Aliphatic Polyesters with White-Light Clusteroluminescence

Harvesting Multicolor Photoluminescence in Nonaromatic Interpenetrated Metal-Organic Framework Nanocrystals via Pressure-Modulated Carbonyls Aggregation

Interpenetrated metal-organic frameworks (MOFs) with nonaromatic ligands provide a unique platform for adsorption, catalysis, and sensing applications. However, nonemission and the lack of optical property tailoring make it challenging to fabricate smart responsive devices with nonaromatic interpenetrated MOFs based on ligand-centered emission. In this paper, the pressure-induced aggregation effect is introduced in nonaromatic interpenetrated Zn4O(ADC)4(Et3N)6 (IRMOF-0) nanocrystals (NCs), where carbonyl groups aggregation results in O─O distances smaller than the sum of the van der Waals radii (3.04 Å), triggering the photoluminescence turn-on behavior. It is noteworthy that the IRMOF-0 NCs display an ultrabroad emission tunability of 130 nm from deep blue (440 nm) to yellow (570 nm) upon release to ambient conditions at different pressures. The eventual retention of through-space n-π* interactions in different degrees via pressure treatment is primarily responsible for achieving a controllable multicolor emission behavior in initially nonemissive IRMOF-0 NCs. The fabricated multicolor phosphor-converted light-emitting diodes based on the pressure-treated IRMOF-0 NCs exhibit excellent thermal, chromaticity, and fatigue stability. The proposed strategy not only imparts new vitality to nonaromatic interpenetrated MOFs but also offers new perspectives for advancements in the field of multicolor displays and daylight illumination.

Recent Progress in Nonconventional Luminescent Macromolecules and their Applications

Traditional π-conjugated luminescent macromolecules typically suffer from aggregation-caused quenching (ACQ) and high cytotoxicity, and they require complex synthetic processes. In contrast, nonconventional luminescent macromolecules (NCLMs) with nonconjugated structures possess excellent biocompatibility, ease of preparation, unique luminescence behavior, and emerging applications in optoelectronics, biology, and medicine. NCLMs are currently believed to produce inherent luminescence due to through-space conjugation of overlapping electron orbitals in solid/aggregate states. However, as experimental facts continue to exceed expectations or even overturn some previous assumptions, there is still controversy about the detailed luminous mechanism of NCLMs, and extensive studies are needed to further explore the mechanism. This Perspective highlights recent progress in NCLMs and classifies and summarizes these advances from the viewpoint of molecular design, mechanism exploration, applications, and challenges and prospects. The aim is to provide guidance and inspiration for the huge fundamental and practical potential of NCLMs.

Thermally Stable and Chemically Recyclable Poly(ketal-ester)s Regulated by Floor Temperature

Chemical recycling to monomers (CRM) offers a promising closed-loop approach to transition from current linear plastic economy toward a more sustainable circular paradigm. Typically, this approach has focused on modulating the ceiling temperature (Tc) of monomers. Despite considerable advancements, polymers with low Tc often face challenges such as inadequate thermal stability, exemplified by poly(γ-butyrolactone) (PGBL) with a decomposition temperature of ∼200 °C. In contrast, floor temperature (Tf)-regulated polymers, particularly those synthesized via the ring-opening polymerization (ROP) of macrolactones, inherently exhibit enhanced thermodynamic stability as the temperature increases. However, the development of those Tf regulated chemically recyclable polymers remains relatively underexplored. In this context, by judicious design and efficient synthesis of a biobased macrocyclic diester monomer (HOD), we developed a type of Tf -regulated closed-loop chemically recyclable poly(ketal-ester) (PHOD). First, the entropy-driven ROP of HOD generated high-molar mass PHOD with exceptional thermal stability with a Td,5% reaching up to 353 °C. Notably, it maintains a high Td,5% of 345 °C even without removing the polymerization catalyst. This contrasts markedly with PGBL, which spontaneously depolymerizes back to the monomer above its Tc in the presence of catalyst. Second, PHOD displays outstanding closed-loop chemical recyclability at room temperature within just 1 min with tBuOK. Finally, copolymerization of pentadecanolide (PDL) with HOD generated high-performance copolymers (PHOD-co-PPDL) with tunable mechanical properties and chemical recyclability of both components.

