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Novolac-phthalonitrile polymers bearing a controlled concentration of phthalonitrile groups were synthesized by condensation of novolac with 4-nitrophthalonitrile. The cure characteristics monitored by DSC and rheometry indicated acceleration of the cure reaction by the phenolic groups. Fourier transform infrared analysis of the cured products indicated that the cure mechanism was dependent on the extent of phthalonitrile substitution. In phenol-rich systems, evidence was obtained for the phenol-mediated reaction of nitrile groups resulting in the formation of isoindoline groups. The phthalonitrile-rich system underwent crosslinking through formation of triazine and phthalocyanine groups. The phenol groups in the phthalonitrile backbone were conducive to building a stronger interphase in their carbon composites, resulting in better mechanical properties. This was corroborated by morphological studies by SEM. However, these groups were detrimental to the thermal stability of the cured resins. The polymers exhibited very high flame retardancy which improved further on increasing the degree of phthalonitrilation. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Recent developments in the area of addition curable phenolic resins are reviewed. The article highlights the chemistry of addition-cure phenolic resins and discusses the different strategies involved in their molecular design. Structural modification through incorporation of thermally stable, addition curable groups on the novolac backbone is one strategy. The transformation of phenolic hydroxyl groups to addition curable functions forms an alternate approach. Cross-linking of novolac or its derivatives with a suitable curative also leads to addition-curable phenolic resin systems. This article examines the synthesis, characterization and curing of noted addition curable phenolic systems. Their thermal, physical and mechanical properties are discussed and the structure–property correlations examined. In selected cases, the adhesive properties of the systems have been examined. The review includes discussions on the properties of the composites in relevant cases. The systems discussed here include mainly allyl- and maleimide-functional phenolics, epoxy–phenolic, polybenzoxazine, bisoxazoline–phenolic, acetylene-functional and propargyl ether phenolics and phenolic-triazine. The relative advantages and demerits of these systems are discussed and their application potentials are considered. [Copyright &y& Elsevier]

Macro chain transfer agents based on mercaptan terminated-polymethyl methacrylate (macrothiol, PMMA-SH) were ob-tained by low-conversion free radical polymerization of methyl methacrylate in presence of 1,6-hexane dithiol as chain transfer agent. The chain transfer constant of 0.82 ensured good functionality and relatively narrow dispersity for the formed macrothiol. On increasing the conversion, the molecular weight of the macrothiol increased and its functionality decreased. A kinetic model was proposed which could satisfactorily explain these variations. Free radical polymerization of styrene in presence of PMMA-SH as chain transfer agent furnished the PS-PMMA diblock copolymer. Styrene exhibited a transfer constant (Ctr) of 3.37 for the macrothiol which was practically the same as that for 1,6-hexane dithiol for the same monomer. The length of polystyrene block in the copolymer decreased with increase in concentration of the macrothiol in the reaction medium. However, the block length was more than that theoretically expected which was attributable to the effect of diffusion controlled kinetics. The block copolymers were characterized by elemental analysis and by gel permeation chromatography using multiple detectors. Attempts to synthesize macrothiol of butyl acrylate and styrene and corresponding block copolymers were not successful due to secondary reaction during chain transfer in these cases. [ABSTRACT FROM AUTHOR]