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The 2-[(2 E ,4 E)-hexa-2,4-dienyloxy]-2-methyl-4 H -1,3,2-benzodioxasiline twin monomer (HD-TM) has been used in simultaneous twin polymerization (STP) with 2,2′-spirobi[4 H -1,3,2-benzodioxasiline] (Spiro) to prepare ternary hybrid materials, where in contrast thermally induced twin polymerization of HD-TM alone failed. Depending on the used catalyst, organic-inorganic hybrid materials consisting of silica, phenolic resin and differently functionalized polysilsesquioxane are generated, as confirmed by solid-state NMR spectroscopy. During the thermally induced STP, DA reactions take place between hexadienyloxy groups and intermediately liberated ortho -quinone methide (oQM) from Spiro. If the HD-TM concentrations are too high, the polymerization process is inhibited by trapping the oQM, which is necessary for the phenolic resin formation. Base-catalyzed STP delivers phenolic resins and hexadienyloxy-functionalized polysilsesquioxanes structures (HDPS) which can be post-derivatized with tetracyanoethylene to a DA-adduct. Acid-catalyzed STP partly leads to a cleavage of the hexadienyl group from the silicon monomer, generating highly condensed inorganic networks. Thus, the hexadienyloxy group serves both as reactant and as an internal molecular probe, allowing statements about mechanistic processes and reactive species during the STP. Image 1 • Synthesis of the twin monomer 2-[(2 E ,4 E)-hexa-2,4-dienyloxy]-2-methyl-4 H -1,3,2-benzodioxasiline. • Simultaneous twin polymerization with 2,2′-spirobi[4 H -1,3,2-benzodioxasiline]. • Formation of various molecular structures in dependence on the used catalyst. • Diels-Alder reactions were evidence during the simultaneous twin polymerization. • Post-derivatization can be performed for both the twin monomer and the hybrid material. [ABSTRACT FROM AUTHOR]

Abstract The radical induced cationic frontal polymerization (RICFP) of the twin monomer 2,2′-spirobi[4 H -1,3,2-benzodioxasiline] (SPIRO) in combination with bisphenol-A-diglycidylether (BADGE) has been developed to fabricate nanostructured hybrid material with domain sizes of 2–5 nm. In one reaction step, an interpenetrating network of phenolic resin, SiO 2 and the epoxy resin is formed in a very short time period, initiated by UV light. That indicates that both polymerization reactions take place simultaneously. The influence of monomer composition on molecular structure was investigated by means of solid state NMR spectroscopies. The envisaged nanostructure of the resulting organic-inorganic hybrid materials is proven by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The thermal properties of the hybrid materials are comparable to "state of the art" materials with the advantage that the silica quantity can be adjusted on demand. Graphical abstract Image 1 Highlights • Synthesis of a ternary hybrid material by frontal polymerization with very short reaction time of just minutes. • First known attempt to start twin polymerization by light. • Nanostructured hybrid materials obtained by radical induced cationic frontal polymerization observed via HAADF-STEM. • 13C and 29Si solid state NMR spectroscopy was used for structure determination. [ABSTRACT FROM AUTHOR]

Abstract: A synthetic procedure for boron oxide/silica/carbon polymer hybrid materials is presented, which does not need water as a reagent. For this purpose, the combined polymerization of the two twin monomers 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] 1 and spiroboronate tetra‐n‐butylammonium bis(ortho‐hydroxymethylphenolato)borate 2 is successful to produce homogeneous hybrid materials by thermal treatment in the melt at 180 °C. The achieved hybrid material shows a ternary composition. It consists of silica, polyborate‐tetra(n‐butyl)ammonium, and phenolic resin. The tetra(n‐butyl)ammonium cation within the hybrid material, originating from monomer 2, can be easily sacrificed by Hofmann degradation at 300 °C. Thereby, it serves as the proton source for the BOH moiety. This thermal treatment finally results in the formation of the boron oxide network. The reaction between both inorganic networks under the formation of SiOB bonds occurs at 450 °C in air atmosphere, which is proven with infrared spectroscopy. Oxidation and carbonization of the hybrid materials provide composite materials with a similar composition of C/B2O3/SiO2. Their use as effective flame retardant materials is demonstrated. [ABSTRACT FROM AUTHOR]

