This thesis deals with synthesis and characterization of well-defined polymers with various architectures. The polymers having complicated structures were prepared by combination of controlled radical polymerization (CRP) technique.
Linear-hyperbranched (L-HB) block copolymer, polystyrene-block-poly(2-(2-bromopropionyloxy)ethyl acrylate) (PS-b-PBPEA), was synthesized by the combination of self-condensing vinyl polymerization (SCVP) and atom transfer radical polymerization (ATRP). The linear-linear analogue L-L PS-b-PBPEA was also synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) processes for the comparison. The significantly smaller hydrodynamic volume of L-HB compared to L-L PS-b-PBPEA was observed in GPC chromatograms. The Br end groups of L-HB PS-b-PBPEA were further transformed to amine via azide modification. The resulting polymers were fabricated as a thin film, and their surface properties were investigated. Microphase separation was clearly observed in AFM images. The contact angle was largely decreased after amino end modification that confirmed the end-group effect on surface energy overwhelmed the structural effect.
Comb-coil block copolymer (CCBCP) poly(methyl methacrylate)-block-poly(2-(2-bromopropionyloxy)ethyl acrylate)-graft-polystyrene (PMMA-b-PBPEA-g-PS) was synthesized by the combination of RAFT and ATRP. The polymer exhibits vertically oriented cylindrical morphologies on various substrates that are driven by this architecture, which overcomes the interactions between the substrates and the polymer chains. The formation of vertically oriented cylindrical pores on patterned surfaces was also demonstrated.
Star-shaped polymers, $[poly(methyl methacrylate)-block-poly(2-((2-bromoisobutyryl)oxy)ethyl methacry-late)-graft-poly(N-isopropylacrylamide)]_n$ $([PMMA-b-PBIEM-g-PNIPAM]_n$ (n = 2, 3, 4)) were synthesized by sequential ATRPs using multifunctional initiators. The architecture, molecular weight, polydispersity, and composition of polymers were precisely tuned. The encapsulation behavior of multi-furcated PMMA-b-PBIEM-g-PNIPAMs with hydrophobic dye, Nile Red, was investigated by fluorescence, and UV/vis spec-troscopy. All polymers including bifurcated ones showed the unimolecular micelle behavior even with a trace of amount of polymer and dye. Maximum loading (ML) capacity of Nile Red was estimated by the relation between the UV/vis absorbance and the molar ratio of Nile Red to polymer. The LCST and hydro-dynamic diameter of polymer solutions were measured by temperature-controlled UV/vis spectroscopy and DLS, respectively. The LCST of polymers strongly depended on the size of PNIPAM shell. Surface images of the polymers on mica, and piranha-treated silicon, were investigated by AFM, and presumably indicated the strong adsorption between PNIPAM shell and the hydrophilic surface.
조절된 라디칼 중합 방법을 이용해 다양한 구조의 잘 정의된 고분자를 합성하였다.
선형-가지형 구조의 블록 공중합체 L-HB PS-b-PBPEA는 원자 이동 라디칼 중합과 자기 축합 비닐 중합 방법을 조합해 합성하였고, 가역적 사슬 전달 중합을 통해 합성한 선형-선형 구조의 블록 공중합체 L-L PS-b-PBPEA의 특성과 비교되었다. L-HB PS-b-PBPEA의 말단 브롬 기는 이후의 반응을 통해 아민 및 아지드 기로 변환할 수 있었으며, 다양한 말단을 갖는 선형-가지형 블록 공중합체들의 표면 특성을 비교 관측하였다.
코일-빗형 구조를 갖는 PMMA-b-PBPEA-g-PS는 가역적 사슬 전달 중합과 원자 이동 라디칼 중합의 조합 방법을 통해 합성되었다. 합성된 고분자는 다양한 기질에서 표면 특성과 관계 없이 항상 수직으로 배열되는 특이한 형태를 보였다.
코어-쉘 구조를 가지며 2, 3, 4개로 분기된 온도감응성 성형 고분자 PMMA-b-PBIEM-g-PNIPAM 역시 원자 이동 라디칼 중합을 통해 합성되었다. 그래프트 중합을 이용해 쉘의 밀도를 높임으로서 보다 안정된 구조의 코어-쉘 고분자를 얻을 수 있었다. 합성된 성형 고분자는 수용액 상에서 단일분자 미셀로 거동하였고, 고분자 코어에 소수성 분자를 포획할 수 있었다.
