Microphase Separation and Thermal Properties for High-χ Ionic Homopolymers: Effect of Side-Chain Dipole Orientation

The heterogeneity of the microstructure for polymer materials determines the differential performance of their macroscopic properties. In this work, <i>para</i>-ionic homopolymers (P4VBC_n-(i)imi) and <i>meta</i>-ionic homopolymers (P3VBC_n-(i)imi) were prepared by reacting poly(4-vinylbenzyl chloride) and poly(3-vinylbenzyl chloride) with long-chain alkyl imidazole, respectively. Microphase separation was achieved through the dominance of long-chain crystallization, resulting in lamellar nanopatterns below 5 nm. The thermal properties of <i>para</i>-ionic homopolymers were higher than those of <i>meta</i>-ionic homopolymers in terms of polymer bulk and microphase separation structure, reflecting a significant dependence of thermal properties on the dipole orientation of the side chains. For the first time, the calculation of the Flory-Huggins parameter (χ) was introduced into the homopolymer systems, providing a simple and efficient method for investigating the effects of the side-chain dipole orientation and ionization on ionic homopolymers. Calculation results showed that the side-chain dipole orientation differentiates χ values for ionic homopolymers. These findings provided a novel research strategy for the correlation between the microstructure and macroscopic properties of homopolymer materials and offered new ideas for the design and manufacture of homopolymer patterned materials.