Hedgehog Buckyball: A High-Symmetry Complete Polyhedral Oligomeric Silsesquioxane (POSS)

In this study, we report UV-MALDI-TOF MS evidence of a fullerene-like silsesquioxane, a high-symmetry polyhedral oligomeric silsesquioxane (POSS or SSO) formulated as R60-Si60O90 or T60 (T = RSiO1.5). The T60 preparation can be performed using a normal hydrolytic condensation of [(3-methacryloxy)propyl]trimethoxysilane (MPMS) as an example. Theoretically, four 3sp3 hybrid orbitals (each containing an unpaired electron) of a Si atom are generated before the bond formation. Then it bonds to another four atom electrons using the four generated hybrid orbitals which produced a stable configuration. This fullerene-like silsesquioxane should exhibit much more functionality, activity and selectivity and is easier to assemble than the double bonds in a fullerene.

The fullerene buckyball (FBB), C 60 , was named "Molecule of the Year" for 1991 by Science [1].Since the discovery of the C 60 buckyball, fullerene science has continued to accelerate, investigating both the basic science and its potential applications [2,3].One investigation involves a major focus on its analogue, the Si 60 cluster [4,5].For Si 60 clusters, the cages should not be very stable due to the use of three (3sp 3 ) orbitals to bond to other Si atoms.Thus, the cages need some other atoms for the fourth bond whereas the C 60 fullerene uses the second period sp 2 orbitals along with a π bond to bond exclusively with other C atoms.Most investigations focus on endohedral Si 60 isomers (using the fourth bond of the 3sp 3 orbital) which are unstable [6].To produce a stable Si 60 configuration, Wang and Yang conducted ab initio calculations based on density functional theory on a Si 60 fullerene-like cage passivated with F or Cl atoms [7]; however, this research is limited by a complex experimental synthesis.
In this study, we report UV-MALDI-TOF MS evidence of a fullerene-like silsesquioxane, a high-symmetry polyhedral oligomeric silsesquioxane (POSS or SSO) formulated as R 60 -Si 60 O 90 or T 60 (T = RSiO 1.5 ) [8].Theoretically, four 3sp 3 hybrid orbitals (each containing an unpaired electron) of a Si atom are generated before the bond formation.Then it bonds to another four atom electrons using the four generated hybrid orbitals which produced a stable configuration.A significant difference between a FBB and T 60 POSS is that the cage in the former is the four-bond (three 2sp 2 hybrid orbits and one original 2p orbital) connection of each C atom on the FBB surface, while it is the three-bond (three of four 3sp 3 hybrid orbits) connection of each Si atom on the POSS surface.The remaining bond to each silicon connects to a pendant organic group adorning the surface of the T 60 cage, showing a hedgehog buckyball (HBB, see Figure 1).These organic groups exhibit much more functionality, activity and showing a hedgehog buckyball (HBB, see Figure 1).These organic groups exhibit much more functionality, activity and selectivity and are easier to assemble than the double bonds in a fullerene, which facilitates the synthesis of POSS-based materials possessing unique properties and the ability to set up applications [9][10][11][12][13][14].The HBB T60 preparation can be performed using a normal hydrolytic condensation of [(3-methacryloxy)propyl]trimethoxysilane (MPMS) that we have used to prepare silsesquioxane coatings [15,16].Hydrolysis and condensation normally give rise to smaller oligomers with a dozen or fewer monomers interconnected into rings [17].By extending the condensation time we are able to produce more viscous products (M-POSS or MSSO) with molecular weights in the range calculated for methacryloxypropy-T60 (10,755 Daltons).
Generally the groups and the location of the groups are determined by FTIR and NMR ( 1 H, 13 C and 29 Si); then all possible predicted structures are established by the molecular weights assigned from the peaks of UVMALDI-TOF MS and the general formula [8,18,19].Figure S1 schemes the structural formula of MSSO, facilitating analysis and assignment of FTIR and 1 H-and 13 C-NMR spectra.The typical FTIR MSSO spectrum (Figure S2b) bands at 417-478 and 1122-1129 cm −1 are primarily ascribed to the stretching of O-Si-O and Si-O-Si; the obvious bands at about 1298, 1410 and 1724 cm −1 derive from stretches of CH=CH2 and C=O groups in methacrylate chains; a decrease in the intensity of the Si-OCH3 group band at 2938 cm −1 is observed relative to the lower molecular weight MSSO, evidenced together with the generation of a broad band at 3423 cm −1 , assigned to -OH groups from Si-OH.Except for bands at 2938 and 3423 cm −1 , these data are in good agreement with those of the MPMS spectrum in Figure S2a and give complementary information for the characterization of the structure.
The following peaks in the 1 H-NMR spectrum (Figure S3) were assigned: 0.698 ppm (1); 1.784 ppm (2); 1.925 ppm ( 7  The HBB T 60 preparation can be performed using a normal hydrolytic condensation of [(3-methacryloxy)propyl]trimethoxysilane (MPMS) that we have used to prepare silsesquioxane coatings [15,16].Hydrolysis and condensation normally give rise to smaller oligomers with a dozen or fewer monomers interconnected into rings [17].By extending the condensation time we are able to produce more viscous products (M-POSS or MSSO) with molecular weights in the range calculated for methacryloxypropy-T 60 (10,755 Daltons).
