Alkoxy Bipyridine Ligands for ATRP of Styrene and Methyl Methacrylate

Young Je Kwark 한국고분자학회 2009 Macromolecular Research Vol.17 No.4

Preparation of Branched Polystyrene Using Atom Transfer Radical Polymerization Techniques and Protection-Deprotection Chemistry

Kwark, Young-Je The Polymer Society of Korea 2008 Macromolecular Research Vol.16 No.3

A new strategy using protection-deprotection chemistry was used to prepare branched polymers using the ATRP method only. Among the several monomers with different protecting groups, vinyl benzyl t-butyloxy carbonate (VBt-BOC) and 4-methyl styrene (4-MeSt) could be polymerized successfully to form backbones using the ATRP method in a controlled fashion. The protected groups in the backbones were converted to alkyl bromides and used as initiating sites for branch formation. The benzyl t-butyloxy carbonate groups in the backbones containing VBt-BOC units were first deprotected to benzyl alcohol by trifluoroacetic acid, then converted to benzyl bromide by reacting them with triphenylphosphine/carbon tetrabromide. The benzyl bromide groups in the backbones containing 4-MeSt units could be generated by bromination of the methyl groups using N-bromosuccinimide/benzoyl peroxide. The structures of the prepared polymers were well-controlled, as evidenced by the controlled molecular weight as well as the narrow and unimodal molecular weight distribution.

Super-Hydrophobicity of Cellulose Triacetate Nanofiber

Young-Il Yoon,Young-Bum Kim,Won-Ho Park,Young-Je Kwark 한국고분자학회 2006 한국고분자학회 학술대회 연구논문 초록집 Vol.2006 No.10

Titanium Complexes: A Possible Catalyst for Controlled Radical Polymerization

Kwark, Young-Je,Kim, Jeong-Han,Novak Bruce M. The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.1

Pentamethylcyclopentadienyltitanium trichloride, bis(cyclopentadienyl)titanium dichloride ($Cp_2TiCl_2$), and bis(pentamethylcyclopentadienyl)titanium dichloride were used in the polymerization of styrene without the aid of Group I-III cocatalysts. The properties of the resulting polymer indicated that polymerization was more controlled than in thermal polymerization. The kinetic studies indicated that a lower level of termination is present and that the polymer chain can be extended by adding an additional monomer. To elucidate the mechanism of polymerization, a series of experiments was performed. All results supported the involvement of a radical mechanism in the polymerization using $Cp_2TiCl_2$. The possibility of atom transfer radical polymerization (ATRP) mechanism was investigated by isolating the intermediate species. We could confirm the activation step from the reaction of 1-PEC1 with $Cp_2TiCl$ by detecting the coupling product of the generated active radicals. However, the reversible deactivation reaction competes with other side reactions, and it detection was difficult with our model system.

Alkoxy Bipyridine Ligands for ATRP of Styrene and Methyl Methacrylate

Kwark, Young-Je The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.4

Photoinitiated RAFT Process of Non-conjugated Monomers

Young-Je KWARK,Junhee CHO,Jisun YU,Nam-Jae SHIN 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Novel Silicon-containing Polynorbornenes as Photoresists for Extreme Ultraviolet Lithography

곽영제,Kwark, Young-Je The Korean Fiber Society 2006 한국섬유공학회지 Vol.43 No.5

Performance requirements for extreme ultraviolet (EUV) resists using photons at $\sim$13 nm may require the development of entirely new polymer platforms. Elements that are commonly used in photoresists at other wavelengths, such as oxygen and fluorine, are highly absorbing in this region making them problematic for EUV applications. We have devised new polymer platform for EUV lithography (EUVL). We have synthesized silicon-containing norbornene copolymers using ring-opening metathesis polymerization (ROMP). The norbornene monomers were prepared and copolymerized with a series of monomers having acid sensitive and polar groups, including nitrile, carboxylic acid, hydroxyl, and anhydride functions to achieve random copolymers with suitable properties for EUVL. From initial exposure studies using an EUV interferometer, we were able to produce patterns having a 150 nm pitch without additional optimization.

Sodium Lignosulfonate 표면처리가 탄산칼슘/폴리프로필렌 복합체에서 탄산칼슘의 분산에 미치는 영향

송준영(Junyoung Song),곽영제(Young-Je Kwark),정영진(Youngjin Jeong) 한국고분자학회 2015 폴리머 Vol.39 No.3

