The substitution of heteroatoms from oxygen to nitrogen drastically changes the TSC and enhances intermolecular interactions, resulting in enhanced emission efficiency. In addition, upon freezing, compression, or embedding into polymer matrices, the emission intensity and color remain well regulated. These results shed new light on the rational modulation of the NTIL and p-RTP of nonconventional luminophores.

Highly Efficient Amide Michael Addition and Its Use in the Preparation of Tunable Multicolor Photoluminescent Polymers

The amide bond is one of the most pivotal functional groups in chemistry and biology. It is also the key component of proteins and widely present in synthetic materials. The majority of studies have focused on the formation of the amide group, but its postmodification has scarcely been investigated. Herein, we successfully develop the Michael additions of amide to acrylate, acrylamide, or propiolate in the presence of phosphazene base at room temperature. This amide Michael addition is much more efficient when the secondary amide instead of the primary amide is used under the same conditions. This reaction was applied to postfunctionalize poly(methyl acrylate-co-acrylamide), P(MA-co-Am), and it is shown that the amide groups of P(MA-co-Am) could be completely modified by N,N-dimethylacrylamide (DMA). Interestingly, the resulting copolymer exhibited tailorable fluorescence with emission wavelength ranging from 380 to 613 nm, which is a desired property for luminescent materials. Moreover, the emissions of the copolymer increased with increasing concentration in solution for all excitation wavelengths from 320 to 580 nm. Therefore, this work not only develops an efficient t-BuP₄-catalyzed amide Michael addition but also offers a facile method for tunable multicolor photoluminescent polymers, which is expected to find a wide range of applications in many fields, such as in anticounterfeiting technology.

Fluorescent linear polyurea based on toluene diisocyanate: Easy preparation, broad emission and potential applications

In contrast to conventional fluorescent polymers featured by large conjugation structures, a new class of fluorescent polymers without above conjugations are gaining constant interest owing to their significant academic importance and promising applications in diverse fields. These unconventional fluorescent polymers are in general composed of heteroatoms (e.g. N, O, P, and S) under different forms. Here we report our recent study on polyurea, prepared by a very simple one step precipitation polymerization of toluene diisocyanate in a binary solvent of water-acetone. This polyurea, basically consisting of phenyl ring and urea group, shows fluorescent emission in a broad concentration range, from very low (10-5 mg/mL) to its solubility limit (50 mg/mL), and in a wide range of emission wavelength from UV to visible regions of up to 500 nm under varied excitation wavelength. The emission behaviors were fully studied under different concentrations and excitations. It was concluded that the emission in UV region was intrinsic due to the conjugation between the phenyl and the adjacent urea unit; while the emission in visible region, strongly excitation dependent, was caused by the cluster formation of the molecular chains, in accordance with the cluster-triggered-emission (CTE) mechanism. The formation of the cluster was tested through dynamic light scattering, FTIR and UV absorbance. Tested in presence of different metal ions, Fe3+ demonstrated a quenching effect with high selectivity. Based on this study, different paper-based sensors were designed to detect Fe3+, H2O2 in bioanalysis and for data encryption. This work provides a simple way to prepare a polyurea, a novel type of unconventional fluorescent polymer, with high emission performance distinct from its known analogues.

Energy-Transfer-Induced Multiexcitation and Enhanced Emission of Hyperbranched Polysiloxane

Fluorescent hyperbranched polysiloxane (HBPSi) has attracted increasing attention due to its good biocompatibility. However, its emission mechanism remains an open question. Unfortunately, the excitation spectra of HBPSi are rarely systematically investigated and show a narrow excitation band, which hinders the emission mechanism study. Herein, we synthesized a series of novel HBPSi containing l-glutamic acid (HBPSi-GA). Surprisingly, these polymers have four excitation peaks and two emission peaks, which are caused by the energy transfer from free functional groups to heterogeneous electron delocalizations in different clusters. Meanwhile, the fluorescence and biocompatibility of HBPSi-GA are significantly improved with increasing l-glutamic acid. Furthermore, HBPSi-GA exhibits dual stimuli-responsive fluorescence to temperature and Fe³⁺ as well as potential application in cell imaging. This research possesses important guidance to develop multiexcitation unconventional fluorescent polymers.

Two-Step 3 D-Printing Approach toward Sustainable, Repairable, Fluorescent Shape-Memory Thermosets Derived from Cellulose and Rosin

Efficiently converting biomass into multifunctional polymerized materials is a challenge to effect high-valued utilization of biomass resources. A two-step 3 D-printing approach has been developed to fabricate a class of robust, fluorescent shape-memory thermosets from cellulose and rosin-based photosensitive 3 D-printing resin solution. The stereolithography 3 D printing was first performed to form the first crosslinked network by UV-induced chain-growth polymerization, which fixed the shape of thermoset. Subsequently, isocyanate was applied to react with hydroxy in the monomer to form the second crosslinked network by thermally induced step-growth polymerization. The formation of a dual-cure network, leading to phase separation and increased crosslinking density, could greatly improve the mechanical and thermal properties of 3 D-printed thermosets and endow them with thermally triggered shape-memory properties and excellent repairability. The 3 D-printed thermosets are found to have strong luminescence resulting from aggregation-induced emission originating from rosin. In addition, these 3 D-printed thermosets could degrade in the presence of NaOH aqueous solution and in situ achieved a range of flexible conductive hydrogels that have important potential application in the flexible electronic materials and smart photoelectric materials.

Recent advances in the development and applications of nonconventional luminescent polymers

Recently, nonconventional luminescent polymers (NLPs) have emerged as the most sought-after alternative luminescent materials. This review provides a thorough description of the importance and applications of each class of state-of-the-art NLPs.