After an introduction reporting the properties and the applications of fluoropolymers, a first part deals with i) the main routes to produce vinylidene fluoride (VDF) monomer, ii) its homopolymerization, and iii) the advantages and uses of polyvinylidene fluoride (PVDF). In a second section, this review, illustrated by numerous examples, extensively reports the synthesis, properties and applications of the copolymers based on VDF with non-halogenated, fluorinated, commercially available or synthesized comonomers. These comonomers exhibit XYC=CZ-Sp-R structures where X, Y, and Z represent H, F, and CF3 groups, Sp a spacer and R a function such as OH, OAc, SAc, CO2R' (R' being a H atom or an alkyl group), CN, P(O)(OR')2 and SO3H. According to the nature and to the amount of the comonomer, the copolymers can be thermoplastic, elastomeric or thermoplastic elastomers. Introducing reactive R side groups brings complementary properties such as hydrophily, ionic exchange or surface properties, or further crosslinking of the resulting copolymers. Then, the kinetics of radical copolymerization of VDF with M comonomers led to the assessment of the reactivity ratios which are compared. Hence, a reactivity series of these M comonomers with respect to a macroradical terminated by VDF is proposed. Usually, these copolymers exhibit random structures but only three comonomers produced alternating copolymers with VDF: hexafluoroisobutylene, F2C=CFCO2CH3, and H2C=C(CF3)CO2R. The controlled radical copolymerizations of VDF with other comonomers (such as chlorotrifluoroethylene, 3,3,3-trifluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether or-trifluoromethacrylic acid) either in the presence of xanthates, borinates or iodo-compounds are also reported. In addition, new VDF-containing copolymers exhibit well-defined architectures, such as block and graft copolymers. They can be synthesized either by conventional techniques or by controlled radical copolymerization. Chemical modifications of PVDF and poly(VDF-co-monomer) copolymers are also presented. Several properties and applications (such as surfactants, dielectrical polymers, thermoplastic elastomers, fuel cell and ultrafiltration membranes, or polycondensates, the fluorinated segments of which bringing softness and thermal stability) of these VDF-containing copolymers will illustrate this review.

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From vinylidene fluoride (VDF) to the applications of VDF-containing polymers and copolymers: recent developments and future trends.

Energy harvesting exploits ambient sources of energy such as mechanical loads, vibrations, human motion, waste heat, light or chemical sources and converts them into useful electrical energy. The applications for energy harvesting include low power electronics or wireless sensing at relatively lower power levels (nW to mW) with an aim to reduce a reliance on batteries or electrical power via cables and realise fully autonomous and self-powered systems. This review focuses on flexible energy harvesting system based on polyvinylidene fluoride based polymers, with an emphasis on manipulating and optimising the properties and performance of the polymeric materials and related nanocomposites through structuring the material at multiple scales. Ferroelectric properties are described and the potential of using the polarisation of the materials for vibration and thermal harvesting using piezo- and pyro-electric effects are explained. Approaches to tailor the ferroelectric, piezoelectric and pyroelectric properties of polymer materials are explored in detail; these include the influence of polymer processing conditions, heat treatment, nanoconfinement, blending, forming nanocomposites and electrospinning. Finally, examples of flexible harvesting devices that utilise the optimised ferroelectric polymer or nanocomposite systems are described and potential applications and future directions of research explored.

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Multiscale-structuring of polyvinylidene fluoride for energy harvesting: the impact of molecular-, micro- and macro-structure

This critical review tersely and concisely reviews the recent development of the polymer electrolyte membranes and the relationship between their properties and affecting factors like operation temperature. In the first section, the advantages and shortcomings of the corresponding polymer electrolyte membrane fuel cells are analyzed. Then, the limitations of Nafion membranes and their alternatives to large-scale commercial applications are discussed. Secondly, the concepts and approaches of the alternative proton exchange membranes for low temperature and high temperature fuel cells are described. The highlights of the current scientific achievements are given for various aspects of approaches. Thirdly, the progress of anion exchange membranes is presented. Finally, the perspectives of future trends on polymer electrolyte membranes for different applications are commented on (400 references).

Advances in the high performance polymer electrolyte membranes for fuel cells.

Advances in Piezoelectric Polymer Composites for Energy Harvesting Applications: A Systematic Review

Low-cost and flexible printed graphene–PEDOT:PSS gas sensor for ammonia detection

Here we report the grafting of N,N-dimethylaminoethyl methacrylate (DMAEMA) directly from poly(vinylidene fluoride) (PVDF) backbone in solution phase by atom transfer radical polymerization (ATRP). The graft length is same for different times of polymerization but graft density increases with increasing polymerization time. Four graft copolymers are prepared and depending on the time of conversion they are designated as PD-6, PD-12, PD-18, and PD-24, the number indicates time (h) of polymerization. A maximum of 36% (w/w) conversion with respect to monomer is achieved in the PD-24 sample. Gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and polymerization kinetics study conclude the ATRP nature of the polymerization. The graft copolymer shows induced solubility in water and the effective particle diameter in aqueous medium decreases from PD-6 to PD-24 samples. The enthalpy of fusion values are same in graft copolymers with more than 50% reduction and the melting points reduce by 5−6 °...

