Effect of synthesis conditions on the mesoscopical order of mesoporous silica SBA-15 functionalized by amino groups

Mesoporous amine-functionalized SBA-15 silica has been synthesized directly by the co-condensation of tetraethyl orthosilicate (TEOS) and aminopropyl-trimethoxysilane (APTMS) under acidic conditions with an APTMS/(APTMS + TEOS) molar ratio of 10%. The effect of synthesis conditions, including TEOS pre-hydrolysis, as well as the heating temperature and time, on the mesoscopical order and pore structure of the functionalized SBA-15 have been studied in detail by means of powder X-ray diffraction, nitrogen sorption, transmission electron microscopy, infrared spectra and solid state ²⁹Si nuclear magnetic resonance. A functionalized SBA-15 silica with a highly ordered two-dimensional P6 mm hexagonal symmetry and a narrow pore size distribution centered at 6 nm can be obtained if TEOS is allowed to pre-hydrolyze for 2 h. For the sample with TEOS pre-hydrolysis time of 4 h, aging at 50°C or 150°C leads to a more ordered pore arrangement compared to 100°C and also a narrower pore size distribution with larger pore volume. Increasing aging time is in favor of the formation of mesoscopically ordered structure, but fails to obtain a superior pore structure.     

Metamorphosis of ordered mesopores to micropores: periodic silica with unprecedented loading of pendant reactive organic groups transforms to periodic microporous silica with tailorable pore size

Ordered porous silicas with unprecedented loadings of pendant vinyl groups have been synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and triethoxyvinylsilane (TEVS) under basic conditions in the presence of cetyltrimethylammonium surfactant. The resulting organosilicate-surfactant composites exhibited at least one low-angle X-ray diffraction (XRD) peak up to the TEVS:TEOS molar ratio of 7:3 (70% TEVS loading) in the synthesis gel. The surfactant was removed from these composites without any structural collapse. Nitrogen adsorption provided strong evidence of the presence of uniformly sized pores and the lack of phase separation up to TEVS:TEOS ratios as high as 13:7 (65% TEVS loading), whereas (29)Si MAS NMR and high-resolution thermogravimetry showed essentially quantitative incorporation of the organosilane. Thus, a hitherto unachieved loading level for pendant groups, considered by many to be impossible to achieve for stable organosilicas because of the expected framework connectivity constraints, has been obtained. The resulting vinyl-functionalized silicas exhibited gradually decreasing pore diameter (from 2.8 to 1.7 nm for TEVS loadings of 25-65%) and pore volume as the loading of pendant groups increased, but the specific surface area was relatively constant. Because of the reactivity of vinyl groups, ordered silicas with very high loadings of these groups are expected to be robust starting materials for the synthesis of other organic-functionalized ordered microporous materials. Herein, we demonstrate that these starting materials can also be transformed via calcination into ordered microporous silicas with pore diameters tailorable from 2.5 to as little as 1.4 nm simply by using an appropriate loading of the vinyl-functionalized precursor. This ease of the micropore size adjustment and the attained degree of structural ordering (as judged from XRD) have not been reported before. The novel ordered microporous materials reported herein are promising as adsorbents and catalyst supports.     

Solvothermal preparation and spectroscopic characterization of copper indium diselenide nanorods

Single-crystalline chalcopyrite CuInSe(2) nanorods (CuInSe(2)NRs) of 50-100 nm in diameter and up to a few micrometers in length have been synthesized solvothermally. High-resolution transmission electron microscopic images of the CuInSe(2)NRs reveal the d-spacing of 0.335 nm for the (112) crystalline planes and a growth direction along [331]. The near-infrared absorption spectrum of the chalcopyrite CuInSe(2)NRs shows a peak maximum at 1162 nm and an onset at 1262 nm, indicating no apparent blue-shift compared with those of Cu-rich CuInSe(2) thin films. An intense peak at 175.1 cm(-1) in the room-temperature Raman scattering spectrum of CuInSe(2)NRs corresponds to the A(1) phonon mode of tetragonal CuInSe(2) chalcopyrite. The narrower full width at half-maximum (fwhm) of 9.5 cm(-1) for CuInSe(2)NRs, in comparison with fwhm approximately 12 cm(-1) for CuInSe(2) films, indicates a uniform size distribution and single crystallization in the nanorods. Analysis of the photoluminescence from the single-crystalline CuInSe(2)NRs measured at 10 K has categorized the emission into seven groups of transitions as characterized by free excitons, bound excitons, conduction band to acceptor levels, and bound excitons at different defects.     

