Piezoelectric polyvinylidene fluoride (PVDF) provided an opportunity for non-invasive in situ electrical stimulation of cell behavior, yet its electroactive β phase was difficult to obtain due to its instability in the molten state. Herein, polyaniline (PANI) protrusions were in situ oxidation-polymerized on molybdenum disulfide (MoS2) nanosheets (PANI-MoS2). Then, PANI-MoS2 was introduced into laser additive-manufactured PVDF scaffolds. On the one hand, PANI protrusions produced steric hindrance between adjacent MoS2 nanosheets and inhibited the stacking and aggregating of MoS2. On the other hand, PANI-MoS2 could serve as a platform to achieve interfacial polarization locking. Specifically, Mo–S dipoles in MoS2 and π electron clouds over the N atom in PANI locked −CH2 dipoles in PVDF through electrostatic and hydrogen bond interactions, respectively, which forced −CH2 to align perpendicularly to the basal plane of MoS2 and bialy to one side of the PVDF main chain, thereby forming a full-reverse planar zigzag configuration of the polarized β phase and maintaining its stable existence. The results demonstrated that the β phase of the scaffolds was significantly increased from 43 to 90%, which resulted in an enhanced electrical output performance. The improved electrical output greatly promoted osteoblast-like cell proliferation and differentiation. Furthermore, owing to the pulling-out effect of MoS2 and improved interfacial stress transfer between MoS2 and the polymer matrix, the mechanical properties of scaffolds were also enhanced. These findings suggested that the piezoelectric scaffolds had great potential in bone tissue engineering.
In this paper, inspired by the cubic bi-continuous gyroid structure self-assembled by block copolymers, we start with the application of a novel and more facile approach, compared to the tedious synthetic procedures of block copolymers, to prepare the bi-continuous phases structured nanocomposite electrolytes. The bi-continuous phase structure is composed of a hard phase of the electrospun poly vinylidene fluoride (PVDF) non-woven scaffold providing the mechanical support for the electrolyte membranes and another soft phase built up then by the infiltration of polyethylene oxide (PEO) electrolyte into the PVDF scaffold membrane to be the ionic conducting phase. Therefore, the nanocomposite polymer electrolytes of the bi-continuous phase structure are prepared with addition of the different amounts of TiO 2 nanoparticles into the PEO electrolyte (containing LiClO 4 ). The nanocomposite electrolyte membranes have systematically been characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), X-ray diffraction (XRD), and tensile test. The tensile results indicate that the infiltration of PEO phase into the PVDF scaffold can greatly improve the elongation of the electrolyte membrane at break, but the tensile strength of the electrolyte membrane is substantially dependent on the electrospun PVDF scaffold. The ionic conductivity measurements show that addition of TiO 2 nanoparticles with an appropriate amount of ca . 10 wt% enhances the ionic conductivity of the nanocomposite electrolytes to 7.60 × 10 −5 S cm −1 at 60 °C, compared to 8.33 × 10 −6 S cm −1 at 60 °C of the PEO–LiClO 4 electrolyte. The effect of TiO 2 nanoparticles on the enhancement of Li + ion conductivity has been investigated by attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), and the results show that a competitive interaction between TiO 2 nanoparticles and Li + ions weakens to some extent the existing complexing action of ether-O…Li + , allowing Li + ions faster transfer. However, we have found by high-resolution transmission electron microscopy (HRTEM) that the real dispersion state of TiO 2 nanoparticles in the nanocomposite electrolytes is in the form of large aggregates instead of the individual primary nanoparticles, which would tremendously depress the surface effect of the individual nanoparticles and greatly impact on the enhancement of the ionic conductivity.
Tianxing Gong,Tingyu Li,Lisha Meng,Yadong Chen,Tao Wu,Jingqiu Zhou,Guoxiu Lu,Zhiguo Wang
Native bone is piezoelectric in nature and generates abundant surface charges under mechanical compression, which regulate osteoblast proliferation, differentiation, adhesion, and so on. Poly (vinylidene fluoride) (PVDF) is becoming one of the most popular piezoelectric polymers because of its easy processability and good biocompatibility. Unfortunately, because only the β and γ crystal phases of PVDF have piezoelectricity, post-treatments, for example, polarizing at high temperature, are required to enhance the piezoelectricity of PVDF scaffolds after fabrication. In this study, we reported a phase-separation-hydration method to fabricate a calcium phosphate silicate (CPS)-doped PVDF scaffold. Our method fabricated a better piezoelectric scaffold than native bone without further processing (∼ 3 pC/N vs. 0.7 pC/N). In addition, the scaffold was mechanically compatible (∼ 7 MPa) with the cancellous bone with sufficient porosity (∼ 45%) to facilitate osteoblast infiltration and bone ingrowth. The in vitro biocompatibility analyses proved that the prepared CPS-PVDF scaffold was biocompatible with osteoblast cells and encouraged osteoblast redifferentiation. In conclusion, our results suggest that this CPS-PVDF scaffold is a promising candidate for bone tissue engineering applications.
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