Double-crossover-like (DXL) molecules are a series of DNA motifs containing two strands with identical or different sequences. These homo- or hetero-dimers can further polymerize into bulk structures through specific hydrogen bonding between sticky ends. DXL molecules have high designability, predictivity and sequence robustness; and their supramolecular polymerization products would easily achieve controllable morphology. In addition, among all available DNA nanomotifs, DXL molecules are small in size so that the cost of DXL-based nanostructures is low. These properties together make DXL-based nanostructures good candidates for patterning, templating, information and matter storage, etc. Herein, we will discuss DXL motifs in terms of the detailed molecular design, and their supramolecular polymerization in various dimensions, and related applications.

This review summarizes the self-assembly of block molecules forming unconventional two-dimensional (2D) periodic nanopatterns. Especially, we emphasize the structural evolution from simple columnar phases to complex 2D tiling morphologies in soft materials including block copolymers, liquid crystals, giant molecules, etc. Then, the state-of-the-art nanofabrication technologies for making sophisticated nanostructures with specific functions via combining both bottom-up assembly and top-down lithography-based methods are discussed, highlighting the use of directed self-assembly processes. Finally, we provide our perspective on this area. By further increasing the complexity of block molecules and the designability of lithography, low-dimensional ordered morphologies will be particularly promising for further application in nanotechnology.

Spiropolymers have gained a great deal of interest from both academic and industrial fields by virtue of their unique geometric structures and physical properties. Herein, we prepared a series of spirocopolymers through the catalyst-free four-component spiropolymerization of diisocyanides, activated alkynes, and two different kinds of monomers with reactive carbonyl groups. It is found that the polymerization reactivity of monomers, feeding modes, and feed ratios play significant roles in spirocopolymerization. Monomers with high reactivity and feeding reactive monomers first contribute to improving the molecular weights and yields of the polymers. The constructed copolymers have two different kinds of spiro structures, which is confirmed by the nuclear magnetic resonance. In addition, the spirocopolymers display the unique cluster-triggered emission and aggregation-induced emission properties, and their emission properties can be well-modulated by altering the ratio of comonomers. It is highly anticipated that this line of research will enrich the methodology of multi-component spiropolymerization, and provide a new insight into developing spiropolymers with various spiro structures and tunable properties.

We present here a novel strategy for the chemical recycling of bio-based poly(ethylene furanoate)s (PEF) to value-added high-performance bio-based poly(ethylene-co-isosorbide furanoate) (PEIF) copolyesters by the combination of cyclodepolymerization method with rapid cascade polycondensation-coupling ring-opening polymerization (PROP). The solution cyclodepolymerization of commercially available PEF affords cyclic oligo(ethylene 2,5-furandicarboxylate)s (COEFs), and the effects of reaction conditions on the yield of COEFs were studied. PEIF copolyesters with different isosorbide (IS) contents were synthesized via the cascade PROP of COEFs with IS, which show significant enhanced glass transition temperature. By melt spinning, PEIF fibers with different orientation factors were prepared, with excellent thermal stability and mechanical performance. The obtained PEIF fibers can lift a weight ~25000 times higher than its weight. The PEIF fibers are stable under ambient conditions but are biodegradable following the “surface erosion” mechanism. These sustainable value-added biodegradable PEIF fibers offer a solution to the environmentally friendly fibers.

Helical poly(phenylacetylene)s (PPAs) have received extensive attention because of their features in dynamic chirality and promising applications. Therefore, understanding relationship among the polymer molecular structures, polymerization conditions and tunability of their chirality is of key scientific value. Recently, we developed a novel class of dendronized PPAs carrying 3-fold dendritic oligo(ethylene glycols) (OEGs) via alanine linkage, and found that these bulky polymers exhibited tunable helical conformations through thermally-mediated dehydration and aggregation. Herein, we report on synthesis of a homologous series of dendronized PPAs that carry 2-fold, 3-fold or 6-fold dendritic OEG pendants, and focus on effects of molecular topological structures, peripheral units and polymerization solvents on the thermoresponsiveness and their conformation switching behaviors. Effects of branching density and peripheral units (ethoxyl or methoxyl) of the dendritic OEG pendants were examined, and found to play a decisive role on the helical conformation and thermoresponsiveness of these dendronized PPAs due to their different bulkiness and overall hydrophilicity. In addition, different polymerization solvents were checked for their possible influence on the polymerization, thermoresponsive behavior and the chirality of the resulting polymers. For polymerization in selective solvents like water or methanol, the obtained dendronized PPAs exhibited weak thermal transitions, while polymerization in non-selective solvent like THF furnished PPAs with characteristic thermoresponsive behavior, indicating that solvents were involved in the process of polymerization of the dendronized macromonomers. More interestingly, different chiralities of the PPAs through polymerization in various solvents were retained, irrelevant to the purification process and solvents treatments. This work suggests that the topological structures together with polymerization solvents can modulate the thermoresponsive behavior and helical conformation of the dendronized PPAs.