孔径可调的介孔SiO2自支持薄膜的溶剂挥发诱导自组装合成与表征

以十六烷基三甲基溴化铵(CTAB)为模板剂, 正硅酸乙酯为硅源, 在弱酸性条件下利用溶剂挥发诱导自组装(EISA)合成出具有介孔结构的二氧化硅薄膜. 通过控制EISA过程中溶剂挥发的环境, 可在1.4~3.1 nm的范围内调节介孔结构的孔径. 实验表明, 较快的溶剂挥发速率有助于较大孔径的介孔结构生成. 用该方法合成的介孔薄膜具有蠕虫状孔道结构和良好的孔径均一性. 在外观上, 该薄膜具有均匀、透明和无缺陷等特点, 可以自支撑, 并且具有一定的韧性.     

Thioether moiety functionalization of mesoporous silica films for the encapsulation of highly dispersed gold nanoparticles

Highly dispersed gold nanoparticles within mesoporous thin films (MTFs) have been synthesized through a newly developed controllable strategy, in which (1,4)-bis(triethoxysilyl)propane tetrasufide (BPTS) organosiloxane coupling agent was co-assembled with tetraethyl orthosilicate (TEOS) to form organic groups functionalized mesoporous composite films followed with oxidization, ion-exchange with Au(en)₂Cl₃ (en: 1,2-ethanediamine) compound and calcination under hydrogen/nitrogen mixing atmosphere. Small-angle X-ray diffraction (XRD) characterization indicated that up to 10 mol% of BPTS could be incorporated into mesoporous hybrid films, and that would not breakup the structural integrity and long-range periodicity. The loaded gold nanoparticles were uniformly distributed due to the molecular level homogenous mixing of the BPTS precursor with TEOS, and its concentration could be controlled via the original ratio of BPTS to TEOS. The nanoparticles had a narrow size distribution with diameters in the size range of 3-7 nm through transmission electron microscopy (TEM) observation and underwent a slight size increase with the higher gold load level. An overall increase in the absorption intensity, a red shift of absorption peak, together with a comparatively narrower bandwidth could be observed at higher gold concentration within composite films from UV-vis spectra. Wide-angle XRD, TEM, X-ray photoelectron spectroscopy (XPS) and UV-vis spectra characterizations all agreed on the fact that the gold loading level could be controlled by the amount of BPTS in the starting sol for preparing MTFs.     

溶胶－凝胶法制备超细SiO_2──制备参数对气凝胶织构性质的影响

ＳｉＯ_２气凝胶超细粉由ＴＥＯＳ（正硅酸乙酯）在乙醇溶液中水解聚合后经超临界流体干燥（ＳＣＦＤ）制得。本文考察了ＴＥＯＳ的浓度、水和ＴＥＯＳ的摩尔比以及焙烧温度对超细粉织构性能的影响。结果表明，超细ＳｉＯ_２的比表面积、总孔容、孔分布、最可几孔径及表现堆密度均随制备参数而改变。而以ＳｉＯ_２气凝胶超细粉体为基本载体材料的Ｃｏ／ＺｒＯ_２－ＳｉＯ_２催化剂显示出高的ＣＯ＋Ｈ_２合成重质烃的活性和选择性。     

Synthesis and characterization of pore size-tunable magnetic mesoporous silica nanoparticles

Magnetic mesoporous silica nanoparticles (M-MSNs) are emerging as one of the most appealing candidates for theranostic carriers. Herein, a simple synthesis method of M-MSNs with a single Fe(3)O(4) nanocrystal core and a mesoporous shell with radially aligned pores was elaborated using tetraethyl orthosilicate (TEOS) as silica source, cationic surfactant CTAB as template, and 1,3,5-triisopropylbenzene (TMB)/decane as pore swelling agents. Due to the special localization of TMB during the synthesis process, the pore size was increased with added TMB amount within a limited range, while further employment of TMB lead to severe particle coalescence and not well-developed pore structure. On the other hand, when a proper amount of decane was jointly incorporated with limited amounts of TMB, effective pore expansion of M-MSNs similar to that of analogous mesoporous silica nanoparticles was realized. The resultant M-MSN materials possessed smaller particle size (about 40-70 nm in diameter), tunable pore sizes (3.8-6.1 nm), high surface areas (700-1100 m(2)/g), and large pore volumes (0.44-1.54 cm(3)/g). We also demonstrate their high potential in conventional DNA loading. Maximum loading capacity of salmon sperm DNA (375 mg/g) was obtained by the use of the M-MSN sample with the largest pore size of 6.1 nm.     

