Polar comonomer

Finally, the dielectric properties of a nonpolar polymer are modified by inclusion of even small amounts of a polar comonomer. In coatings applications the presence of polar repeat units in an otherwise nonpolar polymer reduces the tendency for static buildup during manufacture, printing, and ultimate use. On the other hand, in dielectric applications this increases the power loss and must be kept to a minimum, even to the exclusion of polar initiator fragments. 

A more polar comonomer, eg, an AN comonomer, increases the water-vapor transmission more than VC when other factors are constant. For the same reason, AN copolymers are more resistant to penetrants of low cohesive energy density. AH VDC copolymers, however, are very impermeable to ahphatic hydrocarbons. Comonomers that lower T and increase the free volume in the amorphous phase increase permeability more than the polar comonomers higher acrylates are an example. Plasticizers increase permeabiUty for similar reasons. 

In the organic phase (i.e., monomer + comonomer)-to-water ratio, the polar comonomer concentration in... 

Okamoto, M., Morita, S., Kim, H.Y., Kotaka, T. and Tateyama, H. 2001. Dispersed structure change of smectic clay/polyjmethyl methacrylate) nanocomposites by copolymerization with polar comonomer. Polymer 42 1201-1206. 

Linear, Random Copolymers of Ethylene and Polar Comonomers. 168... 

After five decades of catalyst research there is slowly emerging a family of discrete late transition metal catalysts that are capable of generating high molecular weight, linear, random copolymers of ethylene and polar comonomers such as acrylates. Further advances in the efficiency of these catalysts will likely give rise to new families of commercial polyolefins with a wealth of new performance properties imparted by the polar groups attached to the polymer backbone. 

The recent progress surveyed in this review shows the promise that late transition metal catalysts can provide in the production of new materials. We will continue our exploration of new catalyst design for the synthesis of new functional materials with unconventional topologies. Given the unique features of late transition-metal polymerization catalysts and further improvement in catalyst stability and activity for copolymerization with polar comonomers, the future of designing novel functional polymeric materials with late-transition-metal catalysts is very promising. 

In contrast, monolithic materials are easily amenable to any format. This has been demonstrated by using short monolithic rods prepared by copolymerization of divinylbenzene and 2-hydroxyethyl methacrylate in the presence of specifically selected porogens [93]. Table 2 compares recoveries of substituted phenols from both the copolymer and poly(divinylbenzene) cartridges and clearly confirms the positive effect of the polar comonomer. 

Berlin and coworkers (5,56) desired to obtain a material with an increased mechanical strength. They carried out a plasticization of bulk ami emulsion polystyrene molecular weight 80000 and 200000 respectively at 150-160° C, with polyisobutylene, butyl rubber, polychloroprene, polybutadiene, styrene rubber (SKS-30) and nitrile rubber (SKN 18 and SKN 40). The best results were obtained with the blends polystyrene-styrene rubber and polystyrene-nitrile rubber. An increase of rubber content above 20-25% was not useful, as the strength properties were lowered. An increase in the content of the polar comonomer, acrylonitrile, prevents the reaction with polystyrene and decreases the probability of macroradical combination. This feature lowers the strength, see Fig. 14. It was also observed that certain dyes acts as macroradical acceptors, due to the mobile atoms of hydrogen of halogens in the dye, AX ... 

The product design capability will expand to include polar comonomer incorporation. Copolymerisation of polar comonomers with a-olefins will alter the properties significantly and lead to materials with improved dye-ability and adhesion properties, as well as better compatibility with non-ole-finic polymers. In particular, the novel non-metallocene single-site catalysts, developed by Brookhart, Grubbs and others, are extremely tolerant to polar groups. 

There is an equilibrium between living chain ends which are attached to Nd and dormant chain ends which can be attached to Al, Mg and Zn. Very likely these chain ends exhibit differences in reactivity towards modification agents and polar monomers. This assumption will possibly result in the interpretation of inconsistent results observed in end-group functionalization and block copolymer formation, e.g. with polar comonomers such as e-caprolactone. 

A more detailed presentation of experimental data is presented in the talk. Here highlights are given for a few, well-chosen phase diagrams that summarize the effects of solvent quality, polar comonomer, and of cosolvents. 

The main advantages for the high-pressure process compared to other PE processes are short residence time and the ability to switch from homopolymers to copolymers incorporating polar comonomers in the same reactor. The high-pressure process produces long-chain, branched products from ethylene without expensive comonomers that are required by other processes to reduce product density. Also, the high-pressure process allows fast and efficient transition for a broad range of polymers. 

Polystyrene is one of the most widely used thermoplastic materials ranking behind polyolefins and PVC. Owing to their special property profile, styrene polymers are placed between commodity and speciality polymers. Since its commercial introduction in the 1930s until the present day, polystyrene has been subjected to numerous improvements. The main development directions were aimed at copolymerization of styrene with polar comonomers such as acrylonitrile, (meth)acrylates or maleic anhydride, at impact modification with different rubbers or styrene-butadiene block copolymers and at blending with other polymers such as polyphenylene ether (PPE) or polyolefins. 

The development of SAN was triggered by the idea of building a polar comonomer into polystyrene to improve its resistance to chemicals and to stress cracking. The relatively polar acrylonitrile presented itself as a suitable comonomer in this case. Styrene-acrylonitrile copolymers are further characterized by high rigidity and thermal shock resistance. Two parameters substantially determine the properties of SAN molecular weight and the proportion of acrylonitrile. 

Theoretical attempts to correlate permeation with properties of the various monomers have not been entirely successful. However, molar volume and polarity appear to be important properties, the smaller and more polar comonomers giving rise to less Oj-permeation. No data are available for vinyl bromide however, on the grounds of molar volume and polarity, it may be assumed that O -permeation in VBr is similar to that in VCl. 

Ethylene may be copolymerized with a range of other vinylic compounds, such as 1-butene, 1-octene and vinyl acetate (VA). These are termed comonomers and are incorporated into the growing polymer. Comonomers that contain oxygenated groupings such as vinyl acetate are often referred to as "polar comonomers." Comonomer contents range from 0 to 1 wt% for HOPE up to 40 wt% for some grades of ethylene-vinyl acetate copolymer. 

The range of suitable comonomers depends upon the nature of the catalyst or initiator. For example, Ziegler-Natta catalysts are poisoned by polar comonomers. Hence, commercial copolymers of ethylene and vinyl acetate are currently produced only with free radical initiators. However, some single site catalysts are tolerant of polar comonomers (see section 6.2.1). 

In Chapter 1, it was mentioned that highly branched low density polyethylene and copolymers made with polar comonomers are produced only by free radical polymerization at very high pressure and temperature. (All other forms of commercially available polyethylene are produced with transition metal catalysts under much milder conditions see Chapters 3, 5 and 6.) In this chapter we will review how initiators achieve free radical polymerization of ethylene. Low density polyethylene and copolymers made with polar comonomers are produced in autoclave and tubular processes, to be discussed in Chapter 7,... 

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