Si 웨이퍼에 캐스트된 메틸 메타크릴레이트 아이오노머의 형태

Abstract

아이오노머는 용매에 잘 분산되면 자기조립을 통해 구, 막대, 원판, 관 등을 포함한 다양한 형태의 나노 구조를 형성하는데 이와 같은 아이오노머의 자기조립 특성은 전형적으로 용매와 고분자의 상호작용에 영향을 받는다. 뿐만 아니라 polyion 고분자 사슬-counterion의 이온 상호작용 크기와 고분자 사슬-사슬간의 상대적인 상호작용의 크기도 나노 구조에 큰 영향을 미친다. 다시 말해, 용매의 극성, 고분자 사슬에 있는 이온들의 분포, 이온 함량, 중화도 등의 조건에 따라 아이오노머 콜로이드상의 형태는 큰 영향을 받는다.

본 연구에서는 용액 상태에 있는 아이오노머의 자기조립에 대해 조사하기 위해 기존에 많이 사용하는 폴리스타이렌보다 상대적으로 높은 극성을 띤 폴리메타크릴레이트를 사용하여 수용액내에서 일어나는 아이오노머의 다양한 상호작용과 거대분자의 구조 사이의 관계를 이해하기 위해 랜덤 아이오노머가 회합체를 형성하는 임계회합농도, 회합체의 크기, 형태, 안전성 등에 대해 관찰하고자 하였다.|Ionomers, i.e. polymers having a small amount of ionic groups, were introduced ca. 40 years ago. Since then, the morphologies and physical properties of the ionomers have received considerable attention from both industrial and academic arenas. Extensive studies on the morphology-structure-property relationships in ionomers in bulk have been performed due to their unique properties such as high melt viscosity, percolating properties, permselectivity, etc. In the case of ionomers in solution, the solution properties and morphology of ionomers in either polar or non-polar solutions have also been investigated. Depending on the polarity of the solvents, the ionomer chains in solution behave like polyelectrolytes or lead to the aggregation. It is also known that, under some conditions, block ionomers in solution can form nano-sized micelles. These micelle-like ionomers can be used as drug-delivery systems, micro-reactors, and so on. In the case of random ionomers, it was found that the polystyrene-based ionomers could be dispersed in water as stable colloidal particles. However, the colloidal particle formation of other ionomers has not been explored. Thus, in the present work, the morphology of poly(methyl methacrylate-co-methacrylate) P(MMA-co-MANa) ionomers, neutralized with sodium partly or fully, was investigated using an SEM technique. Prior to the SME study, the critical aggregation concentrations (CAC) of the ionomer solutions were determined using a fluorescence method. It was found that when the un-neutralized PMMA acid form copolymer was cast onto Si wafer from 2 × 10-3 g/mL THF solution, it formed spherical particles of 60-400 nm in their sizes. As the solution concentration decreased, the average size of spherical particles decreased down to 70-210 nm, with decreasing its size distribution. When the neutralization degree increased, the size and size distribution of the spherical particles decreased. At 20% of neutralization, however, the SEM image showed networks-like features of ionomers, and further neutralization resulted in the formation of layer of the ionomers with a rough surface. The surface of the ionomer layer became smoother with increasing degree of neutralization. When the acid content increased to 3.9 mol%, the average size of the spherical particles decreased. At 7.7 mol% of acid content, no more spherical particle was observed, and only a layer with a rough surface formed. Upon the neutralization of acid groups, the size of the particles decreased drastically. The 3.9 mol% ionomers formed not spherical particles but a layer with rough surface. As the last part of the work, the morphology of sulfonated polystyrene ionomers containing sodium dodecylbenzenesulfonate (SDBS) was investigated. It was found that when the sample was prepared from THF solution, the average size of the acid form copolymer/SDBS mixture was larger than that of pure ionomer. It was also found that, in the case of ionomer/SDBS mixtures, the surface of the layer became smoother with increasing the amount of SDBS