泡压-滤速法研究聚丙烯微孔膜的孔径及其分布

膜科学与膜技术作为新兴的材料科学分支之一,在国民经济中发挥着越来越重要的作用．近年来,高分子微孔膜的研究与应用正引起人们日益增长的关注．采用双轴拉伸方法制备的聚丙烯微孔膜同时具备了良好的力学性能和透过性能［１］,克服了单轴拉伸方法各向异性的缺点,是一...     

Atomistic simulation of the formation of nanoporous silica films via molecular chemical vapor deposition on nonporous substrates

To distinguish thin deposited film characteristics clearly from the influence of substrate morphological properties, the growth mechanism and the macroscale and nanoscale properties of nanoporous SiO(2) films deposited on nonporous silica (SiO(2)) substrates from chemical precursors Si(OH)(4) and TEOS (tetraethoxysilane) via low-pressure chemical vapor deposition are the primary targets of this study. This work employs a kinetic Monte Carlo (KMC) simulation method coupled to the Metropolis Monte Carlo method to relax the strained silica structure. The influence of the deposition temperature (473, 673, and 873 K) on the properties of the SiO(x) layers is addressed via analysis of the film growth rates, density profiles of the deposited thin films, pore size distributions, carbon depth profiles (with respect to TEOS), and voidage analysis for layers of different thicknesses (8-18 nm). A comparison of simulation with experimental results is also carried out.     

稳定于具有亚5nm窗口的立方介孔氧化硅的金纳米颗粒及其优异的醇氧化活性

金纳米颗粒在烯烃加氢、水气转化、过氧化氢直接合成和醇类选择性氧化等反应中表现出独特的催化性能,引起了人们广泛关注.通常,金纳米颗粒的催化活性受到尺寸、原子堆积形式、暴露晶面及其与载体的相互作用所影响.而金纳米颗粒的烧结往往导致其催化效率迅速下降.为了解决金颗粒烧结问题,提高其使用寿命,必须控制高温处理时颗粒和原子的迁移.尽管已有很多工作见诸报道,然而到目前为止,仍未完全解决金颗粒烧结问题.本文通过调整有机模板剂和反应温度成功地合成了不同窗口尺寸的立方介孔氧化硅材料(FDU-12),并将预先合成的3 nm金颗粒负载于其上,考察了窗口尺寸对金颗粒烧结的影响.首先,采用小角X射线散射、氮气吸附-脱附、透射电镜和扫描电镜等手段证实成功合成了具有亚5 nm窗口的FDU-12材料,同时以3 nm金颗粒为探针,进一步区分了具有<3 nm和3?5 nm窗口的FDU-12样品.在抗烧结实验中发现,具有3?5 nm窗口尺寸的FDU-12能够在一个较宽的金负载量(1.0?8.3 wt%)下稳定金纳米颗粒.在550oC空气中焙烧5 h后,金颗粒的平均尺寸维持在4.5?5.0 nm.更小的窗口尺寸则会导致3 nm金颗粒无法进入FDU-12孔道,从而带来低的负载能力和差的抗烧结性能.另一方面,具有>7 nm窗口尺寸的FDU-12则只在高的金颗粒负载量(>9 wt%)下才表现出较好的抗烧结性能,低负载量时烧结严重(2.1 wt%,14.2?5.5 nm).我们推测,合适的窗口尺寸(3?5 nm)恰好能允许3 nm金颗粒进入FDU-12的孔道,在高温处理过程中,当金颗粒长大到5 nm左右时,窗口极大地限制了金颗粒的移动,导致其不能在孔与孔之间自由迁移.此外,该FDU-12材料的孔径为18 nm,这使得封装在各个孔内部的金颗粒与其他金颗粒距离较远,不利于其通过原子迁移而发生烧结.因此,拥有3?5 nm窗口尺寸的FDU-12在一个宽的金负载量下表现出良好的抗烧结能力.而对于具有>7 nm窗口尺寸的FDU-12,在高的金负载量下,它可通过自聚焦效应抑制原子迁移,从而具有优良的抗烧结性能.但在低负载量时,介孔氧化硅的绝大部分孔内并不包含多个金颗粒,自聚焦效应无法发挥作用,在高温焙烧时金颗粒可以通过大的窗口尺寸相互融合导致烧结.我们将具有不同金尺寸的AuNP/FDU-12催化剂用于环己醇选择性氧化反应中.结果表明,4.5 nm的金催化剂表现出最好的活性(1544 mmol gAu-1 h-1)和大于99%的选择性(230oC),大大超过了先前报道的基于Ag和Mn为活性中心的催化剂.另外,与负载在商用γ-Al2O3上相比,AuNP/FDU-12体系表现出了很好的选择性,直接脱水产物小于1%.同时可以保持100 h内金颗粒不发生烧结,活性不明显下降.     

