Synthesis of UV‐cured acrylic–silica hybrid nanocomposites from dendritic acrylic oligomer and acrylic‐functionalized silica

An acrylic–silica hybrid polymeric nanocomposite, comprising well‐distributed silica nanoparticles in acrylic matrix, has been synthesized at a markedly rapid rate from a dendritic acrylic oligomer (DAO) and an acrylic‐functionalized silica (A‐silica) via UV‐curing. A‐silica was made by functioning colloidal silica nanoparticles with 3‐methacryloxypropyltrimethoxysilane (MATMS) and DAO was formed by reacting 1,5‐diamino‐2‐methylpentane (MPMDA) with trimethylopropane triacrylate (TMPTA). The MATMS has been found either doubly or singly bonded to silica nanoparticles but not triply bonded, and the inclusion of MATMS into the siloxane network structure increases the size of silica nanoparticles. The well distribution of A‐silica and its good compatibility with DAO cause an increase in T_d of the acrylic–silica hybrid material. Silica nanoparticles are too small to cause any significant light scattering, and do not have deleterious effects on transparency. The “hybrid‐on‐polyethylene terephathalate” films exhibited satisfactory hardness and surface roughness because of silica nanoparticles. The preparation as well as the characterization of the constituting species and the final hybrid material are described in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8149–8158, 2008     

High‐Yield Synthesis of Amido‐Functionalized Polyoctahedral Oligomeric Silsesquioxanes by Using Acyl Chlorides

Homosubstituted amido‐functionalized polyoctahedral oligomeric silsesquioxanes (POSS) have been synthesized by using acyl chlorides in high yields (ca. 95 %). The method proved to be superior over “conventional” syntheses applying carboxylic acids or acid anhydrides, which are much less efficient (ca. 60 % yield). A palette of aryl and alkyl groups has been used as side‐chains. The structures of the resulting amide‐POSS are supported by multinuclear ¹H, ¹³C, ²⁹Si NMR and FTIR spectroscopy and their full conversion into octasubstituted derivatives was confirmed using mass spectrometry. We also demonstrate that the functionalized silsesquioxanes with bulky organic side‐chains attached to cubic siloxane core form spherical‐like, well‐separated nanoparticles with a size of approximately 5 nm.     

Ordered Hybrids from Template‐Free Organosilane Self‐Assembly

Despite considerable achievements over the last two decades, nonporous organic–inorganic hybrid materials are mostly amorphous, especially in the absence of solvothermal processes. The organosilane self‐assembly approach is one of the few opportunities for creating a regular assembly of organic and inorganic moieties. Additionally, well‐established organosilicon chemistry enables the introduction of numerous organic functionalities. The synthesis of periodically ordered hybrids relies on mono‐, bis‐, or multisilylated organosilane building blocks self‐assembling into hybrid mesostructures or superstructures, subsequently cross‐linked by siloxane Si‐O‐Si condensation. The general synthesis procedure is template‐free and one‐step. However, three concurrent processes underlie the generation of self‐organized hybrid networks: thermodynamics of amphiphilic aggregation, dynamic self‐assembly, and kinetically controlled sol–gel chemistry. Hence, the set of experimental conditions and the precursor structure are of paramount importance in achieving long‐range order. Since the first developments in the mid‐1990s, the subject has seen considerable progress leading to many innovative advanced nanomaterials providing promising applications in membranes, pollutant remediation, catalysis, conductive coatings, and optoelectronics. This work reviews, comprehensively, the primary evolution of this expanding field of research.     

Hybrid Porous Materials with High Surface Area Derived from Bromophenylethenyl‐Functionalized Cubic Siloxane‐Based Building Units

Sonogashira cross‐coupling of bromophenylethenyl‐terminated cubic, double four‐ring, siloxane cages with di‐/triethynyl compounds results in microporous poly(ethynylene aryleneethenylene silsesquioxane) networks, simply termed as polyorganosiloxane networks (PSNs). In comparison with porous organic polymers reported previously, these PSNs show relatively high surface area and comparable thermal stability. Their apparent BET specific surface areas vary in the range of 850–1040 m² g^?1 depending on the length and the connectable sites of the ethynyl compounds. Analyses of pore size distribution revealed bimodal micropores with relatively narrow distribution. The degree of cross‐linking affects the degree of cleavage of the siloxane bonds, and this suggests that partial cleavage of the siloxane cages is mainly a result of cage distortion. Hydrogen adsorption was performed to evaluate potential of the PSNs as hydrogen storage media. Uptakes of up to 1.19 wt % at 77 K and 760 Torr and initial isosteric heats of adsorption as high as 8.0 kJ mol^?1 were observed. These materials have been obtained by a combination of structural, synthetic organic, and materials chemistry, which can exploited to synthesize porous hybrid materials with specifically designed structures and functions.     

