Research ArticlePOLYMER NANOCRYSTALS

A general route to nanocrystal kebabs periodically assembled on stretched flexible polymer shish

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Science Advances  27 Mar 2015:
Vol. 1, no. 2, e1500025
DOI: 10.1126/sciadv.1500025
  • Fig. 1 Schematic illustration of the synthesis of organic-inorganic shish-kebab–like nanohybrids (lower right panel) composed of periodic nanodisc-like kebabs (red) on PEO shish (blue) by exploiting amphiphilic worm-like PAA-b-PS diblock copolymer (lower left panel) as nanoreactor.

    Notably, during the threading step, the threaded α-CDs pack closely (upper right panel) because of hydrogen bonding between adjacent α-CDs. After tBA and St monomers are sequentially polymerized (that is, grafted) from the worm-like macroinitiator (central right panel), α-CDs are separated because of steric crowding of the long PtBA and PS chains grafted. There are about 18 PtBA-b-PS chains on each α-CD because of the presence of 18 hydroxyl groups on each α-CD that allows the growth of 18 chains. For clarity, however, only four chains are shown on both sides. The stoppering units at the PEG chain ends in the central left and lower two panels are also omitted for clarity.

  • Fig. 2 TEM images of (A) semiconductor CdSe, (B) magnetic Fe3O4, and (C) ferroelectric BaTiO3 nanonecklaces.

    (D) Schematic illustration of an individual nanonecklace showing dimensions: the diameter (D) and thickness (t) of a nanodisc, the spacing (s) between adjacent nanodiscs, and the total length (L) of a nanonecklace. The PS chains that intimately and permanently capped on the necklace surface, and the PEO stem that connected all nanodiscs are omitted for clarity in (D).

  • Fig. 3 HRTEM images of two nanocrystal kebabs oriented perpendicularly to the substrate.

    (A) Semiconductor CdSe. (B) Magnetic Fe3O4. (C) Ferroelectric BaTiO3. White dashed rectangles are for guidance. Scale bar, 2 nm.

  • Fig. 4 Formation mechanisms of (A) spherical nanoparticle and (B) 1D nanonecklace.

    The growth of Fe3O4 nanonecklace was taken as an example in (B). The formation of Fe3O4 nanonecklace underwent the coordination interaction between the precursors and amphiphilic star-like PAA-b-PS diblock copolymer constituents, followed by the hydrolysis and condensation reaction at elevated temperature to yield Fe3O4 nanonecklace.

  • Fig. 5 The calculated nanonecklace-like morphologies of three different star-like PAA-b-PS diblock copolymers (that is, samples 1 to 3, from which CdSe, Fe3O4, and BaTiO3 nanonecklaces were grown, respectively) threaded in a PEG chain.

    The box size is Lx = Ly = 3Rg (~30 nm).

  • Table 1 Molecular characteristics of worm-like PAA-b-PS diblock copolymers.
    SamplesMn,PAA*Mn, PS*PDI
    Sample 19.6 K4.8 K1.19
    Sample 211.1 K5.2 K1.16
    Sample 36.8 K5.0 K1.15

    *Molecular weight (Mn) of each arm was calculated from 1H NMR data.

    †Polydispersity index (PDI) of PtBA-b-PS, the precursor of PAA-b-PS, was determined by GPC using polystyrene standards for calibration and THF as solvent. Samples 1 to 3 are the diblock copolymer templates for CdSe, Fe3O4, and BaTiO3, respectively.

    • Table 2 Dimensions of CdSe, Fe3O4, and BaTiO3 nanonecklaces.
      SamplesD (nm)*t (nm)*s (nm)*L (nm)*
      CdSe10 ± 14 ± 0.52 ± 0.2220 ± 5
      Fe3O412 ± 13 ± 0.51.5 ± 0.2105 ± 5
      BaTiO38 ± 15 ± 0.52.5 ± 0.2320 ± 5

      *The diameter (D), thickness (t), spacing (s), and length (L) within an individual nanonecklace were determined by TEM and HRTEM.

      • Table 3 Corresponding volume fraction used in calculation.
        SamplesMn, PAAMn, PSfAfB
        Sample 19.6 K4.8 K0.65*0.35
        Sample 211.1 K5.2 K0.750.35
        Sample 36.8 K5.0 K0.450.35

        *The volume fraction of PAA block is defined as Mn, PAA/(Mn, PAA + Mn, PS).

        †The volume fraction of PS block is defined as Mn, PS/(Mn, PAA + Mn, PS).

        ‡To consider the length of PAA block in samples 2 and 3, the volume fraction of PAA block in these two samples is calculated to be [Mn, PAA/Mn, PAA (sample1)] × fA (sample1).

