Ethylene‐bridged Periodic Mesoporous Organosilicas with Large Spherical Pores Templated by PEO‐PPO‐PEO Surfactant Micelles Swollen by Ethylbenzene

Microporous and Mesoporous Materials

2016

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Periodic mesoporous organosilicas (PMOs) with ethenylene (-CH=CH-) bridging groups in the framework and large spherical mesopores of tunable size arranged in facecentered-cubic structures (Fm3m symmetry) were synthesized using Pluronic F127 (EO 106 PO 70 EO 106) as a surfactant and xylene (isomer mixture) as a swelling agent at low temperature (7 °C) under moderately acidic conditions (0.1 M HCl). The resulting PMOs were characterized by small-angle X-ray scattering, nitrogen adsorption, transmission electron microscopy and solid-state 29 Si NMR. The unit-cell parameters were enlarged from 31 to 42 nm and the pore diameters increased from 14 nm to as much as 22 nm while increasing the amount of the swelling agent in the reaction mixture, until these two structural parameters reached a plateau. The enlargement was not accompanied by a loss

Section: Resultssupporting

confidence: 72%

Synthesis of large-pore face-centered-cubic periodic mesoporous organosilicas with unsaturated bridging groups

Manchanda

Microporous and Mesoporous Materials

2016

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“…Still, our results indicate that the earlier nding reects a general behavior and additionally suggest that the temperature at which the change from the consolidated structures to individual (or loosely aggregated) single-micelle-templated nanoparticles takes place depends on the kind of the swelling agent used. The fact that toluene behaved differently from xylene and ethylbenzene is not surprising, as the latter two were shown to have a similar performance as swelling agents in the synthesis of ordered mesoporous silicas and organosilicas, 62,63 while toluene had a somewhat different action. 39,61 It is also clear that the departure from the trend of increasing the pore diameter as the temperature decreases coincided with the change from a singlemicelle-templated structure to a consolidated (or highly aggregated) structure.…”

Section: Effect Of the Swelling Agentmentioning

confidence: 99%

Single-micelle-templated synthesis of hollow silica nanospheres with tunable pore structures

2015

RSC Adv.

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Hollow silica nanospheres (HSNs) were synthesized by using swollen micelles of Pluronic F108 (EO132PO50EO132) block copolymer surfactant as soft templates at low silica-precursor/surfactant ratios. An unprecedented tunability of the pore size was achieved in this single-micelle-templating synthesis through the initial synthesis temperature control in F108/toluene system, for which the pore diameter gradually increased from 16 to 44 nm upon decreasing the synthesis temperature from 25 to 14 °C. An additional pore size adjustment coupled with the change in the size of entrances to the nanospheres can be achieved by selecting the hydrothermal treatment temperature, as shown for the synthesis at 25 °C. The inner diameter of the hollow nanospheres can also be modified by changing the silica alkoxide precursor used or its ratio to the surfactant. Moreover, the formation of hollow nanospheres, their inner void size and its temperature adjustability depend on the swelling agent used. In the cases of xylene and ethylbenzene swelling agents, the pore size adjustment was complicated by the morphology change from loose aggregates of hollow spheres to consolidated particles with multiple mesopores as the temperature was lowered. On the other hand, these swelling agents afforded nanospheres of particularly large diameter (22-26 nm) at 25 °C. Less potent swelling agents (1,3,5-triisopropylbenzene and cyclohexane) afforded largely disordered consolidated structures instead of single-micelle-templated nanospheres. The work demonstrated the potential of Pluronic F108 combined with an appropriate swelling agent to template silica nanospheres with hollow interiors of size and accessibility adjustable in a wide range through simple temperature control.

Tuning of the Temperature Window for Unit‐Cell and Pore‐Size Enlargement in Face‐Centered‐Cubic Large‐Mesopore Silicas Templated by Swollen Block Copolymer Micelles

2015

Chemistry A European J

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The unit-cell size and pore diameter as functions of temperature are investigated in the syntheses of FDU-12 silicas with face-centered cubic structure templated by Pluronic (PEO-PPO-PEO) block copolymer micelles swollen by toluene. The temperature range in which the unit-cell size and pore size strongly increase as temperature decreases is correlated with the critical micelle temperature (CMT) of the surfactant. While Pluronic F127 affords a wide range of unit-cell parameters (28-51 nm) and pore diameters (16-32 nm), it renders moderately enlarged pore sizes at 25 °C. The use of Pluronic F108 with higher CMT affords FDU-12 with very large unit-cell size (∼49 nm) and large pore diameter (27 nm) at 23 °C. Large unit-cell size (40-41 nm) and pore size (22 nm) were obtained even at 25 °C. The application of Pluronics F87 and F88 with much smaller molecular weights and higher CMTs also allows one to synthesize FDU-12 with quite large unit-cell parameters and pore sizes at room temperature. The present work demonstrates that one can judiciously select Pluronic surfactants with appropriate CMT to shift the temperature range in which the pore diameter is readily tunable.