Analytical applications of organized molecular assemblies

Organized molecular assemblies have great potential utility in many types of analytical method. This review is concerned with recent of micelles, reversed micelles and micro-emulsions in shifting acid-base equilibria, and in electrochemical measurements, ultraviolet-visible spectrophotometry, micellar-echanced phosphorimetry and fluorimetry, liquid-liquid extraction, flame and plasmas atomic spectrometry, and high-performance and thin-layer liquid chromatography.     

Effects of spiders’ predational delays in intensive agroecosystems

In this paper we develop a mathematical model for understanding the effect of time lags in the insect predation benefits for spiders in agroecosystems. Bifurcation of equilibria giving stable limit cycles are shown to occur as functions of the time delay.     

Ion trap tandem mass spectrometric identification of thiabendazole phototransformation products on titanium dioxide

The purpose of this study is to artificially produce degradation intermediates of thiabendazole, which could be reasonably similar to those really present in the environment. The formation of by-products from thiabendazole transformation has been evaluated by adopting irradiated titanium dioxide as a photocatalyst. Several species more hydrophilic than the thiabendazole have been identified and characterized by HPLC-multiple MS. A pattern of reactions accounting for the observed intermediates is proposed. Two different parallel pathways are operating (and through these pathways the transformation of the molecule proceeds) leading to several intermediate compounds. The main steps involved are: (1) the hydroxylation of the molecule on the aromatic ring with the formation of a species having [M+H]+ 218; a further oxidation leads to the ring-opening and to the formation of aldehydic and alcoholic structures ([M+H]+ 270, 268 and 152); and (2) the cleavage of a C-C bond and the formation of a species having [M+H]+ 119.     

Phase diagram and thermal and mechanical properties of isotactic polypropylene/hydrogenated oligo(cyclopentadiene) blends

The system formed by isotactic polypropylene (iPP) and hydrogenated oligo(cyclopentadiene) (HOCP) is investigated in order to study the influence of the composition and thermal history on the morphology, phase structure, miscibility and thermal and mechanical properties of the blends. A phase diagram presenting both the lower and the upper cloud point curves is proposed. It is shown that these blends assume different morphologies and consequently present diverse thermal and dynamic-mechanical behaviours depending on quenching processes from one-phase region or two-phase region. From the analyses of the results of optical microscopy, WAXS, DSC and DMTA techniques it is found that: blend films, quenched from the melt of one-phase region to room temperature, contain one amorphous phase and iPP in smectic form; moreover they are transparent and possess a reduced permeability to oxygen and aroma; conversely when the samples are quenched from the melt of two-amorphous phase region there is the formation of two amorphous phases (the iPP-rich phase and the HOCP-rich phase) and at room temperature the iPP crystallizes in the monoclinic α form.     

Tailored polymers by free radical processes

This paper describes a versatile and effective method for the control of free radical polymerization and its use in the preparation of narrow polydispersity polymers of various architectures. Living character is conferred to conventional free radical polymerization by the addition of a thiocarbonylthio compound of general structure S=C(Z)SR, for example, S=C(Ph)SC(CH₃)₂Ph. The mechanism involves Reversible Addition-Fragmentation chain Transfer and, for convenience of referral, we have designated it the RAFT polymerization. The process is compatible with a very wide range of monomers including functional monomers such as acrylic acid, hydroxyethyl methacrylate, and dimethylaminoethyl methacrylate. Examples of narrow polydispersity (≤1.2) homopolymers, copolymers, gradient copolymers, end-functional polymers, star polymers, A-B diblock and A-B-A triblock copolymers are presented.