Phosphine-Capped Effects Enable Full-Color Clusteroluminescence in Nonconjugated Polyesters

Full-color luminophores have advanced applications in materials and engineering, but constructing color-tunable clusteroluminescence (CL) from nonconjugated polymers based on through-space interactions remains a huge challenge. Herein, we develop phosphine-capped nonconjugated polyesters exhibiting blue-to-red CL (400-700 nm) based on phosphine-initiated copolymerization of epoxides and cyclic anhydrides, especially P1-0.5TPP, which exhibits red CL (610 nm) with a high quantum yield of 32%. Experiments and theoretical calculations disclose that the phosphine-capped effect in polyesters brings about conformational changes and induces phosphine-ester clusters by through-space (n,π*) interactions. Moreover, CL colors and efficiencies can be easily tailored by types of phosphines, compositions and structures of polyesters, and concentration. Significantly, the role of polymer motions (group, segmental, and chain motions) on CL originating from microregions inside polyesters is revealed. Further, phosphine-capped nonconjugated polyesters are demonstrated to be nonconjugated dyes and fluorescent fibers and are also used for multicolor light-emitting diodes including white light. This work not only provides an engineering strategy based on the end-group effect to prepare full-color clusteroluminogens but also broadens the prospects for material applications.

Cluster-Triggered Self-Luminescence, Rapid Self-Healing, and Adaptive Reprogramming Liquid Crystal Elastomers Enabled by Dynamic Imine Bond

The integration of advanced functions and diverse practical applications calls for multifunctional liquid crystal elastomers (LCEs); however, the structure-intrinsic luminescence and excellent mechanical properties of LCEs have not yet been explored. In this study, clusteroluminescence (CL)-based LCEs (CL-LCEs) are successfully fabricated without depending on large conjugated structures, thereby avoiding redundant organic synthesis and aggregation-caused quenching. The experimental and theoretical results reveal that secondary amine (-NH-) and imine (-C = N-) groups play vital roles in determining the presence of fluorescence in CL-LCEs. Based on the above observation, the strategy universalization and a molecular library for constructing CL-LCEs are further demonstrated. Meanwhile, the dynamic bond of imine bonds endows the CL-LCE system with rapid self-healing under mild conditions (70 °C in 10 min), excellent stretchability, and adaptive programmable characteristics. Furthermore, the self-luminescent performance enables visual detection of the self-healing process. Finally, CL-based information storage and anticounterfeiting are successfully realized and their applications in fiber actuators and fluorescent textiles are demonstrated. The distinctive luminescence and dynamic chemistry presented in this work has significant implications in elucidating the mechanism of CL and providing new strategies for the rational design of novel multifunctional LCE materials.

Regulation of Photophysical Behaviors in Hyperbranched Aggregation-Induced Emission Polymers for Reactive Oxygen Species Scavenging

Developing nonconjugated materials with large Stokes shifts is highly desired. In this work, three kinds of hyperbranched aggregation-induced emission (AIE) polymers with tunable n/π electronic effects were synthesized. HBPSi-CBD contains alkenyl groups in the backbone and possesses a promoted n-π* transition and red-shifted emission wavelength with a large Stokes shift of 186 nm. Experiments and theoretical simulations confirmed that the planar π electrons in the backbone are responsible for the red-shifted emission due to the strong through-space n···π interactions and restricted backbone motions. Additionally, the designed HBPSi-CBD could be utilized as an ROS scavenger after coupling with l-methionine. The HBPSi-Met exhibits remarkable ROS scavenging properties with a scavenging capacity of 77%. This work not only gains further insight into the structure-property relationship of nonconjugated hyperbranched AIE polymers but also provides a promising ROS-scavenging biomaterial for the treatment of ROS-related diseases.

Red-Shifted Luminescence of Acrylonitrile-Containing Copolymers: A Matter of One Methyl Unit

Copolymerization provides an effective approach to tune the photophysical properties of non-conventional luminescent polymers (NCLPs). In this study, the controlling of intrinsic emissions of polyacrylonitrile (PAN) copolymers is revealed by a delicate difference of secondary monomers. The introduction of methacrylate comonomers can induce a 70-nm red-shifting in the PL emission of copolymers compared with that of acrylate-containing copolymers. The mechanism of such "copolymerization induced red-shifting" in PAN copolymers is investigated. It is demonstrated that the presence of the α-methyl group in the copolymers can enhance the chain rigidity and through-space conjugation (TSC) of C≡N groups, resulting in the red-shifting of emission.

