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A flexible and portable triboelectric nanogenerator (TENG) based on electrospun polyvinylidene fluoride (PVDF) doped with copper oxide (CuO) nanoparticles (NPs, 2, 4, 6, 8, and 10 wt.-% w.r.t. PVDF content) was fabricated. The structural and crystalline properties of the as-prepared PVDF-CuO composite membranes were characterized using SEM, FTIR, and XRD. To fabricate the TENG device, the PVDF-CuO was considered a tribo-negative film and the polyurethane (PU) a counter-positive film. The output voltage of the TENG was analyzed using a custom-made dynamic pressure setup, under a constant load of 1.0 kgf and 1.0 Hz frequency. The neat PVDF/PU showed only 1.7 V, which further increased up to 7.5 V when increasing the CuO contents from 2 to 8 wt.-%. A decrease in output voltage to 3.9 V was observed for 10 wt.-% CuO. Based on the above results, further measurements were carried out using the optimal sample (8 wt.-% CuO). Its output voltage performance was evaluated as a function of varying load (1 to 3 kgf) and frequency (0.1 to 1.0 Hz) conditions. Finally, the optimized device was demonstrated in real-time wearable sensor applications, such as human motion and health-monitoring applications (respiration and heart rate).

Flexible pressure sensors have played an increasingly important role in the Internet of Things and human–machine interaction systems. For a sensor device to be commercially viable, it is essential to fabricate a sensor with higher sensitivity and lower power consumption. Polyvinylidene fluoride (PVDF)-based triboelectric nanogenerators (TENGs) prepared by electrospinning are widely used in self-powered electronics owing to their exceptional voltage generation performance and flexible nature. In the present study, aromatic hyperbranched polyester of the third generation (Ar.HBP-3) was added into PVDF as a filler (0, 10, 20, 30 and 40 wt.% w.r.t. PVDF content) to prepare nanofibers by electrospinning. The triboelectric performances (open-circuit voltage and short-circuit current) of PVDF-Ar.HBP-3/polyurethane (PU)-based TENG shows better performance than a PVDF/PU pair. Among the various wt.% of Ar.HBP-3, a 10 wt.% sample shows maximum output performances of 107 V which is almost 10 times that of neat PVDF (12 V); whereas, the current slightly increases from 0.5 μA to 1.3 μA. The self-powered TENG is also effective in measuring human motion. Overall, we have reported a simpler technique for producing high-performance TENG using morphological alteration of PVDF, which has the potential for use as mechanical energy harvesters and as effective power sources for wearable and portable electronic devices.

Among the many fluoropolymers, polyvinylidiene fluoride (PVDF) has been well-known since 1960s and is preferred for various electronic applications owing to its lower cost, inordinate mechanical properties, and tunable polymorphism. It is well known that PVDF exhibits five different crystalline polymorphs (α). Among all, β-crystalline phase is the most important with excellent piezoelectric, ferroelectric, and pyroelectric properties.Metal oxide nanoparticles (MO-NPs) are used in diverse applications, aided by their unique electrical, optical, magnetic, and catalytic properties. Many reports are available with a focus on the synthesis of Fe, Co, and Ni oxide magnetic NPs for data storage and sensor applications. More importantly, transition metal cations can exist in several different valence states and their crystallite size increased with increasing addition of metal doping. Incorporation of MO and doped MO with PVDF plays pivotal a role in improving the sensitivity of the piezoelectric sensor. This review covers the doping of PVDF with MO-NPs and their effectiveness towards in applications.

Hyperbranched polymers (HBPs) are a common type of soft nanomaterial, but creating them from readily available monomers with a well-defined dendritic structure is difficult. Advances in the quantitative description and control of hyperbranched fine topological structures will aid their development and application in a variety of fields, including traditional polymer materials and engineering as well as energy materials, and optoelectronic materials and devices. Using a sequential polycondensation technique based on commercially accessible monomers, we present a one-pot synthesis of aromatic HBP with configurable structure and high degree of branching. Generation 1 (G1) aromatic HBP (Ar.HBP) based on diphenolic acid and pentaerythritol has been synthesized in the presence of p-toluene sulfonic acid as catalyst. Kinetics reaction was monitored using FTIR spectroscopy. –C=O absorption band of ester was used to track the conversion of acid to ester. The reaction of Ar.HBP-G1 synthesis takes approximately 21 h for completion according to kinetic parameters computed from IR spectral data.

