Effect of g-PVDF on enhanced thermal conductivity and dielectric property of Fe-rGO incorporated PVDF based flexible nanocomposite film for efficient thermal management and energy storage applications† Sumanta Kumar Karan, Amit Kumar Das, Ranadip Bera, Sarbaranjan Paria, Anirban Maitra, Nilesh Kumar Shrivastava and Bhanu Bhusan Khatua * Here, we investigate the effect of thermal conductivity of g-crystallites of PVDF in Fe-rGO/PVDF nanocomposite, which are of potential use as actuators and temperature sensors for thermal management applications. The formation of g-crystallites help to increase the thermal conductivity of the nanocomposite up to 0.89 W mK 1 at low level of filler loading (3 wt%) and we showed that the thermal conductivity depends on the amount of crystalline polar g-phase in addition to filler concentration. Although thermal conductivity depends on the crystallinity of the nanocomposite, here enhancement of thermal conductivity is not related only to crystallinity, as the crystallinity is decreased compared to neat PVDF. However the thermal conductivity increases because of the generation of a higher number of g-crystallites of small size. Furthermore, the nanocomposite at low filler loading also shows high dielectric constant with low dielectric loss of the order of z57 and z0.13, respectively, at 1 kHz. Moreover, the energy storage property and its dependence on g-crystallite size reveals that the material can also exhibit superior released energy density (1.45 J cm 3 ) as compared to pure PVDF. 1. Introduction Recently, polymer nanocomposite having large thermal conductivity and high dielectric constant are highly necessary due to their diverse applications in electric and electronic industries 1,2 including stress control, sensors, actuators, embedded capacitors, electromagnetic shielding, and most latest energy storage devices. 2–4 The enhancement of thermal conductivity of the polymer nanocomposite is still a most urgent challenge for the dissipation of heat from micro/nano electronic devices during operation. We thus need to enhance the thermal conductivity to a certain limit for easy dissipation of heat from the system. Although polymer composites exhibit a wide variety of applications from generators to automobile parts, including in heat exchangers and power generation, they also have a great potential application in micro/nano electronic devices. Polymer composites have advantages for practical application compared to other systems due to their easy proc- essability. 4 Poly(vinylidene uoride) (PVDF) is a promising piezoelectric and ferroelectric polymer for the preparation of polymer based embedded capacitors owing to its valuable properties, such as high energy storage, high dielectric constant, high heat resistance and sustainability in high electric eld range due to the presence of spontaneous arrangement of –C(F)– dipoles in the crystalline phases (a, b, g, d and 3). 3,5–7 Although several research groups have prepared PVDF-based nanocomposite having high dielectric constant, only a few reports 4,8–11 on the investigation of thermal conductivity, as well as dielectric properties of the polymer nanocomposite, have been reported so far. Moreover, low thermal conductivity of these polymer nanocomposite restricts the heat dissipation and thereby leads to a decrease in dielectric strength of the mate- rials. 12 Rapid and efficient dissipation of heat generated from electronic materials is essential to maintain the operating temperature at the desired level. Recently, conducting nano- llers such as, CNT, 13 exfoliated graphite 12 and graphene 14 have been of great interest due to their ability to form conducting network at very low ller loading in polymer nanocomposite, which signicantly improves thermal conductivity by easy dissipation of heat. Among these, graphene is believed to be the most ideal nanoller due to its light weight, excellent corrosion resistance, large surface area, high aspect ratio, low manufacturing cost, high electrical conductivity 15 and excellent thermal conductivity (z4000–5000 W mK 1 ). 16 However, reports on the studies of thermal and electrical conductivity of Materials Science Centre, Indian Institute of Technology, Kharagpur-721302, India. E-mail: khatuabb@matsc.iitkgp.ernet.in; Tel: +91 3222 283982 † Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra04365h Cite this: RSC Adv. , 2016, 6, 37773 Received 18th February 2016 Accepted 3rd April 2016 DOI: 10.1039/c6ra04365h www.rsc.org/advances This journal is © The Royal Society of Chemistry 2016 RSC Adv. , 2016, 6, 37773–37783 | 37773 RSC Advances PAPER Published on 05 April 2016. Downloaded by Indian Institute of Technology Kharagpur on 18/04/2016 14:20:24. View Article Online View Journal | View Issue