서강대학교

초록/요약

We have rationally designed and synthesized new mass tags that are heterolytically cleavable upon UV-irradiation; these tags are based on a ferrocene or 6,11-dihydrothiochromeno[4,3-b]indole skeleton. Unless exposed to UV light, the dithioacetal group maintained its stability under normal conditions. After chemical conjugation of the mass tags with biomolecules of interest, such as proteins, the resulting conjugates efficiently and selectively generated the corresponding mass-tag fragment ions without the aid of a matrix under laser desorption/ionization (LDI) conditions. We envision that these new ferrocene or dithioacetal-based tags would provide a new platform of the so-called matrix-free laser desorption ionization mass spectrometry (LDI-MS) that would allow multiple detection of biomarkers with high sensitivity and selectivity. Unfortunately, detection of biomolecules using the mass tags based on ferrocene failed due to their poor solubility. On the other hand, biomolecules detection using the mass tags based on 6,11-dihydrothiochromeno[4,3-b]indole improved in terms of solubility was successful. The limit of detection (LOD) of these tags was measured to be 5 fmol in the case of non-conjugated mass tag themselves and 2.8 fmol in the case of mass-tag-conjugated myoglobin. When we were studying the development of photocleavable mass tags under the matrix-free laser desorption ionization mass spectrometry (LDI-MS) (described in Chapter 2), we accidentally observed quaternary ammonium (QA) cation was well-detected under the same matrix-free conditions. Because [QA]+ is a preformed ion, it requires no matrix to be released to the gas phase for detection in LDI-MS. We synthesized some QA iodides by simple N-alkylation and conducted research to investigate the detection efficiency of QAs depending on the counter anion, QA size and structure in matrix-free LDI-MS detection. Here we report the first phosphonic acid or triol end-functionalized P(S-r-MMA) random copolymers for neutral brush which can be used for perpendicular microdomain orientation of lamella-forming P(S-r-MMA). The phosphonic acid and triol group are stronger anchoring groups than a hydroxyl group and used to end-graft the chains to the silicon oxide wafer. By using these anchoring group, we could reduce the annealing time from 24 h to less than 5 min to achieve neutral surface for perpendicular orientation of lamella forming P(S-r-MMA). The phosphonic acid-functionalized P(S-r-MMA) random copolymers were prepared with low polydispersity by the “living” nitroxide mediated radical polymerization technique using a unimolecular initiator based on a TEMPO group. Especially, we developed an efficient synthetic route toward suitable alkoxyamine initiator functionalized phosphonate groups, which has no effect on polymerization. The deprotection of the phosphonate group using TMSBr results in a phosphonic acid. We developed another end-functionalized random copolymer which is prepared via SARA ATRP based on Cu(0) metal; triol group end-functionalized P(S-r-MMA). Compared with phosphonic acid-functionalized P(S-r-MMA) described mentioned, synthesis of triol-functionalized P(S-r-MMA) is much easier and economical. By using this polymer, we could also reduce the annealing time 0.5 min (at 200 ˚C) to achieve neutral surface for perpendicular orientation of lamella forming P(S-r-MMA). Self-assembly of ultra-high molecular weight block copolymers is very difficult because their mobility is too slow to reach the thermodynamically equilibrated state. For this reason, formation of perpendicularly lamellar patterns with relatively large periods through the block copolymer self-assembly turns out to be very challenging. To circumvent this problem, we paid our attention to the use of bottle brush block copolymers. They are comprised of a linear polymer backbone and side polymer brushes. Since the side polymer brushes are densely attached to the backbone, there is significant steric congestion, which makes the backbone highly stretched and rigid. Here we report the first “graft-through” synthesis of well-defined bottle brush PS-b-PMMA and their self-assembly into the perpendicular lamellae (~ 80 nm) in thin films by the only thermal annealing process. We have employed both anionic polymerization and ring-opening metathesis polymerization (ROMP) through the following process: (1) initiator preparation, (2) anionic polymerization for brushes, (3) post polymerization-modification of the end group, and (4) ROMP based on the Grubbs catalyst.