Heteroatom-facilitated blue to near-infrared emission of nonconjugated polyesters

Making nonconjugated polymers to emit visible light remains a formidable challenge, let alone near-infrared (NIR) light, although NIR luminophores have many advanced applications. Herein, we propose an electron-bridging strategy of using heteroatoms (O, N, and S) to achieve tunable emission from blue to NIR regions (440-800 nm) in nonconjugated polyesters. Especially, sulfur-containing polyester P4 exhibits NIR clusteroluminescence (CL) on changing either the concentration or excitation wavelength. Experimental characterization and theoretical calculation demonstrate that the introduction of heteroatoms significantly enhances the through-space interactions (TSIs) via the electron-bridging effect between heteroatoms and carbonyls. The strength of the electron-bridging effect follows the order of S > N > O, based on two synergistic effects: electronic structure and van der Waals radius of heteroatoms. This work provides a low-cost, scalable platform to produce new-generation nonconjugated luminophores with deeper insight into the photophysical mechanism.

Chirality-Regulated Clusteroluminescence in Polypeptides

The low emission efficiency of clusteroluminogens restricts their practical applications in the fields of sensors and biological imaging. In this work, the clusteroluminescence of ordered/disordered polypeptides was observed, and the photoluminescence (PL) intensity of polypeptides can be modulated by the chirality of amino acid residues. Polyglutamates with different chiral compositions were synthesized, and the racemic polypeptides exhibited a significantly higher PL intensity than the enantiopure ones. This emission originates from the n-π* transition between C═O groups of polypeptides and is enhanced by clusterization of polypeptides. CD and Fourier transform infrared spectra demonstrated that the enantiopure and racemic polypeptides form α-helix and random coil structures, respectively. The disordered polypeptides can form more chain entanglements and interchain interactions because of their high flexibility, leading to more clusterizations and stronger PL intensity. The rigidity of ordered helical structures restrains the chain entanglements, and the formation of intrachain hydrogen bonds between amide groups of the backbone impairs the interchain interaction between polypeptides, resulting in lower PL intensity. The PL intensity of the polypeptides can also be manipulated by the addition of urea or trifluoroacetic acid. Our study not only elucidates the chirality/order-based structure-property relationship of clusteroluminescence in peptide-based polymers but also offers implications for the rational design of fluorescent peptides/proteins.

How the Length of Through-Space Conjugation Influences the Clusteroluminescence of Oligo(Phenylene Methylene)s

The length and mode of conjugation directly affect the molecular electronic structure, which has been extensively studied in through-bond conjugation (TBC) systems. Corresponding research greatly promotes the development of TBC-based luminophores. However, how the length and mode of through-space conjugation (TSC), one kind of weak interaction, influence the photophysical properties of non-conjugated luminophores remains a relatively unexplored field. Here, we unveil a non-linear relationship between TSC length and emission characteristics in non-conjugated systems, in contrast to the reported proportional correlation in TBC systems. More specifically, oligo(phenylene methylene)s (OPM[4]-OPM[7]) exhibit stronger TSC and prominent blue clusteroluminescence (CL) (≈440 nm) compared to shorter counterparts (OPM[2] and OPM[3]). OPM[6] demonstrates the highest solid-state quantum yield (40 %), emphasizing the importance of balancing flexibility and rigidity. Further theoretical calculations confirmed that CL of these oligo(phenylene methylene)s was determined by stable TSC derived from the inner rigid Diphenylmethane (DPM) segments within the oligomers instead of the outer ones. This discovery challenges previous assumptions and adds a new dimension to the understanding of TSC-based luminophores in non-conjugated systems.

Enabling nonconjugated polyesters emit full-spectrum fluorescence from blue to near-infrared

Near-infrared luminophores have many advantages in advanced applications, especially for structures without π-conjugation aromatic rings. However, the fabrication of red clusteroluminogens from nonconjugated polymers is still a big challenge, let alone the near-infrared clusteroluminogens. Here, we develop nonconjugated luminophores with full-spectrum from blue to near-infrared light (470 ~ 780 nm), based on color phenomenon of nonconjugated polyesters synthesized from the amine-initiated copolymerization of epoxides and cyclic anhydrides. We reveal that amines act as initiators attached to polymer chain ends. The formation of various amine-ester complexes in polyesters induces red to near-infrared light, conceptually, amine-ester complexed clusteroluminescence via intra/inter-chain charge transfer. Significantly, emission colors can be easily tuned by the contents and types of amines, microstructures of polyesters, and their concentration. This work provides a low-cost, scalable platform and strategy for the production of high-efficiency, multicolor luminescent materials.

