Rapid access to discrete and monodisperse block co-oligomers from sugar and terpenoid toward ultrasmall periodic nanostructures

Discrete block co-oligomers (BCOs) are gaining considerable attention due to their potential to form highly ordered ultrasmall nanostructures suitable for lithographic templates. However, laborious synthetic routes present a major hurdle to the practical application. Herein, we report a readily available discrete BCO system that is capable of forming various self-assembled nanostructures with ultrasmall periodicity. Click coupling of propargyl-functionalized sugars (containing 1–7 glucose units) and azido-functionalized terpenoids (containing 3, 4, and 9 isoprene units) afforded the discrete and monodisperse BCOs with a desired total degree of polymerization and block ratio. These BCOs microphase separated into lamellar, gyroid, and cylindrical morphologies with the domain spacing (d) of 4.2–7.5 nm. Considering easy synthesis and rich phase behavior, presented BCO systems could be highly promising for application to diverse ~4-nm nanofabrications.

MALDI-TOF MS were prepared by mixing a THF solution of a sample (5.0 mg mL -1 , 1.0 μL) and a matrix (2,5-dihydroxybenzoic acid, 10 mg mL -1 , 5.0 μL). For the measurement, the mixed solution of the sample and matrix (1.0 μL) was loaded on a sample plate, which was coated by a solution of NaI (1.0 μL, 1.0 mmol L -1 ) as the cationic agent in acetone, was used.

Fourier transform infrared spectroscopy (FT-IR).
The FT-IR analysis was carried out using a PerkinElmer Frontier MIR spectrometer equipped with a single reflection diamond universal attenuated total reflection (ATR) accessory.

Grazing incidence small-angle X-ray scattering (GISAXS) experiments. GISAXS
experiments for thin film samples were performed at BL11 beamline of the ALBA Synchrotron (Barcelona, Spain) or at 3C beamline of the Pohang Accelerator Laboratory (PLA; Pohang, Korea).
At the ALBA, the X-ray wavelength and exposure time were 1.00 Å and 30 s, respectively. A PILATUS3 1M (Dectris Ltd., Switzerland) detector, with 981 × 1043 pixels at a pixel size of 172 × 172 μm, and a counter depth of 20 bits (1,048,576 counts), was used for data acquisition. The sample-to-detector distance was calibrated using the scattering patterns of silver behenate. The GISAXS profiles were acquired under ambient condition. At the PLA, scattering data were measured at room temperature in vacuum using X-ray radiation sources with a wavelength of 1.21 Å and a two-dimensional (2D) charge-coupled detector (CCD) (model Rayonix 2D SX 165, Rayonix, Evanston, IL, USA); each scattering image was normally collected for 10 -30 s. The sample-to-detector distance was calibrated using the scattering patterns of silver behenate.

Synthesis of N-maltotetraosyl-3-acetamido-1-propyne (Glc4-C≡CH)
Synthesis of propargyl-functionalized oligosaccharide was conducted as follows (Method A): Maltotetraose (2.00 g, 3.00 mmol) and propargylamine (3.80 mL, 60.0 mmol) were stirred under a nitrogen atmosphere for 72 h. The reaction mixture was dissolved in minimum amount of dry MeOH and precipitated into CH2Cl2. The precipitate was filtered and washed with CH2Cl2. The obtained precipitate was dissolved in a mixture of acetic anhydride and dry MeOH (1/2(v/v), 100 mL) and stirred for 48 h. The excess of acetic anhydride was removed by co-evaporation with a mixed solvent of toluene and MeOH. The resulting residue was freeze dried to give Glc4-C≡CH as a white solid (1.86 g, yield: 85.9%).

Synthesis of maltose-solanesol hybrid polymer (Glc2-b-Sol)
Method C was used for the click reaction of N3-Sol (6.00 g, 7.79 mmol) and Glc2-C≡CH

Synthesis of Glc1-b-Toc
Method C was used for the click reaction of N3-Toc (2.00 g, 3.51 mmol) and Glc1-C≡CH

Synthesis of N3-Far
Method B was used for the reaction of farnesol (mixture of isomers; 6.00 g, 27.0 mmol) and

Synthesis of Glc1-b-Far
Method C was used for the click reaction of N3-Far (420 mg, 1.16 mmol) and Glc1-C≡CH