Heng Shen

Bioinspired Modification of h-BN for High Thermal Conductive Composite Films with Aligned Structure

With the development of microelectronic technology, the demand of insulating electronic encapsulation materials with high thermal conductivity is ever growing and much attractive. Surface modification of chemical inert h-BN is yet a distressing issue which hinders its applications in thermal conductive composites. Here, dopamine chemistry has been used to achieve the facile surface modification of h-BN microplatelets by forming a polydopamine (PDA) shell on its surface. The successful and effective preparation of h-BN@PDA microplatelets has been confirmed by SEM, EDS, TEM, Raman spectroscopy, and TGA investigations. The PDA coating increases the dispersibility of the filler and enhances its interaction with PVA matrix as well. Based on the combination of surface modification and doctor blading, composite films with aligned h-BN@PDA are fabricated. The oriented fillers result in much higher in-plane thermal conductivities than the films with disordered structures produced by casting or using the pristine h-BN. The thermal conductivity is as high as 5.4 W m(-1) K(-1) at 10 vol % h-BN@PDA loading. The procedure is eco-friendly, easy handling, and suitable for the practical application in large scale.

Bioinspired Materials: from Low to High Dimensional Structure

The surprising properties of biomaterials are the results of billions of years of evolution. Generally, biomaterials are assembled under mild conditions with very limited supply of constituents available for living organism, and their amazing properties largely result from the sophisticated hierarchical structures. Following the biomimetic principles to prepare manmade materials has drawn great research interests in materials science and engineering. In this review, we summarize the recent progress in fabricating bioinspired materials with the emphasis on mimicking the structure from one to three dimensions. Selected examples are described with a focus on the relationship between the structural characters and the corresponding functions. For one-dimensional materials, spider fibers, polar bear hair, multichannel plant roots and so on have been involved. Natural structure color and color shifting surfaces, and the antifouling, antireflective coatings of biomaterials are chosen as the typical examples of the two-dimensional biomimicking. The outstanding protection performance, and the stimuli responsive and self-healing functions of biomaterials based on the sophisticated hierarchical bulk structures are the emphases of the three-dimensional mimicking. Finally, a summary and outlook are given.

Facile in situ synthesis of silver nanoparticles on boron nitride nanosheets with enhanced catalytic performance

An environmentally friendly and facile approach was developed to synthesize boron nitride nanosheet/Ag nanoparticle hybrids (BNNS/Ag) in aqueous solution at room temperature without additional reductants. BNNSs were modified with a thin layer of tannic acid–ferric ion (TA–Fe) complex. Silver nanoparticles with a uniform diameter of approximately 7 nm were in situ formed on the surface of the modified BNNSs due to the strong reducibility of TA. The resultant nanohybrids showed excellent catalytic activity in reduction of 4-nitrophenol. BNNS/Au and BNNS/Pd nanohybrids can also be fabricated by this means, implying its extensive promise in catalytic, bio-medical and sensing fields.

Intelligent rubber with tailored properties for self-healing and shape memory

A strategy for combining covalent and non-covalent cross-links to construct multifunctional rubber materials with intelligent self-healing and shape memory ability is demonstrated. Rubbers were prepared by self-assembly of complementary polybutadiene oligomers bearing carboxylic acid and amine groups through reversible ionic hydrogen bonds via the acid–base reaction, and then further covalently cross-linked by tri-functional thiol via the thiol-ene reaction. The resulting polymers exhibit self-healing and shape memory functions owing to the reversible ionic hydrogen bonds. The covalent cross-linking density can be tuned to achieve tailorable mechanical and stimuli-responsive properties: a low covalent cross-linking density maintains the remarkable self-healing capability of rubber at ambient temperature without any external stimulus, while a high covalent cross-linking density improves the mechanical strength and induces shape memory behavior, but effective self-healing needs to be triggered at high temperature. This strategy might open a promising pathway to fabricate intelligent multifunctional polymers with versatile functions.

Facile fabrication of robust superhydrophobic porous materials and their application in oil/water separation

Utilizing superhydrophobic porous materials in oil/water separation has attracted increasing research interest, however, most of these materials are usually complicated to fabricate or easily lose their functions in harsh circumstances. In this study, dispersion of poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) micro–nano aggregations in acetone/water was facially prepared via a simple phase separation method. The aggregations can be easily coated on the skeletons of various 2D and 3D porous substrates, endowing the porous materials with superhydrophobicity. The prepared superhydrophobic materials show excellent resistance to chemical erosion, mechanical abrasion, and high temperature (up to 400 °C). This robust superhydrophobicity promises application of the resultant porous materials in harsh environments, and examples of using these superhydrophobic porous materials to separate oil/water mixtures have been demonstrated. This simple and universal method is suitable for the large-scale preparation of porous materials with robust superhydrophobicity.

Fabrication of oriented hBN scaffolds for thermal interface materials

Thermal interface materials are widely used in thermal management, and usually require a high thermal conductivity, low coefficient of thermal expansion (CTE) and adequate softness. Herein, hBN/PDMS composites are fabricated by the infiltration of a PDMS prepolymer in the hBN scaffolds followed by a thermal curing process. The scaffolds are prepared by an ice templating method with hBN microplatelets, leading to a good alignment of hBN platelets along the z direction in the PDMS matrix. This unique structure results in a high thermal conductivity, which is about 3 times higher than that of the composites fabricated by a casting method, and the thermal conductivity is as high as 1.4 W m−1 K−1 along the z direction at ∼20 wt% of hBN microplatelets. The composites also possess low CTEs which are <100 ppm K−1 along the z direction and maintain an adequate softness.

Solvent free nanoscale ionic materials based on Fe3O4 nanoparticles modified with mussel inspired ligands

Mussels exhibit robust adhesion capability with varied materials mainly due to the strong affinity of catechol moieties in their adhesive proteins. Nanoscale ionic materials (NIMs) are special organic-inorganic hybrid materials comprising a charged oligomer corona attached to inorganic nanoparticle cores, which can behave from glassy solids to liquids in the absence of any solvent. Herein, Fe3O4 nanoscale ionic materials (NIMs) exhibiting inorganic-organic core-shell structure and liquid-like behavior were obtained by using a mussel-inspired bifunctional ligand of 3,4-dihydroxybenzenepropanoic acid (DHPA), which could link Fe3O4 nanoparticles core and cationic organic shell, respectively. A simplified one-step aqueous co-precipitation method to prepare DHPA decorated Fe3O4 nanoparticles is developed, which shows advantages in productivity and is more environmental friendly compared with the traditional core preparation first and then surface modification. This research proposes a simple and effective approach to obtain solvent-free NIMs with tailorable core-shell structure using versatile adhesion of mussel mimetic adhesives and various available ion pairs.