Structure–property co‐relationship of fluorinated poly(imide‐siloxane)s

Eight poly(imide‐siloxane)s co‐polymers have been prepared by one pot solution imidization method. The polymers are synthesized by the reaction of bisphenol‐A‐dianhydride (BPADA) with fluorinated diamine 4,4′‐bis(3″‐trifluoromethyl‐p‐aminobiphenyl ether) biphenyl, and aminopropyl‐terminated polydimethylsiloxane (APPS). The polymers are synthesized by varying the siloxane loading to 5, 10, 15, 20, 25, 30, 35, and 40 wt%, respectively. Thermal, mechanical, rheological, and dielectric properties of these polymers have been evaluated with respect to siloxane loading. The polymers showed glass transition temperature of 107–203°C and tensile strength at break of 24–75 MPa depending on siloxane loading. The elongation break of the polymers ranges from 24 to 144% depending on siloxane loading. The amounts of char residue in the polymers have been correlated with incorporated siloxane in the polymer by NMR techniques. The polymers showed very low water absorption and dielectric constant as low as 2.43 when the siloxane loading is 40 wt%. Copyright © 2008 John Wiley & Sons, Ltd.     

Novel siloxane‐carrying dithiol derived from 5‐membered cyclic dithiocarbonate and its curing reactions for coating application

A new efficient and straightforward method to convert amines into siloxane‐thiol hybrid molecules was developed. The method relies on the nucleophilic addition of amines to a cyclic dithiocarbonate having siloxane moiety (DTC‐Si), and the successive ring‐opening reaction of the dithiocarbonate moiety to give the corresponding acyclic thiourethane having a thiol moiety. Based on this method, amine‐terminated poly(propylene glycol) was successfully transformed into the corresponding polyether having thiol‐terminals and siloxane groups. In the presence of moisture, the alkoxysilyl moiety underwent condensation reaction to make the polyether cured into a transparent resin having solvent‐resistance. Addition of bisphenol A diglycidyl ether (Bis A‐DGE) to the curing process resulted in two simultaneous reactions, i.e., (1) condensation of siloxane part and (2) addition reaction of the thiol terminal and the epoxide group. When this curing process was carried out on a glass surface, the siloxane part reacted with silanol group on the surface, forming a coating layer having excellent mechanical toughness graded as maximum 7H by pencil toughness test (JIS‐K5400). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5119–5126, 2005     

Preparation of co‐polymethyl(alkoxy)siloxanes by acid‐catalyzed controlled hydrolytic copolycondensation of methyl(trialkoxy)silane and tetraalkoxysilane

Polymethyl(alkoxy)siloxane copolymers, poly(MTES‐co‐TEOS), and poly(MTMS‐co‐TMOS), are prepared by acid‐catalyzed controlled hydrolytic co‐polycondensation of methyl(trialkoxy)silane MeSi(OR)₃ (R = Et (MTES) and Me (MTMS)) and tetra‐alkoxysilane Si(OR)₄ (R = Et (TEOS) and Me (TMOS)), respectively. The products are purified by fractional precipitation to provide polymethyl(alkoxy)siloxane copolymers with molecular weight 1000–10,000 (poly(MTES‐co‐TEOS)) or 1700–100,000 (poly(MTMS‐co‐TMOS)) that are stable to self‐condensation. These polymers are soluble in common organic solvents except for hexane, and form flexible and transparent free‐standing films with a tensile strength of 4.0–10.0 MPa. The structure of the polymethyl(alkoxy)siloxane copolymers is thought to be a random or a block co‐polymer. They are found to provide coating films with an adhesive strength up to 10, a refractive index of 1.36–1.40, and a dielectric constant of 3.5–3.6. The products also show better weathering stability than polyethoxysiloxane due to the hydrolytic polycondensation of TEOS. Field emission‐scanning electron micrography analysis reveals that coating films are composed of a micro‐phase separated structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4732–4741     

Siloxane‐Based Hybrid Semiconducting Polymers Prepared by Fluoride‐Mediated Suzuki Polymerization

