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Design and Synthesis of Bottlebrush Copolymers as Functional Additives for Various Applications
Joona Bang(방준하) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Bottlebrush polymers (BBPs) have been of significant interest for over two decades due to their unique physical and solution properties. With recent progress in synthetic techniques, their three-dimensional architectures can be precisely controlled with various monomers. In this presentation, I will demonstrate the potential ability of BBPs as functional additives in various applications. First, BBPs with statistical sidechains were employed as additives to induce the perpendicular orientation of high χ block copolymer in thin films through architecture-induced surface segregation. As another examples, BBPs were used as functional additives for cathode in Li-ion battery or epoxy resins to improve their desired properties by taking advantage of BBP architectures and functionalities.
Joona Bang(방준하) 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1
Bottlebrush polymers (BBPs) have been of significant interest for over two decades due to their unique physical and solution properties. With recent progress in synthetic techniques, their detailed architectures can be precisely controlled with various monomers. The most popular method to synthesize BBPs is ring-opening metathesis polymerization (ROMP) with Grubbs’ catalyst. In this case, it has been well recognized that the purity of macromonomers (MMs) is critical for a successful ROMP reaction. To provide a better guide of MM synthesis for a ROMP, we investigated the impact of various impurities on MM-ROMP by adding possible poisoning species to purified MMs. As an example of BBP application, we demonstrate that BBPs with statistical side-chains were employed as additives to induced the perpendicular orientation of high χ block copolymer lamellae in thin films through architecture-induced surface segregation.
코어쉘 공중합체 첨가제 도입을 통한 에폭시 접착제 물성 향상
문준수(Junsoo Moon),허윤(Yoon Huh),최영선(Youngson Choe),방준하(Joona Bang) 한국고분자학회 2021 폴리머 Vol.45 No.5
본 연구에서는 코어쉘 구조의 공중합체(CSP)를 합성하여 에폭시 수지의 첨가제로 적용하였고, 나노 구조체에 따른 에폭시 물성 변화를 확인하였다. CSP는 divinylbenzene(DVB) 가교제를 통해 rubbery한 poly(butylacrylate)(PBA) 코어와 에폭시 수지와의 혼용성을 갖는 poly(ethylene glycol)(PEG) 쉘의 형태로 합성하였다. 코어쉘 구조의 물성 향상 효과는 선형 구조의 블록 공중합체(LP)와의 비교를 통해 확인하였으며, 인장 전단 실험과 파단면 관찰, 나노 구조체 확인을 통해 분석하였다. 두 가지 첨가제 모두 잘 분산된 나노 구조체를 형성하여 효과적으로 외부 응력을 분산하는 것으로 나타났다. CSP가 도입된 경우 약 160%, 그리고 LP가 도입된 경우 약 130% 인장 전단 강도가 증가하는 것으로 측정되었다. 이를 통해 CSP 첨가제가 에폭시 물성 향상에 매우 유용함을 확인하였다. A core-shell structured copolymer (CSP) that consists of a rubbery core and an epoxy-miscible shell was synthesized and used as additives in the epoxy resin. The poly(butylacrylate) (PBA) core functions as a rubbery particle that induces the nanocavitation effect, while the poly(ethylene glycol) (PEG) shell allows uniform dispersion within the epoxy resin due to its miscibility with epoxy. A divinylbenzene (DVB) crosslinker was used to bind the core and to synthesize a stable CSP. The mechanical properties of the additive-modified epoxy resin were investigated by measuring the adhesion strength using a universal testing machine. When using CSP as additives in the epoxy resin, the adhesion strength was increased by 160%, while the linear copolymer (LP) only showed a 130% increase. The morphology of the CSP-modified epoxy and the fracture surface morphologies confirm the role of the nanocavitation effect and the void formation in improving the mechanical properties of the CSP-modified epoxy resins
SNIPS 공정을 이용한 블록공중합체 분리막의 구조 형성에 관한 연구
우상훈 ( Sanghoon Woo ),김진희 ( Jinhee Kim ),이정현 ( Junghyun Lee ),방준하 ( Joona Bang ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.2
In this work, we fabricated PS-b-P4VP block copolymer membranes from self-assembly and non-solvent induced phase separation (SNIPS), which combines the block copolymer self-assembly and conventional NIPS process. While previous studies mostly focused on the fabrication of well-defined structures, we systematically examined various processing parameters such as polymer concentration, solvent evaporation duration, solvent composition, and humidity, to optimized the membrane structures. As a result, the morphology of PS-b-P4VP membranes was optimized at a certain polymer concentration in solution and composition of volatile solvent at low humidity conditions, resulting in SNIPS separation membranes with well-defined nanopores on the surface, 75% of membrane porosity, and 18% of surface porosity.
광개시제 종류에 따른 유기 박막의 경화 특성과 플렉서블 디스플레이 봉지 소재로의 적용성 분석
오준기(Junki Oh),김소현(So Hyun Kim),정인조(Kevin Injoe Jung),허준(June Huh),정현욱(Hyun Wook Jung),방준하(Joona Bang) 한국고분자학회 2020 폴리머 Vol.44 No.6
플렉서블 디스플레이에 적용할 수 있는 유기 박막 개발을 위해 광경화성 소재에 대한 특성화를 진행하였다. 광경화에 필수적인 요소인 광개시제는 광 조사 시 분해되며 라디칼을 생성하는 Type-1 개시제와 분해없이 라디칼을 생성하는 Type-2 개시제 유형으로 구분된다. Type-2 개시제는 미반응물에 의한 아웃가스 배출이 거의 없는 특성으로 인해 디스플레이 봉지 유기층 제조에 결정적인 역할을 할 수 있다. 본 연구에서는 봉지층에 사용될 유기 코팅액의 경화물성을 최적화하기 위해 Type-1, Type-2 개시제에 의한 실시간 가교 물성을 비교 분석하였다. 잉크젯 코팅공정으로의 적용 가능성을 평가하기 위하여 경화 이전 코팅액의 점도와 표면 장력 등과 같은 기본 유동 물성을 측정하였다. 또한 경화된 박막 필름의 투과율, 굴절률 등과 같은 광학적 물성들을 분석하였다. 다양한 실험 결과로부터 아웃가스 저배출 성능이 뛰어난 Type-2 개시제가 유기막의 핵심 성분으로 디스플레이 봉지 기술을 개발하는데 매우 유용함을 확인하였다. In this work, we examined photocurable materials for organic layers that can be used as an encapsulation layer in flexible displays. Photo-initiators, which are essential for UV-crosslinking, can be classified into two categories: Type-1 initiators that produce free radicals through the cleavage reaction caused by UV irradiation and Type-2 initiators that generate free radicals without the cleavage reaction. Type-2 initiators are more desirable for the encapsulation organic layer of the flexible display due to the low outgassing of unreacted components. To optimize the curing properties of organic coatings, the effect of initiator type on the real-time crosslinking behaviors were mainly scrutinized. The flow properties of pre-cured coatings such as shear viscosity and surface tension were also measured to evaluate the applicability in the inkjet coating process, and transmittance and refractive index were analyzed for the optical properties of cured thin films. As a result, it was found that Type-2 initiators, exerting the intrinsic low outgassing performance, are more advantageous in developing the display encapsulation technology as a key component in the organic layer.