Iranian polymer journal
Volume:14 Issue: 10, 2005

Using methyl 4-nitrobenzenesulfonate as an initiator and o-dichlorobenzene as a solvent, decenyl (D) and heptyl (H) oxazolines monomers in ratio of 20/80 were copolymerized. Substitute oxazolines via ring opening copolymerization resulted in a random DH copolymer with a degree of polymerization of 100. Solution copolymerization as living cationic system is very sensitive to the presence of any trace of water in reaction vessel. Narrow molecular weight distribution was obtain by using purified chemical agents and well controlled copolymerization reaction. The copolymer can be considered as the poly(N-acylethylenimine)s with allyl pendant groups randomly attached to the far end of their polymethylene side chains. Chemical structure and moleculare wieght of the polymer were characterized by NMR and GPC.

Rice straw after exraction with organic solvents was subjected to benzylation and acetylation reactions. Products of mentioned reactions were characterized by their FTIR and 1H NMR spectra. Thermal stability of products were evaluated by TGA thermograms and it was observed that the thermal stability of products was higher than that of starting materials. Thermoplastic behaviour of products was characterized by TMA thermograms and it was observed that the thermoplasticity of products was higher than that of starting materials. As a second pretreatment, rice straw was hydrolyzed. Then it was subjected to benzylation and acetylation reactions. FTIR and 1H NMR spectra of products were recorded. TGA and TMA thermograms of products show that they havehigher thermal stability and thermplasticity in comparrison with starting materials.

Acrylic acid and methacrylic acid hydrogels were prepared by N,N’- methylene bis acrylamid as a cross-linking agent in aqueous solution. The rate of swelling of prepared hydrogels in different buffers were studied and their molar mass and density of cross-linking were determined. The results indicated that at higher pHs, the acrylic acid hydrogels have higher degree of swelling than the methacrylic acid hydrogels. The complex formation between polyethylene glycol and either of acrylic and methacrylic acid hydrogels at various pHs were also studied. It was found that methacrylic acid hydrogelscan form stronger complexes with polyethylen glaycol, than acrylic acid hydrogels, and the acidic pHs promote the complex formation. However the complexed hydrogels indicated lower degree of swelling.

UV radiation of polymers causes photo-oxidation degradation which results in loss of physical and mechanical properties and limits their applications. In order to study long term stability of the radiated cross-linked polyethylene films on outdoor exposure, low density polyethylene (PE) in pure form mixed with photostabilizers and antioxidant (PE-st) was irradiated by electron beam in air at 30-300 kGy doses. The irradiated samples were exposed to the outdoor condition for 24 months.The gel content of irradiated samples demonstrated that cross-linking reaction has occurred and caused the increasing of mechanical properties. The results of FTIR measurments show that upto 200 kGy carbonyl formation is negligible. Increase of carbonyl groups and decrease of mechanical properties in irradiated and outdoor exposed samples are indication of degradation progress in cross-linked polymer structure. In addition, some of the irradiated samples were buried under the soil. Observation of unchanged chemical structure of buried samples after 24 months, proves that UV light and oxygen are the main factors of their degradation.

Mixing and injection processes of polycarbonate and ABS (acrylonitrile-butadienestyrene) blend were studied in order to optimize the impact strength. Mixing time (rotation speed) and temperature were selected as the main mixing process factors. In the course of injection step, temperature and pressure of injection, and mould temperature were chosen as process factors and blend composition was selected as material factor. The Taguchi orthogonal array was applied to determine the significance level of each factor. An experimental model was developed to predict and optimize the impact strength. Based on the analysis of variance (ANOVA), blend composition, mixing time, and temperature, and mould and injection temperatures, had more effect on impact strength of the blend, respectively. However, injection pressure has no significat effect. Then, the level of each factor for maximum impact strength was determined. The validation test approves the result. Hence, the model is suitable for PC/ABS part design with desired impact strength.

Hydroxymethylated carbon black (HCB) was graft-copolymerized with methyl acrylate in an alkali solution, using potassium diperiodatocuprate (III) (DPC) as an initiator. The dependence of grafting parameters on temperature, time, monomer and initiator concentrations, and the volume ratio of water/dioxane were investigated. It was found that the grafting parameters were relatively higher than those by other methods, indicating that DPC-CB-OH redox pair was an efficient initiator for this grafting. The proof of grafting was obtained from infrared spectra. It was confirmed by transmission electron and scanning electron microscopies, and ultraviolet visible spectrophotometery techniques that the graft HCB has much better effect on dispersability and consistancy of copolymer than the carbon black (CB). At the same time we blended the graft HCB with PVC and improved its impact strength.

Low molecular weight Friedel-Crafts polyetherketones were synthesized from pchloroanisole, 1,4-phenylenedioxy diacetylchloride, chloroacetylchloride, 1,2-dichloroethane, and dichloromethane in the presence of anhydrous aluminium chloride and carbon disulfide. The polymer samples were characterized by IR spectral study. The percentage of chlorine content of the resins was determined by the method of Carius.The molecular weights and polydispersities of the resins were obtained by gel permeationchromatography. Thermogravimetric analysis and differential scanning calorimetry wereemployed to study the thermal properties. All the polyetherketones were tested for theirbiological activity against bacteria, fungi, and yeast. It was observed that polyetherketonescould inhibit the growth of the microorganisms to a considerable extent.

Anew class of optically active poly(amide-imide-urethane)s (PAIUs) was synthesized via one-step diisocyanate route under microwave irradiation. 4,4’-methylenebis-(4-phenylisocyanate) (MDI) was reacted with bis(p-amido benzoic acid)-Ntrimellitylimido- L-leucine (BPABTL) and polyethyleneglycol-diols (PEG)s to furnish a series of new PAIUs. The effect of different reaction conditions such as irradiation power, irradiation time, reaction solvent, soft segment length, and reaction catalysts as well as no catalyst condition were investigated. Also, the possibility of the synthesis of modified thermoplastic polyether urethanes by introducing the imide and amide functions in the polyurethane (PU) backbone was explored. The resulting multiblock copolymers haveinherent viscosities in the range of 0.09-0.63 dL/g. These copolymers are optically active,thermally stable and soluble in amide-type solvents.

Prodrugs of β-cyclodextrin (β-CD) conjugated with nonsteroidal anti-inflammatory drugs such as ibuprofen and indomethacin were prepared under mild conditions by two different routs. In the first procedure, β-CD was either reacted with ibuprofencarboxy chloride or treated with ibuprofen in the presence of dicyclohexylcarbodiimide (DCC). Also conjugated β-CD-indomethacin was prepared via reacting of β-CD with indometacin in the presence of DCC. In the second procedure, acid terminated poly (ethyleneglycol) (PEG, Mw = 600) was connected to the β-CD in the presence of DCC andthe resulted polymer reacted with ibuprofen. In the similar reactions, β-CD was linked toPEG then ibuprofen and indomethacin simultaneously reacted with resulted polymer. Thehydrolysis of drug-polymers was carried out in the aqueous buffer solutions in pH 1, 7.4,and 8 at 37oC. The quantity of hydrolyzed drugs was determined by using UV spectrophotometer.