The ring-opening polymerization of heterocyclic monomers and the reversed ring-closing depolymerization of corresponding polymers with neutral thermodynamics are broadly explored to establish a circular economy of next-generation plastics. Polythioesters (PTEs), analogues of polyesters, are emerging materials for this purpose due to their high refractive index, high crystallinity, dynamic property and responsiveness. In this work, we synthesize and polymerize a series of _D-penicillamine-derived β-thiolactones (N^RPenTL) with varied side chain alkyl groups, and study the structure-property relationship of the resulting polymers. The obtained PTEs exhibit tunable glass transition temperature in a wide range of 130−50 °C, and melting temperature of 90−105 °C. In addition, copolymerizations of monomers with different side chains are effective in modulating material properties. The obtained homo and copolymers can be fully depolymerized to recycle monomers. This work provides a robust molecular platform and detailed structure-property relationship of PTEs with potential of achieving sustainable plastics.

Multicomponent polymerizations (MCPs) are powerful tools to synthesize functional polymers with great structural diversity, low cost and high efficiency, which usually generate single polymer product. Herein, a robust one-pot diamines, CS₂ and monoisocyanide-participated catalyst-free polymerization was developed at room temperature to produce polythiourea and thioformamide simultaneously in equal equivalent, which was featured with cheap monomers, simple operation and mild condition, affording various polythioureas with high M_ws of up to 4.75×10⁴ g/mol in high yields of up to 98%. Polythioureas with varied chain composition and sequence-controlled structure could be synthesized in 62 g-scale from copolymerization or multicomponent tandem polymerization, enabling facile tuning of thermal property, crystallinity, mechanical property, and fluorescence. The abundant irregular hydrogen bonds endowed the polythioureas excellent glassy state self-healing property at room temperature or below 0 °C. This polymerization provided an efficient and economic approach to access functional polythioureas.

Polyimine represents a rapidly emerging class of readily accessible and affordable covalent adaptable networks (CANs) that have been extensively studied in the past few years. While being highly malleable and recyclable, the pioneering polyimine materials are relatively soft and not suitable for certain applications that require high mechanical performance. Recent studies have demonstrated the possibility of significantly improving polyimine properties by varying its monomer building blocks, but such component variations are usually not straightforward and can be potentially challenging and costly. Herein, we report an in situ oxidation polymerization strategy for preparation of mechanically strong poly(imine-amide) (PIA) hybrid CANs from simple amine and aldehyde monomers. By converting a portion of reversible imine bonds into high-strength amide linkages in situ, the obtained hybrid materials exhibit gradually improved Young’s modulus and ultimate tensile strength as the oxidation level increased. Meanwhile, the PIAs remain reprocessable and can be depolymerized into small molecules and oligomers similar as polyimine. This work demonstrates the great potential of the in situ transformation strategy as a new approach for development of various mechanically tunable CANs from the same starting building blocks.

Donor-acceptor (D-A) conjugated polymers comprising electron-deficient aromatic dicarboximide units represent an important type of organic semiconductors, especially for electron transporting properties. Pyrene-1,5,6,10-tetracarboxyl diimide (PyDI), a new PAH dicarboximide molecule recently reported by us, provides a fine balance between the electron-stabilizing ability and π-stacking tendency, as compared to the naphthalenediimide (NDI) and perylenediimide (PDI) analogues. In this study, using thienylene-vinylene-thienylene (TVT) and biselenophene (BS) as the electron donating comonomer, along with PyDI as the acceptor moiety, we develop two new D-A type conjugated polymers, which exhibit impressive electron-transporting performance. Specifically, in the solution-processed OFET devices, electron mobility of 0.18 and 0.20 cm²·V⁻¹·s⁻¹ are achieved with these polymers, respectively. Such findings further prove the optimal potential of PyDI for application as an electron-acceptor building block in the development of polymeric n-type semiconductors among all various high-performance functional D-A polymers.

