Chain‐length dependent termination in rotating sector polymerization, 1. The evaluation of the rate constant of chain propagation kp

The chain‐length distributions (CLDs) of polymers prepared by rotating‐sector (RS) techniques under pseudostationary conditions were simulated for the case of chain‐length dependent termination and analysed for their suitability of determining the rate constant of chain propagation k_p from the positions of their points of inflection. The tendency to underestimate k_p is a little more pronounced than in pulsed‐laser polymerization (PLP) but, interestingly, the situation improves in the presence of chain‐length dependent termination. The estimates also were found to be more precise a) for smaller rates of initiation, b) for higher order points of inflection, c) if termination is by combination, d) if the role played by the shorter one of the two chains becomes less dominant. Taken in all, the determination of k_p from the points of inflection in the CLD of RS‐prepared polymers may well compete with the more famous PLP method, especially if some care is taken with respect to the choice of experimental conditions.     

Crosslinkable hole‐transporting polymers by palladium‐catalyzed C—N‐coupling reaction

Combination of spin‐coating and crosslinking allows low‐cost fabrication of large area displays with multiple layers by simple solution processing. For this purpose, a series of novel crosslinkable polymers containing hole‐transporting triarylamine units in the main chain were synthesized via palladium‐catalyzed C—N‐coupling reaction. Additionally, they contain varying amounts of polymerizable oxetane groups as side chains. The polymers were photo‐crosslinked to yield absolutely insoluble networks. Thin films were used as hole‐transport layer in two‐layer blue light‐emitting diodes.     

Quantum Nuclear Delocalization and its Rovibrational Fingerprints

Quantum mechanics dictates that nuclei must undergo some delocalization. In this work, emergence of quantum nuclear delocalization and its rovibrational fingerprints are discussed for the case of the van der Waals complex . The equilibrium structure of is planar and T-shaped, one He atom solvating the quasi-linear He−H⁺−He core. The dynamical structure of , in all of its bound states, is fundamentally different. As revealed by spatial distribution functions and nuclear densities, during the vibrations of the molecule the solvating He is not restricted to be in the plane defined by the instantaneously bent chomophore, but freely orbits the central proton, forming a three-dimensional torus around the chromophore. This quantum delocalization is observed for all vibrational states, the type of vibrational excitation being reflected in the topology of the nodal surfaces in the nuclear densities, showing, for example, that intramolecular bending involves excitation along the circumference of the torus.     

The incorporation of side reactions into pseudostationary polymerization, 1. The closed solution of a kinetic scheme comprising chain-transfer to monomer or solvent

A procedure is developed that allows the calculation of chain length distributions of polymers prepared by periodic modulation of the initiation process, considering termination by disproportionation and chain transfer. For the case of a (pseudostationary) laserpulse initiated polymerization process a closed solution can be derived for the chain length distribution (cld) of dead polymer and its O^th, 1^st and 2^nd moments. By analysis of the detectability of the “extra-peaks” appearing in the cld (which represent the key for the determination of propagation constants) as a function of the parameters chosen the optimum conditions can be predicted for experiments.     

Polymers with indane units by cationic polymerization

In spite of the difunctionality of the monomers, cationic polymerization of 1,3- and 1,4-diisopropenylbenzene does not lead to branched or cross-linked products. Instead, soluble polymers are obtained, containing the 1,1,3-trimethylindane system as repetitive unit along the backbone. These polymers are interesting materials because of their high glass transition temperature (200°C-250°C) and good thermal stability in air (2% weight loss at 450°C). Although the molar mass of the polyindanes seems to be limited due to a side reaction, it is possible to produce telechelic polyindanes. Substitution of an alkyl side chain onto the isopropenyl groups of 1,4-diisopropenylbenzene leads to monomers which yield substituted polyindanes with glass transition temperatures as low as 26°C. Such polymers still exhibit good thermal stability: at 340°C a weight loss of only 2% occurs. 1,4-Diisopropenylbenzene can even be anionically polymerized to linear polymers. In this case, the resulting polymer possesses isopropenyl phenyl side groups, which can be used as initiators for cationic polymerization of isobutene to obtain grafted copolymers.     

Pseudostationary Polymerization: Improving the Determination of the Rate Constant of Propagation

Pulsed-laser initiated polymerization (PLP) leads to chain length distributions with characteristic extrapeaks. The low molecular weight side points of inflection L_LPI are located near to (multiples) of a specific chain length L₀ which is equal to the product of pulse separation t₀ and propagation frequency k_p[M], i.e. rate constant of propagation k_p times monomer concentration [M], allowing a direct determination of k_p. However, Poissonian broadening inherent in the polymerization process as well as Gaussian broadening due to axial dispersion caused by the size exclusion chromatographic (SEC) device leads to a shift of L_LPI as compared to L₀ – its extent depending on the experimental parameters chosen – which in turn causes an error up to 10–20% in the rate constants evaluated. Fortunately, comparison of the experimental peak width with some sort of theoretical peak width yields several types of correction factors and furthermore master-correction functions which are able to reduce the remaining error on average by at least a factor of 10.     

First Diazosulfonate Homopolymer by Enzymatic Polymerization

The polymerization behavior of phenolic azosulfonates and triazene by means of enzymatic polymerization using horseradish peroxidase was studied. While for the latter one, only oligomerization was observed, sodium 4‐hydroxybenzenediazosulfonate was successfully homopolymerized. The obtained polymer had an average molecular weight of M _n = 3 000 with a polydispersity index of 1.51. This is the first example of a homopolymer bearing an azosulfonate function in every monomer unit.

     

Amphiphilic poly(oxazoline)s – synthesis and application for micellar catalysis

Homogeneous and heterogeneous catalytic processes compete on industrial scale for more then three decades [1]. The advantages of homogeneous catalysis are beside others high activity, mild reaction conditions, high selectivity and no diffusion problems. The disadvantages of such systems include difficulties with recycling of the catalyst and product separation [2].