Polymer nanocomposites are a promising concept to improve energy storage density of capacitors, but realizing their hypothetical gains has proved challenging. The introduction of high permittivity fillers often leads to reduction in breakdown strength due to field exclusion, which intensifies the applied electric field within the polymer matrix near nanoparticle interfaces. This has prompted research in developing new nanoparticle functionalization chemistries and processing concepts to maximize particle separation. Herein, we compare the dielectric performance of blended nanocomposites to matrix free assemblies of hairy (polymer grafted) nanoparticles (HNPs) that exhibit comparable overall morphology. The dielectric breakdown strength of polystyrene grafted BaTiO₃ (PS@BaTiO₃) systems was over 40% greater than a blended nanocomposite with similar loading (~25% v/v BaTiO₃). Hairy nanoparticles with TiO₂ cores followed similar trends in breakdown strength as a function of inorganic loading up to 40% v/v. Dielectric loss for PS@BaTiO₃ HNPs was 2–5 times lower than analogous blended films for a wide frequency spectrum (1 Hz to 100 kHz). For content above 7% v/v, grafting the polymer chains to the BaTiO₃ significantly improved energy storage efficiency. Overall this study indicates that polymer grafting improves capacitor performance relative to direct blending in likely two ways: (1) by mitigating interfacial transport to lower dielectric loss, irrespective of the dielectric contrast between matrix and nanoparticle, and (2) by restricting particle–particle hot-spots by establishing a finite minimum particle separation when the dielectric contrast between matrix and nanoparticle is large.

聚合物纳米复合材料是提高电容器储能密度的一个有前途的概念，但事实证明，实现其假想的收益具有挑战性。高介电常数填料的引入通常由于电场排斥而导致击穿强度降低，这增强了在纳米颗粒界面附近的聚合物基质内施加的电场。这促使人们在开发新的纳米粒子功能化化学方法和处理概念方面进行研究，以最大程度地实现粒子分离。在这里，我们将混合纳米复合材料的介电性能与具有可比较的整体形态的毛状（聚合物接枝）纳米颗粒（HNP）的无基质组装相比较。聚苯乙烯接枝BaTiO ₃（PS @ BaTiO ₃的介电击穿强度）系统比具有相似负载量（〜25％v / v BaTiO ₃）的混合纳米复合材料大40％以上。具有TiO ₂核的毛状纳米颗粒在分解强度方面的相似趋势是无机负载量高达40％v / v的函数。在宽频谱（1 Hz至100 kHz）下，PS @ BaTiO ₃ HNP的介电损耗比类似的共混膜低2-5倍。如果含量高于7％v / v，则将聚合物链接枝到BaTiO _3上大大提高了储能效率。总体而言，这项研究表明，相对于直接共混，聚合物接枝可通过两种方式改善电容器性能：（1）通过降低界面传输降低介电损耗，而与基质和纳米粒子之间的介电对比度无关；（2）通过限制粒子间相互作用当基质和纳米颗粒之间的介电对比度大时，通过建立有限的最小颗粒间距来形成热点。