Multifunctional Hydrophilic Poly(vinylidene fluoride) Graft Copolymer with Supertoughness and Supergluing Properties

Hierarchical nanostructured polyaniline functionalized graphene/poly(vinylidene fluoride) composites for improved dielectric performances

A new compatibilizer (P2) containing thiophene moiety and poly(dimethylamino ethyl methacrylate) (PDMAEMA) group is prepared by atom transfer radical polymerization (ATRP). The dispersion of multiwalled carbon nanotube (MWNT) with P2 in N,N-dimethylformamide (DMF) is stable for >3 months. The UV–vis spectrum of the MWNT/P2 dispersion shows a blue shift, and the photoluminescence (PL) spectrum also indicates a quenching suggesting a significant interaction between MWNT and P2. SEM and TEM micrographs suggest a good dispersion and coating of P2 on MWNT surface. The Raman D/G band intensity ratio remains unchanged, and a small shift of >C═O vibration peak to lower energy suggests an interaction between P2 and MWNT. The presence of CH−π and π–π interactions between P2 and MWNT is evidenced from UV–vis, PL, Raman, FTIR, and NMR spectral results facilitating the wrapping of P2 on MWNT surface. Poly(vinylidene fluoride) (PVDF)/P2/MWNT composites (PCMx, x indicates wt % of MWNT) are prepared by solvent casting me...

Noncovalent Functionalization of Multiwalled Carbon Nanotube by a Polythiophene-Based Compatibilizer: Reinforcement and Conductivity Improvement in Poly(vinylidene fluoride) Films

Poly(methyl methacrylate) (PMMA) functionalized multi-walled carbon nanotubes (MWNT) (f-MWNT) are prepared using nitrene chemistry and atom transfer radical polymerization. The >CO groups in the f-MWNT interact with the >CF2 groups of poly(vinylidene fluoride) (PVDF) to achieve a compatible blend. An increase of the glass transition temperature (Tg), relaxation temperatures of the crystal-amorphous interface and crystalline phases are observed in the composites over pristine PVDF. The thermal stability of the composites increases with increasing f-MWNT concentration. The storage modulus increases significantly with increasing f-MWNT concentration and the highest increase of 120% over PVDF is observed for 1 wt% f-MWNT at 50 °C. An increase in tensile strength with a decrease of the strain at break, and increase of Young's modulus and toughness indicate the formation of a very hard and ductile composite material. The electrical conductivity is high (1 × 10−4 S cm−1, for 5% f-MWNT) and shows a very low percolation threshold (0.36% w/w at 30 °C). Analysis of the conductivity data yields the magnitude of percolation exponent 2.1, suggesting three-dimensional percolation is a suitable model for the conduction of the composites. The temperature variation of the conductivity suggests that the conduction might occur through a temperature fluctuation induced tunnelling mechanism. The I–V characteristic curves indicate the semiconducting nature of the composites.

Physical properties of poly(vinylidene fluoride) composites with polymer functionalized multiwalled carbon nanotubes using nitrene chemistry

A new route for the synthesis of low cost, flexible, high dielectric constant functional polymer nanocomposite is successfully fabricated by introducing molybdenum disulfide (MoS2) into poly(vinylidene fluoride) (PVDF) using polyaniline (PANI) as an interlinker. The strategy adopted is to exfoliate MoS2 (E-MoS2) by simple sonication of bulk MoS2 in N,N′-dimethyl formamide (DMF) and in situ polymerization of aniline with E-MoS2 in water to produce MoS2–PANI showing novel raspberry type morphology. MoS2–PANI shows good dispersion in PVDF matrix implying strong interaction onto the PVDF interface, and it acts as a nucleating agent for PVDF crystallization. Synergistic nucleating effect of MoS2–PANI onto PVDF led to the formation of dominant polar β-phases in the MoS2–PANI/PVDF (MPF) composite films. With 10% filler content, the MPF material shows 86% polar β-phase PVDF due to its good interaction and dispersion of MoS2–PANI. The maximum increment of dielectric constant (e′) of that sample is 586 at 102 Hz, which is 42 times higher than that of neat PVDF and it can be well explained by interfacial polarization along with the formation of nanocapacitor network in PVDF matrix. This intriguing synthesis method of MoS2–PANI/PVDF nanocomposite will open up new opportunities for fabricating nanostructured polymer composites to produce high dielectric materials.

Amit Mandal

Papers

Multifunctional Hydrophilic Poly(vinylidene fluoride) Graft Copolymer with Supertoughness and Supergluing Properties

Hierarchical nanostructured polyaniline functionalized graphene/poly(vinylidene fluoride) composites for improved dielectric performances

Noncovalent Functionalization of Multiwalled Carbon Nanotube by a Polythiophene-Based Compatibilizer: Reinforcement and Conductivity Improvement in Poly(vinylidene fluoride) Films

Physical properties of poly(vinylidene fluoride) composites with polymer functionalized multiwalled carbon nanotubes using nitrene chemistry

High dielectric poly(vinylidene fluoride) nanocomposite films with MoS2 using polyaniline interlinker via interfacial interaction