본 연구에서는 탄산칼슘(CaCO3)의 폴리프로필렌에 분산과 탄산칼슘 입자의 크기가 폴리프로필렌의 결정성에 미치는 영향을 연구하였다. 무기물로 충전된 고분자복합재료는 일반적으로 취성(brittleness)의 문제를 가지고 있으며, 이러한 문제는 주로 무기물입자의 크기와 분산에 의해서 영향을 받는다. 따라서 탄산칼슘의 분산성을 향상시키기 위한 방법으로 sodium lignosulfonate(SLS)의 함량을 달리하면서 탄산칼슘을 전처리하고 이에 따른 분산효과를 고찰하였다. 그 결과 3 wt%의 SLS로 처리된 탄산칼슘은 미처리 탄산칼슘에 비해 우수한 분산성을 보였으며, 열분석에서도 빠른 결정형성능을 보였다. 이러한 결정형성능은 탄산칼슘 입자의 크기에 의해서도 영향을 받았으며, 입자의 크기가 커지면 용융과 결정화 과정에서의 엔탈피 출입이 줄어드는 것으로 관찰되었다. 이러한 결과들은 무기물 고분자복합재료의 취성을 해결할 수 있는 단서를 제공한다고 할 수 있겠다. The dispersion of calcium carbonate (CaCO3) in polypropylene (PP) and the effect of CaCO3 size on the crystallinity of PP were studied. Polymer composite usually suffers from the brittleness when reinforced with inorganic fillers. The problem is generally related to the size and dispersion of fillers. First, the dispersion was studied for the nanosize CaCO3 with 15~40 nm average diameter. To enhance the dispersibility in PP, the surface of the CaCO3 was treated with sodium lignosulfonate (SLS). CaCO3/PP composites were prepared via melt compounding. The CaCO3 coated with more than 3 wt% SLS was uniformly distributed within the PP matrix, while the uncoated CaCO3 formed aggregated structures in the PP. Even with 30 wt%, the SLS-CaCO3 was well dispersed in the PP matrix. Also, the transition enthalpy of CaCO3/PP increased and the full-width of half maximum of the crystallization peak decreased regardless of SLS coating and size of CaCO3. However, the crystallinity of PP was more influenced by nano CaCO3. These results imply that the nano CaCO3 coated with SLS may reduce the brittleness of polymer composites.

조절 라디칼 중합법을 이용한 PAN 함량이 많은 PEO-b-PAN 블록 공중합체의 합성

김태영,곽영제,Kim, Tae-Young,Kwark, Young-Je 한국섬유공학회 2015 한국섬유공학회지 Vol.52 No.1

Poly(ethylene oxide-b-acrylonitrile) (PEO-b-PAN) block copolymers were prepared as precursors to mesoporous carbons. Redox-initiated radical polymerization and controlled radical polymerization techniques, such as reversible addition-fragmentation chain transfer (RAFT) and activators regenerated by electron transfer atom-transfer radical polymerization (ARGET ATRP), were successfully applied to prepare PEO-b-PAN block copolymers with high PAN content. Radical polymerization of acrylonitrile (AN) using ceric ion as redox initiator gave block copolymers with PEO:PAN ratio of up to 1:38.4, but their high molecular weight and polydispersity index (PDI) indicated that the structure was not controlled. Therefore, in order to achieve better control on the structure of the PAN block, controlled radical polymerization techniques were used. Poly(ethylene oxide) with trithiocarbonate (PEO-CTA) and bromide (PEO-Br) end groups were synthesized as polymeric chain transfer agent for the RAFT process and as initiator for the ATRP process, respectively. The RAFT process of AN using PEO-CTA gave block copolymers with PAN block length 0.53-3.58 times that of the PEO block. Moreover, ARGET ATRP allowed to prepare block copolymers with a very high molecular weight of 72,000, while maintaining a PDI value as low as 1.20.

Miscibility and Crystallization Behaviors of Poly(trimethylene terephthalate)/Poly(ethylene naphthalate) Blends

Choi, Jae-Won,Kwark, Young-Je,Kim, Young-Ho The Korean Fiber Society 2007 Fibers and polymers Vol.8 No.3

Poly(trimethylene terephthalate) (PTT)/poly(ethylene naphthalate) (PEN) blends of various compositions were prepared by the solution-blending and melt-blending methods. The changes in miscibility and crystallization behaviors of the blends upon thermal treatment above the melting temperature of the blends at $280^{\circ}C$ were investigated by using DSC, DMA, $^1H$ NMR, and SAXS analyses. Without any thermal treatment, the blend systems were not miscible, and the thermal transitions, such as glass transition, cold crystallization, and crystal melting of the individual components were observed in the DSC and DMA analyses. With thermal treatment, though, they became miscible as the thermal transitions of each component disappeared and single glass transition peaks were observed in the thermal analysis. The chain randomness determined using $^1H$ NMR spectroscopy revealed that thermal treatment at $280^{\circ}C$ for more than 30 min brought about transesterification reactions between the PTT and PEN segments resulting in an increase in their miscibility. These results were confirmed by the small angle X-ray analysis conducted to determine the long period (L), the thickness of the crystalline lamella stack ($l_c$), and the thickness of the amorphous region ($l_a$). After short thermal treatment, the melt-blended sample followed the values for the individual components. However, with extended thermal treatment, the blend became homogeneous, possessing different crystalline morphologies which resulted in different values of L, $l_c$, and $l_a$.