A Self-Assemble Supramolecular Film with Humidity Visualization Enabled by Clusteroluminescence

Clusteroluminescence (CL) has recently gained significant attention due to its unique through-space interactions associated with a high dependence on the aggregation of subgroups. These distinct features could easily transform the stimuli into visual fluorescence and monitor the fluctuation of the environment but have not received sufficient attention before. In this work, supramolecular films are designed based on the neutralization reaction of anhydride groups and the self-assembly of dynamic covalent disulfide bonds in NaOH aqueous solution. The self-assembly of hydrophilic carboxylate chromophores and hydrophobic disulfide-containing five-membered rings could be observed by the variation of the aggregation state of carboxylate in CL. Furthermore, the dynamic cross-linking films obtained with water-sensitive carboxylate chromophores could alter the aggregation distance stimulated by surrounding water vapor, causing the emission wavelength to change from 534 to 508 nm by varying the relative humidity. This work not only provides an approach to monitor the self-assembly of clusteroluminogens but also offers new strategies for designing stimuli-responsive materials that utilize the intrinsic features of CL.

Luminescent polypeptides

Polypeptides, as biomacromolecules, hold immense potential in various biological applications such as tissue engineering, immunomodulating agents, and target binding. Among these applications, the attention towards luminescent polypeptides has grown significantly, due to their ability to visualize biological processes effectively. In this perspective, we have compiled information on three distinct types of luminescent polypeptides: natural fluorescent proteins, luminophores-bioconjugated polypeptides, and synthesized polypeptides with clusteroluminescence. Last, we shed light on the significance and prospects of clusteroluminescent polypeptides, which are expected to emerge as crucial new-generation bioluminophores, offering high emission efficiency and tunable emission wavelengths.

Pillar[5]arene-Based Fluorescent Supramolecular Polymers Without Conventional Chromophores

Fluorescent supramolecular polymers have garnered significant attention due to their successful integration of supramolecular polymers and fluorescence, offering vast potential for applications in sensing, imaging, optoelectronics, and photonics. In this study, we present a novel supramolecular polymer based on P5-OH, derived from mono-substituted pillararene macrocycles. Notably, these formed supramolecular polymeric aggregates exhibit a prominent blue emission, representing a rare instance of fluorescent polymers devoid of conventional chromophores. Furthermore, through the modification of alkyl chain ending groups attached to pillar[5]arenes, slight shifts in the emission peak could be observed. This research expands the scope of functional supramolecular polymeric systems utilizing pillararenes, providing valuable insights for the design of innovative luminescent materials and optical devices.

Hyperbranched Polyborosiloxanes: Non-traditional Luminescent Polymers with Red Delayed Fluorescence

Non-traditional fluorescent polymers have attracted significant attention for their excellent biocompatibility and diverse applications. However, designing and preparing non-traditional fluorescent polymers that simultaneously possess long emission wavelengths and long fluorescence lifetime remains challenging. In this study, a series of novel hyperbranched polyborosiloxanes (P1-P4) were synthesized. As the electron density increases on the monomer diol, the optimal emission wavelengths of the P1-P4 polymers gradually red-shift to 510, 570, 575, and 640 nm, respectively. In particular, P4 not only exhibits red emission but also demonstrates delayed fluorescence with a lifetime of 9.73 μs and the lowest critical cluster concentration (1.76 mg/mL). The experimental results and theoretical calculations revealed that the synergistic effect of dual heteroatom-induced electron delocalization and through-space O⋅⋅⋅O and O⋅⋅⋅N interaction was the key factor contributing to the red-light emission with delayed fluorescence. Additionally, these polymers showed excellent potential in dual-information encryption. This study provides a universal design strategy for the development of unconventional fluorescent polymers with both delayed fluorescence and long-wavelength emission.

Recent progress on polymerization-induced emission

The aggregate luminescence behaviors of polymeric luminescent materials have been attracting great attention. However, the importance of the polymerization process on luminescence, namely, polymerization-induced emission (PIE), has rarely been overviewed. In this review, recent advances in polymerization with PIE effects are summarized, including PIE with aromatic rings based on one-/two-/multi-component polymerizations, and PIE without aromatic rings according to disparate mechanisms of polymerizations. Typical examples are selected to elaborate the basic design principles, as well as the properties and potential applications of the luminous polymers. Moreover, the challenges and perspectives in this area are also discussed.

