فهرست مطالب سیدمحمدمهدی مرتضوی

Demand for the use of polymers in different industries with different properties is increasing. However, pure polymer does not have the ability to create a wide range of desired features. To solve this problem, various additives are used, many of which are minerals. The polar nature of these additives has made them impossible to use in non-polar polymers, such as polyolefins, due to the incompatibility and poor interface adhesion. Various methods are used to increase compatibility, one of which is the use of compatibilizers. Functionalized waxes are among the materials that researchers have studied over the years. The backbone of functional waxes is miscible with a polymer, and the functional groups on the wax surface can interact with the groups present on the additive surface. Therefore, their use improves the dispersion and distribution of additive particles in the polymer. Also, due to their low molecular weight, these waxes can penetrate the pores and capillaries on the additive surface and act as a successful co-compatibilizer. In this study, first, the methods of increasing compatibility and the cases used for this purpose are briefly reviewed. Then, the performance of functionalized waxes as a compatibilizer and co-compatibilizer and their effect on the physical, mechanical, and thermal properties of the polymer composites are investigated in details.

Poly(α-olefins) have non-polar structures and the development of polarity with different functionalities expands their application. The structure, number and size of the branches of the main chain affect the properties and design of new macromolecules. Active groups in α-olefin chains improve their interaction with silica nanoparticles. Furthermore, the amount of crosslinking changes the adsorption properties of hydrocarbon solvents.

The free radical copolymerization of 1-hexene and 1-decene with maleic anhydride was performed under different conditions. The structure and thermal properties of α-olefin (6 and 10 carbon) -maleic anhydride comb-like copolymers with different numbers and sizes of branches were investigated by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC) and thermogravimetric and differential thermal analysis (TGA/DTGA) methods. The effect of functionalized monomers of 2-ethylhexyl acrylate (2-EHA) and 3-chloro-2-methylpropene (3-C2MP) on the copolymerization reaction and their final structure was investigated. Polymerization reactions of styrene, maleic anhydride and 1-hexene were performed in the presence of silica nanoparticles. New hydrogels were synthesized with esterified poly1-hexene/ maleic anhydride with 2-decanol. The steps of nanohybrid and hydrogel synthesis and their thermal properties were characterized by FTIR and TGA/DTGA methods.

Various functionalized 1-hexane and 1-decen/ maleic anhydride comb-like copolymers with different molecular structures were synthesized and characterized. The results showed that by increasing the branch size of α-olefin from 4 to 8 carbons, the reaction conversion percent decreases and the branched of 2-EHA comonomer increases the reaction conversion. In the obtained nanocomposite, there is an interaction between maleic anhydride monomer and silica nanoparticles. Styrene/1-hexene/maleic anhydride nanocomposites containing 4 and 5.6% by weight of nanosilica were also synthesized. Structural design including functionalities and branch size, and also reaction conditions have a great influence on the properties of synthesized macromolecules and hydrogels.

During the last decades, multinuclear catalysts have captured the researcher's attention and also have shown impressive progress. The multinuclear catalysts such as metallocene-based complexes can be mono (homo) or multi (hetero) metallic(s). Albeit, reason and mechanism of the results from olefin polymerization and copolymerization in the presence of these catalysts are explained suggestively but a number of practical-theoretical studies confirmed cooperative effects between centers in relation to the structures. Among this class of catalysts, the sort of center and linkage are the main factors in comparison to their mononuclear analogs. Totally, the sort of catalyst center (active site), steric hindrance, electronic effects and inter-center distances can cause a variation in performance and catalyst behavior, producing polyolefin with different microstructure and properties. Moreover, such designed multinuclear structures exhibit the unprecedented levels of polyolefin branching, enhanced enchainment selectivity for functional and unfunctional α-olefin comonomers, enhanced polyolefin tacticity and molecular weight, modified chain transfer kinetics and LLDPE synthesis with a single binuclear catalyst and ethylene. In the following, diverse results of multinuclear metallocene-based catalysts are reported such as increasing or decreasing catalyst activity, average molecular weight, molecular weight distribution, stereospecific index, selectivity, content and type of branching or even maintaining catalytic and polymeric characteristics.