Nanostructured aniline formaldehyde resin/polysilazane hybrid materials are produced by twin polymerization of 2,2′-spirobi[3,4-dihydro-1 H-1,3,2-benzodiazasiline] ( 1). An alternative synthetic concept for similar hybrid materials, the apparent twin polymerization, is employed by using the combination of the deficient twin monomer tetrakis(phenylamino)silane ( 2) with hexamethylenetetramine (HMTA). Both processes for the synthesis of polysilazane hybrid materials occur under volatilization of byproducts such as ammonia or aromatic nitrogen compounds. The thermal properties of the twin monomer 1 and the combination of 2/HMTA, respectively, are investigated by differential scanning calorimetry and thermogravimetric analysis. Aniline-formaldehyde resin/polysilazane hybrid materials are characterized by solid state 13C- and 29Si-NMR spectroscopy and transmission electron microscopy. The inorganic network remains hydrolyzable and can be functionalized after polymerization at temperatures below 500 °C due to residuary reactive Si−N bonds. Thermal treatment at 1100 °C leads to the formation of amorphous Si/C/N hybrid materials. [ABSTRACT FROM AUTHOR]

The synthesis of Zr and Hf twin monomers of type [M(2-OCH2 cC4H3O)4( x HOCH2 cC4H3O)] ( 3, M=Zr, x=0; 4, M=Hf, x=1) and M[(2-OCH2-C6H4O)2(2-HOCH2-C6H4OH)] ( 5, M=Zr; 6, M=Hf) by reacting M(OR)4 (M=Zr, R= nC3H7, 1; M=Hf, R= nC4H9, 2) with 2-furylmethanol or 2-hydroxybenzyl alcohol is discussed. Complexes 3- 6 were homopolymerized under acidic conditions. Additionally, 5 and 6 were copolymerized with 2,2′-spirobi[4 H-1,3,2-benzodioxasiline] (SBS). Under acidic conditions SBS forms a phenolic resin/SiO2 nanostructured material. The resulting hybrid materials from the homopolymerization of 3- 6 and the copolymerized materials from 5 and 6 were characterized by standard solid-state analytics. The inorganic lattice of the MO2 materials from the homopolymerized complexes 3- 6 and SiO2/MO2 from the copolymerization of 5 and 6 with SBS was obtained by air oxidation. The oxide materials were characterized by X-ray powder diffraction (XRPD) and energy-dispersive X-ray analysis, which proved their identity. The inner surface area was determined by N2 adsorption/desorption studies, which revealed surface areas of 100 m2 g−1 for MO2. The mixed oxides SiO2/MO2 were additionally investigated by differential scanning calorimetry and variable-temperature XRPD to study the thermal behavior. It was found that crystallization of tetragonal MO2 nanoparticles is characteristic within the SiO2 matrix, but higher sintering temperatures caused crystallization of the SiO2 lattice. [ABSTRACT FROM AUTHOR]

Simultaneous twin polymerization was used to synthesize hybrid materials composed of tin oxide, silica, and a phenolic resin starting from a mixture of 2,2′-spirobi[4 H-1,3,2-benzodioxasiline] (Si-spiro) with either the tin(IV) alkoxides 2,2′-spirobi[4 H-1,3,2-benzodioxastannine] ( A), 2,2′-spirobi[6-methyl-4 H-1,3,2-benzodioxastannine] ( B), and 2,2′-spirobi[6-methoxy-4 H-1,3,2-benzodioxastannine] ( C) or the novel tin(II) alkoxides tin(II)-2-(oxidomethyl)-4-methoxyphenolate ( D) and tin(II)-2-(oxidomethyl)-5-methoxyphenolate ( E). In addition, the twin polymerization of the twin monomer Si-spiro in the presence of tin-containing additives, such as Sn(O tBu)4, Sn(O nBu)2, Sn(OAc)4, and Sn(OAc)2, was investigated for comparison. The as-prepared hybrid materials were characterized using solid-state NMR spectroscopy (13C, 29Si, 119Sn) and high-angle annular dark field scanning transmission electron microscopy, and were finally converted under Ar/H2 atmosphere at 600 °C to tin nanoparticles (10-200 nm) in porous carbon/silica hybrid materials (Sn/C/SiO2) with BET surface areas up to 352 m2 g−1. [ABSTRACT FROM AUTHOR]

Spirocyclic silicon alkoxides were synthesized by reaction of Si(OMe)4 with derivatives of salicylic alcohol and studied by in situ differential scanning calorimetry with regard to twin polymerization (TP). Both, thermally induced and proton-assisted TP gave nanostructured hybrid materials composed of a phenolic resin and silica. Carbonization and subsequent treatment with HF(aq) resulted in microporous carbon, whereas oxidation in air provided mesoporous silica. DFT calculations were performed to obtain a more detailed insight into the first reaction steps of proton-assisted TP and to support the hypothesis of a reactivity scale based on steric and electronic features of the silicon-containing precursors (twin monomers). The calculated reaction barriers for the initial reaction steps of proton-assisted TP are qualitatively in accordance with the Hammett constants of the substituents at the salicylate moiety. This result offers a simple method to predict the reactivity for twin monomers. [ABSTRACT FROM AUTHOR]

