New Polymer Syntheses, 108. Controlled Degradation and In‐Situ Functionalization of Polycarbonates by Means of Bu2SnO

It was found that diphenyl carbonate reacts with Bu₂SnO above 140°C yielding CO₂ and Bu₂Sn(OPh)₂. This insertion reaction was also successfully applied to a polycarbonate prepared from polytetrahydrofuran diol‐1000 and Bu₂SnO containing macrocyclic polyTHF dioxides. Bu₂SnO reacted analogously with poly(bisphenol A) carbonates yielding tin‐containing rapidly crystallizing cyclic oligocarbonates. Their treatment with 1,2‐ethanedithiol gave linear oligocarbonates having two OH end groups. Bu₂Sn‐containing macrocyclic oligocarbonates reacted in‐situ with several carboxylic acid chlorides, forming telechelic oligocarbonates with functional ester end groups. Bu₂Sn‐containing macrocycles also reacted in‐situ with terephthaloyl chlorides yielding a poly(ester carbonate).     

A molecular mechanics force field for rhodium(I) carbonyl phosphine complexes and its application on the oxidative addition reactions of these complexes

The main purpose of the development of an Rh(I) Carbonyl Phosphine force field was to predict the molecular structure of Rh(I) complexes as well as to compute possible intermediates or transition states during the oxidative addition of CH₃I to these complexes. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 692–703, 2000     

Characterization of Microbial Degradation Products of Steviol Glycosides

Steviol glycosides were subjected to bacteria present in a soil sample collected from a Stevia plantation in Paraguay. During the incubation experiments, next to the aglycon steviol, steviol degradation products were also formed. X-ray analysis and NMR methods in combination with chemical synthesis and GIAO NMR calculations were used to fully characterize the structure of these compounds as a tricyclic ketone and the corresponding reduced form. They were nicknamed monicanone and monicanol. The latter has the (S)-configuration at the alcohol site.     

R&D Intensification in Polymer Catalyst and Product Development by Using High‐Throughput Experimentation and Simulation

Currently laboratory automation is a rapidly growing field of interest in chemical process research and development. The idea of using automated and parallel methods for the optimization of chemical processes was initiated by the extensive implementation of combinatorial techniques in medicinal chemistry. The techniques applied involve all methods and concepts aimed at dramatically increasing the output of research by extensive use of automation, parallelization and miniaturization, fast analysis, advanced data handling and by efficient automated planning, scheduling and tracking. In this paper, the “Combi” or high‐throughput experimentation approach consists of the integration of parallel experimentation with four key modeling and simulation methodologies, modeling, multivariate statistics, statistical design of experimentation and empirical model generation.

Integrated automated liquid and solid handling.     

Strain-Controlled Tensile Deformation Behavior and Relaxation Properties of Isotactic Poly(1-butene) and Its Ethylene Copolymers

The tensile deformation behaviour of poly(1-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery and stress relaxation properties and in-situ WAXS patterns during the deformation process. As for a series of semicrystalline polymers in previous studies, a strain-controlled deformation behaviour was found. The differential compliance, the recovery properties and the stress relaxation curves changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constant for the different samples despite their different percentage crystallinities. The well-defined way in which the different samples respond to external stresses complies with the granular substructure of the crystalline lamellae in a semicrystalline polymer.