Herein, we report significantly enhanced mechanical properties and thermal conductivity of polyimide (PI) by incorporating a small amount (0.01 wt %) of individualized boron-doped high-quality graphene as a filler. The boron-doped expandable graphite (B-EG) was synthesized by mixing boric acid ( H3BO4) with expandable graphite (EG) and thermally treating the mixture at 2450 °C for 30 min using a graphite furnace in an argon atmosphere. The boron-doped graphene (B-g) was prepared by the solution-phase exfoliation of B-EG with an ultrasonication process, which is a method to obtain individualized graphene as well as few-layer graphene. The PI nanocomposites were prepared using the obtained graphene. The PI nanocomposites synthesized with high-quality B-graphene (B-g) showed enhanced mechanical properties and thermal conductivity compared to those of pure PI due to the doping effects and strong interfacial interactions between graphene and the PI matrix.

In this study, we studied the alignment characteristics of liquid crystal on polyimide substrate when irradiated with ion beam in oblique direction on uniformly coated polyimide substrate. The inclined irradiation angle of the ion beam was set to 30 degree, 45 degree and 60 degree and the characteristics were observed for 1 minute and 2 minutes at an ion beam irradiation intensity of 600 to 3,000 eV for each angle. The Alignment of the liquid crystals were observed using a polarized microscope after preparing antiparallel specimens. The pretilt angle of the liquid crystal using the crystal rotation method was measured, and the applicability to actual products was evaluated. Experimental results showed that uniformly aligned liquid crystals could be obtained in samples irradiated at 1 and 2 minutes with an ion beam intensity of 1200 eV or higher when irradiated with 30 degree and 45 degree tilted ion beams. And, at 60 tilted degree, It shows that uniformly aligned liquid crystals could be obtained in samples irradiated at 1 and 2 minutes with an ion beam intensity of 2400 eV or higher. The pretilt angle of the liquid crystal showed the best characteristics when irradiated with ion beam inclined at 45 degrees, and it was confirmed that the pretilt angle was 0.2 to 1.3 degrees, which is usable for horizontally oriented LCD.

Current petrochemical product mainly comes from light olefin, such as ethylene and propylene. these olefins can be obtained as mixture form of olefin/paraffin, which is co-product of naphtha cracking process. However, the mixture of light olefin and paraffin is considerably difficult to separate because they have similar physicochemical properties such as density, boiling point, and molecular weight. Cryogenic distillation is currently utilized, but still suffered from high operating cost. Membrane separation with polyimide-based material is a promising alternative due to its lower energy cost and modular operation. Here, we synthesized composite membrane with metal-organic framework (MOF) based on polyimide exhibiting high permeability and selectivity in propylene/propane separation, as well as simple preparation and high stability.

Polymer membrane-based gas separation has been attracting recent interest due to its ease of operation and low operational cost. Polyimides (PIs) are the most widely used polymers for this application due to their toughness and moderate gas separation properties. However, the gas separation performance of the current polymers, including PIs, do not meet the requirement for the industrial applications. We report herein multi-block PIM-co-PIs as novel polymer membranes for CO2 separation. Synthesis, characterization and their properties including gas separation performance of various compositions of PIM-PI block copolymer membranes will be discussed in details.

수소는 고부가가치의 신재생 수송원료이자 탄소자원화 화학제품 제조의 기초 원료로 사용할 수 있으며 이를 위해 경제성 있는 분리소재 및 분리공정기술이 중요하다. 본 연구에서는 철강부생가스 COG내 수소를 회수할 수 있는 건습식 방사법에 의한 비대칭 구조의 폴리이미드 중공사막의 제조를 연구하였다. 이를 위해 지환족 다이안하이드를 사용한 유기용매에 대한 용해성이 높은 폴리이미드 소재를 합성하여 수소, 메탄, 질소, 산소 등의 기체투과특성을 확인하였고 그 중 가장 수소 선택성이 높은 DOCDA-ODA를 이용하여 용해성 폴리이미드를 합 성하였다. 합성된 폴리이미드는 H-NMR, FT-IR을 통하여 합성이 성공적으로 이루어진 것을 확인하였으며 확보된 폴리이미드를 이용해 건습식 방사법에 의한 중공사막을 제조하였다.

폴리이미드는 뛰어난 기계적 강도, 내열성, 내화학성 및 여러 기체에 대한 높은 투과선택성을 가지고 있으나 유기용매에 대한 낮은 용해성으로 인해 제막할 경우 많은 제약을 받고 있다. 따라서 유기용매에 가용성을 가지는 폴리이미드에 대한 연구가 필요하다. 본 연구에서는 지환족 다이안하이드라이드인 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicar boxylic (DOCDA) 와 다양한 다이아민을 이용하여 DOCDA계 폴리이미드를 합성하였다. FT-IR을 통해 합성이 잘 이루어졌음을 확인하였고, 용해도 테스트를 통해 여러 유기용매에 대한 용해성을 확인하였다. 또한, 기체투과특성을 알아보기 위하여 time-lag 장비를 이용하여 투과도 및 선택도를 알아보았다.

4,4'(hexafluoroisopropylidene) diphthalic anhydride (6FDA)와 4,4'-oxydianiline (ODA)로부터 용해성이 있는 폴리이미드인 chloromethylated polyimide(CPI)를 합성하고 이를 chloromethylmethyl ether로 hloromethylatation 시켰 다. 다음 CPI를 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) 촉매 존재하에서 carboxy-terminated PEG와 반응함으로써 PEG-grafted polyimide를 합성하였다. 합성된 고분자는 1H-NMR, FT-IR, DSC, TGA 등으로 구조 분석하였다. PEG-grafted polyimide의 고분자 고체전해질로의 응용을 위해 lithium trifluoromethanesulfonate와 lithium perchlorate 등의 리티움염을 섞은 후 impedance spectroscopy를 이용하여 이온전도도를 측정하였는데 그 결과 상온 에서 10-5 ~ 10-6 S/cm 정도의 전도도를 얻었다.

Membrane-based gas separation is one of the next generations’ gas separation technology for carbon capture and storage (CCS). Membrane process has the advantages of i) low energy consumption without a phase change during the separation, ii) small footprint and easy scale-up of membrane modules, and iii) clean process without any emission of harmful byproducts. However, the requirement of CO2 separation membrane for CCS has limited the application of gas separation membranes in the industrial field. Here, we demonstrate the strategies to approach to the current limitation by developing a high flux of polymeric hollow fiber membrane. The membrane performance in this work is 900 GPU (1 GPU = 10-6 cm3/cm2‧sec‧cmHg) of CO2 permeance. The CO2 capture pilot plant using multi-stage membrane processes at KDHC has been on-site tested.