Effect of Molecular Weight on Packing during Latex Film Formation

A UV-visible technique is used to study the evolution of transparency during film formation from latex particles. Latex particles with high and low molecular weight (HM and LM) polymethyl methacrylate (PMMA) are used to prepare films. Two sets of films with different latex content were prepared from HM and LM particles separately, by annealing PMMA particles above the glass transition temperature. Transmitted photon intensity, I(tr), from HM and LM films increased as the annealing temperature was increased. The increase in the transmitted photon intensity is attributed to the latex content (film thickness) for the annealed film samples. It is suggested that as the latex particles are packed (film thickness is increased) fewer voids or cracks are formed in the films. Positive and negative absorption coefficients are measured below and above 210 and 180 degrees C annealing temperatures for the HM and LM films. Packing coefficients are obtained for films in various latex contents. It is observed that LM particles are packed much easier than HM particles. Copyright 2001 Academic Press.     

Synthesis of Phenyl‐Substituted Conduritol B and Its Mechanism of Formation

The phenyl‐substituted conduritol B 8 was prepared in racemic form in a five‐step sequence starting from 2‐phenyl‐1,4‐benzoquinone ( 10 ) (Scheme 1). The reaction mechanism of the key step 12b → 13 is discussed (Scheme 2).     

[Bis­(di­phenyl­phosphino)­methane][1,3-bis­(di­phenyl­phosphino)­propane]­platinum(II) dibromide

The asymmetric unit of the title compound, [Pt(C₂₅H₂₂P₂)(C₂₇H₂₆P₂)]Br₂ or [Pt(dppm)(dppp)]Br₂, where dppm is bis­(di­phenyl­phosphino)­methane and dppp is 1,3-bis­(di­phenyl­phosphino)­propane, consists of a discrete [Pt(dppm)(dppp)]²⁺ cation and two Br⁻ anions at van der Waals distances. This is the first reported platinum(II) complex containing both dppm and dppp ligands. Noticeable features are that the coordination of platinum by the differing dppm and dppp ligands produces a distorted coordination geometry with differing ligand bite angles (and to a lesser extent bond distances), and that the strain induced by the formation of the four-membered dppm chelate ring has a marked effect upon the bond angles at the P atoms of this ligand.     

2′-Methyl-3′-nitroflavone

The crystal and molecular structure of the title compound has been determined by direct methods and refined to a final R of 0.044. The compound crystallizes in space group P2₁/n with cell dimensions a = 16.681(2), b = 3.838(1), c = 20.550(4) Å, and β = 104.21(2)°. The phenyl and benzene rings of the title molecule are quite planar. The γ-pyrone ring exhibits maximum deviation 0.032(4) Å from planarity and makes a dihedral angle of 139.8(2)° with the 2-phenyl substituent.     

Approximate analytical solutions of a two-term diatomic molecular potential with centrifugal barrier

Approximate analytical bound state solutions of the radial Schr?dinger equation are studied for a two-term diatomic molecular potential in terms of the hypergeometric functions for the cases where q?≥?1 and q?=?0. The energy eigenvalues and the corresponding normalized wave functions of the Manning–Rosen potential, the ‘standard’ Hulthén potential and the generalized Morse potential are briefly studied as special cases. It is observed that our analytical results are the same with the ones obtained before.     

Perspectives of aerosol-photopolymerization: organic-inorganic hybrid nanoparticles

The technique of aerosol-photopolymerization is employed for the generation of organic-inorganic spherical polymer-matrix nanocomposites (PMNCs). The loading amount of well-distributed ZnO nanoparticles in polymer networks is varied in a broad range up to 40 wt.%. Similar hybrid particles are produced without the addition of a conventional photoinitiator by making use of the UV absorptivity of ZnO nanoparticles only. Highlights of the process are the continuous, aerosol-based setup with a flow-through photoreactor operated at ambient temperature and atmospheric pressure. Aerosol-photopolymerization possesses great potential of incorporating various materials in situ into a polymer matrix, resulting in hybrid materials for diverse applications. Furthermore, the process can be integrated with further unit operations for the design of smart materials.