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Abstract:New approaches to organo-transition-metal catalyzed-polymerizations of methyl methacrylate

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Summary: A new class of melt blend material was prepared by extruding a mixture of 3‐aminopropyltriethoxysilane (APTES), maleic anhydride‐grafted poly(propylene) (PP‐g‐MA) with different molecular weight and MA content and poly(propylene) powder produced with a TiCl3‐based catalyst (PP‐A). A suitable selection of PP‐g‐MA provided extremely high melt strength (MS) of resultant blend materials. Such a superior melt property was caused by the synergy between the present melt reaction and the higher molecular weight portion containing PP‐A. The gel content measurements of typical blend materials and PP‐g‐MA/APTES blends indicated that an excessive amount of inert PP suppresses the formation of gels. The reaction between PP‐g‐MA and APTES was then investigated by analyzing crystalline polymer fractions separated from the atactic PP/PP‐g‐MA/APTES and atactic PP/PP‐g‐MA blends. The FT‐IR analysis of the fractions revealed that the NH2 group in APTES readily reacts with MA grafted on PP and the reaction leads to the formation of imide linkage. Moreover, the GPC analysis of the fraction showed that higher molecular weight polymers were formed in the presence of APTES. Since a trace amount of water surely produces in the vicinity of active silyltriethoxy groups during the reactive extrusion, such polymers were formed by the condensation between hydrolyzed APTES‐grafted polymer chains. These results led us to the conclusion that long‐chain‐branched PP (LCB‐PP) was certainly produced and its formation is essential for the increase in MS of the present blend materials.Relationship between log(MS) and log(MFR) for PP/PP‐g‐MA/APTES and commercial PP resins.magnified imageRelationship between log(MS) and log(MFR) for PP/PP‐g‐MA/APTES and commercial PP resins.

Low-melting point polypropylene prepared with metallocene catalysts was modified with maleic anhydride and acrylate monomers. The degree of modification depends on the tacticity of the base polypropylene. Low-melting point polypropylene can be easily modified compared to high isotactic polypropylene. The reason came from the low crystallinity of the lowmelting point polypropylene and the random arrangement of methyl groups. The base polymer molecular weight was almost constant at the low temperature modification condition. Polypropylene is one of the most common materials used in various industrial fields. The material is mainly used in nonpolar systems, but is unsuitable for use with polar materials such as polar polymer, glass, or metal.To use polypropylene with polar materials, free-radical reactions with unsaturated monomers, such as maleic anhydride or acrylic acid derivatives are often used.1-20 Polypropylene is partly polarized by this method, and can be utilized in many products, such as adhesives, 19 coatings, improvement materials for polar polymers, 20 master batch 21 for inorganic materials, and colors. However, the characteristics are limited considering the use of polypropylene from the conventional catalyst system. Isotactic and atactic polypropylene are mainly used for industry, and some fields like adhesives utilize atactic polypropylene for its low melting point and high fluidity. An effective method to change the properties of base polymer over a wide range is to use metallocene catalyst.Some metallocene catalyst systems are formed using a combination of a co-catalyst and a transition metal compound having a cross-linked structure with two cross-linking groups and offer a characteristic structure. 22 Homo polypropylene obtained from the catalyst system has middle-range tacticity, and shows a low melting point under 100C. The conventional catalyst system can also offer low melting point polypropylene by lowering its tacticity and by copolymerization. However, in this case, low molecular weight polymer and atactic polymer are provided, and often have adverse effect on the mechanical properties of the polymer. These adverse-effect components do not appear in metallocene catalyst systems. This catalyst system gives polypropylene ranging from low-molecular weight to high-molecular weight. Therefore, various application ranges may be expected from metallocene type polypropylene.This polymer also has non-polar characteristics, and can be modified with unsaturated monomers for wide-range utilization. As this polymer has low melting-point and high solubility, different reaction systems can be used to obtain the modified polypropylene. Especially this polymer is useful for research of modification mechanism. Many papers deal with the modification of isotactic 6-14 and atactic polypropylene, 15-18 but tacticity effect is not considered because of the difference of molecular weight. And broad molecular weight distribution and un-uniform tacticty further make difficult to understand the effect of tacticity...