Frequent seizures and polytherapy are associated with lower QOL in persons with epilepsy.

Phthalonitrile polymers are known for their high thermal stability and good mechanical properties. However, their brittle nature limits their application as structural composites in many critical areas. The present study investigates the feasibility of toughening novolac-phthalonitrile (NPN) resin using chemically modified poly(ether ether ketone) (PEEK). A telechelic PEEK bearing a phthalonitrile end group (PEEKPN) was synthesized via nucleophilic substitution of nitrophthalonitrile with the corresponding phenol-telechelic poly(ether ether ketone) (PEEKOH). Different compositions of NPN and PEEKOH-PEEKPN blends with curing agent, i.e. diaminodiphenylsulfone, were investigated for their cure behaviour and mechanical properties of their carbon fabric composites. In NPN-PEEKOH blends, crosslinking of the phthalonitrile groups was facilitated by phenol-mediated reactions resulting in the reduction of cure temperatures by around 130 ∘ C with substantial improvement in thermal stability. Blending the resin with the thermoplastic enhanced the mechanical properties of the composites. The apparent flexural strength and impact strength of carbon fabric-reinforced composites were improved by more than 200 and 150%, respectively, on incorporation of 20 wt% PEEKOH in the NPN matrix. However, higher concentration of PEEKOH had a detrimental effect on the properties. Substitution of phenol end groups by phthalonitrile moieties led to integration of the PEEK moieties with the NPN matrix. However, it was not as conducive as PEEKOH for improving the matrix properties. The better performance of PEEKOH is attributed to the formation of polar heterocyclic groups like isoindoline by way of the phenol-nitrile reaction.

The intrinsic viscosities [η] and viscosity constants of high molar mass poly(acrylonitrileco-itaconic acid) copolymer in DMF were obtained by the methods of Huggin, Fuoss, Martin and Schulz-Blaschke. The values of [η] by averaging procedures suggested by Sakai were close to those from Huggins method. There was an abnormal positive deviation from the rectilinearity of the reduced viscosity (η red ) versus concentration (c) plot in all the cases in the dilute regime, which was attributed to the polyelectrolytic effect. This was further confirmed by the analysis by Fuoss method. The deviation from the Huggins dependence is discussed for a good solvent (DMF) alone and in the presence of a non-solvent, methanol. The deviation cross-over points c and c changed with molecular weight, and the concentration range greater than c and less than c * was taken for a more reliable determination of intrinsic viscosity. The non-solvent played a key role in determining the polymer-polymer interactions. The Huggins coefficient increased and the cross-over points c and c shifted to higher concentration regime as the mixed solvent became poorer. The inter-and intra-polymer interactions increased in the presence of methanol. In poor solvent, the enhanced intramolecular interactions caused the polymer to shrink in size, causing a reduction in [η] and hydrodynamic volume.

Polyacrylonitrile terpolymers of various compositions consisting of acrylonitrile (AN), itaconic acid (IA) and methyl acrylate (MA) were synthesized by solution polymerization in dimethylsulfoxide. Increase in concentration of either IA or MA retarded the overall polymerization rate and the polymer molecular weight. The system consisting of AN + MA and varying IA concentration was more prone to retardation in comparison with the system composed of AN + IA with variable MA concentration. The retardation factors were quantified. Minor quantities of MA boost the reactivity of IA in the terpolymer system. The terpolymer was richer in MA vis-à-vis the feed. The thermal characteristics of the terpolymer were examined as a function of its composition. In contrast to the copolymer of AN and IA requiring 1-1.5 mol% IA, the terpolymer required an IA content of approximately 2.5 mol% for optimum thermal stability. The polymer with 90 mol% AN, 2.5 mol% IA and 7.5 mol% MA exhibited reasonably good charforming characteristics and thermal stability. The overall crystallinity and crystallite size of the polymers were found to decrease on incorporation of the comonomers. The 'aromatization index' of the copolymer increased with the temperature of pyrolysis through re-organization of the tetrahydropyridine ladder structure.

The very high dope viscosity of concentrated dope of poly[acrylonitrile-co-(methyl acrylate)-co-(itaconic acid)] (with M v = 10.67 × 10 5 g mol −1 ) in DMF could be diminished significantly by the addition of oxalic acid (OXA). The change in steady shear rheological behaviour caused by OXA has been analysed for the dope using a rheometer working in the viscosity mode. The temperature dependence of η 0 conformed to the Arrhenius-Frenkel-Eyring equation. G v decreased marginally with OXA concentration, and the least value was observed at an OXA concentration of 0.63 % by weight. Shear thinning behaviour was observed under higher shear rates for the terpolymer solutions in the presence and absence of OXA. The pseudoplasticity index (n) showed an abrupt initial increase on addition of OXA. The OXA concentration of 0.63 % by weight was advantageous for decreasing the viscosity of the polymer dope. The reduction in viscosity is attributed to the disturbed polymer-polymer interactions by way of H-bonding of OXA with the polymer. OXA-containing dope at higher shear rate could achieve very low viscosities.