Twin polymerization was used to prepare composite materials composed of SnO2 nanoparticles entrapped in a polymer matrix. Novel, well-defined tin-containing molecular precursors, so-called twin monomers, were synthesized by transesterification starting from Sn(OR)4 (R= tBu, tAm) to give Sn(OCH2C4H3O)4 ( 1), [Sn(OCH2C4H3S)4 ⋅HOCH2C4H3S]2 ( 2), [Sn(OCH2-2-OCH3C6H4)4 ⋅HOCH2-2-OCH3C6H4]2 ( 3), [Sn(OCH2-2,4-(OCH3)2C6H3)4 ⋅HOCH2-2,4-(OCH3)2C6H3]2 ( 4), 2,2′-spirobi[4 H-1,3,2-benzodioxastannine] ( 5), 2,2′-spirobi[6-methylbenzo(4 H-1,3,2)-dioxastannine] ( 6), and 2,2′-spirobi[6-methoxybenzo(4 H-1,3,2)dioxastannine] ( 7). 13C and 119Sn NMR spectroscopy in the solid state and in solution as well as IR spectroscopy and elemental analysis were used to characterize the tin alkoxides. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray diffraction analysis. The moisture sensitivity of the tin(IV) alkoxides was demonstrated by the formation of the tin oxocluster [Sn3(μ3-O)(μ2-OH)(μ2-OCH2C4H3S)3(OCH2C4H3S)6(HOCH2C4H3S)]2 ( 2 a), a hydrolysis product of compound 2. Polymerization reactions in the melt (for 1 and 5) and in solution (for 2- 4) resulted in cross-linked nanocomposites of the type polymer/SnO2. Subsequent oxidation of the composites gave SnO2 with BET surface areas up to 178 m2 g−1. Simultaneous twin polymerization of compounds 5- 7 with the silicon derivative 2,2′-spirobi[4 H-1,3,2-benzodioxasiline] resulted in the formation of polymer/SnO2/SiO2 hybrid materials. Oxidation gave porous materials with SnO2 nanoparticles embedded in a silica network with BET surface areas up to 378 m2 g−1. The silica acts as a crystal growth inhibitor, which prevents sintering of the SnO2 nanoparticles 20-32 nm in size. [ABSTRACT FROM AUTHOR]

The trifunctional (3‐aminopropyl)‐tris‐furfuryloxysilane monomer (1) is able to undergo both twin polymerization and reaction with electrophilic compounds such as isocyanates. 1 can be readily synthesized from 3‐aminopropyptrimethoxysilane (APTMS) and furfuryl alcohol (FA). The reaction of 1 with three different aromatic isocyanates, namely phenyl isocyanate, diphenylmethane‐4,4′‐diisocyanate (MDI), and a prepolymer consisting of MDI end‐capped polytetramethylene ether glycole (PTMEG), to the corresponding substituted urea derivatives is presented. Three urea derivatives 1‐phenyl‐3‐(3‐tris‐furfuryloxysilyl)propylurea (2), diphenylmethan‐4,4′‐bis[3(tris‐furfuryloxysilyl)propyl]urea (3), bis[3(tris‐furfuryloxysilyl)‐propyl]urea‐capped PTMEG‐MDI‐prepolymer (4) as well as 1 were polymerized to multicomponent organic/inorganic hybrid materials in a one step procedure using methane sulfonic acid as catalyst. The simultaneous formations of poly furfuryl alcohol and polysiloxane networks within the hybrid material are proven by means of solid‐state NMR spectroscopic measurements. The homogeneous distribution of silicon within the solidified hybrid materials is analyzed by scanning electron microscopy, energy dispersive X‐ray spectroscopy, and high‐angle annular dark field‐scanning transmission electron microscopy (HAADF)‐STEM. Homogeneous nanostructured hybrid materials with silicon cluster sizes in the range of 2 nm have been obtained by polymerization of the urea derivatives 2, 3, and 4. [ABSTRACT FROM AUTHOR]