Effects of pH on mechanical and morphological studies of silica filled polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposite

Effects of pH on mechanical properties as well as morphological studies of sol–gel derived in situ silica in polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposites are reported. In particular, a range of acid concentrations was investigated. These nanocomposites were prepared by solution casting technique and tetraethoxysilane (TEOS) was used as the silica precursor. The prepared nanocomposites were characterized using tensile test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tensile test indicated that the highest mechanical strength was at 30% TEOS added for the nanocomposite prepared at pH 2.0. At pH 1.0 and 1.5 the maximum tensile strength reading was at 20% TEOS added with value of 24.3 and 24.5 MPa, respectively. SEM and TEM revealed the dispersion of silica particles in the polymer matrix. For nanocomposites prepared at pH 1.0 and 1.5, the silica particles were finely dispersed with the average size of 60 nm until 20% TEOS added. Meanwhile for nanocomposite prepared at pH 2.0, silica particles were homogenously distributed in the polymer matrix with average diameter of 30 nm until 30% TEOS and agglomerated after 30% TEOS loading.     

Synthesis of Mesoporous TiO2/SiO2 Hybrid Films as an Efficient Photocatalyst by Polymeric Micelle Assembly

Thermally stable mesoporous TiO₂/SiO₂ hybrid films with pore size of 50 nm have been synthesized by adopting the polymeric micelle‐assembly method. A triblock copolymer, poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide), which serves as a template for the mesopores, was utilized to form polymeric micelles. The effective interaction of titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) with the polymeric micelles enabled us to fabricate stable mesoporous films. By changing the molar ratio of TEOS and TTIP, several mesoporous TiO₂/SiO₂ hybrid films with different compositions can be synthesized. The presence of amorphous SiO₂ phase effectively retards the growth of anatase TiO₂ crystal in the pore walls and retains the original mesoporous structure, even at higher temperature (650 °C). These TiO₂/SiO₂ hybrid films are of very high quality, without any cracks or voids. The addition of SiO₂ phase to mesoporous TiO₂ films not only adsorbs more organic dyes, but also significantly enhances the photocatalytic activity compared to mesoporous pure TiO₂ film without SiO₂ phase.     

Low Dielectric Constant Organosilicate Films Prepared by Sol-Gel and Templating Methods

Low dielectric constant organosilicate films with controllable microstructure have been successfully synthesized by multiple-step sol-gel process and templating method, which are the two basic methods to establish porous network in the films. Ultra-low dielectric constant (k) of around 2.0 can be achieved for both films. The microstructure such as porosity, pore interconnection and pore size of the two types of the films have been studied and compared. It has been found that the sol-gel films have a higher level of porosity comparing to the templating films to obtain the same k value. The sol-gel film has a majority of closed pores with pore size around 5 nm. The templating film has a closed pore structure with pore size around 10 nm. Preliminary results present a very positive prospective for intermetal dielectric applications.     

