Highly Macroporous Polyimide with Chemical Versatility Prepared from Poly(amic acid) Salt-Stabilized High Internal Phase Emulsion Template.

Macroporous polymers have gained significant attention due to their unique mass transport and size-selective properties. In this study, we focused on Polyimide (PI), a high-performance polymer, as an ideal candidate for macroporous structures. Despite various attempts to create macroporous PI (Macro PI) using emulsion templates, challenges remained, including limited chemical diversity and poor control over pore size and porosity. To address these issues, we systematically investigated the role of poly(amic acid) salt (PAAS) polymers as macrosurfactants and matrices. By designing 12 different PAAS polymers with diverse chemical structures, we achieved stable high internal phase emulsions (HIPEs) with >80 vol % internal volume. The resulting Macro PIs exhibited exceptional porosity (>99 vol %) after thermal imidization. We explored the structure-property relationships of these Macro PIs, emphasizing the importance of controlling pore size distribution. Furthermore, our study demonstrated the utility of these Macro PIs as separators in Li-metal batteries, providing stable charging-discharging cycles. Our findings not only enhance the understanding of emulsion-based macroporous polymers but also pave the way for their applications in advanced energy storage systems and beyond.

Ambient air-operated thermo-switchable adhesion of N-isopropylacrylamide-incorporated pressure sensitive adhesives.

Owing to the rise in global population and living standards, waste treatment has inevitably become a critical issue for a sustainable environment. In particular, for an effective recycling process, it is vital to disassemble different types of materials by removing adhesives used in the packaging. However, this removal process requires harsh solvents (acidic and organic) that are unfriendly to nature and may cause additional pollution. To address this issue, functional adhesive materials that can be removed without the use of harsh solvents have drawn significant attention. One promising approach is to utilize the stimuli-responsive polymers to synthesize pressure sensitive adhesives (PSAs); however, it is technically challenging to simultaneously satisfy (i) strong initial adhesion (without stimulus), (ii) stimuli-responsive sufficient reduction of adhesion, and (iii) reversibility. In this study, thermo-switchable PSAs were synthesized by copolymerizing N-isopropylacrylamide (NIPAM), which possesses thermal-responsive properties; acrylic acid, which endows adhesive properties; and 2-ethylhexyl acrylate, which has a low glass transition temperature to attain sufficient flexibility. The synthesized NIPAM-based thermo-switchable PSAs exhibited significantly high peel strength at room temperature (∼15.41 N/25 mm at 20 °C), which decreased by ∼97% upon heating (∼0.46 N/25 mm at 80 °C). Importantly, no residues remained due to the cohesive nature of NIPAM at high temperature. The reversible adhesion behaviour of the thermo-switchable PSAs was retained during repeated heating and cooling cycles. Therefore, the developed thermo-switchable PSA can enhance the reusability and recyclability of valuable materials and minimize the use of toxic chemicals for adhesive removal, contributing to a more sustainable future.