Incorporating polymers within a single‐crystal: From heterogeneous structure to multiple functions

Energy Harvesting Using Optimized ZnO Polymer Nanocomposite-Based 3D-Printed Lattice Structure

A 3D-printable polymer can provide an effective solution for developing piezoelectric structures. However, their nanocomposite formulation and 3D printing processability must be optimized for fabricating complex geometries with high printability. In the present study, we optimized the 3D-printable piezoelectric composite formulation for developing complex geometries by an additive manufacturing approach. The zinc oxide (ZnO) nanomaterial was synthesized by the hydrothermal method. The ZnO loading in the 3D-printed flexible resin was optimized to exhibit good interfacial adhesion and enable 3D printing. The lattice structure was fabricated to improve the piezoelectric response compared with the solid structure. The lattice structure block printed with 10 wt% ZnO showed a good piezoelectric response, with a linear increase in the generated output voltage for an increase in force. The maximum power density of 0.065 μW/cm2 was obtained under 12 N force at 1 Hz. The fabricated structure generated a peak-peak voltage of ~3 V with a foot heel strike.

Spatioselective Occlusion of Copolymer Nanoparticles within Calcite Crystals Generates Organic-Inorganic Hybrid Materials with Controlled Internal Structures

Efficient occlusion of particulate additives into a single crystal has garnered an ever-increasing attention in materials science because it offers a counter-intuitive yet powerful platform to make crystalline nanocomposite materials with emerging properties. However, precisely controlling the spatial distribution of the guest additives within a host crystal remains highly challenging. We herein demonstrate a unique, straightforward method to engineer the spatial distribution of copolymer nanoparticles within calcite (CaCO3) single crystals by judiciously adjusting initial [Ca2+] concentration used for the calcite precipitation. More specifically, polymerization-induced self-assembly is employed to synthesize well-defined and highly anionic poly(3-sulfopropyl methacrylate potassium)41-block-poly(benzyl methacrylate)500 [PSPMA41-PBzMA500] diblock copolymer nanoparticles, which are subsequently used as model additives during the growth of calcite crystals. Impressively, such guest nanoparticles are preferentially occluded into specific regions of calcite depending on the initial [Ca2+] concentration. These unprecedented phenomena are most probably caused by dynamic change in electrostatic interaction between Ca2+ ions and PSPMA41 chains based on systematic investigations. This study not only showcases a significant advancement in controlling the spatial distribution of guest nanoparticles within host crystals, enabling the internal structure of composite crystals to be rationally tailored via a spatioselective occlusion strategy, but also provides new insights into biomineralization.

Constructing Multifunctional Composite Single Crystals via Polymer Gel Incorporation

The non-uniformity of a single crystal can sometimes be found in biominerals, where surrounding biomacromolecules are incorporated into the growing crystals. This unique composite structure, combining heterogeneity and long-range ordering, enables the functionalization of single crystals. Polymer gel media are often used to prepare composite single crystals, in which the growing crystals incorporate gel networks and form a bi-continuous interpenetrating structure without any disruption to single crystallinity. Moreover, dyes and many kinds of nanoparticles can be occluded into single crystals under the guidance of gel incorporation. On this basis, the bio-inspired method has been applied in crystal morphology control, crystal dyeing, mechanical reinforcement, and organic bulk heterojunction-based optoelectronics. In this paper, the composite structure, the incorporation mechanisms, and the multiple functions of gel-incorporated single crystals are reviewed.

Multi-Functionalization of Single crystals Mediated by Gel-Incorporation: A Bioinspired Strategy

Biominerals are inherently organic-inorganic crystal composites. Drawing inspiration from this biomineral structure, functionalized single crystals can be synthesized using the gel-grown method, resulting in the incorporation of gel-networks into the host crystals. By incorporating gel-networks, diverse guest materials, such as nanoparticles and dye molecules, can be uniformly and isotropically distributed within the crystals, thereby imparting non-intrinsic optical or magnetic properties to the host crystals. Additionally, gel-incorporation enhances the toughness and stability of the crystals as the incorporated gel-fibers and accompanying guest materials act as bridges to prevent crack propagation. Furthermore, gel-incorporation enables protein crystals to exhibit self-healing properties, which can be attributed to the dynamic bonding interaction between gel-networks and crystals. Notably, recent research has demonstrated that the incorporation of zwitterionic gel-networks enhances the charge effects on crystal morphology evolution as the charged groups become bound to the developing crystal surfaces, and their detachment is impeded by the interconnected gel-networks. Therefore, preparing single crystals with gel-incorporation is a remarkable strategy for synthesizing functionalized crystal materials.

