2,5-Dimethyl-1,4-bis(carboxyalkyl)benzenes were prepared in almost quantitative yield by alkylation of malonic esters from 2,5-dimethyl-1,4-dibromomethylbenzene obtained by bromomethylation of 1,4-dimethylbenzene. The methyl groups on the central benzene ring induce intramolecular, regiospecific cycloeliminations leading selectively to the diketones, the precursors of the corresponding 1,5-dihydro-s-indacenes, which also were obtained in very high yield. These new ligand precursors were easily converted to the mono- or dianions, which were characterized by means of the mono- or disilylated compounds. Disilylation occurs in cis and trans position. The structure of the trans-1,5-bis(trimethylsilyl)-2,6-diethyl-4,8-dimethyl-s-indacene was obtained by X-ray diffraction. Hexaalkyl-1,5-dihydro-s-indacenes underwent regioselective monosilylation and regiospecific and stereoselective disilylation. Disilylation of the less hindered tetraalkyl-1,5-dihydro-s-indacenes was regioselective and stereoselective.

Abstractchemical structure image Poly(butylene terephthalate)‐poly(ethylene oxide)‐poly(dimethyl siloxane)‐poly(ethylene oxide) block copolymers, (PBT‐PEO‐PDMS‐PEO)m, are synthesized by polycondensation (PC) of dimethylterephtalate (DMT), 1,4‐butanediol (BDO) and PEO‐PDMS‐PEO. The soft block has been incorporated from 10 to 70 wt‐%; the total molecular weight (MW) of the block‐copolymers amounts to 16000 ‐ 20000 g/mol.One major problem of polyether‐PBT thermoplastic elastomers is their poor thermo‐oxidative stability. Due to the excellent heat stability of PDMS, the resistance of this new thermoplastic elastomer against thermo‐oxidative degradation has been increased 80 %!From differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) in the PEO‐PDMS‐PEO based COPEs, three phases can be distinguished. Besides the crystalline PBT phase, an amorphous mixed phase of PBT and PEO and an almost pure PDMS phase have been found. Due to the high concentration of the mixed PBT‐PEO phase, the low temperature modulus and the glass transition temperature, Tg, are not dominated by the pure PDMS phase (Tg = −114°C). Depending on the amount of PBT and PEO present, the main glass transition lies in the range of −50°C to 50°C.

New classes of amphiphilic polyesters were prepared from metallated (Si, Ge) fatty methyl ester (FAME) precursors and poly(tetramethylene oxide) glycol. Hydrosilylation of 10-undecenoic methyl ester by tetramethyldisiloxane occurred at 80 degrees C in the presence of Karstedt's catalyst, and hydrogermylation of the same FAME derivative was obtained at the same temperature under radical AIBN initiation. These diester precursors, obtained in high yields (approximately 90%), reacted with poly(tetramethylene oxide) glycol under free solvent to give silicon polymers or germanium oligomers. These condensed materials display both the characteristic of organic-inorganic hybrid materials and those of amphiphilic polymers. The nature of organometallic fragment (hydrophobicity of tetramethyldisiloxy and sterical hindrance of diphenylgermyl) was shown to influence the chemical reactivity of the polymerizable monomers and the physical properties of the resulting copolymers. The amphiphilicity of these materials provides a driving force for the formation of small objects (approximately 1 nm), making them very attractive as hybrid nanocontainers.

New cyclic oligomers of dimesitylgermylene carbodiimides (Mes2GeNCN) n (n = 3 (1) and 4 (2)) were synthesized by reactions of dimesityldichlorogermane with either cyanamide in the presence of triethylamine or lithium cyanamide. The reactions always gave 1, the trimer of the hypothetical (Mes2GeN−CN), as the major compound. Higher oligomers 3 (n up to 20−30) also can be isolated, depending on the reaction conditions. In THF solution at room temperature, 2 and 3 slowly isomerize to 1, which seems to be the most stable compound. X-ray analysis of trimer 1 and tetramer 2 shows unstrained tetrahedral germanium atoms and linear diimine linkers.