Reverse enantioselectivity in the lipase-catalyzed desymmetrization of prochiral 2-carbamoylmethyl-1,3-propanediol derivatives

Enantioselective acetylation of 2-carbamoylmethyl-1,3-propanediol derivatives was catalyzed effectively by lipase PS to give monoacetates with high enantioselectivity: The enantioselectivity depended on the 2-carbamoylmethyl groups. The reaction of N-monoalkylcarbamoylmethyl-1,3-propanediol afforded the monoacetate with the (S)-configuration, whereas N,N-dialkylcarbamoylmethyl-1,3-propanediol gave the monoacetate with the (R)-configuration.     

An abstract approach to Loewner chains

We present a new geometric construction of Loewner chains in one and several complex variables which holds on complete hyperbolic complex manifolds and prove that there is essentially a one-to-one correspondence between evolution families of order d and Loewner chains of the same order. As a consequence, we obtain a univalent solution (f _t : M → N) of any Loewner-Kufarev PDE. The problem of finding solutions given by univalent mappings (f _t : M → ? ⁿ ) is reduced to investigating whether the complex manifold ∪ _t≥0 f _t (M) is biholomorphic to a domain in ? ⁿ . We apply such results to the study of univalent mappings f: B ⁿ → ? ⁿ .     

Univalence criterion and quasiconformal extension of holomorphic mappings

In this paper we are concerned with solutions, in particular with the univalent solutions, of the Loewner differential equation associated with non-normalized subordination chains on the Euclidean unit ball B in ${\mathbb{C}^n}$ . We also give applications to univalence conditions and quasiconformal extensions to ${\mathbb{C}^n}$ of holomorphic mappings on B. Finally we consider the asymptotical case of these results. The results in this paper are complete generalizations to higher dimensions of well known results due to Becker. They improve and extend previous sufficient conditions for univalence and quasiconformal extension to ${\mathbb{C}^n}$ of holomorphic mappings on B.     

Room‐temperature epitaxial growth of high‐quality m ‐plane InGaN films on ZnO substrates

The authors have grown high‐quality m ‐plane In_0.36Ga_0.64N (1 00) films on ZnO (1 00) substrates at room temperature (RT) by pulsed laser deposition (PLD) and have investigated their structural properties. m ‐plane InGaN films grown on ZnO substrates at RT possess atomically flat surfaces with stepped and terraced structures, indicating that the film growth proceeds in a two‐dimensional mode. X‐ray diffraction measurements have revealed that the m ‐plane InGaN films grow without phase separation reactions at RT. The full‐width at half‐maximum values of the 1 00 X‐ray rocking curves of films with X‐ray incident azimuths perpendicular to the c ‐ and a‐axis are 88 arcsec and 78 arcsec, respectively. Reciprocal space‐mapping has revealed that a 50 nm thick m ‐plane In_0.36Ga_0.64N film grows coherently on the ZnO substrate, which can probably explain the low defect density that is observed in the film. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Molecular Weight Development in Free‐Radical Polymerization with Polyfunctional Chain‐Transfer Agents, 2. Substitution Effects

The analytic expression for the weight‐average molecular weight development proposed in the first part of this series^[1] is extended to account for the substitution effects of the functional groups in a polyfunctional chain‐transfer agent. The obtained functional form of the matrix formula, P_w = W { D _w + ( I + T ) SPE ( I – TSPE )^–1 D _f } is essentially the same as for equal reactivity model, but the NxN square matrixes, S and P in the equal reactivity model is now expanded to NxfN and fNxfN matrixes, respectively, to account for the different reactivities of f functional groups. The number of chain types, N is extrapolated to infinity to obtain the P_w‐value for free‐radical polymerization. Practically, such extrapolation can be conducted with calculated P_w‐values for only three different N‐values. Illustrative calculations show that the obtained results agree with those from the Monte Carlo method. The present approach provides newer insight into the branched structure formation during complex polymerization reactions.     

Molecular Weight Development in Free‐Radical Polymerization with Polyfunctional Chain‐Transfer Agents, 1. Equal Reactivity Model

The analytic expression for the weight‐average molecular weight development in free‐radical polymerization that involves a polyfunctional chain‐transfer agent is proposed. Free‐radical polymerization is kinetically controlled; therefore, the probability of chain connection with a polyfunctional chain‐transfer agent as well as the primary chain‐length distribution changes during the course of polymerization. We consider the primary chains formed at different times as different types of chains, and the heterochain branching model is used to obtain the weight‐average chain length at a given conversion level in a matrix formula, described as P_w = W { D _w + ( I + T ) SP ( I – TSP )^–1 D_f }. Because the primary chains are formed consecutively, the number of chain types N is extrapolated to infinity, but such extrapolation can be conducted with the calculated values for only three different N values. The criterion for the onset of gelation is simply described as a point at which the largest eigenvalue of the product of matrixes, TSP reaches unity, i. e., det  ( I – TSP ) = 0. The present model can readily be extended for the star‐shaped polyfunctional initiators, and the relationships between the model parameters and kinetic rate expression for such reaction systems are also shown.     

A simulation model for long-chain branching in vinyl acetate polymerization: 1. Batch polymerization

A new simulation model for the kinetics of long-chain branching formed via chain transfer to polymer and terminal double-bond polymerization is proposed. This model is based on the branching density distribution of the primary polymer molecules. The theory of branching density distribution is that each primary polymer molecule experiences a different history of branching and provides information on how each primary polymer molecule is connected with other chains that are formed at different conversions, therefore making possible a detailed analysis on the kinetics of the branched structure formation. This model is solved by applying the Monte Carlo method and a computer-generated simulated algorithm is proposed. The present model is applied to a batch polymerization of vinyl acetate, and various interesting structural changes occurring during polymerization (i.e., molecular weight distribution, distribution of branch points, and branching density of the largest polymer molecule) are calculated. The present method gives a direct solution for the Bethe lattice formed under nonequilibrium conditions; therefore, it can be used to examine earlier theories of the branched structure formation. It was found that the method of moments that has been applied successfully to predict various average properties would be considered a good approximation at least for the calculation of not greater than the second-order moment in a batch polymerization. © 1994 John Wiley & Sons, Inc.     

Adhesion of a pair of polyethylene moldings by polyethylene gels

It was found that polyethylene gels in solvents such as benzene, toluene, xylene, decalin, tetralin, tetrachloroethylene, 1,1,2,2-tetrachloroethane, and chlorobenzene are effective for adhesion of a pair of polyethylene plates. In particular, the adhesion strength of polyethylene gels in decalin, tetralin and tetrachloroethylene was strong enough for practical use.Adhesive effect appears due to local dissolution of the surface of polyethylene plate in contact with the gel with increasing temperature, and subsequent recrystallization.