Branched Copolymers with Tunable Clusteroluminescence in High Quantum Yield

A novel type of fluorescence without large conjugated structures called clusteroluminescence (CL) has attracted a great deal of attention in recent years. Despite its many advantages, the emerging CL still encounters difficulties of low quantum yield (QY) and preliminary mechanisms. In this work, the branched structure was introduced into poly(maleic anhydride-alt-vinyl acetate) by chain transfer monomer. The emission wavelength of the branched copolymers is red-shifted with the increase of branching degree, and the absolute QY of solids can reach up to 29.87%. Further characterizations reveal that the branched structure can improve the flexibility of polymer chains, thereby promoting the intrachain interactions of subgroups. Furthermore, in the case of branched anhydride copolymers, the equilibrium between intrachain interactions and nonradiative transitions holds a crucial significance in determining the QY. This endeavor not only offers new insights into the mechanism of CL but also presents a novel approach to surmount the low QY of anhydride copolymers, thus broadening the horizons of CLgens to unexplored domains.

Tunable Aggregation-induced Emission and Emission Colors of Imidazolium and Pyridinium Based Hydrazones

Aggregation-induced emission (AIE) materials have drawn great attention for their wide applications as optical materials. The applications of AIE materials, however, are restricted by the complicated syntheses, hydrophobic properties and short emission wavelengths. Herein, an imidazolium based hydrazone (E)-1-(4-methoxyphenyl)-2-((1-methyl-1H-imidazol-2-yl)methylene)hydrazine hydrochloride (1) and a pyridinium based hydrazone (E)-1-(4-methoxyphenyl)-2-(pyridin-4-ylmethylene)hydrazine hydrochloride (2) have been synthesized. Notably, 1 and 2 in crystals show distinct green and near-infrared (NIR) fluorescence, with emission peaks at 530 and 688 nm, and Stokes shifts of 176 and 308 nm, respectively. After grinding the crystals to powder, the absolute fluorescence quantum yield (ΦF) of 1 is increased from 4.2% to 10.6%, and the ΦF of 2 is increased from 0.2% to 0.7%. X-ray crystallography studies together with theoretical calculations indicate that the enhanced emission of 1 arises from hydrogen bonding induced rigid network, and the fluorescence in the NIR region and large Stokes shift of 2 are attributed to its twisted molecular structure and strong push-pull effect.

Multicolor Luminescence of a Polyurethane Derivative Driven by Heat/Light-Induced Aggregation

The study of aggregate formation and its controllable effect on luminescence behavior has a far-reaching influence in establishing a universal aggregation photophysical mechanism. In this paper, we obtained clusters with different extents of aggregation by heat-induced or light-triggered aggregation of a new polyurethane derivative (PUE). The controllable regulation of multicolor fluorescence of a single (nondoped) polymeric material is realized. The luminescence behavior of PUE varies with microscopic control of the aggregation structure. Compared with the powder state, the enhanced atom-atom and group-group interactions of PUE-gel effectively limit the nonradiative transitions in the excited state and result in a red-shift in emission. This work avoids complex organic synthesis and demonstrates a simple strategy to induce aggregation and regulate the emitting color of macromolecules, providing a template for developing new materials for multicolor fluorescence. In addition, a pattern was constructed with encryption, anticounterfeiting, and information transmission functions which provide a proof-of-concept demonstration of the practical potential of PUE as a smart material.

Nonconventional Luminescent Piperazine-Containing Hyperbranched Polysiloxanes with Pure n-electron

Nonconventional luminogens with high quantum yield (QY) possess very potential applications in various fields. However, the preparation of such luminogens remains a great challenge. Herein, the first example of piperazine-containing hyperbranched polysiloxane exhibiting blue and green fluorescence is reported under the irradiation of different excitation wavelength and a high QY of 20.9%. The density functional theory (DFT) calculations and experimental results revealed that the through-space conjugation (TSC) within the clusters of N and O atoms is produced via the induction of multiple intermolecular hydrogen bonds and flexible SiO units, which is accountable for the fluorescence. Meanwhile, the introduction of the rigid piperazine units not only rigidifies the conformation, but also enhances the TSC. In addition, the fluorescence of both P1 and P2 shows concentration-, excitation-, and solvent-dependent emission, especially exhibits significant pH-dependent emission and obtains an ultrahigh QY of 82.6% at pH 5. The synthetic luminogens show excellent applications in fluorescence detection for Fe3+ and Co2+ , information encryption, and fluorescent film. This study provides a novel strategy to rationally design high-efficiency nonconventional luminogens.

