Table 2.

Summary of structural modification of polymers, improvement, and deterioration of dielectric properties.

S/N	Structural Modification	Improvement in Dielectric	Deterioration in Dielectric Properties	References
1	Increase in free volume via rigid backbone (e.g., SO2-PPO)	Increased ε′ due to improved dipole alignment (ε′ = 8.2)	Increased dipole rotation and mobility leads to decrease in ε″.	[40,44]
2	Blending PEI and PVH	Higher ε′ from dipole alignment due to PVH groups	Limited ε′ at high PEI content due to constrained dipole mobility.	[45]
3	Methyl side groups	None observed	Increased free volume lowers ε′	[22]
4	Rigid polymer chains (e.g., PPO)	Reduced ε″ due to restricted dipole mobility	Minimal ε′, reduced flexibility.	[52]
5	Nanofillers with high ε′ (e.g., BaTiO3, CNFs, BST)	Higher ε′, enhanced interfacial polarization	Reduced EBD due to inhomogeneous fields at high filler volume.	[75,108]
6	Use of low-ε′ fillers (e.g., alumina)	Improved ε′ with stable EBD	None observed.	[104]
7	Smaller nanoparticle sizes (<20 nm)	Enhanced ε′ due to larger interfacial regions	None observed.	[104]
8	1-D nanorods in nanocomposites	Significant ε′ improvement due to extended interfacial regions	None observed.	[105]
9	Blending PI with PEI	Higher EBD, reduced void density (EBD ~1000 MV/m)	None observed.	[28]
10	Cyclic polystyrene (cPS) vs. linear polystyrene	50% enhancement in EBD, 80% increase in energy density	None observed.	[55]
11	Multilayered structures (e.g., PC and P[VDF-HFP])	Increased EBD via barrier effect	None observed.	[130,131]
12	Nanoconfinement	Increased EBD and ε″	Reduction in ε′.	[121,122,123,127]
13	Polymer chain annealing	Improved EBD and reduced ε″	None observed.	[64]