• Bulletin of the Korean Chemical Society
• /
• 제33권12호
• /
• pp.4103-4108
• /
• 2012

Efficient double click methods for the synthesis of diblock codendrimers were developed. The synthetic strategy involved the sequential click reactions between an alkyne and an azide. The short core building block, 1,4-diazidobutane, was chosen to serve as the azide functionalities for dendrimer growth via click reactions with the alkyne-functionalized PAMAM dendrons as hydrophilic dendron and alkyne-functionalized Fr$\acute{e}$chet-type dendrons as hydrophobic dendron. The structure of diblock codendrimers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.

• Bulletin of the Korean Chemical Society
• /
• 제35권10호
• /
• pp.3001-3004
• /
• 2014

A series of hydroxyl-derivatized quaternized polymers were successfully synthesized by atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry), followed by quaternization reactions. ATRP was employed to synthesize poly(2-hydroxyethyl methacrylate) (PHEMA), followed by introduction of alkyne groups using pentynoic acid, leading to HEMA-Alkyne. 2-Azido-1-ethanol and 3-azido-1-propanol were combined with the HEMA-Alkyne backbone via click reaction, resulting in triazole-ring containing hydroxyl-derivatized polymers. Quaternization reactions with methyl iodide were conducted on the triazole ring of each polymer. Molecular weight, molecular weight distribution, and the degree of quaternization (DQ) were determined by gel permeation chromatography (GPC) and $^1H$ NMR spectroscopy. The average molecular weight ($M_n$) of the resulting polymers ranged from $5.9{\times}10^4$ to $1.05{\times}10^5g/mol$ depending on the molecular architecture. The molecular weight distribution was low ($M_w/M_n$ = 1.26-1.38). The transmission spectra of the 0.1 wt % aqueous solutions of the resulting quaternized polymers at 650 nm were measured as a function of temperature. Results showed that the upper critical solution temperature (UCST) could be finely controlled by the level of DQ.

• Bulletin of the Korean Chemical Society
• /
• 제32권11호
• /
• pp.3933-3940
• /
• 2011

General, fast, and efficient stitching methods for the synthesis of dendrimers with linear PEG units at a core, as dendritic-linear-dendritic materials, were developed. The synthetic strategy involved the click reaction between an alkyne and an azide. The linear core building blocks, three dialkyne-PEG units, were chosen to serve as the alkyne functionalities for dendrimer growth via click reactions with the azide-dendrons. These three building blocks were employed together with the azide-functionalized Fr$\acute{e}$chet-type dendrons in a convergent strategy to synthesize the Fr$\acute{e}$chet-type dendrimers with different linear core units. Their structure of dendrimers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.

• Bulletin of the Korean Chemical Society
• /
• 제30권1호
• /
• pp.157-162
• /
• 2009

General, fast, and efficient methods for the synthesis of Fréchet-type dendrimers having core diversities were elaborated. Two core building blocks, 4,4'-(3,5-bis(propargyloxy)benzyloxy)bisphenyl and N,N,N',N'-tetra(prop-2- ynyloxycarbonylethyl)-1,2-diaminoethane, were designed to serve as the alkyne functionalities for dendrimer growth via click reactions with the azide-dendrons. The synthetic strategy involved an 1,3-dipolar cycloaddition reaction between an alkyne and an azide- functionalized Fréchet-type dendrons in the presence of Cu(I) species which is known as the best example of click chemistry.

• 폴리머
• /
• 제33권1호
• /
• pp.67-71
• /
• 2009

프레체형태 덴드리머의 합성을 위한 연결 방법이 알카인기와 아지드기 사이의 클릭 화학을 이용하여 개발되었다. 덴드리머의 핵으로 작용할 수 있는 단위체인 4,4'-(3,5-비스(아지도프로필옥시)벤질옥시)비스페닐이 알카인덴드론과 클릭 반응을 통해 덴드리머의 구축을 위해 사용되었다. 즉, 구리촉매 존재하에서 다중(아지드)화합물과 말단 알킨기를 가지는 폴리(벤질에테르)덴드론 사이치 클릭 반응을 통해 덴드리머의 합성 전략이 완성되었다.

• 폴리머
• /
• 제36권3호
• /
• pp.295-301
• /
• 2012

선형 PEG단위를 덴드리머의 중심에 갖는 덴드리머의 합성을 위한 효율적인 연결 방법이 개발되었다. 합성전략은 알카인과 아자이드기 사이의 반응을 구리(1)촉매의 존재하에서 진행하는 클릭화학을 이용하였다. 덴드리머의 핵으로 작용할 수 있는 단위체인 옥타(에틸렌글리콜)디아자이드와 도데카(에틸렌글리콜)디아자이드를 합성하였고, 이 두 화합물의 아자이드기는 덴드리머의 형성에 이용되었다. 두 디아자이드화합물을 알카인 덴드론과 클릭 반응을 통해서 덴드리머의 핵의 선형 길이가 다른 두 종류의 덴드리머 제조에 대한 수렴형 합성법을 완성하였다.

