## 2 High-\(k\) Dielectric Polymers
by combining hard silicon segments in a soft dielectric matrix was recently reported, where 1,6-bis(trichlorosyl! )hexane (C\({}_{6}\)) was used as organosilane cross-linking agent to functionalized carboxy terminal liquid reactive rubber, dicarboxy-terminated poly(acrylonitrile-co-butadiene) (CTBN). Figure 2 represents a sketch for the formation of elastomeric network dielectric film from CTBN and C\({}_{6}\). They reported self-organized C\({}_{6}\) aggregates acting as nanofillers in the dielectric matrix, and enhancing the dielectric strength by inhibiting electrical treeing growth [75]. A similar strategy was reported by [PERSON] et al., where statistical copolymer poly(styrene-co-methyl methacrylate) was designed via a reversible addition-fragmentation chain \begin{table}
\begin{tabular}{c c} \hline
**Polymers** & **Breakdown Strength (MV/m)** \\ \hline Polytetrafluoroethylene (PTFE) & 600–700 \\ Polypropylene (PP) & 640 \\ Polyvinylidene fluoride (PVDF) & 590 \\ Polyethylene terephthalate (PET) & 570 \\ Polycarbonate (PC) & 528 \\ SU-8 & 440 \\ Polyvinyl chloride (PVC) & 140–210 \\ \hline \end{tabular}
\end{table} 
Table 1: Breakdown strength (dielectric strength) of some selected polymers. transfer (RAFT) process. Since the RAFT process involves ionic liquids, they reported a superior ionic conductivity of the resulting polymeric gel, as well as the enhanced device performance in transistor gating experiments [76]. The quasi-permanent dipole polarization or surface charge exhibited by polytetrafluoroethylene (PTFE) incited the researchers to use PTFE thin films produced by radio frequency (RF) magnetron sputtering or plasma-enhanced chemical vapor deposition [77]. Since PTFE possesses excellent chemical stability and dielectric properties, they are ideal to use as electr materials in organic electronics [78]. [PERSON] et al. reported nearly isotropic and dimensionally stable silica-filled PTFE flexible laminates obtained by a hot pressing (SMECH process) technique for microwave circuit applications. The author reports the dielectric constant of 2.9 at the X-band frequency (8.2-12.4 GHz) for the maximum loading of fused silica (60 wt%) [78], whereas PTFE/rutile (rutile is a mineral primarily composed of titanium  
Figure 1: Illustrations representing the fabrication of the soft vibrotactile actuator based on ePVC–silicon dioxide nanoparticle (ePVC-SDN) gels. (**a**) Composition of the vibrotactile actuator. (**b**) Bottom surface of the upper layer. (**c**) Assembled vibrotactile actuator. Adapted with permission from [70], IEEE, 2018. Figure 2: Schematic representation of the elastomeric network dielectric film formation using CTBN and C6. Adapted with permission from [75], American Chemical Society, 2018.  
dioxide) nanocomposites, which exhibited a dielectric constant of above 7.0 at the X-band frequency for the 50 wt% loading of nano-rutile [79]. The polypropylene carbonate (PPC) dielectric film reported by [PERSON], et al. showed excellent compatibility with semiconducting pentacene and N,N'-Dioctyl-3,4,9,10 perylenedicarboximide (PTCDI-C8). Furthermore, the reported PPC film showed a surface energy of 47 mN m\({}^{-1}\) with a dielectric constant of 3, which was utilized as a substrate material for organic thin film transistors (OTFTs) and organic inverters [80]. A sketch was drawn and presented in Figure 3, for understanding the basic design of OTFT and a bottom-gate top-contact OTFT on the PPC substrate. We can notice that an ultra-thin silver (Ag) metal gate was deposited on the PPC and thick layer (970 nm) of the biocompatible dielectric polyvinylpyrrolidone (PVPy) which was spin coated on the PPC layer. In addition, fabric-based wearable bioelectric and biochemical sensors were designed by loading silver nanoparticles in plastisols. These polymers can be easily screen-printed on textiles, since they adhere well to the fabrics [81].