Long-Range Ordered Organic Bulk-Heterojunction: C60 and O-IDTBR Single Crystals Penetrated by Crystalline P3HT Fibrous Networks

The long-range ordering of bulk-heterojunctions (BHJs) significantly facilitates exciton diffusion and dissociation as well as charge transport. A feasible bio-inspired strategy to realize such a heterostructure is crystallization in gel media where the growing host crystals incorporate the surrounding guest materials of gel networks. Until now, the host-guest pairs forming ordered BHJs are still very limited and, more importantly, the used gel-network guests are structurally amorphous, spurring investigation toward crystalline gel-networks. Here, single crystals of fullerene and non-fullerene acceptors (NFAs) in poly(3-hexylthiophene) (P3HT) organogel are prepared, forming C₆₀ :P3HT and (5Z,5″Z)-5,5″-((7,7″-(4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b″]dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadiazole-7,4-diyl))bis(methanylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one) (O-IDTBR):P3HT BHJs. The crystalline P3HT network penetrates the crystal matrix without significantly disturbing the single crystallinity, resulting in long-range ordered BHJs. This bi-continuous structure, together with an improved overall ordering, contributes to enhanced charge/energy transfer. As a result, photodetectors based on these ordered BHJs exhibit ameliorated responsivity, detectivity, bandwidth, and stability as compared to the conventional BHJs with short-range ordering. Therefore, this work further extends the scope of long-range ordered BHJs toward crystalline polymer donors and NFAs, providing a generally applicable strategy for the design of organic optoelectronic devices with superior performance.

Synergistic Effect of Hydroxyl and Carboxyl Groups on Promoting Nanoparticle Occlusion within Calcite

Direct occlusion of guest nanoparticles into host crystals enables the straightforward preparation for various of nanocomposite materials with emerging properties. Therefore, it is highly desirable to elucidate the 'design rules' that govern efficient nanoparticle occlusion. Herein, a series of sterically-stabilized nanoparticles are rationally prepared, where the surface stabilizer chains of such nanoparticles are composed of either poly(methacrylic acid), or poly(glycerol monomethacrylate), or poly((2-hydroxy-3-(methacryloyloxy)propyl)serine). Systematic investigation reveals that hydroxyl groups and carboxyl groups play a synergistic role in driving nanoparticle incorporation into calcite crystals, where the hydroxyl groups enhance colloidal stability of the nanoparticles and the carboxyl groups provide binding sites for efficient occlusion. The generality of these findings is further validated by extending it to polymer-stabilized gold nanoparticles. This study demonstrates that precision synthesis of polymer stabilizers comprising of synergistic functional groups can significantly promote nanoparticle occlusion, thus enabling the efficient construction of organic-inorganic hybrid materials via nanoparticle occlusion strategy.

Metal-Organic Frameworks@Calcite Composite Crystals

The direct incorporation of guest crystals into another type of host crystals during the formation of the latter is technically challenging due to the large difference in surface energy for different crystalline components. Nevertheless, we herein demonstrate that metal-organic frameworks (MOFs, UiO-66-NH₂ as a model guest crystal) after postsynthetic modification with poly(methacrylic acid) can be efficiently incorporated into calcite single crystals, forming a unique composite structure where the MOF crystals are uniformly distributed throughout the whole calcite host crystals. Remarkably, such MOF@calcite composite crystals exhibit superior performance in fluoride removal compared with the MOF or calcite alone. Moreover, this incorporation strategy is general as it can be extended to other guest particles. In principle, this study opens up a versatile avenue for the rational design and preparation of a wide range of hybrid functional materials with controllable compositions and enhanced physicochemical properties.

Polymer-Inorganic Crystalline Nanocomposite Materials via Nanoparticle Occlusion

Efficient occlusion of guest nanoparticles into host single crystals opens up a straightforward and versatile way to construct functional crystalline nanocomposites. This new technique has attracted increasing research interest because it enables the composition, structure and property of the resulting nanocomposites to be well-controlled. In this review article, we aim to provide a comprehensive summary of nanoparticle occlusion within inorganic crystals. First, we summarize recently-developed strategies for the occlusion of various colloidal particles (e.g., diblock copolymer nanoparticles, polymer-modified inorganic nanoparticles, oil droplets, etc.) within host crystals (e.g., CaCO₃ , ZnO or ZIF-8). Second, new results pertaining to spatially-controlled occlusion and the physical mechanism of nanoparticle occlusion are briefly discussed. Finally, we highlight the physicochemical properties and potential applications of various functional nanocomposite crystals constructed via nanoparticle occlusion and we also offer our perspective on the likely future for this research topic. This article is protected by copyright. All rights reserved.