• Bulletin of the Korean Chemical Society
• /
• 제35권4호
• /
• pp.1144-1148
• /
• 2014

Here we report a facile synthesis of ruthenium (Ru) Nanoparticles (NPs) by chemical co-precipitation method. The calcination of ruthenium hydroxide samples at $500^{\circ}C$ under hydrogen atmosphere lead to the formation of $Ru^0$ NPs. The size and aggregation of Ru NPs depends on the pH of the medium, and type of surfactant and its concentration. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope image (TEM) analyses of particles indicated the formation of $Ru^0$ NPs, and have 10 to 20 nm sizes. As-synthesized $Ru^0$ NPs are characterized and investigated their catalytic ability in click chemistry (azidealkyne cycloaddition reactions), showing good results in terms of reactivity. Interestingly, small structural differences in triazines influence the catalytic activity of $Ru^0$ nanocatalysts. Click chemistry has recently emerged to become one of the most powerful tools in drug discovery, chemical biology, proteomics, medical sciences and nanotechnology/nanomedicine. In addition, preliminary tests of recycling showed good results with neither loss of activity or significant precipitation.

• Macromolecular Research
• /
• 제17권7호
• /
• pp.499-505
• /
• 2009

General, fast, and efficient stitching methods are presented for the synthesis of Fr$\acute{e}$chet-type dendrimers with linear units at a core, as a preliminary investigation for the synthesis of dendritic-linear-dendritic materials. The synthetic strategy involved an inexpensive, 1,3-dipolar, cycloaddition reaction between an alkyne and an azide in the presence of the Cu(I) species, which is known as the best example of click chemistry. The linear core building blocks, 1,7-octadiyne and 1,6-diazidohexane, were chosen to serve as the alkyne and azide functionalities for dendrimer growth via click reactions with the azide and alkyne-dendrons, respectively. These two building blocks were employed together with the azide- and alkyne-functionalized Fr$\acute{e}$chet-type dendrons in a convergent strategy to synthesize two kinds of Fr$\acute{e}$chet-type dendrimers with different linear core units. This comparative efficiency of the click methodology supports the fast and efficient synthesis of dendritic-linear-dendritic materials with the tailor made core unit.

• Bulletin of the Korean Chemical Society
• /
• 제35권9호
• /
• pp.2694-2698
• /
• 2014

A multisegmented polystyrene (PS) with pH-cleavable ester and carbamate linkages was successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). ATRP was employed to synthesize polystyrene from hydroxyl-terminated initiator using CuBr/N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) as the catalyst. The reaction of the resulting PS with sodium azide yielded the azido-terminated polymer. The hydroxyl group in the other end of the polymer was reacted with 4-nitrophenyl chloroformate (NPC), followed by reaction with propargylamine to produce an alkyne end group with a carbamate linkage. The PS with an alkyne group in one end and an azide group in the other end was then self-coupled in the presence of CuBr/2,2'-bipyridyl (bpy) in DMF to yield a desired multisegmented PS. Molecular weight and molecular weight distribution of the self-coupled polymer increased with time, as in the typical step-growth-type polymerization processes. Finally, we demonstrated that the ester and carbamate linkages of the multisegmented PS were hydrolyzed in the presence of HCl to yield individual PS chains.

• 생체재료학회지
• /
• 제22권4호
• /
• pp.235-248
• /
• 2018

Background: Injectable hydrogels have been extensively researched for the use as scaffolds or as carriers of therapeutic agents such as drugs, cells, proteins, and bioactive molecules in the treatment of diseases and cancers and the repair and regeneration of tissues. It is because they have the injectability with minimal invasiveness and usability for irregularly shaped sites, in addition to typical advantages of conventional hydrogels such as biocompatibility, permeability to oxygen and nutrient, properties similar to the characteristics of the native extracellular matrix, and porous structure allowing therapeutic agents to be loaded. Main body: In this article, recent studies of injectable hydrogel systems applicable for therapeutic agent delivery, disease/cancer therapy, and tissue engineering have reviewed in terms of the various factors physically and chemically contributing to sol-gel transition via which gels have been formed. The various factors are as follows: several different non-covalent interactions resulting in physical crosslinking (the electrostatic interactions (e.g., the ionic and hydrogen bonds), hydrophobic interactions, ${\pi}$-interactions, and van der Waals forces), in-situ chemical reactions inducing chemical crosslinking (the Diels Alder click reactions, Michael reactions, Schiff base reactions, or enzyme-or photo-mediated reactions), and external stimuli (temperatures, pHs, lights, electric/magnetic fields, ultrasounds, or biomolecular species (e.g., enzyme)). Finally, their applications with accompanying therapeutic agents and notable properties used were reviewed as well. Conclusion: Injectable hydrogels, of which network morphology and properties could be tuned, have shown to control the load and release of therapeutic agents, consequently producing significant therapeutic efficacy. Accordingly, they are believed to be successful and promising biomaterials as scaffolds and carriers of therapeutic agents for disease and cancer therapy and tissue engineering.