The effects of process conditions and their interactions on the catalyst activity in 1-hexene polymerization were studied with design of experiments by response surface methodology (RSM) using a commercial Ziegler-Natta (ZN) catalyst in the form of TiCl4/MgCl2/Di-n-butyl phthalate. The effect of different operational variables on the catalyst activity was examined by performing the primary experiments of 1-hexene polymerization. Among different operational variables, three variables including monomer concentration, polymerization temperature and cocatalyst/catalyst molar ratio (Al/Ti) were considered as the main parameters which affected the catalyst activity in the 1-hexene polymerization. The Box-Behnken model with three main parameters in three level responses for each factor was applied to analyze the parameter relationships. After demonstrating the reproducibility of the experimental results, the statistical analysis of experimental data showed that the monomer concentration and Al/Ti molar ratio affected the catalyst activity significantly. It was found that, at room temperature, by increasing the monomer concentration from 80.0 mmol to 239.9 mmol, the activity of the studied ZN catalyst increased from 75.2 to 265.1 gpoly(1-hexene)/gcat. In addition, by changing the Al/Ti ratio from 45.9 to 136.8, the catalyst activity increased from 145.2 to 265.1 gpoly(1-hexene)/gcat. The maximum activity of catalyst was obtained at the polymerization temperature around 25°C, and by increasing the temperature the activity of studied catalyst decreased. Based on the RSM, the best polymerization condition was obtained at a polymerization temperature of about 35°C, Al/Ti ratio of 136.8, and monomer concentration of 239.9 mmol, which resulted in maximum productivity of the catalyst.

Olefinic copolymers of ethylene/1-hexene were synthesized by three main types of supported catalysts, including Philips, Ziegler-Natta and metallocene catalysts, and the specific microstructural features delivered by each class of the catalysts were studied. The heterogeneity of comonomer distribution was studied by thermal fractionation using successive self nucleation annealing (SSA) as a novel method. It was observed that the comonomer incorporation ability decreased in the order of metallocene > Ziegler-Natta > Philips. The chemical composition distribution (CCD) of the produced copolymers was investigated by differential scanning calorimetry (DSC). Interestingly, we found that the copolymers produced by the directly supported metallocene catalyst possessed heterogeneous comonomer distributions, similar to the samples produced by Ziegler–Nata and Philips catalysts. The lamellar thickness distributions of the copolymers were calculated by the DSC curve deconvolution into a number of standard distribution functions. It was shown that the type of the supported catalyst did not affect the lamella thickness distribution to a discernible extent. The range of lamellar thickness was about 2-29 Å for the polymers produced using directly supported metallocene, Zigler-Natta and Philips catalysts, while the corresponding value for copolymers made by homogeneous metallocene catalyst was in the range of 2-7 Å. It could be concluded that in-situ supporting of metallocene catalyst increased the comonomer incorporation in a more homogeneous fashion. In addition, comonomer units were distributed more homogeneously at higher 1-hexene concentrations as could be realized from the approach of DSC index (DSCI) which showed that the DSC index moved towards unity at higher comonomer levels.

The bis (indenyl) zirconium dichloride catalyst was synthesized by a modified method at room temperature. Terpolymerization of ethylene، propylene and diene monomers were carried out using this metallocene catalyst under different conditions of different feed ratios of monomers، co-catalyst/catalyst ratios and polymerization temperatures. Methylaluminoxane (MAO) was used as a co-catalyst. The highest activity of catalyst was obtained at total pressure 4 bar، co-catalyst/catalyst ratio [Al] / [Zr] =600، polymerization temperature 60°C and E/P=67:33 and momomer feed ratio of 1700 kgEPDM/molZrh. The activity of catalyst showed bell-shaped behaviors versus co-catalyst/catalyst ratio ([Al] / [Zr]) and polymerization temperatures. The viscosity-average molecular weight (Mv) of terpolymers increased with increasing total pressure at different feed ratios of monomers. However، the viscosity-average molecular weight of terpolymers decreased at higher co-catalyst/catalyst ratios ([Al] / [Zr]) and higher polymerization temperatures. The increases in propylene and diene monomers in the feed ratios decreased the catalyst activity and viscosity-average molecular weight of terpolymers. The ratio of maximum average rate of terpolymerization to an average rate of terpolymerization at the end of the polymerization (DI) for different terpolymerization conditions was relatively high; an indication of the decay kinetics for this type of metallocene catalyst. Increasing the co-catalyst/catalyst ratio up to [Al] / [Zr] = 500 increased the Et% and ENB% in the final obtained polymers. However، increasing the polymerization temperature، diene and propylene concentrations in the feed ratio decreased the Et% and increased the ENB% contents in the final obtained polymers. Tg of the final terpolymers was between -64 and -52°C. The study on microstructures of some polymer revealed block type of chain microstructures.