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A novel unsymmetrical phthalimide-containing phthalonitrile (PIPN) was successfully synthesized. The chemical structure of the PIPN monomer was confirmed by various spectroscopic techniques. Rheology and differential scanning calorimetry (DSC) revealed that the self-promoted curing reaction of the PIPN was an extremely sluggish process. The fully cured PIPN polymers showed excellent thermal properties revealed by thermogravimetric analysis (TGA) and DSC. IR and solid-state UV-Vis diffusion reflectance spectra confirmed the formation of the triazine and phthalocyanine ring during the curing reaction.Rheometric studies suggested that the curing reaction of phthalonitrile with a phthalimide group was faster compared to the reaction with a benzimidazole ring, and a nucleophilic addition reaction mechanism was successfully introduced to explain this phenomenon.

Microrobots have shown great potential in minimally invasive surgery, targeted therapy, and biological manipulation. [1,2] The features of excellent shape morphing and highly efficient locomotion are very important for microrobots. To take the microgripper and microstent as examples, shape morphing is essential for grasping or unfolding, [3] and efficient locomotion is necessary for the transport of the microrobots to a defined position. [4] Magnetically driven microrobots can achieve rapid locomotion with a controllable change in direction and have advantages of noncontact, harmless to living organisms. [5,6] To develop magnetic microrobots with shape morphing ability, methods such as introducing flexible joints/hinges [7,8] or combining magnetic nanoparticles (NPs) with stimuli-responsive materials [4] were developed. Joints/hinges can significantly increase the shape morphing ability of the microrobot, while the fabricating process of the microrobot with joints/hinges is complicated. [9] In contrast, combining magnetic NPs with stimuliresponsive materials ensures that the microrobot not only performs an excellent deformability but also avoids the complicated fabricating process. Stimuli-responsive hydrogels which are able to swell and shrink in response to different stimuli such as temperature, pH, and light represent a promising strategy to fabricate shape morphing microstructures. [9,10] Inhomogeneous swelling/ shrinking of hydrogel microstructures results in bending, twisting, folding, and even more complex deformation. [11,12] The deformable microstructures can be fabricated by advanced manufacturing such as two-photon direct laser writing (DLW) system, [13,14] UV lithography, [15] and projection microstereolithography. [16] Thus, combining stimuli-responsive hydrogels with magnetic materials provides an attractive solution to fabricate microrobots with both shape morphing and locomotion abilities. [17] To magnetically drive a hydrogel microstructure, magnetic material must be incorporated into the polymeric portions. In general, two typical methods can be used to add magnetic material. One is mixing the magnetic particles into the uncured material to obtain structures with particles embedded in volume, [18][19][20][21] i.e., volume embedding structures. The other is depositing the magnetic particles on the surface of the polymer portions [22][23][24] or oil-in-water self-assembly [25] to obtain structures with particles coated on the surface, i.e., surface coating structures. Thus, certain microrobots could locomote under the actuation of external magnetic field and deform flexibly in response

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Emerging three-dimensional (3D) printing techniques for soft active materials have demonstrated fascinating applications in various areas including programmable and reconfigurable structures, tissue engineering, and soft robotics. For example, polymeric gels, which consist of polymer networks swollen with solvent molecules, are capable of deforming and swelling/deswelling in response to external stimuli. Although polymeric gels are used to print structures, little attention has been paid to the effect of printing parameters on the cross-sectional shape of 3D-printed gel filaments or further to the dynamic responses of the printed structures. Due to the flow of the precursor solution before fully cured, the cross section of a printed gel filament is usually asymmetric. When immersed in water, the asymmetry in the cross section causes the printed filament to bend, and the interdiffusion of the two solvents leads to the alternation in bending direction. The bending curvature and response rate can be adjusted by turning printing parameters. As applications of this mechanism, we demonstrated various types of gel structures, capable of deforming from 1D strips to 2D spiral or sinusoidal shapes, warping from 2D flat sheet to 3D cylindrical helix when swollen, or wrapping and manipulating objects under external stimuli.

The rigid rod-like 4,4 0 -bis(6-hydroxyhexyloxy)biphenyl (BHHBP) units were distributed in either the epoxy or polyurethane to become SR-epoxy and PU (with or without BHHBP) polymer matrices. The interpenetrating polymer networks (IPNs) of PU (with or without BHHBP) and SR-epoxy were synthesized through simultaneous polymerization, and connected each other via the grafting reaction between the À ÀNCO groups of the PU polymer network and the À ÀOH groups on the side chains of SR-epoxy network. The thermal and mechanical characteristics, compatibilities, and morphologies of these PU (with or without BHHBP)/SR-epoxy graft-IPNs were investigated. The polyether-type PU(PPG series)/SRepoxy graft-IPNs exhibited two-phased morphologies (i.e., phase separation occurred), and higher fracture energies (G IC ). Whereas the polyester-type PU(PBA series)/SRepoxy graft-IPNs were homogeneous (no phase separation), and exhibited higher tensile and Izod impact strengths.

A novel epoxy containing rigid rods in the side chain (SR-epoxy) was synthesized by bulk polymerization. The SR-epoxy resins were characterized by Fourier transform infrared. The cured SR-epoxies showed excellent mechanical properties and high thermal stabilities. Scanning electron microscopy (SEM) of the cured SR-epoxy illustrated a fiber-like morphology. The thermal properties, dynamic mechanical properties, compatibility, and morphology of the SR-epoxies were extensively investigated in the study.SEM photographs showed that there were some fiber-like structures in the system of the SR-epoxy containing the rigid-rod group 4,4Ј-bis(6-hydroxyhexoxy) biphenyl, which formed a self-reinforcing composite.