Siloxane‐containing materials are a large and important class of organic‐inorganic hybrids. In this report, a practical variation of the Suzuki polymerization to generate semiconducting polymeric hybrids based on siloxane units, which proceeds under essentially nonbasic conditions, is presented. This method generates solution‐processable poly(diketopyrrolopyrrole‐alt‐benzothiadiazole) (PDPPBT‐Si) consisting of the hybrid siloxane substituents, which could not be made using conventional methods. PDPPBT‐Si exhibits excellent ambipolar transistor performance with well‐balanced hole and electron FET mobilities. The siloxane‐containing DPP‐thiophene polymer classes (PDPP3T‐Si and PDPP4T‐Si), synthesized by this method, exhibit high hole mobility of up to 1.29 cm² V^?1 s^?1. This synthetic approach should provide access to a variety of novel siloxane‐containing conjugated semiconductor classes by using a variety of aryldihalides and aryldiboronic acids/esters.     

Room‐Temperature‐Phosphorescence‐Based Dissolved Oxygen Detection by Core‐Shell Polymer Nanoparticles Containing Metal‐Free Organic Phosphors

The highly sensitive optical detection of oxygen including dissolved oxygen (DO) is of great interest in various applications. We devised a novel room‐temperature‐phosphorescence (RTP)‐based oxygen detection platform by constructing core–shell nanoparticles with water‐soluble polymethyloxazoline shells and oxygen‐permeable polystyrene cores crosslinked with metal‐free purely organic phosphors. The resulting nanoparticles show a very high sensitivity for DO with a limit of detection (LOD) of 60 nm and can be readily used for oxygen quantification in aqueous environments as well as the gaseous phase.     

Using a Multi‐Shelled Hollow Metal–Organic Framework as a Host to Switch the Guest‐to‐Host and Guest‐to‐Guest Interactions

A bio‐inspired design of using metal–organic framework (MOF) microcrystals with well‐defined multi‐shelled hollow structures was used as a matrix to host multiple guests including molecules and nanoparticles at separated locations to form a hierarchical material, mimicking biological structures. The interactions such as energy transfer (ET) between different guests are regulated by precisely fixing them in the MOF shells or encapsulating them in the cavities between the MOF shells. The proof‐of‐concept design is demonstrated by hosting chromophore molecules including rhodamine 6G (R6G) and 7‐amino‐4‐(trifluoromethyl)coumarin (C‐151), as well as metal nanoparticles (Pd NPs) into the multi‐shelled hollow zeolitic imidazolate framework‐8 (ZIF‐8). We could selectively establish or diminish the guest‐to‐framework and guest‐to‐guest ET. This work provides a platform to construct complex multifunctional materials, especially those need precise separation control of multi‐components.     

Poly(silarylene–siloxane)polyimides from allyl‐terminated oligoimides and hydride‐functional silarylene–siloxanes via hydrosilylation polymerization

This research was focused on the design and execution of new synthetic routes to low‐temperature‐curable poly(silarylene–siloxane)polyimides. The synthesis of individual oligoimide and silarylene–siloxane blocks was followed by hydrosilylation polymerization to produce crosslinked copolymers. The silarylene–siloxane and polyimide blocks were structurally characterized by IR and ¹H NMR spectroscopy and size exclusion chromatography. The high‐temperature resistance of the copolymers was evaluated through the measurement of heat distortion temperatures (T_HD's) via thermomechanical analysis and by the determination of the weight loss at elevated temperatures via thermogravimetric analysis. Glass‐transition temperatures (T_g's) of the silarylene–siloxane segments were measured by differential scanning calorimetry. Hydrosilylation curing was conducted at 60 °C in the presence of chloroplatinic acid (H₂PtCl₆). The copolymers displayed both high‐temperature resistance and low‐temperature flexibility. We observed T_g of the silarylene–siloxane segment as low as ?77 °C and T_HD of the polyimide segment as high as 323 °C. The influence of various oligoimide molecular weights on the properties of copolymers containing the same silarylene–siloxane was examined. The effect of various silarylene–siloxane molecular weights on the properties of copolymers containing the same oligoimide was also examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4922–4932, 2005     

Well‐Defined Metal–Organic Framework Hollow Nanocages

Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well‐defined MOF (MOF‐5, Fe^II‐MOF‐5, Fe^III‐MOF‐5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface‐energy‐driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre‐synthesized poly(vinylpyrrolidone)‐ (PVP) capped noble‐metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.     