Excited-State Odd-Even Effect in Through-Space Interactions

The odd-even effect is a fantastic phenomenon in nature, which has been applied in diverse fields such as organic self-assembled monolayers and liquid crystals. Currently, the origin of each odd-even effect remains elusive, and all of the reported odd-even effects are related to the ground-state properties. Here, we discover an excited-state odd-even effect in the through-space interaction (TSI) of nonconjugated tetraphenylalkanes (TPAs). The TPAs with an even number of alkyl carbon atoms (C2-TPA, C4-TPA, and C6-TPA) show strong TSI, long-wavelength emission, and high QY. However, the odd ones (C1-TPA, C3-TPA, C5-TPA, and C7-TPA) are almost nonexistent with negligible QY. Systematically experimental and theoretical results reveal that the excited-state odd-even effect is synthetically determined by three factors: alkyl geometry, molecular movability, and intermolecular packing. Moreover, these flexible luminescent TPAs possess tremendous advantages in fluorescent information encryptions. This work extends the odd-even effect to photophysics, demonstrating its substantial importance and universality in nature.

Regulation of Nontraditional Intrinsic Luminescence (NTIL) in Hyperbranched Polysiloxanes by Adjusting Alkane Chain Lengths: Mechanism, Film Fabrication, and Chemical Sensing

Biocompatible polymers with nontraditional intrinsic luminescence (NTIL) possess the advantages of environmental friendliness and facile structural regulation. To regulate the emission wavelength of polymers with NTIL, the alkane chain lengths of hyperbranched polysiloxane (HBPSi) are adjusted. Optical investigation shows that the emission wavelength of HBPSi is closely related to the alkane chain lengths; namely, short alkane chains will generate relatively long-wavelength emission. Electronic communication among functional groups is responsible for the emission. In a concentrated solution, HBPSi molecules aggregate together due to the strong hydrogen bond and amphiphilicity, and the functional groups in the aggregate are so close that their electron clouds are overlapped and generate spatial electronic delocalizations. HBPSi with shorter alkane chains will generate larger electronic delocalizations and emit longer-wavelength emissions. Moreover, these polymers show excellent applications in the fabrication of fluorescent films and chemical sensing. This work could provide a strategy for regulating the emission wavelengths of unconventional fluorescent polymers.

Hydrogen-Bonding-Driven Nontraditional Photoluminescence of a β-Enamino Ester

Nontraditional luminogens (NTLs) do not contain any conventional chromophores (large π-conjugated structures), but they do show intrinsic photoluminescence. To achieve photoluminescence from NTLs, it is necessary to increase the extent of through-space conjugation (TSC) and suppress nonradiative decay. Incorporating strong physical interactions such as hydrogen bonding is an effective strategy to achieve this. In this work, we carried out comparative studies on the photoluminescence behaviors of two β-enamino esters with similar chemical structures, namely methyl 3-aminocrotonate (MAC) and methyl (E)-3-(1-pyrrolidinyl)-2-butenoate (MPB). MAC crystal emits blue fluorescence under UV irradiation. The critical cluster concentration of MAC in ethanol solutions was determined by studying the relationship between the photoluminescence intensity (UV-visible absorbance) and concentration. Furthermore, MAC exhibits solvatochromism, and its emission wavelength redshifts as the solvent polarity increases. On the contrary, MPB is non-emissive in both solid state and solutions. Crystal structures and theoretical calculation prove that strong inter- and intramolecular hydrogen bonds lead to the formation of large amounts of TSC of MAC molecules in aggregated states. No hydrogen bonds and thus no effective TSC can be formed between or within MPB molecules, and this is the reason for its non-emissive nature. This work provides a deeper understanding of how hydrogen bonding contributes to the luminescence of NTLs.

