S. M. Mokhtar

The Synthesis Characterization and Polymerization of Novel Thiophene Substituted Maleimide

Ethyl 2-amino 4,5,6,7-tetrahydrobenzo thiophene-3-carboxylate maleimide (ETTCM) has been synthesized and investigated as a new thio-maleimide derivative. The structure of the prepared compounds has been elucidated by elemental and spectral analyses. The free radical polymerization of (ETTCM) has been conducted in several solvents using azobisisobutyronitrile (AIBN) as an initiator. The kinetic parameters of polymerization of ETTCM were investigated, and it was found that the polymerization reaction follows the conventional free radical scheme. The initial rate of polymerization, the overall activation energy Ea was determined (Ea = 57.013 kJmol−1) and intrinsic viscosity was measured ([η] = 0.04 dl/g). The prepared polymer is a good chelating agent with some metal ions and a moderate antifungal and antibacterial effect. The monomer reactivity ratios for the copolymerization of ETTCM with methyl methacrylate MMA, vinyl acetate VA, and vinyl ether VE were calculated by two methods, the Kelen-Tüdös and a nonlinear method. Thermal stability of the ETTCM polymers and copolymers were investigated by thermogravimetric analysis.

Dielectric relaxation of poly(tetrafluoroethylene–perfluorovinyl ether) films

Dielectric constant and dielectric loss have been studied for poly(tetrafluoroethylene–perfluorovinyl ether) (PFA) films over a wide temperature range in the frequency range 0.1–100 kHz. Two relaxation peaks were observed, one at room temperature (αa-relaxation) and the other in the range 170–140 K (β-relaxation), with activation energies of 143·2 and 16·4 kcal/mol, respectively. The β-absorption is attributed to the short segmental local mode motion of the main chains. The αa-relaxation can be interpreted as due to large-scale conformational rearrangement. The Cole–Cole diagrams are given at different temperatures and the distribution parameters (ϵ0–ϵ∞) and (1–α) of the relaxation times were calculated. The X-ray diffraction pattern of PFA shows both a diffuse halo and sharp reflections, characteristic of amorphous and crystalline phases of conventional semicrystalline polymers. Also, no evidence of crystallinity in the films due to thermal treatment during dielectric measurements was observed. IR spectra revealed the absence of any new peaks after the heat treatment.

Some investigations and characterization of radiation-initiated graft polymerization onto fluorinated copolymer

Preparation of a good hydrogel supported on a fluorinated polymer film has been achieved by means of simultaneous radiation-induced grafting of N-vinyl-2-pyrrolidone (NVP) onto (tetrafluoroethylene-perfluorovinyl ether) copolymer (PFA). The conditions at which the graft polymerization proceeded with a suitable yield were determined. Ammonium ferrous sulphate (Mohrs salt), as an inhibitor, failed to inhibit the homopolymerization of NVP during the radiation grafting process. In contrast, the addition of Cu2Cl2 (0.5 wt%) effectively inhibited the homopolymerization process and smooth grafted films with suitable grafting yield were obtained. The grafting onto PFA films, which scarcely swell in any solvent or monomer, was critically controlled by the diffusivity of reactants through the grafted layers initially formed near the film surface. The addition of ZnCl2 (3 wt%) to the monomer solution slightly enhanced the grafting and much smoother grafted films were obtained. The dependence of initial rate of grafting on NVP concentration was of the order 0.54. The graft copolymer possessed good mechanical properties and high thermal and chemical stability. Such non-ionic supported hydrogel on fluorinated polymer may be of interest for some practical use in which high electrical conductivity is not required, as in biomaterials.

Study on non-ionic membrane prepared by radiation-induced graft polymerization

The preparation of good hydrogel supported on polymeric material was carried out by means of direct radiation-induced graft polymerization of N-vinyl-2-pyrrolidone (NVP) onto low density polyethylene films (LDPE). The optimum conditions were determined, at which the grafting process occurred and suitable degrees of grafting were obtained with a homogeneous distribution of the graft chains throughout the polymer. The effect of different inhibitors, addition of ZnCl2 and monomer concentration on the grafting yield was also studied. Some investigations and characterization on the prepared graft copolymer were investigated and the possibility of its practical use was discussed. Mechanical properties, thermal and chemical stability and hydrophilic properties of such prepared grafted films showed a great promise in some practical applications.

Radiation-induced grafting of acrylic acid and vinyl acetate monomers onto heavy-duty poly(ethylene-vinyl acetate) films

The preparation of graft films was carried out by direct radiation-induced graft polymerization of acrylic acid and vinyl acetate comonomer onto heavy-duty poly(ethylene-vinyl acetate) films. The effect of various comonomer compositions on the degree of grafting was investigated. The characterization and some selected properties of the graft copolymers prepared were studied. Thermal stability, mechanical and electrical properties of the films showed great promise for some practical applications.

Study on acrylamide-vinyl pyrrolidone copolymer

SummaryThe solution copolymerization of acrylamide (AAm) with N-vinyl pyrrolidone (NVP) was investigated using azobisisobutyronitrile (AIBN) as an initiator at 60°C. The study was performed by measuring the rate of the copolymerization reaction, the molecular weights and by determining the monomer reactivity ratios. In addition, the thermal properties (thermal conductivity, thermal diffusivity and volumetric heat capacity) of the resulted copolymers in aqueous solutions were investigated at various temperatures. The kinetic results and the apparent reactivity ratios indicate that NVP is more reactive than AAm towards the copolymerization process. The values of the thermal properties whowed that the behaviour of such parameters depend on the polymer concentration, the temperatures and the content of vinyl pyrrolidone in the copolymeric chains.