Organofunctional silanes are hybrid materials of silanes having attracted greater attention since the last decade owing to its versatile properties and wide range of applications. In this review, we have summarized the types of organosilanes (RnSiX4-n), their reactions, and applications. Organosilanes usually have two reactive groups, organofunctional groups and hydrolyzable alkoxy groups, which undergo hydrolysis and condensation. Silanols (Si-OH) and siloxane (Si-O-Si) structures are formed by hydrolysis and condensation reactions, respectively. In general, organosilanes acts as excellent binding agent due to its bridging capacity through (Si-O-Si) bond linkage with metal surfaces. From the extensive literature survey carried out, we understand that the silanes are synthesized without comprehending the reaction kinetics mechanism. In the past few decades, significant advances were witnessed in the development of various organofunctional silanes, which were used in a wide range of research areas based on its bifunctional characteristics.

According to our exhaustive examination of the literature on hyperbranched polymers (HBPs), the majority of published reviews have focused solely on their production or uses. We anticipate that the various end-capping procedures will increase the use of end-capped HBPs for a variety of applications. This review paper is organized in the following order: general HBP structure, different end-group functionalities and end-capping pathways, associated obstacles, and future research scope. The role of HBP end-group functionalities in numerous industrial applications is our first goal. Our second goal is to investigate the differences in material properties before and after HBP end-capping. From applications point of view, end-capped HBPs have found use in storage devices to catalysis. Challenges and perspectives for future developments are discussed. Overall, the structural properties of end-capped HBPs will be of interest to academics working in this field as a result of the alterations described in this review paper.

In this paper, we prepared two spun-cast PVDF-TrFE/hyperbranched polyester (HBP) blend (90/10 wt.-%) film samples on KBr substrate (Blend-AC sample). One of the AC sample was thermally treated at 130oC (Blend-AN sample). Crystal transition behavior were studied by treating both AC and AN samples to 30→120→30oC cycle by in-situ FTIR spectroscopy under transmission (TS) mode. From qualitative FTIR data, absorption intensity of A1 band at 1289.5 cm-1 for AC and 1292 cm-1 for AN decreased gradually during heating for both the samples. However, it is increased at 30oC condition for AC sample, whereas it reached the initial intensity for AN sample at 30oC condition. Blend-AC and Blend-AN thin film samples exhibit irreversible and reversible phase transitions, respectively. Further, the FTIR-TS heating-cooling data were subjected to Factor Analysis (FA). AN sample exhibited reversible phase transition (70%↔70%), while AC sample displayed irreversible transition (50%↔70%), which signifies the importance of this study.

In this review, we have discussed on the latest development in metal nanoparticle composites based on PVDF via electrospinning process for electronic applications. Human robotics, wireless-data communication, nanogenerators, wearable biocompatible/bio-inspirable sensors, motion detectors, and actuators have become a key component in self-powered IoT devices. Due to the power demand, an urge is in the industry for fabricating portable, flexible, and sustainable green micro and nano devices. PVDF and its copolymers have attracted greater attention because of their excellent piezoelectric, dielectric, magnetic, and good mechanical properties, suitable for lightweight application and due to the biocompatible nature. Piezoelectric property can be enhanced with the addition of different metal nanoparticles and can be used for various application like sensor, actuators, energy harvesters, health monitors, EMI shielding. Interesting results reported by many research groups working in this field is consolidated in this review paper.

Since the last decade, hyperbranched polymers (HBPs) have gained wider theoretical interest and practical applications in sensor technology due to their ease of synthesis, highly branched structure but dimensions within nanoscale, a larger number of modified terminal groups and lowering of viscosity in polymer blends even at higher HBP concentrations. Many researchers have reported the synthesis of HBPs using different organic-based core-shell moieties. Interestingly, silanes, as organic-inorganic hybrid modifiers of HBP, are of great interest as they resulted in a tremendous improvement in HBP properties like increasing thermal, mechanical and electrical properties compared to that of organic-only moieties. This review focuses on the research progress in organofunctional silanes, silane-based HBPs and their applications since the last decade. The effect of silane type, its bi-functional nature, its influence on the final HBP structure and the resultant properties are covered in detail. Methods to enhance the HBP properties and challenges that need to be overcome in the near future are also discussed.