Facile conversion of water to functional molecules and cross-linked polymeric films with efficient clusteroluminescence

Exploring approaches to utilize abundant water to synthesize functional molecules and polymers with efficient clusteroluminescence properties is highly significant but has yet to be reported. Herein, a chemistry of water and alkyne is developed. The synthesized products are proven as nonaromatic clusteroluminogens that could emit visible light. Their emission colors and luminescent efficiency could be adjusted by manipulating through-space interaction using different starting materials. Besides, the free-standing polymeric films with much high photoluminescence quantum yields (up to 45.7%) are in situ generated via a water-involved interfacial polymerization. The interfacial polymerization-enhanced emission of the polymeric films is observed, where the emission red-shifts and efficiency increases when the polymerization time is prolonged. The synthesized polymeric film is also verified as a Janus film. It exhibits a vapor-triggered reversible mechanical response which could be applied as a smart actuator. Thus, this work develops a method to synthesize clusteroluminogens using water, builds a clear structure-property relationship of clusteroluminogens, and provides a strategy to in situ construct functional water-based polymeric films.

Hydrophobic modified agar: Structural characterization and application in encapsulation and release of curcumin

In this study, three kinds of anhydrides with different structures were introduced into agar molecules to study the effects of varying degrees of substitution (DS) and anhydride structures on the physicochemical properties and curcumin (CUR) loading capacity. Increasing the carbon chain length and saturation of the anhydride affects the hydrophobic interaction and hydrogen bonding of the esterified agar, thereby changing the stable structure of the agar. Although the gel performance declined, the hydrophilic carboxyl group and the loose porous structure provide more binding sites for the adsorption of water molecules, hence providing excellent water retention (1700 %). Next, CUR was used as a hydrophobic active ingredient to study agar microspheres' drug encapsulation and in vitro release ability. Results showed that the excellent swelling and hydrophobic structure of esterified agar could promote the encapsulation of CUR (70.3 %). The release process is controlled by pH, and the release of CUR under weak alkaline conditions is significant, which can be explained by the pore structure, swelling characteristics, and carboxyl binding of agar. Therefore, this study shows the application potential of hydrogel microspheres in loading hydrophobic active ingredients and sustained release and provides the possibility for the application of agar in drug delivery systems.

Tunable Red Clusteroluminescence Polymers Prepared by a Simple Heating Process

Clusteroluminescence (CL) has drawn much attention in recent years. However, the design of red emission clusteroluminogens (CLgens) with tunable CL is still in its infancy. Herein, we report a simple heating process to prepare red emission poly(maleic anhydride-alt-vinyl acetate) (PMV) derivatives with a tunable maximum emission wavelength between 620 and 675 nm. First, heating above the glass transition temperature (T_g) would promote the movement of polymer chains and facilitate the formation of clusters in both solid and solution states. Then, heating beyond the decomposition temperature at which vinyl acetate converts into C═C is favorable to the formation of new clusters and large through-space conjugation among subgroups in polymer chains. Their synergistic effects realize the adjustable emission wavelength and higher quantum yield of polymers. Additionally, low-cost and eco-friendly core-shell PMV particles are prepared as agricultural light conversion agents and exhibit great compatibility with polyethylene.

Controlling the Fluorescence Performance of AIE Polymers by Controlling the Polymer Microstructure

Aggregation-induced emission (AIE) polymers with expected emission wavelength/color and fluorescence efficiency are valuable in applications. However, most AIE polymers exhibit irregular emission wavelength/color changes compared to the original AIE monomers. Here, we report the synthesis of AIE polymers with unchanged emission wavelength by ring-opening (co)polymerizations of 4-(triphenylethenyl)phenoxymethyloxirane (TPEO) and other epoxides or phthalic anhydride. The chemical structures/physical properties of all (co)polymers were characterized by NMR, SEC, MALDI-TOF, and DSC. The co-polyether microstructures were revealed by calculating the reactivity ratios and visualized by Monte Carlo simulation. The photoluminescence quantum yields of all the (co)polymers were determined in the solid state. We systematically correlated the fluorescence performance with molecular weights, crystallinity, monomer compositions, glass transition temperatures, side lengths, and flexibility/rigidity.

