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ChemComm
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DOI: 10.1039/C7CC04778A
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multiple functional groups dispersed at the lateral periphery,
have been successfully used to fabricate various
nanomaterials, such as 2D-polymer films8 and polymer
nanocapsules.9 Therefore, appending functional groups,
particularly reactive ones, on the lateral position of the
pillararenes is
a challenging goal for developing novel
functional nanostructures and nanomaterials.
Herein, we report a facile synthesis of lateral modificated
pillar[5]arene derivatives through bromination reaction at the
methylene bridge of the dimethoxypillar[5]arene to generate
methylene-bridge brominated pillar[5]arenes (Scheme 1a). By
using this novel lateral functionalized pillararene derivatives as
building block, polymer nanocapsules and 2D-polymer films
have been constructed successfully (Scheme 1b and 1c).
Considering the characteristic of the pillararenes and
previous failure of lateral functionalization, we use NBS
reaction in optimizing conditions to prepare methylene bridge
substituted pillararenes. The lateral bromo-pillar[5]arenes
(BDMP5) is synthesized through radical bromination at the
methylene bridge of the dimethoxypillar[5]arene (Scheme 1a
and supporting information). The detail of the synthesis is
shown in the supporting information. The mass spectrum
shows a main strong molecular ion peaks at 1144.3 (Figure S2)
accordance with the expected m/z ratio for the fivefold
BDMP5. Additionally, there are other small molecular ion
peaks accordance with the fourfold BDMP5 (the peak of
1065.0 is accordance with fourfold BDMP5) and threefold
BDMP5 (the peak of 983.0 is accordance with threefold
BDMP5) (Figure S2). The BDMP5 can also be distinguished by
13C-NMR (Figure S3) data by the main chemical shifts: δ (ppm)
148, 130, 112 (C of phenyl), 58 (C of methoxy group), 42 ppm
(C of methylene bridge). Compared with the 13C-NMR of DMP5
that Tomoki Ogoshi reported,1a it can found that the peak of
the C of methylene bridge have shifted from 29.5 to 42. While,
the peak of C of other posits has no change, thus also
indicating the methylene bridge of the pillar[5]arenes have
been modified with bromine. The FTIR analyses (Figure S4)
further confirm the BDMP5, as the peak 676 cm-1
corresponding to C-Br stretching vibrations occurs.
Figure 1. a) SEM image. b) and c) and d) TEM images (the red
arrows indicate the thickness of the shell of capsules and the
thickness is estimated for 1.2 nm). e) DLS data (size
distribution by number).
nanocapsules are consist of single molecular layer through
lateral covalently cross-linking pillar[5]arenes (for reason that
the height of DMP5 is about 1 nm). Dynamic light scattering
(DLS) studies reveal that the polymer nanocapsules have an
average diameter of 371 nm (Figure 1e). All the results
demonstrate that the thin shell polymer nanocapsules have
been successfully synthesized by covalent self-assembly of
BDMP5 with hexanediamine. To further demonstrate that
these nanospheres have cavity in the interior. Covalent self-
assembly of of BDMP5 with hexanediamine in the presence of
Rhodamine B (RHB) followed by dialysis produced a polymer
nanocapsule encapsulating RHB (RHB-Nanocap) with an
average diameter of 380 nm as confirmed by fluorescence
microscope (Figure S7-a) and DLS (Figure S7-b).
Some factors have effects on the formation of polymer
nanocapsules. For example, the size of the polymer
nanocapsule is controlled by the length of the linkers. Covalent
self-assembly of of BDMP5 with cystamine dihydrochloride
(NH2CH2CH2S-SCH2CH2NH2) (about as same length as
hexanediamine) in MeCN generates nanocapsules with
diameter size about 365 nm (Figure 2a and S8a). When the
linker is 1, 4-diaminobutane that is shorter than
hexanediamine, the covalent self-assembled nanocapsules
have diameter size about 298 nm (Figure 2b and Figure S8b).
While, when the linker is ethanediamine, no polymer
nanocapsule generates in MeCN. Solvent medium also plays an
important role in the formation of the polymer nanocapsules.
For instance, polymerization of BDMP5 and hexanediamine in
MeOH produces polymer nanocapsules with good
morphologies and the size of diameter reaches about 447 nm
that much bigger than prepared in MeCN (Figure 2c and Figure
S8c). Additionally, the ratio of reactants can also affect the
capsules formation. Uniform polymer capsules with large size
of diameter can generate if slightly excessive ratio of
hexanediamine is added (Figure 2d and Figure S8d). While, no
polymer nanocapsules has been found on the condition of
large excess of hexanediamine.
The lateral distribution of bromine at periphery makes it
possible for the BDMP5 as new building block to lateral cross-
react with diamine to form some high-performance 2D-
polymer under appropriate conditions. When stirring of a
mixture of 30.0 mg BDMP5 (mixed BDMP5 without seperating
them) and 15.7 mg hexanediamine in 30 mL MeCN in the
presence of N2 at 70 oC for 5 h, well-defined nanospheres
generate. The FTIR spectrum of nanocapsules (Figure S4-c)
shows that the wavenumber of 676 cm-1 corresponding to C-Br
stretching has disappear and the peak of 3300-3500 cm-1
corresponding to N-H stretching occurs, indicating the BDMP5
has covalently cross-linked with diamine. SEM images (Figure
1a) show that these nanospheres have well-defined
morphologies with a narrow size distribution. TEM images
reveal that these nanospheres are hollow interior structures
(Figure 1b) and surrounded by a thin shell with thickness
estimating at 1.2±0.2 nm (the shell is indicated by red arrows)
(Figure 1c and 1d), which indicates that the polymer
2 | J. Name., 2012, 00, 1-3
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Fu, Shuang