There are significant societal repercussions from our excessive use of plastic products derived from petroleum. In response to the increasing environmental implications of plastic wastes, biodegradable materials have been proven to be an effective means of mitigating environmental issues. Therefore, protein- and polysaccharide-based polymers have gained widespread attention recently. In our study, for increasing the strength of a biopolymer (Starch), we used ZnO dispersed nanoparticles (NPs), which resulted in the enhancement of other functional properties of the polymer. The synthesized NPs were characterized using SEM, XRD, and Zeta potential values. The preparation techniques are completely green, with no hazardous chemicals employed. The floral extract employed in this study is Torenia fournieri (TFE), which is prepared using a mixture of ethanol and water and possesses diverse bioactive features and pH-sensitive characteristics. The prepared films were characterized using SEM, XRD, FTIR, contact angle and TGA. The incorporation of TFE and ZnO (SEZ) NPs was found to increase the overall nature of the control film. The results obtained from this study confirmed that the developed material is suitable for wound healing and can also be used as a smart packaging material.

Many research groups around the world are working towards enhancing the β-crystallinity content (%) in polyvinylidene fluoride (PVDF) by blending with other polymers. The aim of this study is to electrospin (i). neat PVDF and (ii) PVDF/aliphatic hyperbranched polyester of 1st generation (HBP-G1) blend (80/20 w/w) and their piezoelectric sensor measurement studies. Aliphatic HBP-G1 used in this study was synthesized and characterized using spectral and thermal measurements. Further, electrospinning of neat PVDF and PVDF/HBP-G1 (80/20 w/w) blend was carried out under controlled conditions and their electrospun nanoweb samples were used in the fabrication of piezoelectric sensors and studied for their piezoelectric characteristics. A customized dynamic pressure instrument was used to measure the output peak-to-peak voltage (Vp-p) signals which were transferred to the preamplifier. Compared to neat PVDF (Vp-p = +0.95 V), the PVDF/HBP-G1 (80/20) blend sample exhibited higher Vp-p (+1.67 V), which is an evidence that the incorporation of HBP (20 wt-%) has a significant contribution in enhancing the energy harvesting efficiency of PVDF based piezoelectric sensors. The reaction mechanism behind this crystallinity enhancement is analyzed in-depth and the results are reported in detail.

In this study, neat polyvinylidene fluoride (PVDF), PVDF/polyoctafluoropentyl acrylate (PFA, 90/10 w/w) and PVDF-PFA/hydroxyapatite (HAP, 0 to 20 wt% HAP w.r.t. PVDF-PFA content) were electrospun under controlled conditions, and studied for their piezo-responsive behaviours as a function of nanoweb stacking arrangement (constructive and destructive) and folding architectures (simple, series and parallel connection of electrodes between each folding). Influence of varying HAP content (0, 3, 7, 10, and 20 wt%) on the molecular orientation of CH2-CF2 dipoles in PVDF-PFA/HAP blends were investigated using FTIR, XRD and SEM analysis. Quantitative analysis showed increased β-crystalline content for the 7 wt% HAP sample. From the peak-to-peak output voltage, 7 wt% HAP sample exhibited significantly higher output voltage (Vp-p = 1.21 V) compared to neat PVDF-PFA sample (Vp-p = 0.46 V). Overall, the combinative effect of HAP addition and folding played a vital role in improving the piezoelectric output signals of PVDF-PFA/HAP, which signifies the importance of this study.

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In this study, as cast (AC, at 30 °C) and annealed (AN, at 130 °C, 3 h) samples of polyvinylidene fluoride (PVDF) and PVDF/hyperbranched polyester (HBP) (90/10) blend ultrathin films were subjected to heating-cooling (30 → 210 → 30 °C) cycle, and studied for their changes in crystalline phase transition behavior using in-situ Fourier transform infrared-transmission spectroscopy (FTIR-TS) and grazing incident reflection absorption spectroscopy (FTIR-GIRAS) techniques. Factor analysis was employed to extract the pure crystalline and amorphous spectra as well as the percentage content of ferroelectric crystallinity for both the samples. Irrespective of the thermal treatment (AC or AN) and spectral measurement (FTIR-TS or GIRAS) techniques, neat PVDF sample exhibited irreversible phase transitions during heating-cooling cycle associated with the transformation from ordered β-crystalline (1276 cm−1) into disordered amorphous (1234 cm−1) form. Interestingly, annealed PVDF/HBP blend sample measured using FTIR-GIRAS exhibited reversible crystalline phase transition behavior similar to a ‘dipole memory effect’ even after heating to 210 °C (>Tm) and then cooled to 30 °C. Compared to neat PVDF, higher ferroelectric crystallinity and reversible phase transition in PVDF/HBP blend may be attributed to (i) the existence of H-bonding between HBP (C O and OH groups) and PVDF ( CH2 and CF2) and/or (ii) HBP acting as a nanoparticle in PVDF matrix.