Generally the groups and the location of the groups are determined by FTIR and NMR ( 1 H, 13 C and 29 Si); then all possible predicted structures are established by the molecular weights assigned from the peaks of UVMALDI-TOF MS and the general formula [8,18,19].Figure S1 schemes the structural formula of MSSO, facilitating analysis and assignment of FTIR and 1 H-and 13 C-NMR spectra.The typical FTIR MSSO spectrum (Figure S2b) bands at 417-478 and 1122-1129 cm −1 are primarily ascribed to the stretching of O-Si-O and Si-O-Si; the obvious bands at about 1298, 1410 and 1724 cm −1 derive from stretches of CH=CH 2 and C=O groups in methacrylate chains; a decrease in the intensity of the Si-OCH 3 group band at 2938 cm −1 is observed relative to the lower molecular weight MSSO, evidenced together with the generation of a broad band at 3423 cm −1 , assigned to -OH groups from Si-OH.Except for bands at 2938 and 3423 cm −1 , these data are in good agreement with those of the MPMS spectrum in Figure S2a and give complementary information for the characterization of the structure.
The following peaks in the 1 H-NMR spectrum (Figure S3) were assigned: 0.698 ppm (1); 1.784 ppm (2); 1.925 ppm (7) [20][21][22][23]: −65.681 ppm is characteristic of the T 3 species, and -56.577 ppm can be assigned to T 2 structures, Si-(O-Si) 2 (OH), from incompletely condensed species in the product mixture; no T 0 or T 1 structures were present in the 29 Si-NMR spectrum which is consistent with higher molecular weight and cyclic MSSO. Figure 2 shows the UV-MALDI-TOF MS in the m/z = 0-11,000 Da range corresponding to MSSO molecules.Three high-symmetry complete MSSOs, T 8 , T 20 and T 60 (see Figure 3), were assigned (see Table 1).These predicted structures have a compliance between the experimental measurement value and the calculated molecular weight according to ion adducts (M w + H + or M w + Na + or M w + K + ) [24], however, there are still few differences, probably from ion adducts selected, solvent used for the measurement operation, calculations and so on.T 60 , one of three high-symmetry complete MSSOs, is a fullerene-like HBB and is denoted as MP-HBB as shown in Figure 3c.The difference between HBB and FBB (as mentioned above) provides an ideal vehicle for exciting research which will be timely, rapidly evolving, multidisciplinary and even appealing on an aesthetic level.
Polymers 2016, 8, 315 3 of 6 Figure 2 shows the UV-MALDI-TOF MS in the m/z = 0-11,000 Da range corresponding to MSSO molecules.Three high-symmetry complete MSSOs, T8, T20 and T60 (see Figure 3), were assigned (see Table 1).These predicted structures have a compliance between the experimental measurement value and the calculated molecular weight according to ion adducts (Mw + H + or Mw + Na + or Mw + K + ) [24], however, there are still few differences, probably from ion adducts selected, solvent used for the measurement operation, calculations and so on.T60, one of three high-symmetry complete MSSOs, is a fullerene-like HBB and is denoted as MP-HBB as shown in Figure 3c.The difference between HBB and FBB (as mentioned above) provides an ideal vehicle for exciting research which will be timely, rapidly evolving, multidisciplinary and even appealing on an aesthetic level.Figure 2 shows the UV-MALDI-TOF MS in the m/z = 0-11,000 Da range corresponding to MSSO molecules.Three high-symmetry complete MSSOs, T8, T20 and T60 (see Figure 3), were assigned (see Table 1).These predicted structures have a compliance between the experimental measurement value and the calculated molecular weight according to ion adducts (Mw + H + or Mw + Na + or Mw + K + ) [24], however, there are still few differences, probably from ion adducts selected, solvent used for the measurement operation, calculations and so on.T60, one of three high-symmetry complete MSSOs, is a fullerene-like HBB and is denoted as MP-HBB as shown in Figure 3c.The difference between HBB and FBB (as mentioned above) provides an ideal vehicle for exciting research which will be timely, rapidly evolving, multidisciplinary and even appealing on an aesthetic level.Additional corroborating evidence for the proposed cyclic structures can be observed in the gel permeation chromatography (GPC) chromatograms obtained for the MSSO samples.Figure 4 shows the mass distribution of the MSSOs measured by a GPC device which provides refractive index data.The distribution profiles indicate that the oligomers are formed in three successive groups with average molecular weights of 1413.8, 4538.8 and 16,260.0(see Figure 4b3, b2 and b1, respectively) corresponding to fractions containing the T 60 , T 20 and T 8 cyclic compounds [25].Additional corroborating evidence for the proposed cyclic structures can be observed in the gel permeation chromatography (GPC) chromatograms obtained for the MSSO samples.Figure 4 shows the mass distribution of the MSSOs measured by a GPC device which provides refractive index data.The distribution profiles indicate that the oligomers are formed in three successive groups with average molecular weights of 1413.8, 4538.8 and 16,260.0(see Figure 4b3, b2 and b1, respectively) corresponding to fractions containing the T60, T20 and T8 cyclic compounds [25].
Further research will be conducted on this MP-HBB to separate it from multiple MSSO structures using a gel permeation column.The intensity of the MP-T60 present can be determined by GPC or size exclusion chromatography (SEC), and the mass of the elutant is again measured by a mass spectrometer [25,26].
easier to assemble than the double bonds in a fullerene, which facilitates the synthesis of POSS-based materials possessing unique properties and the ability to set up applications [9-14].

