Then, the electron-poor molecule, N,N
0 -bis(n-butyl)pyromellitic diimide, was added
to form an “exo-wall” complex with electron-rich pillar[5]arene due to the π•••π
stacking, thus affording the linear Eu(III)-coordination fluorescent supramolecular
polymer.
13.2.4 Supramolecular Polymer Constructed by Covalent Polymer
The researches on covalent polymer-based supramolecular polymer was firstly
conducted by Harada and coworkers, in which the cyclodextrins were used as the
host molecules to encapsulate the linear polymer, such as PPG, PEG, and PVA, to
form the polypseudorotaxane [22]. This combination of macrocyclic molecules and
covalent polymers could expand the application of traditional polymer and construct
functional materials, such as self-healing materials, slipping materials, isolated
molecular wires, etc. Pillar[n]arene, as a new generation of host molecules with
excellent properties, could also be applied to construct this type of supramolecular
polymers, and the researches were mainly focused on two parts, one is to form the
main chain encapsulated polymers, and the other is the side-chain supramolecular
polymers.
Similar with cyclodextrin-based main chain encapsulated polymers, Ogoshi and
coworkers firstly reported the main chain polypseudorotaxane, by incorporating
pillar[5]arene and viologen polymer (VP-8)) (Fig. 10) [23]. In this work, the
inclusion complex was formed both in DMSO and the mixed solution of CH 3 CN
and acetone and results in the charge transfer complex while exhibiting different
dynamic behaviors. In the CH 3 CN and acetone system, the pillar[5]arene shuttling
along the polymer axis was faster than the NMR time scale, concluded from NMR
spectra. While in the DMSO solution, this shuttling movement was much slower
than the NMR time scale. This dynamic behavior depended on the external temperature, at temperature above 60
C, the shuttling movement of pillar[5]arene was
faster than the NMR time scale, and pillar[5]arene molecules dethreaded from the
viologen polymer chain at temperature above 110
C. Moreover, the alkyl linker
length between viologen motifs also affected the formation of supramolecular
polymer; the shorter chain would decrease the potential to form inclusion complex.
The adamantyl group was applied for the conversion of polypseudorotaxane to
polyrotaxane as the stopping group, which exhibited excellent to stabilize the radical
cation species due to the electron donors of pillar[5]arene molecules. Besides the
viologen polymer, the polyaniline could also be concluded by pillar[5]arene for the
strong reducing ability of the EB form in polyaniline. And tri(ethylene oxide)
modified pillar[5]arene encapsulated polytetrahydrofuran to form the similar
polyrotaxane.
Some researches are also conducted to synthesize conjugated polymer incorporated pillar[5]arene. The pioneering work was firstly conducted by Müllen and
coworkers by using the Sonogashira polycondensation between the diyne modified pillar[5]arene and dihalo-aromatic compound to obtain the conjugated
polymer with the number-average molecular weight at 16 kDa [24]. However,
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X. Wu et al.
0 -bis(n-butyl)pyromellitic diimide, was added
to form an “exo-wall” complex with electron-rich pillar[5]arene due to the π•••π
stacking, thus affording the linear Eu(III)-coordination fluorescent supramolecular
polymer.
13.2.4 Supramolecular Polymer Constructed by Covalent Polymer
The researches on covalent polymer-based supramolecular polymer was firstly
conducted by Harada and coworkers, in which the cyclodextrins were used as the
host molecules to encapsulate the linear polymer, such as PPG, PEG, and PVA, to
form the polypseudorotaxane [22]. This combination of macrocyclic molecules and
covalent polymers could expand the application of traditional polymer and construct
functional materials, such as self-healing materials, slipping materials, isolated
molecular wires, etc. Pillar[n]arene, as a new generation of host molecules with
excellent properties, could also be applied to construct this type of supramolecular
polymers, and the researches were mainly focused on two parts, one is to form the
main chain encapsulated polymers, and the other is the side-chain supramolecular
polymers.
Similar with cyclodextrin-based main chain encapsulated polymers, Ogoshi and
coworkers firstly reported the main chain polypseudorotaxane, by incorporating
pillar[5]arene and viologen polymer (VP-8)) (Fig. 10) [23]. In this work, the
inclusion complex was formed both in DMSO and the mixed solution of CH 3 CN
and acetone and results in the charge transfer complex while exhibiting different
dynamic behaviors. In the CH 3 CN and acetone system, the pillar[5]arene shuttling
along the polymer axis was faster than the NMR time scale, concluded from NMR
spectra. While in the DMSO solution, this shuttling movement was much slower
than the NMR time scale. This dynamic behavior depended on the external temperature, at temperature above 60
C, the shuttling movement of pillar[5]arene was
faster than the NMR time scale, and pillar[5]arene molecules dethreaded from the
viologen polymer chain at temperature above 110
C. Moreover, the alkyl linker
length between viologen motifs also affected the formation of supramolecular
polymer; the shorter chain would decrease the potential to form inclusion complex.
The adamantyl group was applied for the conversion of polypseudorotaxane to
polyrotaxane as the stopping group, which exhibited excellent to stabilize the radical
cation species due to the electron donors of pillar[5]arene molecules. Besides the
viologen polymer, the polyaniline could also be concluded by pillar[5]arene for the
strong reducing ability of the EB form in polyaniline. And tri(ethylene oxide)
modified pillar[5]arene encapsulated polytetrahydrofuran to form the similar
polyrotaxane.
Some researches are also conducted to synthesize conjugated polymer incorporated pillar[5]arene. The pioneering work was firstly conducted by Müllen and
coworkers by using the Sonogashira polycondensation between the diyne modified pillar[5]arene and dihalo-aromatic compound to obtain the conjugated
polymer with the number-average molecular weight at 16 kDa [24]. However,
352
X. Wu et al.