钴掺杂二氧化硅膜的制备、表征及氢气分离性能

采用正硅酸乙酯(TEOS)和Co(NO3)2.6H2O为前驱体通过溶胶-凝胶法制备掺钴微孔二氧化硅膜,研究钴在二氧化硅膜材料中的存在状态、膜材料孔结构以及膜材料的气体渗透和分离性能。结果表明钴元素以Si-O-Co的形式存在于SiO2骨架之中,掺杂Co 10%的微孔SiO2膜具有典型的微孔结构,其孔体积为0.119 cm3·g-1,平均孔径在0.52 nm左右且孔径主要分布在0.4～0.55 nm之间。氢气在膜材料中的输运低温下遵循Knudsen扩散机理,高于100℃时遵循活化扩散机理,300℃时膜材料的H2渗透率达到6.41×10-7 mol.m-2.s-1.Pa-1,H2/CO2分离系数达到6.61,高于Knudsen扩散的理想分离系数。     

Poly (ether amide) and silica nanocomposites derived from sol–gel process

The sol–gel derived chemically combined organic–inorganic nanocomposites were synthesized from poly(etheramide) and tetraethoxysilane. Reaction of a mixture of 4-aminophenyl ether and 1,3-phenyldiamine with terephthaloyl chloride (TPC) in dimethylacetamide (DMAc) produced the amide chains. These chains were modified with carbonyl chloride end groups using a slight excess of diacid chloride and were then reacted with aminophenyl trimethoxysilane (APTMOS), where the amine group reacted with carbonyl chloride end groups. Hydrolysis/condensation of tetraethoxysilane (TEOS) and alkoxy groups present in APTMOS developed bonding between the polyamide chains and inorganic silica network generated in situ. By changing the relative proportions of the polymer solution and the amount of TEOS, the composition of hybrid films was varied. Thin hybrid films with various concentrations of silica network obtained after evaporation of the solvent were subjected to mechanical, dynamic mechanical thermal and morphological measurements. The results indicate a gradual increase in the modulus (3.84 GPa) and tensile strength (121 MPa) up to 15-wt.% silica relative to the pure polyamide. The elongation at break point and toughness gradually decrease with addition of silica content. These hybrids were found to be thermally stable up to a temperature of 500 °C. The weight retained above 800 °C was roughly proportional to amount of silica in the matrix. The glass transition temperature and the storage moduli increased with increasing silica concentration. The maximum increase in the T _g value (358 °C) was observed with 15-wt.% silica. Scanning electron micrographs indicated the uniform distribution of silica in the composites with an average particle size ranging from 9 to 47 nm.     

Supercritical carbon dioxide processing of fluorinated surfactant templated mesoporous silica thin films

The effect of processing mesoporous silica thin films with supercritical CO2 immediately after casting is investigated, with a goal of using the penetration of CO2 molecules in the tails of fluorinated surfactant templates to tailor the final pore size. Well-ordered films with two-dimensional hexagonal close-packed pore structure are synthesized using a cationic fluorinated surfactant, 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)pyridinium chloride, as a templating agent. Hexagonal mesopore structures are obtained for both unprocessed films and after processing the cast films in CO2 at constant pressure (69-172 bar) and temperature (25-45 degrees C) for 72 h, followed by traditional heat treatment steps. X-ray diffraction and transmission electron microscopy analysis reveal significant increases in pore size for all CO2-treated thin films (final pore diameter up to 4.22 +/- 0.14 nm) relative to the unprocessed sample (final pore diameter of 2.21 +/- 0.20 nm) before surfactant extraction. Similar pore sizes are obtained with liquid and supercritical fluid treatments over the range of conditions tested. These results demonstrate that combining the tunable solvent strength of compressed and supercritical CO2 with the "CO2-philic" nature of fluorinated tails allows one to use CO2 processing to control the pore size in ordered mesoporous silica films.     

Influence of polymer molecular weight on the chemical modifications induced by UV laser ablation