        Supplementary Materials

        • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/2/e1500025/DC1

          Fig. S1. Gel-like polypseudorotaxane α-CD–PEG–Ts2 inclusion complexes, in which α-CDs are threaded by linear PEG-Ts2.

          Fig. S2. 1H NMR spectrum of polyrotaxane α-CD–PEG–MA2 in DMSO-d6.

          Fig. S3. 1H NMR spectrum of polyrotaxane macroinitiator 18Br–α–CD–PEG-MA2 in CDCl3.

          Fig. S4. 1H NMR spectrum of worm-like PtBA (sample 1 in Table 1) in CDCl3.

          Fig. S5. 1H NMR spectrum of worm-like PtBA-b-PS (sample 1 in Table 1) in CDCl3.

          Fig. S6. 1H NMR spectrum of worm-like PAA-b-PS (sample 1 in Table 1) in DMF-d7.

          Fig. S7. GPC traces of worm-like PtBA (blue) and PtBA-b-PS (red) (sample 1 in Table 1).

          Fig. S8. XRD pattern of semiconductor CdSe nanonecklaces.

          Fig. S9. XRD pattern of magnetic Fe3O4 nanonecklaces.

          Fig. S10. XRD pattern of ferroelectric BaTiO3 nanonecklaces.

          Fig. S11. EDS spectrum of semiconductor CdSe nanonecklaces.

          Fig. S12. EDS spectrum of magnetic Fe3O4 nanonecklaces.

          Fig. S13. EDS spectrum of ferroelectric BaTiO3 nanonecklaces.

          Fig. S14. Graphic illustration of the initial condition for qA(r, 0).

          Fig. S15. Spherical micelles of 18-arm star-like diblock copolymer in the mixed solvents of DMF/BA.

          Fig. S16. The calculated density profiles of A block (inner PAA) and B block (outer PS) in star-like diblock copolymers.

          Fig. S17. (a) TEM image of a number of CdSe nanonecklaces obtained by drop-casting a high-concentration CdSe nanonecklace DMF solution on the TEM grid. (b) The corresponding histogram of the length distribution of CdSe nanonecklaces shown in (a).

          Fig. S18. An ultralong CdSe nanonecklace.

          Table S1. Calculated dimensions of elongated ellipsoid-shaped PAA-b-PS diblock copolymers on the PEG chain.

          Scheme S1. Chain-extension reaction for the formation of chain-extended linear PEG.

        • Supplementary Materials

          This PDF file includes:

          • Fig. S1. Gel-like polypseudorotaxane α-CD–PEG–Ts2 inclusion complexes, in which α-CDs are threaded by linear PEG-Ts2.
          • Fig. S2. 1H NMR spectrum of polyrotaxane α-CD–PEG–MA2 in DMSO-d6.
          • Fig. S3. 1H NMR spectrum of polyrotaxane macroinitiator 18Br–α–CD–PEG-MA2 in CDCl3.
          • Fig. S4. 1H NMR spectrum of worm-like PtBA (sample 1 in Table 1) in CDCl3.
          • Fig. S5. 1H NMR spectrum of worm-like PtBA-b-PS (sample 1 in Table 1) in CDCl3.
          • Fig. S6. 1H NMR spectrum of worm-like PAA-b-PS (sample 1 in Table 1) in DMF-d7.
          • Fig. S7. GPC traces of worm-like PtBA (blue) and PtBA-b-PS (red) (sample 1 in Table 1).
          • Fig. S8. XRD pattern of semiconductor CdSe nanonecklaces.
          • Fig. S9. XRD pattern of magnetic Fe3O4 nanonecklaces.
          • Fig. S10. XRD pattern of ferroelectric BaTiO3 nanonecklaces.
          • Fig. S11. EDS spectrum of semiconductor CdSe nanonecklaces.
          • Fig. S12. EDS spectrum of magnetic Fe3O4 nanonecklaces.
          • Fig. S13. EDS spectrum of ferroelectric BaTiO3 nanonecklaces.
          • Fig. S14. Graphic illustration of the initial condition for qA(r, 0).
          • Fig. S15. Spherical micelles of 18-arm star-like diblock copolymer in the mixed solvents of DMF/BA.
          • Fig. S16. The calculated density profiles of A block (inner PAA) and B block (outer PS) in star-like diblock copolymers.
          • Fig. S17. (a) TEM image of a number of CdSe nanonecklaces obtained by dropcasting a high-concentration CdSe nanonecklace DMF solution on the TEM grid. (b) The corresponding histogram of the length distribution of CdSe nanonecklaces shown in (a).
          • Fig. S18. An ultralong CdSe nanonecklace.
          • Table S1. Calculated dimensions of elongated ellipsoid-shaped PAA-b-PS diblock copolymers on the PEG chain.
          • Scheme S1. Chain-extension reaction for the formation of chain-extended linear PEG.

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