Below is a paragraph from an academic paper. Polish the writing to meet the academic style, improve the spelling, grammar, clarity, concision and overall readability. When necessary, rewrite the whole sentence. Furthermore, list all modification and explain the reasons to do so in markdown table. Paragraph:Recently, significant improvements in the dielectric constant of polymer matrixes have been made by several groups via grafting dipolar groups onto the side chains of polar dielectric polymers.(Qiao et al., 2013; Pei et al., 2014; Wei et al., 2015; Wei and Zhu, 2020; Ren et al., 2021b; Zhang et al., 2023). Treufeld et al. prepared novel polyimides by introducing polar nitrile groups(-CN), with high dipolar moment of 4.0 Debye, to the diamine monomers and achieved the increase of permittivity.(Treufeld et al., 2014) It is found that the more the nitrile groups(-CN) were grafted, the more dipolar moments were obtained, then the polyimides with much more higher permittivity were investigated. However, instead of varying the number of polar groups, groups with higher dipolar moments, such as sulfonyl groups (-S=O), possessing high dipolar moment of 4.30 Debye, are appealing to a good deal of researchers. For example, a kind of dipolar glass polymer, with sulfonyl groups on the side chains of poly(methyl methacrylate) (PMMA) matrix, was synthesized. Attribute to the side chain grafting, the permittivity of the polymer was increased from 5.0 to 9.2 at 50℃, but the dielectric loss was as high as 0.02, which could be interpreted as the limited free volume limits the free rotation of sulfonyl groups.(Wei et al., 2015) To mitigate the high dielectric loss, Wei et al. attached the sulfonyl groups to a poly(ether ether ketone) (PEEK) matrix via flexible ester bonds.(Wei et al., 2019) This approach achieved a big boost on the permittivity, which from 3.15 to 5.0, and also realized low dielectric loss which is due to the large temperature window from β to α transition and the flexible mobile dipolar side groups. However, the sulfonylated PEEK (PEEK-SO2) could only be operated at room temperature owing to its low Tg, which is only 176℃. Therefore, sulfonyl groups (S=O) were introduced into the intrinsically heat-resistant material poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to enhance the energy storage performance of the polymers at elevated temperatures.(Zhang et al., 2018b) This modification resulted in high permittivity, improved from 3.5 to 6.2, high energy storage density (>22 J/cm3) at room temperature and high temperature capability up to 150℃,which were attributed to the high rigidity of the PPO backbone and the presence of polar sulfonyl groups. Similarly, polyimide (PI), another intrinsically heat-resistant material, achieved significantly enhanced energy storage performance by introducing sulfonyl groups (S=O) to the diamine monomers.(Tong et al., 2019a) The permittivity of the sulfonylated polyimides, ranging from 4.5 to 5.98, were much higher than conventional PI (about 3.5). What’s more, high charge-discharge efficiency (91.3%) and high discharge energy density of 7.04 J/cm3 at 500 MV/m were realized at room temperature. In a word, the introducing of sulfonyl groups leads to the huge improvement of permittivity, but most of the research focuses on the side chain grafting or variations in the diamine monomers of PI.