This paper investigates the influence of polymer molecular weight (M(W)) on the chemical modifications of poly(methyl methacrylate), PMMA, and polystyrene, PS, films doped with iodonaphthalene (NapI) and iodophenanthrene (PhenI), following irradiation at 248 nm (KrF excimer laser, 20 ns fwhm and hybrid excimer-dye laser, 500 fs fwhm) and at 308 nm (XeCl excimer laser, 30 ns fwhm). The changes of intensity and position of the polymer Raman bands upon irradiation provide information on cleavage of the polymer bonds. Degradation of PMMA, which is a weak absorbing system at 248 nm, occurs to a higher extent in the case of a larger M(W), giving rise to the creation of unsaturation centers and to degradation products. For highly absorbing PS, no degradation is observed upon irradiation with a KrF laser. Consistently irradiating doped PS at 308 nm, where the absorption is low, induces degradation of the polymer. Results provide direct support for the bulk photothermal model, according to which ejection requires a critical number of broken bonds. In the case of irradiation of doped PMMA with pulses of 248 nm and 500 fs, neither degradation nor dependence with polymer M(W) are observed, indicating that mechanisms involved in the femtosecond laser ablation differ from those operating in the case of nanosecond laser ablation. Participation of multiphoton/avalanche processes is proposed.     

Synthesis and characterization of uniform alumina-mesoporous silica hybrid membranes

The synthesis and characterization of alumina-mesoporous silica (alumina-MS) hybrid membranes are reported. The hybrids are formed using a variation of the evaporative-induced self-assembly (EISA) process reported by Hayward et al. (Langmuir 2004, 20, 5998) based on dip coating of an Anopore 200 nm membrane with a Brij-56/TEOS/HCl/H2O solution. Numerous analytical methods are used to probe both the hybrid material and the silica phase after dissolution of the Anopore substrate. Most importantly, He/N2 permeation measurements show that the effective pore size of the membrane can be tuned from 20 to 5 nm based on the number of dip-coating cycles used. The observed He/N2 permselectivity of 2.7 +/- 0.11 is nearly identical to the theoretical value obtained (2.65) assuming Knudsen diffusion dominates. The selectivity of these membranes is higher than that of most commercial "5 nm" membranes (2.29), which is ascribed to the lack of pinhole defects in the materials reported here. The hybrid membranes as well as the silica obtained after dissolution of the Anopore substrate have been characterized using scanning and transmission electron microscopy and X-ray diffraction. Those results indicate that the silica deposited in the Anopore membrane possesses uniform pores approximately 5 nm in size, consistent with the permeation studies. The current work presents an alternative approach to materials that possess many of the properties of mesoporous silica thin films (i.e., pores of controlled size and topology) without the difficulty of growing mesoporous silica thin films on porous supports.     

高比表面积多孔Si层柱蒙脱土材料的合成和表征

汽车排放是大气的重要污染源之一。柴油中的含硫分子燃烧后产生的硫氧化物直接导致酸雨,也是城市氮氧化物和颗粒物排放的主要来源。为减少柴油中硫对环境的危害,世界各国相继颁布了严格的柴油含硫标准,加之市场对超低硫柴油的需求,使得各种柴油脱硫技术的开发成为一大热点。而开发高活性的加氢脱硫催化剂则是既经济又简单的方法。     

Synchrotron X-ray scattering study of the mechanism of nanopore generation in nanoporous organosilicate thin films imprinted with a reactive six-armed porogen

In situ grazing incidence small-angle X-ray scattering analysis was successfully performed during the thermal processing of film blends of polymethylsilsesquioxane (PMSSQ) precursor and triethoxysilyl-terminated six-arm poly(epsilon-caprolactone) (mPCL6) porogen. In addition, thermogravimetric analysis of the films was carried out in a nitrogen atmosphere. These measurements provide important information about the structures of the blend films and of the resulting porous films. In particular, they are used in this paper to establish the mechanism of the formation of imprinted pores within the blend films. During the heating run, the sacrificial thermal degradation of the porogen component commenced at 320 degrees C, generating pores in the resulting cured PMSSQ films. Only very limited porogen aggregation occurred during the blend film formation process (spin-coating and subsequent drying), and these porogen aggregates were of relatively small size and narrow size distribution. The observed restriction of the formation of such porogen aggregates was found to result from the favorable hybridization reaction of the porogen's reactive end groups with the reactive functional groups of the PMSSQ precursor, which competes with aggregation via reaction between the porogen molecules. The average radius (or half-size) of the porogen aggregates was in the range 2.45-3.98 nm, depending on the porogen loading (10-40 wt %). The porogen aggregates retained their size and size distribution until thermal degradation, which resulted in the imprinting of nanopores in the cured PMSSQ films with size and size distribution corresponding to those of the porogen aggregates. The porosities of the resulting nanoporous films were in the range 12.4-41.7%, depending on the initial porogen loading.