Sigrid Böhme

Polymers of carbonic acid, 31: Cyclic polycarbonates by hydrolytic polycondensation of bisphenol-A bischloroformate

The hydrolytic polycondensation of bisphenol-A bischloroformate in NaOH/CH 2 Cl 2 was studied using triethylamine as the catalyst. Reaction conditions were optimized towards high molar masses. The isolated polycarbonates were characterized by means of SEC and MALDI-TOF mass spectrometry. The fraction of cyclic polycarbonates strongly increased with higher molecular weights and in the best sample only cycles were detectable (up to 50000 Da). The largest cycles can compete with cyclic DNS of microorganisms.

LC-polyimides—8. thermotropic poly(ester-imide)s from n-(4-carboxyphenyl)-4-nitrophthalimide

Abstract Two imide monomers were prepared starting from 4-nitrophthalic anhydride, viz. N -(4′-carboxyphenyl), 4-(4′-carboxyphenoxy)phthalimide and its dimethylester. Nematic aromatic polyesters were prepared by polycondensation with chlorohydroquinone or phenylhydroquinone. Four polyesters were obtained by polycondensation with aliphatic diols. These “aliphatic polyesters” exclusively form isotropic melts but a smectic layer structure in the solid state. All the polyesters were characterized by elemental analyses, inherent viscosities, WAXS powder patterns, DSC measurements and optical microscopy.

Macrocycles, 16. Macrocyclic Dibutyltin Dicarboxylates via Thermodynamically Controlled Polycondensations

Various dibutyltin derivatives were polycondensed with aliphatic α,ω-dicarboxylic acids having chain lengths from 4 (succinic acid) to 22 carbon atoms. White crystalline products were obtained from all experiments, and the structure of the products was independent of the synthetic method. Viscosity measurements revealed low molecular weights (M n ≤ 1 500 Da) in all cases. Vapor pressure osmometry (VPO) measurements and matrix assisted laser desorption time-of-flight (MALDI-TOF) mass spectrometry proved that cyclic dimers and trimer were formed from dicarboxylic acids having 6 to 16 carbons, but mainly the monomeric cycle from docosane dioic acid. Heating to 250 °C did not change the structure. Therefore, the results indicate that the macrocycles are the result of a thermodynamically controlled ring-closing polycondensation. This means that linear high-molecular weight poly(dibutyltin dicarboxylate)s cannot exist above room temperature.