Triboelectric nanogenerators (TENGs) based on conjunctive effects of contact electrification (CE) and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables, Internet of Things (IoTs), etc. The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs, but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design. Taking advantages of the surface-sensitive characteristic of CE effect, this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs. Firstly, four different kinds of surface microstructures, namely planar surface (PS) and three combinations of two basic surface microstructures, i.e., micro lens arrays (MLAs), fabric textures (FTs), and hierarchical structures of MLAs on FTs (MLA/FTs), were elaborately designed and introduced for an identical triboelectric material (i.e., silicone elastomer) by a (micro)molding synthesis route. Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions. Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine, it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density, effective contact area and contacting/separating velocity, rather than simple increase of its surface area.

The development of optical films with high transparency, high thermal resistance and low birefringence remains a challenge in the flexible display industry. In this work, we designed and synthesized a series of fluorinated colorless polyimides (CPIs) materials using 2,5-substituted m-phenylenediamine diamine monomers and 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA). We systematically studied the effects of fluorinated group substitutions on the thermal, mechanical, optical and dielectric properties of CPI films. The introduction of alicyclic CHDA dianhydride affords high transparency and low yellowness, while the 2,5-substituted m-phenylenediamine diamines offer the CPIs with quite low birefringence as well as high glass transition temperatures. A particular CHDA/o3FBDA film with simple chemical structure stands out, exhibiting well-balanced overall properties.

A family of new triphenylmethane (TPM)-based polyimides (PIs) containing bulky tert-butyldimethylsiloxy (TBS) side-groups (PI-TPMOSis) has been prepared by a post-polymerization modification via a simple silyl ether reaction of TPM-based PIs containing hydroxyl (OH) groups (PI-TPMOHs). The attachment of TBS side-groups in PI-TPMOSis can be achieved up to 100%, as confirmed by the ¹H-NMR and IR spectra. Due to the presence of the TPM structure, PI-TPMOSi films still display the excellent thermal stability with high glass transition temperature (T_g) of 314−351 °C and high degradation temperature (T_d5%) of 480−501 °C. It is quite remarkable that the introduction of TBS side-groups into PI-TPMOSi chains results in more superior optical, dielectric and solubility properties in comparison with the precursor PI-TPMOH films, probably due to the reductions of the packing density and charge-transfer complexes (CTCs) formation. The optical transmittance at 400 nm (T₄₀₀) of PI-TPMOSi films is significantly increased from 45.3%−68.8% to 75.4%−81.6% of the precursor PI-TPMOH films. The dielectric constant (D_k) and dissipation factor (D_f) at 1 MHz of PI-TPMOSi films are reduced from 4.11−4.40 and 0.00159−0.00235 to 2.61−2.92 and 0.00125−0.00171 of the precursor PI-TPMOH films, respectively. Combining the molecular design and simple preparation method, this study provides an effective approach for enhancement of various properties of PI films for microelectronic and photoelectric engineering applications.

The design and development of highly permeable, selective and stable polymer membranes are great challenges in the gas separation industry. Herein, we constructed two intrinsic microporous polyimides (6FPCA and 6FMCA) derived from two isometric diamines (PCA and MCA), which were synthesized by palladium catalyzed C―N coupling reaction. The PCA and MCA diamines contain a hollow beaded structure of 2,2’-paracyclophane as a building block with a specified window size of 3.09 Å. The chemical structures of monomers, polyimides were confirmed by NMR, FTIR, and elementary analysis. 6FPCA and 6FMCA exhibit good solubility, excellent thermal stability, and mechanical properties. 6FPCA exhibits much larger microporosity (434 versus 120 m²·g⁻¹), FFV (0.22 versus 0.15), d-spacing (6.9 versus 5.9 Å), and over 10 times higher permeability with a very little decrease in selectivity than the corresponding polyimide (6FpA) with a plane structure, which remarkably increased their separation performance from far below the 2008 Robeson Upper bounds to reach these limitations for O₂/N₂ and CO₂/CH₄. Additionally, the 6FPCA also demonstrates good plasticization resistance, moderate aging properties, and high CO₂/CH₄ mixed-gas separation performance. These results indicate that paracyclophane subunit can be successfully incorporated into polymers to enhance their ultra-microporosity and separation properties, which open a new avenue for developing high performance gas separation membranes with topological ultra-micropores.

