The novel monovinyl-functional silsesquioxane cage 1-(9-decenyl)-3,5,7,9,11,13,15-heptaethylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane has been prepared and copolymerized with ethene and propene. The monovinyl-functional spherosiloxane was obtained from the octahydridosilsesquioxane (HSiO3/ 2)8 via hydrosilation with dibrominated decadiene, followed by reaction of the nonreacted SiH groups with ethene, debromination, and chromatographic separation. Homopolymerization and copolymerization with ethene and propene was performed using different methylalumoxane-activated metallocene catalysts. Depending on catalyst structure comonomer incorporation between 17 and 25 wt % was achieved. High molar mass copolymers were obtained containing pendant octasiloxane cubes. Characterization by 13C, 1H, and 29Si NMR spectroscopy confirmed that the catalyst did not modify the Si−O−Si framework. Incorporation up to 25 wt % (1.2 mol %) of the spherosiloxane-based monomer accounted for a decrease of the melting temperature by 18 K with respect to polyethene. As demonstrated by means of thermal gravimetric analysis, thermostability under air was improved in the polyethene copolymer in comparison to polyethene.

The homologous series of 8-fold alkyl-substituted octasilsesquioxane has been prepared by hydrosilation of alkenes with octakis(hydridosilsesquioxane) (HSiO3/2)8. Ethene, propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene were employed either in bulk or in toluene solution. The homologous series of 1,3,5,7,9,11,13,15-octaalkylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxanes, which are interesting model compounds for silsesquioxane-based materials was characterized by 1H, 13C, and 29Si NMR spectroscopy, IR and mass spectroscopy, and elemental analysis. Melting points of the compounds were studied by DSC, revealing a strong decrease of the melting point from the octapropyl-substituted T8 to the octapentyl derivative. Melting points for derivatives with longer n-alkyl chains showed an odd−even effect. TGA evidenced thermal stability under nitrogen up to temperatures between 200 and 400 °C and under air up to temperatures between 200 and 250 °C.

Thirty-eight WHO grade II astrocytomas and 10 malignant recurrent gliomas in these patients were examined for the presence of TP53 alterations. Seventeen/38 low grade astrocytomas and 6/10 malignant recurrent tumors harbored mutations of the gene detected by SSCP analysis and direct sequencing of PCR products. TP53 mutations in five out of six high grade mutant tumors were already present in the corresponding low grade astrocytomas. In two cases, TP53 mutations present in the low grade astrocytoma could not be demonstrated in the recurrent glioma. Immunohistochemistry with two different antibodies to the human TP53 protein revealed nuclear immunoreaction of tumor cells in 11/38 low grade and in 8/10 recurrent tumors. There was no correlation between the presence of TP53 alteration and clinical course. We conclude that, although TP53 mutations are detectable in a substantial fraction of WHO grade II astrocytomas, they do not appear to play a role in the malignant progression of these tumors and they are not of prognostic significance.