Contrasting Effects of Graphene Oxide and Poly(ethylenimine) on the Polymorphism in Poly(vinylidene fluoride)

Abstract

The nature of interaction between a heteronucleating agent (graphene oxide, GO) and a strongly polar macromolecule (poly(ethylenimine), PEI) with poly(vinylidene fluoride) (PVDF) influencing the crystalline structure and morphology has been systematically investigated in this work. PEI interacts with PVDF via ion-dipole interaction, which helps in lowering the free energy barrier for nucleation thereby promoting faster crystallization. In contrast, besides interacting with PVDF, GO also promotes heteronucleation in PVDF. We observed that both GO and PEI have very different effects on the overall crystalline morphology of PVDF. For instance, the neat PVDF showed a mixture of both α and β phases when cooled from the melt. However, incorporation of 0.1 wt % GO resulted in phase transformation from the stable α-phase to polar β-polymorph in PVDF. In contrast, PEI, which also resulted in faster crystallization in PVDF predominantly, resulted in the stable α-phase. Various techniques like Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry were employed to confirm the phase transformations in PVDF. PEI was further grafted onto GO nanosheets to understand the combined effects of both GO and PEI on the polymorphism in PVDF. The PVDF/PEI−GO composite showed a mixture of phases, predominantly rich in α. These phenomenal effects were further analyzed and corroborated with the specific interaction between GO and PEI with PVDF using X-ray photon scattering (XPS) and NMR. In addition, the dielectric permittivity increased significantly in the presence of GO and PEI in the composites. For instance, PVDF/PEI−GO showed the highest permittivity of 39 at 100 Hz.

Significant enhancement of the electroactive β-phase of PVDF by incorporating hydrothermally synthesized copper oxide nanoparticles

“…This indicates that the addition of well-dispersed CONPs as the nucleating agent lowers the free energy barrier of nucleation, thus accelerating the crystallization of PVDF, which manifests in a higher crystallization temperature for the nanocomposite lms. 28 The faster nucleation kinetics is also evident from the FESEM micrograph of PCO5 (Fig. 6a) where smaller spherulites are observed in comparison to neat PVDF.…”

“…The smaller size of the spherulites for sample PCO5 in comparison to that of the neat PVDF represents the faster nucleation kinetics in the CONP-PVDF composite lms 28 due to the presence of additional CONP nucleation centers, and the enhancement of the b-phase fraction may be achieved in the composite lm due to the existence of the large number of favorable nucleation centers. 28 UV-visible spectroscopy. Fig.…”

HDPE/UHMWPE hybrid nanocomposites with surface functionalized graphene oxide towards improved strength and cytocompatibility

“…In figure 1e, the absorption bands of GO at 1717, 1584, 1165 and 3337 cm 21 are attributed to the stretching bonds of C¼O (carboxylic groups), -C¼C-, the epoxy ring and the hydroxyl group, respectively [6]. The successful conjugation of the carboxyl group of GO and amino group of PEI was confirmed by the diminishing of the peak corresponding to the COOH group and the appearance of the characteristic IR bands of the amide bond at 1622 cm 21 (C¼O) and 1567 cm 21 (N-H) [48]. The absence of the IR band at 1165 cm 21 corresponding to the epoxy ring was observed in GO [29].…”

Design of In Situ Poled Ce3+-Doped Electrospun PVDF/Graphene Composite Nanofibers for Fabrication of Nanopressure Sensor and Ultrasensitive Acoustic Nanogenerator

“…The degree of the total (χ c t ), β- (χ c β ) and γ-crystallinity (χ c γ ) are calculated and labeled in Figure a,b (detail calculation is shown in Text S1). Soin et al and Abolhasani et al reported that (χ c t ) of neat electrospun PVDF NFs is ∼53%. , Whereas the incorporation of graphene visibly improves the (χ c t ) of PVDF (Figure b), which directly influences the material properties . The increased crystallinity is probably because graphene can efficiently restrict and order the PVDF chain arrangement (defined as a “molecule movement restriction” effect), because of its super mechanical strength (Figure S2).…”