Polymerization-Induced Crystallization of Dopant Molecules: An Efficient Strategy for Room-Temperature Phosphorescence of Hydrogels

Conventional hydrogels such as polyacrylamide and polyacrylic acid ones seldom exhibit phosphorescences at ambient conditions, which limit their applications as optical materials. We propose and demonstrate here a facile strategy to afford these hydrogels with room-temperature phosphorescence by polymerization-induced crystallization of dopant molecules that results in segregation and confinement of the gel matrix with carbonyl groups and thus clusterization-induced phosphorescence. As a model system, crown ethers (CEs) are dissolved in an aqueous solution of concentrated acrylamide that greatly increases the solubility of CEs. During the polymerization process, CEs crystallize to form large spherulites in the polyacrylamide hydrogel. The crystallization arises from the drastically reduced solubility of CEs after the conversion of monomers to polymers during the gel synthesis. The resultant composite hydrogel with a water content of 67 wt % exhibits extraordinary phosphorescence behavior yet maintains good stretchability and resilience. We found that the partial gel matrix is squeezed and confined by in situ-formed crystals, leading to carbonyl clusters and thus phosphorescence emission. The composite gel shows green phosphorescence with an emission peak at 512 nm and a lifetime of 342 ms. The afterglow emission is detectable by the naked eye for several seconds. This strategy has good universality, as validated in other hydrogels with different polymeric matrices and dopant molecules. The development of hydrogels with good mechanical and phosphorescent properties should merit the design of multifunctional soft machines with applications in biomedical and engineering fields.

Recent Advances in Sequence-Controlled Ring-Opening Copolymerizations of Monomer Mixtures

Transforming renewable resources into functional and degradable polymers is driven by the ever-increasing demand to replace unsustainable polyolefins. However, the utility of many degradable homopolymers remains limited due to their inferior properties compared to commodity polyolefins. Therefore, the synthesis of sequence-defined copolymers from one-pot monomer mixtures is not only conceptually appealing in chemistry, but also economically attractive by maximizing materials usage and improving polymers' performances. Among many polymerization strategies, ring-opening (co)polymerization of cyclic monomers enables efficient access to degradable polymers with high control on molecular weights and molecular weight distributions. Herein, we highlight recent advances in achieving one-pot, sequence-controlled polymerizations of cyclic monomer mixtures using a single catalytic system that combines multiple catalytic cycles. The scopes of cyclic monomers, catalysts, and polymerization mechanisms are presented for this type of sequence-controlled ring-opening copolymerization.

A Dynamic Supramolecular H-bonding Network with Orthogonally Tunable Clusteroluminescence

Enabling dynamically tunable emissive systems offers opportunities for constructing smart materials. Clusteroluminescence, as unconventional luminescence, has attracted increasing attention in both fundamental and applied sciences. Herein, we report a supramolecular poly(disulfides) network with tunable clusteroluminescence. The reticular H-bonds synergize the rigidity and mobility of dynamic networks, and endow the resulting materials with mechanical adaptivity and robustness, simultaneously enabling efficient clusteroluminescence and phosphorescence at 77 K. Orthogonally tunable luminescence are achieved in two manners, i.e., slow backbone disulfide exchange and fast side-chain metal coordination. Further exploration of the reprocessability and chemical closed-loop recycling of intrinsic dynamic networks for sustainable materials is feasible. We foresee that the synergistic strategy of dynamic chemistry offers a novel pathway and potential opportunities for smart emissive materials.

Photoinduced Clusteroluminescence Redshift of Poly(methyl acrylate) via Radicals

One-step photopolymerization and photochromism of clusteroluminescence (CL) polymers mean that the polymer materials can be prepared on a large scale and applied widely. Herein, we reported unique photochromic CL polymers prepared by one-step radical photopolymerization. Seven copolymerized films (PMA_xBA) with methyl acrylate and butyl acrylate as monomers, a cross-linked PMA (PMA-CL) film, a double-network PMAPBA film based on the first network PMA-CL, and four PMA films with increasing content of photoinitiator ethoxy benzoin (BEE) were prepared to study CL formation and transition. Experimental results prove that increasing the ratio of the PMA chains in PMA_xBA enhances the photochromic effect, which verifies the main role of PMA chains with the shorter branched alkanes. Surprisingly, cross-linking in PMA-CL strengthens interchain packing and interchain through-space interactions (TSIs), leading to the formation of larger clusters and further CL redshift from 410 to 491 nm, whereas the PBA chains filled in the cross-linked network weakens interchain TSIs among PMA chains and makes CL red shift from 410 to 472 nm. In addition, as the BEE content increases in the PMA films, a higher radical concentration also promotes the formation of TSIs and clusters, which benefits the photochromism. For applications, colorless, dissolvable, and thermoplastic PMA featuring photochromism in this case can be widely used in information loading, rewriting, and multifunctional coating. This work provides a new strategy to enrich the properties of CL polymers toward diverse applications.