Polyolefins polar functionalities

A long-standing goal in polyolefins is the synthesis of polymers bearing polar functional groups such as acrylate, esters, or vinyl ethers, etc [24,40]. These copolymers might endow polyolefins with useful properties such as adhesiveness, dyeability, paintability, and print-ibility. Advances have recently been made in polymerizing polar monomers with cationic metallocene catalysts... 

As mentioned, polymer hybrids based on POs are effective as a compati-bilizer between the olefinic materials and polar ones. Furthermore, some polymer hybrids, such as PP-g-PMMA, etc., show good mechanical strength as polymer materials. On the other hand, surface modification of the molded polymer is one of the most attractive methods to let polyolefin materials functionalize. In this sense, surface polymerization of functional monomers on polyolefins is an important subject for polyolefin hybrids. As previously referred to, the growth of PS on PP via the RAFT process has been reported [92]. 

The second article by Kawahara and his coworkers focuses on polyolefin (PO)-based hybrid materials (POH), in view of their synthesis, structures, and properties. POs are currently the most widely and conveniently used polymeric materials as recognized by the production amount of over one hundred million tons annually in the world, due to the cheap price yet good properties. They are basically hydrocarbon polymers, and hence hydrophobic and less polar. These basic properties are to be modified by introducing a polar function for a wider use in practical applications. Preparation of POHs is one of the best ways to... 

Just as polydienes and polyolefins have been modified in solution, they have also been surface-modified. For example, polar functional groups have been introduced to syndiotactic 1,2 polybutadiene surfaces by photolytic addition of thiols, as well as treatment with aqueous permanganate. Such si ace functionalization leads to changes in wettability, as evidenced by contact angle measurements. Furthermore, the surface functionalization can be reconstructed upon heating. In turn, polyolefins have been surface modified by oxidation, chlorination, sulfonation, etc. °... 

PMMA is slightly affected by the addition of layered silicates in a wide temperature range below and above Tg. On the other hand, copolymers of methyl methacrylate (MMA) with small amounts of polar monomer show a significant increase in the storage shear modulus, G [Okamoto et al 2001]. It could be assumed that the increased polymer polarity results in better interaction with the silicate surface. This view is supported by a study performed on the effect of sulfonation of PS chains on their ability to interact with silicate. The need to provide polar functionality for PS originates in the observation that the Tg value of PS-based CPNC increases with the degree of sulfonation at a constant silicate content [Mauritz et al., 2004]. As suggested by Kawasumi et al. [1997], silicate layers, even those modified by nonpolar alkyl chains, are polar and thus immiscible with nonpolar polymers such as polyolefins (POs). 

As a compatibilizer, a polyolefin modified with polar functional groups, in an amount of between 5-10% may be added. 

However, this task becomes more challenging with polyolefins, and it is generally necessary to have some polar functionality present, most commonly by inclusion of MA grafted polymer in the composition (typically at a 5% polymer addition level) [114], Aco-rotating twin-screw extruder is frequently recommended for this purpose, however the form of screw profile used and feed location of the components, can influence the structure and properties of compounds produced [115]. For example, it was reported that combined dosing of polymer and filler at the feed end of the extruder gave better intercalation than downstream addition of the clay. 

Another great challenge in polyolefin technology has been the production of polyolefins with polar functionalities. The most advanced method for producing functional polyolefins, in addition to free radical reactions and grafting reactions, is copolymerization with co-ordination catalysts. 

Beyond unfunctionalized olefins, 65 is also capable of polymerizing olefin monomers that incorporate polar functional groups. Coates and coworkers synthesized polyolefin elastomers by addition of small amounts of ureidopyrimidone (UP) functionalized hexene to polymerizations of 1-hexene (Rieth, Eaton, and Coates, 2001). Polymers incorporating 2% UP-functionalized monomer were obtained with narrow molecular-weight distributions = 1.2-1.4). The resultant polymers exhibited reversible, noncovalent... 

The incorporation of highly polar functional groups such as carboxylic, sulfonic and phosphonic acids produce materials that prove difficult to make industrially. These precision polyolefins are not only useful models in understanding stracture and property, but also attractive in advanced applications such as precision ionomers, biomedical materials, and membrane technologies. 

Surface tension, 7, is a key parameter in describing a surface. It is defined as the reversible work associated with the creation of truncated bonds and molecular conformations that occur at the surface (outside of the bulk). For any given material, the Uterature typically offers a range of values for y, which is a testament to the experimental and theoretical complexities of its determination. Table 9 hsts one compilation of the surface energies of common polymers, both the composite value and the breakdown by polar/nonpolar interactions. Fluorocarbons and polyolefins are quite low in polar functionality and thus have... 

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