Several precursor polymer routes to poly(p-phenylenevinylene)4, poly[(2,5-dimethyl-p-phenylene)vinylene]10 and poly[(2,5-dimethoxy-p-phenylene)vinylene]15 are described. Base induced polymerisation of bis-sulfonium salt monomers afforded the polyelectrolytes 3 and 9 which were converted respectively directly into either polymer 4 or 10. Optimised conditions for the complete displacement of sulfonium groups by methanol to produce the corresponding methoxy precursor polymers 5, 11 and 17 are reported. The fully conjugated polymers obtained after heat and acid treatment of these precursors have been characterised and compared with those obtained via different precursor routes. The 1H NMR spectra of the precursor polymers, as well as IR and UV–VIS data of both the precursor polymers and the materials obtained after conversion into the poly(arylenevinylene)s are discussed.

Precursor route chemistry and electronic properties of poly(p-phenylenevinylene), poly[(2,5-dimethyl-p-phenylene)vinylene] and poly[(2,5-dimethoxy-p-phenylene)vinylene]

This review highlights the developments in the field of cation-exchange, anion-exchange, composite and thermally regenerable resins. The main focus is on the literature on synthesis and physico-chemical properties. Cation-exchange and anion-exchange resins have been discussed on the basis of the nature of monomers involved in the synthesis of polymeric matrices of the resins. Composite ion-exchange resins which incorporate inert materials and magnetic particles are discussed. The polymerization techniques adopted to synthesize thermally regenerable ion-exchange resins possessing the maximum possible thermally regenerable capacity are dealt with.

Synthetic ion-exchange resins

Sulfone-type crosslinks in sulfonation of macronet polystyrene backbone

Physical characterization of suspension- crosslinked polystyrene particles and their sulphonated products: 1. Nonionic networks

Friedel-Crafts crosslinking methods for polystyrene modification: 1. Preparation and kinetics

Slightly crosslinked polystyrene networks are preferable to linear polystyrene in commercial uses where increased thermal properties are favoured. A novel method of production of macrocrosslinked networks has been developed by reaction of polystyrene with mono- and difunctional derivatives of p-xylene, durene and oligomeric chains (n<10) thereof. The reaction system consists of a common organic solvent such as acetic acid or butyl acetate and a catalyst such as H2SO4 or HClO4; the reaction temperature varies between 60°C and 100°C. The degrees of crosslinking and thermal properties of the produced networks depend on the reaction system, the molar ratio of polymer to crosslinking agent and the reactivity of the functional groups; the gelation time varies between 3–12 hours for a fully crosslinked network. Promotion of the formation of regular structure networks without branches in the chains between crosslinks is achieved by the use of difunctional monomers, which favour the formation of linear polybenzylene chains between the polystyrene chains. Use of monofunctional monomers leads usually to branched and slightly crosslinked or grafted polystyrene. In both cases the regions of Tg and Tm increase up to 115°C and 350°C respectively as judged by DSC analysis. This novel crosslinking method has been also applied to crosslinking of copolymers of polystyrene and polymeric chains with aromatic structure in their backbone chain.



Die Gebrauchseigenschaften von leicht vernetztem Polystyrol sind denen von linearem Polystyrol vorzuziehen, wenn hohere thermische Stabilitat erforderlich ist. Eine neue Methode zur Darstellung makrovernetzter Polymerer wurde entwickelt, indem Polystyrol mit mono- und difunktionellen Derivaten von p-Xylol, Durol und deren Oligomeren umgesetzt wurde. Das Reaktionssystem bestand aus einem normalen organischen Losungsmittel wie Essigsiiure oder Butylacetat und einem Katalysator wie H2SO4 oder HClO4: die Reaktionstemperatur wurde zwischen 60 und 100°C variiert. Vernetzungsgrad und thermische Eigenschaften der erhaltenen Netzwerke hangen vom Reaktionssystem. dem Molverhaltnis von Polymerem zu Vernetzungsmittel und der Reaktivitat der funktionellen Gruppen ab. Die Zeit fur die vollstandige Vernetzung variiert zwischen 3 und 12 Stunden. Die Bildung von Netzwerken eineitlicher Struktur ohne Kettenverzweigungenzwischen den Netzstellen wird durch die Verwendung von difunktionellen Monomeren erreicht, die die Bildung linearer Polybenzylenketten zwischen den Polystyrolketten begunstigen. Der Einsatz von monofunktionellen Monomeren fuhrt normalerweise zu verzweigtem und schwach vernetztem oder gepfropftem Polystyrol. In beiden Fallen steigen die Bereiche fur Tg und Tm bis auf 115 bzw. 350°C. wie sich aus DSC-Messungen ergibt. Diese neue Vernetzungsmethode wurde auch auf Styrol-Copolymere und auf Polymere mit aromatischer Struktur in der Hauptkette angewandt.

Crosslinking of polystyrene by mono‐ and difunctional agents

A new method for the production of polydimethylbenzylenes,, involves the polycondensation of the mono- and dichloromethyl and mono- and diacetoxymethyl derivatives of p-xylene via an acid-catalyzed reaction in anhydrous acetic acid. The reaction of the difunctional derivatives is slower than the reaction of the monofunctional ones, leading to linear, predominantly crystalline, high-melting polymers with molecular weights of 2000–3000. Polycondensation of both monomers under different feed ratios leads to polymers with the same structure, and the monofunctional monomers condense with themselves more favorably than with the difunctional ones. Thus a head-to-head structure is preferred, and crystalline polymers of high structural purity are obtained.

Polycondensation of mono‐ and difunctional derivatives of p‐xylene

Polydimethylbenzylenes, , have been obtained by polycondensation of the monochloromethyl, acetoxymethyl, and methoxymethyl derivatives of p-xylene, via an acid-catalyzed reaction in anhydrous acetic acid and in 1-nitropropane In the highly ionizing solvent acetic acid, because of ionic depolymerization, chain growth takes the form of an equilibrating polycondensation, of a maximum number-average molecular weight of 2200 In the noninteracting solvent 1-nitropropane, the molecular weight distribution is more random, and soluble polymers of number-average molecular weight up to 3900 are formed The polycondensation reaction in 1-nitropropane is also initiated by perchlorate salts, in support of the suggestion of a “hot carbonium ion” propagation mechanism The results are explained by a cataionic polycondensation reaction, yielding crystalline “living polymers” of high structural purity

George N. Valkanas

Papers

Crosslinking of polystyrene by mono‐ and difunctional agents

Polycondensation of mono‐ and difunctional derivatives of p‐xylene

Aspects of the synthesis and the properties of linear poly‐2,5‐dimethylbenzylenes