Figure 1 .
Figure 1.The molecular structures: (a) FBB, the C atom on the FBB surface connects the other three C atoms; (b) HBB, the Si atom connects the bridged three O atoms on the T60 surface and one organic group R outside the HBB surface.

Figure 1 .
Figure 1.The molecular structures: (a) FBB, the C atom on the FBB surface connects the other three C atoms; (b) HBB, the Si atom connects the bridged three O atoms on the T 60 surface and one organic group R outside the HBB surface.

Figure 2 .
Figure 2. The UV-MALDI-TOF MS in the m/z = 500-11,000 Da range correspond to the MSSO oligomers.

Figure 2 .
Figure 2. The UV-MALDI-TOF MS in the m/z = 500-11,000 Da range correspond to the MSSO oligomers.

Figure 2 .
Figure 2. The UV-MALDI-TOF MS in the m/z = 500-11,000 Da range correspond to the MSSO oligomers.

Figure 4 .
Figure 4.The mass distribution of the MSSO oligomers measured by a GPC device which provides refractive index data: (a) reaction under 70 °C for 12 days; (b) reaction under 35 °C for 20 days, average molecular weights of oligomers formed in three successive groups with (b1) 16,260.0,(b2) 4538.8 and (b3) 1413.8,corresponding to fractions containing the T60, T20 and T8 cyclic compounds.