Investigations of morphology of moisture‐cured silicone–urethanes

Results of studies on synthesis and properties of siloxane–urethane prepolymers as well as on selected properties of moisture‐cured silicone–urethanes have already been published. In this paper, some results of investigations of the effect of chemical structure of such silicone–urethane polymers on their phase seggregation investigated using mainly (TEM) transmission electron microscopy and small‐angle x‐ray scattering (SAXS) techniques are presented. It was found in TEM studies that in silicone‐urethanes obtained by moisture‐curing of NCO‐terminated prepolymers prepared from siloxane oligomer diols (SOD) and isophoronediisocyanate (IPDI), two factors determine the morphology of samples: length of siloxane chain and NCO/OH ratio. SAXS investigations showed that these silicone–urethanes had a lamellar structure. It was found that the long period of this structure changed from 4 to 9 nanometers as the siloxane chain length increased nine times. The increase of the long period correlated with the decrease of Young's modulus of the corresponding samples. TEM investigations of silicone–urethanes obtained by moisture‐curing of NCO‐terminated prepolymers prepared from the blends of SOD and polyoxypropylenediol (PPG) revealed complex morphology which depended on the SOD/PPG ratio. Copyright © 2000 John Wiley & Sons, Ltd.     

Preparation and characterization of Fe3O4@SiO2/APTPOSS core–shell composite nanomagnetics as a novel family of reusable catalysts and their application in the one‐pot synthesis of 1,3‐thiazolidin‐4‐one derivatives

Octakis[3‐(3‐aminopropyltriethoxysilane)propyl]octasilsesquioxane (APTPOSS) as a polyhedral oligomeric silsesquioxane derivative was prepared and used as a pioneer reagent to obtain a novel core–shell composite using magnetic iron oxide nanoparticles as the core and the inorganic–organic hybrid polyhedral oligomeric silsesquioxane as the shell. Fe₃O₄@SiO₂/APTPOSS were confirmed using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, dynamic light scattering, thermogravimetric analysis, X‐ray diffraction and vibrating sample magnetometry. The inorganic–organic hybrid polyhedral oligomeric silsesquioxane magnetic nanoparticles were used as an efficient new heterogeneous catalyst for the one‐pot three‐component synthesis of 1,3‐thiazolidin‐4‐ones under solvent‐free conditions. Moreover, these nanoparticles could be easily separated using an external magnet and then reused several times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and properties of polybenzoxazine/poly(imide‐siloxane) alloys: In situ ring‐opening polymerization of benzoxazine in the presence of soluble poly(imide‐siloxane)s

Benzoxazine monomer (Ba) was blended with soluble poly(imide‐siloxane)s in various weight ratios. The soluble poly(imide‐siloxane)s with and without pendent phenolic groups were prepared from the reaction of 2,2′‐bis(3,4‐dicarboxylphenyl)hexafluoropropane dianhydride with α,ω‐bis(aminopropyl)dimethylsiloxane oligomer (PDMS; molecular weight = 5000) and 3,3′‐dihydroxybenzidine (with OH group) or 4,4′‐diaminodiphenyl ether (without OH group). The onset and maximum of the exotherm due to the ring‐opening polymerization for the pristine Ba appeared on differential scanning calorimetry curves around 200 and 240 °C, respectively. In the presence of poly(imide‐siloxane)s, the exothermic temperatures were lowered: the onset to 130–140 °C and the maximum to 210–220 °C. The exotherm due to the benzoxazine polymerization disappeared after curing at 240 °C for 1 h. Viscoelastic measurements of the cured blends containing poly(imide‐siloxane) with OH functionality showed two glass‐transition temperatures (T_g's), at a low temperature around ?55 °C and at a high temperature around 250–300 °C, displaying phase separation between PDMS and the combined phase consisting of polyimide and polybenzoxazine (PBa) components due to the formation of AB‐crosslinked polymer. For the blends containing poly(imide‐siloxane) without OH functionalities, however, in addition to the T_g due to PDMS, two T_g's were observed in high‐temperature ranges, 230–260 and 300–350 °C, indicating further phase separation between the polyimide and PBa components due to the formation of semi‐interpenetrating networks. In both cases, T_g increased with increasing poly(imide‐siloxane) content. Tensile measurements showed that the toughness of PBa was enhanced by the addition of poly(imide‐siloxane). Thermogravimetric analysis showed that the thermal stability of PBa also was enhanced by the addition of poly(imide‐siloxane). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2633–2641, 2001     

