Polyhedral oligomeric silsesquioxane (POSS) cubic cage systems (octa-n-octadecyloctasilsesquioxane, (T8C18) and octakis(n-octadecyldimethylsiloxy)octasilsesquioxane, (Q8C18)) were synthesised with eight long n-alkyl chain (R = C18H37) substituent arms, as model nano-functionalized compounds. The crystalline packing morphology of the cages was studied using time-resolved Small- and Wide-angle X-ray scattering (SAXS/WAXS), thermal and optical techniques. From thermal analysis the melting and crystallization temperatures of the Q8 cage were significantly less than those for the T8 cage. X-ray scattering showed that both cage systems have long-range crystalline ordering where the alkyl chains align in a parallel axial disposition from the POSS core giving a 'rod-like' self-assembled packing morphology. The packing length-scale can be directly related to the overall dimensions of the POSS molecules. Compared to the T8 cages, the Q8 cages pack more efficiently allowing the interdigitation of the alkyl chain arms. Different packing modes and thermal behaviour observed for the T8 and Q8 cages is directly attributed to their structural chemistry. For the Q8 cage, the presence of the OSiMe2 spacer groups which tether the alkyl chain arms to the cage (absent in the T8 cages) allows greater flexibility of the arms letting them interdigitate with each other when packing which is not observed for the analogous T8 cages.

The homologous series of octa-n-alkylsilsesquioxanes (nalkylPOSS) was prepared by hydrosilylation of octahydrido-octasilsesquioxane H 8 T 8 with terminal n-alkenes in good yields (n = 2−18). The compounds were characterized by NMR spectroscopy ( 1 H, 13 C, 29 Si), MALDI−TOF and ESI MS. Most of them have also been characterized using X-ray crystallography, including some polymorphs. The packing systems of the octa-n-alkylsilsesquioxanes are reported. Two types of packing have been observed, rod-like and disk-like (interdigitated). Some n-alkylPOSS crystals were formed in which the chains are tilted away from the axes of the cubic core. It was also observed that as alkylchains are flexible they can take up a variety of conformations. Melting points of the homologous series showed an odd−even alternating effect for alkyl chains longer than four CH 2 units. The TGA of n-alkylPOSS under nitrogen showed that the thermal stability temperatures are between 200 and 400°C. Pyrolysis-gas chromatography/mass spectrometry has been used to elucidate the thermal degradation process of T 8 (n-C n H 2n+1 ) 8 (n = 11 and 18). Thermal cracking along the whole alkyl chain was observed rather than simple loss of the complete arm.

The dispersal, quiescent crystallization kinetics and morphology of a series of unique polyethylene -polyhedral oligomeric silsesquioxanes (PE-POSS) nanocomposite blends is presented. POSS molecules with long linear alkyl-chain substituents were blended at one composition into a commercial low density polyethylene. Time-resolved Small-and WideAngle X-Ray scattering (SAXS/WAXS) and thermal techniques were used to elucidate the affect that POSS and its substituent groups have on the dispersal and crystallization kinetics of the host polymer. The miscibility and dispersal of the POSS molecules was seen to increase with the increasing alkyl-chain length substituents suggesting increased compatibility and interaction with the host polymer chains. The POSS molecules act as nucleating agents increasing the crystallinity, crystallization kinetics and influencing the final lamellar morphology. Thus, these unique POSS compounds show great potential as nancomposite filler particles in polyolefins where the alkyl-chain substituent plays a vital role in its compatibility and subsequent improvement of physical properties in the host polymer.

A range of fluoride-encapsulated octasilsesquioxane cage compounds have been prepared using the TBAF route. Our studies suggest that whilst it is relatively straightforward to prepare fluoride-encapsulated octasilsesquioxane cage compounds with adjacent sp(2) carbons, leading to a range of aryl and vinyl substituted compounds, the corresponding sp(3) carbon derivatives are more capricious, requiring an electron withdrawing group that can stabilize the cage whilst not acting as a leaving group. Analysis by X-ray crystallography and solution (19)F/(29)Si NMR spectroscopy of R(8)T(8)@F(-) reveal very similar environments for the encapsulated fluoride octasilsesquioxane cages. Migration of a fluoride ion from inside the cage to outside the cage without breaking the T(8) framework and the possibility of encapsulating other anions within silsesquioxane cages have been also investigated.

The self-assembled long-range ordering, packing morphology and thermal behavior of a series of polyhedral oligomeric silsesquioxanes (POSS) T 8 cage systems with long n-alkyl chain pendant groups is presented. State-of-the-art timeresolved small-and wide-angle X-ray scattering (SAXS/WAXS), thermal and optical techniques were used to elucidate their morphology. X-ray scattering showed long-range crystalline ordering where the alkyl chains align in an axial disposition from the POSS core giving a "rod-like" self-assembled packing morphology with a length-scale correlating to the overall molecular dimensions. Phase transitions observed by thermal methods were comparable to those seen in the crystallization of bulk nalkanes. Optical measurements and crystallization kinetics confirmed a lamellar macromorphology again being similar to the crystal structure of bulk n-alkanes. This study reveals for the first time, the direct effect that the alkyl chain length has on the selfassembled crystalline packing morphology of this novel and potentially commercially relevant, series of POSS systems.

The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2) n -Si­(OEt)3 (where n = 1–3 and the electron-withdrawing group EWG contains an Si–C­(sp3) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by 19F and 29Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T8 cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past.

The novel coordinate compounds T 8 [(CH 2 ) n -EWG] 8 F − -18-crown-6-M + were prepared by reaction of EWG-(CH 2 ) n -Si(OEt) 3 (where n = 1−3 and the electron-withdrawing group, EWG, contains an Si−C(sp 3 ) bond) with an 18-crown-6-M + F − complex (where M + is K + , Cs + , and Rb + ) in the presence of a limited amount of water. The EWG facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. The reaction takes place by complexing an alkali metal in the crown ether, catalyzing silsesquioxane cage formation, and concomitant encapsulation of a fluoride ion within the final T 8 cage. The reaction is simple and takes place in a single step with excellent yields of 81−95%. These novel materials have been studied by 19 F and 29 Si NMR spectroscopy and X-ray crystallography as well as by MALDI-TOF and ESI mass spectrometry. The T 8 [(CH 2 ) n -EWG] 8 F − -18-crown-6-M + compounds can be also synthesized by a facile reaction of 18-crown-6-M + F − with the corresponding T 8 [(CH 2 ) n -EWG] 8 cage in nearly quantitative yield. Surprisingly, the single-crystal X-ray diffraction analysis has revealed the presence of 1D and 3D polymeric complexes of T 8 [(CH 2 ) n -EWG] 8 F − -18-crown-6-M + . To the best of our knowledge, this represents the first dual-encapsulation host−octasilsesquioxane system. The results from thermostability experiments monitored by 19 F NMR and 1 H NMR and DSC suggest that compound T 8 [CH 2 CH 2 (CF 2 ) 3 CF 3 ] 8 F − -18-crown-6-K + is a potential ionic liquid (IL).

The self-assembly and crystal packing of a unique series of nanocrystalline fluoride ion-encapsulated polyhedral oligomeric silsesquioxane (F-POSS) compounds, with substituted electron-withdrawing group (EWG) perfluorinated alkyl chain arms of varying lengths, were investigated.