A new route of fabrication of cathodes for lithium–sulfur (Li–S) batteries with high cycle stability is reported. The cathodes are fabricated using porous carbon materials obtained from hybrid materials synthesized by twin polymerization on sulfonated polystyrene microparticles. The sulfonic acid groups act as room temperature catalyst for twin polymerization resulting in the formation of nanostructured phenolic resin/silica hybrid materials on the surface of sulfonated polystyrene particles. The shell formed by phenolic resin is transformed into carbon by simple pyrolysis and the polystyrene core is decomposed simultaneously at the pyrolysis temperature yielding porous carbon/silica nanocomposite hollow spheres. After silica removal, a hierarchical, highly porous carbon is obtained. Melt mixing of the carbon with sulfur is used for the fabrication of cathodes for Li–S batteries. The presence of silica on one hand imposes strength to the sphere wall during the carbonization and depolymerization of polystyrene, and on the other hand generates microporous carbon material for lithium–sulfur batteries. The nanostructured hybrid cathode allows very high capacity of 800–1000 mAh gsulfur−1 and remarkable reversible cycling stability and rate capability over 200 cycles at 0.1C rate and over 440 cycles at 1C rate for Li–S batteries. Twin polymerization is performed on self‐catalyzing sulfonated polystyrene colloidal crystal arrays for producing carbon substrate for sulfur. This twin monomer upon polymerization and carbonization leads to the formation of hierarchical porous carbon‐silica hybrid functional material, which results in hierarchical porous carbon. After sulfur filling into the pores by melting, the cathodes show remarkable cycle stability and rate performance. [ABSTRACT FROM AUTHOR]

Front Cover: Nanostructured aniline formaldehyde resin/polysilazane hybrid materials are produced by twin polymerization of 2,2′‐spirobi[3,4‐dihydro‐1H‐1,3,2‐benzodiazasiline]. This is the first step to the formation of amorphous Si/C/N hybrid materials at higher temperatures. Further details can be found in the article by Lysann Kaβner, Anja Knoblauch, Andreas Seifert, Rolf‐Egbert Grützner, Gerhard Cox, Arno Lange, Szilard Csihony, Frank Simon, Susann Anders, Lothar Kroll, Mahfujur Rahaman, Dietrich Zahn, Lutz Mertens, Marcus Weber, Michael Mehring, and Stefan Spange* on page 2462. [ABSTRACT FROM AUTHOR]

Abstract The complex reaction cascade of 2-(3-amino- n -propyl)-2-methyl-4 H -1,3,2-benzodioxasiline (APSI) with the tetra-functional epoxide reactant 4,4′-methylenebis(N , N -diglycidylaniline) (MDGA) has been applied to coat polyethylene terephthalate substrates with a nanostructured inorganic-organic hybrid layer. APSI is suitable to undergo twin polymerization and step growth polymerization processes to both poly(3-aminopropyl methyl)siloxane and phenolic resin as well as epoxy resin moieties, simultaneously. The molecular structure formation of the hybrid material formed is proven by solid state 13C and 29Si nuclear magnetic resonance spectroscopy of reference samples prepared as bulk materials. The formation of three polymer structures during one procedure allows the accurate adjustment of the surface morphology that is strongly determined by the ratio of reactant quantities used. In the coatings, at higher MDGA contents, increasingly larger areas of segregated polymer phases up to the micro scale occur. With increasing APSI amount, the surface becomes smoother and more homogeneous. This has a positive effect on the optical properties of the coatings. With a pure APSI layer, a transmission increase of 2% could be achieved. Highlights • The sequence of twin polymerization in thin coatings differs from that in the bulk. • Epoxide addition promotes formation of phase domains in the coatings. • Surface morphology can be influenced by the ratio of the reactants. • The optical transmittance of the substrate can increased due to the layer deposition. [ABSTRACT FROM AUTHOR]

Homogeneous hybrid materials composed of phenolic resins, crosslinked polydialkylsiloxane moieties with linear epoxide/amine composites have been synthesized by twin polymerization of 2-(3-amino- n -propyl)-2-methyl-4 H -1,3,2-benzodioxasiline (APSI) combined with addition polymerization of bisphenol-A-diglycidylether (BADGE). The ternary formation of three different polymer structures within one procedure in the melt process occurs smoothly as evidenced by solid state 13 C and 29 Si NMR spectroscopy. The formation of in situ generated twin monomer moieties with higher functionalities f = n • 2 (n > 2, n is the assumed average degree of polymerization of the linear chain fragments resulting intermediately from APSI and BADGE), compared to the primary reactant APSI ( f = 2, n = 1), triggers the polysiloxane network formation. A novel type of polysiloxane resin is produced by this methodology. Highly thermally stable materials are accessible by appropriate adjustment of reaction conditions and the molar ratio of the reactants. Potential applications are inter alia in the field of glue adhesives, veneers, and casting resins. [ABSTRACT FROM AUTHOR]