Photoluminescent properties of poly(p‐phenylene vinylene thiophene‐co‐siloxane)

A new p‐phenylene–vinylene–thiophene‐based siloxane block copolymer has been synthesized. The copolymer consists of alternating rigid and flexible blocks. The rigid blocks are composed of phenylene–vinylene–thiophene‐based units, and the flexible blocks are derived from 1,3‐dialkyldisiloxane units. The former component acts as the chromophore, and allows fine tuning of band gap for blue‐light emission, while the latter imparts good solubility of the copolymer in organic solvents, and thus, should enhance processibility of the resulting copolymer. The thermal properties of the copolymer have been characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The photoluminescence (PL) of the copolymer in solution and in cast film has been studied. The effects of concentration on the PL intensity of the new copolymer in polymer blends with poly(methyl methacrylate) (PMMA) and poly(vinyl carbazole) (PVK) have also been described. Efficient energy transfer from PVK to the new block copolymer in the blended film was observed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1450–1456, 2000     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of phosphonate‐containing polysiloxanes

Phosphonate‐functionalized polysiloxanes have been prepared with a new siloxane/phosphonate monomer. The reaction of 3‐chloropropylmethyldimethoxysilane with trimethylphosphite or triethylphosphite produces several new monomers containing pendant phosphonate groups. Copolymerization with dimethyldimethoxysilane has produced polymers soluble in most organic solvents. The acid hydrolysis of the phosphoryl esters has produced hydrophilic siloxane polymers containing phosphonic acid groups. The thermal properties of the polymers and several related small molecules have been compared with thermogravimetric analysis. Both the monomers and the resulting polymers have been characterized with ¹H, ¹³C, ³¹P, and ²⁹Si NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 48–59, 2003     

Fabrication of Luminescent CdS Nanoparticles on Short‐Peptide‐Based Hydrogel Nanofibers: Tuning of Optoelectronic Properties

The pH‐induced self‐assembly of three synthetic tripeptides in water medium is used to immobilize luminescent CdS nanoparticles. These peptides form a nanofibrillar network structure upon gelation in aqueous medium at basic pH values (pH 11.0–13.0), and the fabrication of CdS nanoparticles on the gel nanofiber confers the luminescent property to these gels. Atomic force microscopy, field‐emission scanning electron microscopy, and high‐resolution transmission electron microscopy clearly reveal the presence of CdS nanoparticles in a well‐defined array on the gel nanofibers. This is a convenient way to make organic nanofiber–inorganic nanoparticle hybrid nanocomposite systems. The size of the CdS nanoparticles remains almost same before and after deposition on the gel nanofiber. Photoluminescence (PL) measurement of the CdS nanoparticles upon deposition on the gel nanofibers shows a significant blue shift in the emission spectrum of the nanoparticles, and there is a considerable change in the PL gap energy of the CdS nanoparticles after immobilization on different gel nanofibrils. This finding suggests that the optoelectronic properties of CdS nanoparticles can be tuned upon deposition on gel nanofibers without changing the size of the nanoparticles.     

Preparation and applications of novel cross‐linked fluoroalkyl end‐capped oligomeric nanocomposites possessing aromatic siloxane segments as core units

Fluoroalkyl end‐capped N,N‐dimethylacrylamide oligomer and N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer were reacted with phenylene‐ and biphenylene‐bridged ethoxysilanes under alkaline conditions to yield cross‐linked fluoroalkyl end‐capped oligomeric composites possessing aromatic siloxane segments as core units. These isolated fluorinated composite powders were found to be nanometer size‐controlled fine particles with a good dispersibility and stability in water and organic solvents. Nitrogen adsorption–desorption isotherms confirmed the presence of micropores in these nanocomposites; the micropore size estimated by the HK method was 0.7–0.8 nm. Interestingly, fluorinated nanocomposites possessing a higher micropore volume ratio were found to exhibit a selective encapsulation ability of fullerene into their composite cores. These fluorinated nanocomposites were also applied to the surface modification of poly(methyl methacrylate) film, resulting in a good oleophobicity imparted by fluorine on the surface. In addition, fluorescence emission was visibly observed only from the modified PMMA film surface treated with fluorinated nanocomposites possessing biphenylene units when irradiated by light. Copyright © 2009 John Wiley & Sons, Ltd.