Combining the strategies of introducing larger heteroatom, regio-regular backbone and extended branching position of side-chain, we developed polymer semiconductors (PPCPD) with narrow band-gap to construct the photosensing layer of thin-film photodiodes and image arrays. The spectral response of the resulting organic photodiodes spans from the near ultra-violet to short-wavelength infrared region. The performance of these short-wavelength infrared photodiodes in 900–1200 nm range achieved a level competitive with that of indium gallium arsenide-based inorganic crystalline detectors, exhibiting a specific detectivity of 5.55×10¹² Jones at 1.15 μm. High photodetectivity and quantum efficiency in photodiode with amorphous/nanocrystalline thin-films of 100−200 nm thickness enabled high pixel-density image arrays without pixel-level-patterning in the sensing layer. 1 × 256 linear diode arrays with 25 μm × 25 μm pixel pitch were achieved, enabling high pixel-density short-wavelength infrared imaging at room temperature.

Uniform and well-aligned organic semiconductor single crystals (OSSCs) are critical for high-performance electronic and optoelectronic device applications due to their long-range order and low defect density. However, it is still challenging to fabricate uniform and well-aligned OSSCs by an efficient and facile method. Here, we report a vapor-induced coating method to prepare uniform organic semiconductor stripe single crystals with well-aligned orientation. The coating velocity and solution concentration are important to control the stripe crystals’ morphology, which influence the triple-phase contact line dewetting behavior and then change the mass transport of the meniscus. Insufficient solute supply causes the generation of dendritic crystals. Uniform stripe single crystals of high quality and pure orientation are prepared in the condition of a sufficient and suitable solute supply. Moreover, the electronic and optoelectronic properties are evaluated. Notably, the polarization-sensitive photodetectors based on the uniform stripe crystals exhibit high polarization sensitivity and its dichroic ratio of photocurrent is 1.98. This method is efficient for the preparation of various high-quality and uniform organic semiconductor stripe single crystals, opening an opportunity for high-performance organic functional devices.

The research and application of responsive materials have long been hampered by their complicated designs and tedious construction processes. Besides, many current responsive materials show retard or weak responsiveness. In this study, responsive hybrid poly(vinyl alcohol) hydrogel membranes with embedded poly(N-isopropylacrylamide-acrylic acid) microgels as valves were constructed by simple mixing and subsequent freezing-thawing process. In the structure of the membranes, the matrix poly(vinyl alcohol) chains thread through and entangle with the microgels, and the microgels are firmly constrained within the hybrid hydrogel network. The fast and sharp temperature responsiveness of the embedded microgels was largely retained and endowed the hydrogel membrane with excellent temperature and pH responsiveness. Moreover, the hydrogel membrane showed excellent fatigue resistance in both temperature and pH-responsive flux examination. This study presented the great potential of these hybrid hydrogel membranes in biomedical applications and provided a new strategy for the future design and construction of responsive biomaterials.

Synthesizing orientated liquid crystal elastomers (LCEs) via the two-stage thiol-acrylate Michael addition and photopolymerization (TAMAP) reaction is extensively used. However, excess acrylates, initiators, and strong stimuli are inevitably involved in the second stage crosslinking. Herein, we simplify the strategy through taking advantage of a volatile alkaline (originally added to catalyze the thiol-acrylate addition in the first crosslinking stage). Without excess functional groups, the residual catalyst after annealing is still enough to trigger reactions of dynamic covalent bonds at a relatively mild temperature (80 °C) to program the alignment of LCEs. The reversible reaction switches off by itself after this process since the catalyst gradually but totally evaporates upon heating. The obtained soft actuators exhibit robust actuation during repeated deformation (over 1000 times). Many shape-morphing modes can be achieved by rationally designing orientation patterns. This strategy not only facilitates the practical synthesis of LCE actuators, but also balances the intrinsic conflict between stability and reprogrammability of exchangeable LCEs. Moreover, the method of applying volatile catalysts has the potential to be extended to other dynamic covalent bonds (DCBs) applied to crosslinked polymer systems.