Reactions at polymer interfaces: A Monte Carlo Simulation

Reactions at a strongly segregated interface of a symmetric binary polymer blend are investigated via Monte Carlo simulations. End functionalized homopolymers of different species interact at the interface instantaneously and irreversibly to form diblock copolymers. The simulations, in the framework of the bond fluctuation model, determine the time dependence of the copolymer production in the initial and intermediate time regime for small reactant concentration $\rho_0 R_g^3=0.163 ... 0.0406$. The results are compared to recent theories and simulation data of a simple reaction diffusion model. For the reactant concentration accessible in the simulation, no linear growth of the copolymer density is found in the initial regime, and a $\sqrt{t}$-law is observed in the intermediate stage.Comment: to appear in Macromolecule

Theoretical study on a family of organic molecules with planar tetracoordinate carbon

Based on the most stable structure of C3B2H4 and its substitution of H with -Cl, -CH2OH, -CHOH, -C=O and -COOH groups, a series of derivatives containing the planar tetracoordinate carbon (ptC) atoms as well as crown ether-like compounds from the assembling of C3B2H4 units have been constructed. At the B3LYP/6-311++G** and MP2/6-31G** levels of theory, these ptC compounds were predicted to be stable and they generally have large HOMO-LUMO gaps. The IR characteristic bands arising from the symmetrical and asymmetrical stretching vibrations of C-ptC, the stretching vibrations of C-B and B-H as well as the breath vibration of the two three-membered rings of C3B2 appear at 1000, 1250. 1600, 2800, and 1700 cm(-1). respectively. Calculations also show that these ptC molecules have strong aromaticities and the ptC atom obeys the octal rule. Furthermore, the derivatives C3B2H2(COOH)(2) and tetra-C3B2H2-16-crown-4 can serve as the chelate ligands and form stable complexes with uranyl. (C) 2009 Elsevier B.V. All rights reserved.Shaanxi Normal University ; National Science Foundation of China [20673087, 20733002, 20873105]; Ministry of Science and Technology [2004CB719902

Stability Rules of Main-Group Element Compounds with Planar Tetracoordinate Carbons

We have investigated the structures, stabilities, aromaticities, and Wiberg bond indices of four types of compounds (8-like, trapezia, umbrella-like, and quadrangle) containing planar tetracoordinate carbon (ptC), and the stability rules for the compound with ptC were concluded on the basis of extensive calculations. Generally, the stability or viability of compound with ptC strongly depends on the number of three-membered ring and conjugated three-membered ring, as well as pi electrons. These rules can be successfully used to identify the stability of other compounds reported in previous studies. On the basis of these rules, eight stable compounds with planar tetracoordinate nitrogen (ptN) are successfully constructed.Shaanxi Normal University ; National Science Foundation of China [20673087, 20733002, 20873105]; Ministry of Science and Technology [2004CB719902

P.G.; “Scaling Concepts in Polymer

2633 5.3 X cm2 s-l within an experimental error of 10% from the linear plot of the relaxation time 7, of the decay profile of the diffraction intensity vs. d2, the square of the grating spacing. The value is larger than Dslow by a factor of about 5, even ABSTRACT Time-average and time-dependent intensity of light scattered by linear polyethylene (LPE), Dutch State Mines sample L30-4-6, in a good organic solvent, 1,2,4-trichlorobenzene at 135 "C, was measured as a function of polymer concentration at scattering angles between 35 and 145O. Molecular properties determined were the z-average radius of gyration, = 50 nm, the z-average hydrodynamic radius, (Rh-');l = 27 nm, the weight-average molecular weight, (M)w = 570, the weight distribution, Fw(M), and the second virial coefficient, Az = 1.5 X lom3 g" mL mol. The main purpose of this article was to determine F J M ) for a LPE based on (M)w, (R:),, A2, and the characteristic line width distribution G(r) computed from an inverse Laplace transform of the measured single-clipped time correlation function, Gk@)( 7). We have demonstrated thh nonintrusive technique to be particularly useful in obtaining an approximate Fw(M) for polydisperse synthetic high polymers which are difficult to characterize by more established analytical techniques such as gel permeation chromatography (GPC)