Comonomers reactivity

To identify catalysts with this type of difference in comonomer reactivity, we performed copolymerizations of ethylene and 1-octene at relatively high f2. Several different families of catalysts were evaluated under these conditions. The resulting copolymer... 

To demonstrate this technology, we targeted a copolymer with blocks of both high density polyethylene (HDPE, density 0.94 g cm 3) and very low density polyethylene (VLDPE, density -0.88 g cm 3). Process and product characterization details are given in Table 6. We chose the pyridylamide precatalyst 18 [41] for this study due to its high comonomer reactivity, high M°, and demonstrated CCTP ability. 

These structures are fictional in the sense that these sequences do not correspond to the actual statistical polymerization based on the comonomer reactivity ratio, although it was said that the results have significance with respect to Nafion structural optimization and guidance in the search for Nafion replacements. Also, the non-insignificant degree of crystallinity of Nafion was not accounted for in the model. 

After the demonstrations of preparation of stereoregular polymers having novel properties by means of special ionic methods, die possibilities of free radical methods were examined extensively. It must be concluded that in free radical systems the structures of homopolymers and copolymers can be little influenced by specific catalysts and other reaction conditions, but are determined largely by monomer structure. This is consistent with the relative uniformity of comonomer reactivity ratios in radical copolymerizations. However, it has been found possible to obtain somewhat more syndiotactic structure, dldl. than normally obtained by radical reactions, at low temperatures and by selecting solvents. Examples are polyvinyl chlorides of higher than usual crystallinity from polymerizations at low temperature e.g.. —50°C under ultraviolet light... 

From comonomer reactivity ratios, Wall (15) observed that certain critical monomer compositions were possible which he designated co-... 

The different reactivities of the olefins are important for the copolymerisation. The comonomer reactivity ratio, rj, in copolymerisation with ethylene appears to decrease with increasing steric hindrance around the double bond in the a-olefin in to the following order [250] ethylene > propylene > 1-butene > linear a-olefin > branched a-olefin. 

The copolymer composition is a function of the comonomers reactivities. For example, the carborane concentration in a poly (diene-co-acryloyloxymethyl carborane) is higher than that of the carborane monomer in the initial solution 20>. Chloroprene, which has a higher reactivity than the other monomers, is an exception. 

Otherwise, the method can be very misleading it failed badly when published data from certain copolymerizations were scrutinized by a specially developed analytical method for copolymerization data (52, 53). For these reasons, any published data on copolymerization reactivity ratios must be approached with caution, and the reader should be assured that the criteria just mentioned have been properly met. These precautions are especially true for siloxane copolymerizations, because reversibility can be established quickly, and rapid redistribution of comonomer units between rings and chains via equilibria 2 and 3 will confound any meaningful study of comonomer reactivity ratios. 

As mentioned in Chapter 1, ethylene is always the more reactive olefin in systems used to produce copolymers involving a-olefins (LLDPE and VLDPE). An important process consideration for copolymerizations is the reactivity ratio. This ratio may be used to estimate proportions needed in reactor feeds that will achieve the target resin. However, fine tuning is often required to obtain the density or comonomer content desired. Reactivity ratios were discussed previously (Chapter 2) in the context of free radical polymerization of ethylene with polar comonomers. Reactivity ratios are also important in systems that employ transition metal catalysts for copolymerization of ethylene with a-olefins to produce LLDPE. Discussions of derivations and an extensive listing of reactivity ratios for ethylene and the commonly used a-olefins are provided by Krentsel, et al. (1). 

Another aspect of free radical polymerizations under pressure which has been recently studied is the effect of pressure on comonomer reactivity ratios (5). In two copolymerization systems—styrene-acrylonitrile and methyl methacrylate-acrylonitrile—it was found that the product of the reactivity ratios, rif2, approaches unity as the pressure is increased. The monomer-polymer composition curves for these two copolymerizations at 1 and 1000 atm. are illustrated in Figures 1 and 2. The effect of pressure on the individual reactivity ratios and on the fit2 product is given in Table II. 

Simple propagation models discussed earlier fail to provide good fits when there is compositional heterogeneity in the polymer structure because of different comonomer reactivity ratios or deviations from the statistical combinations of comonomer placements on polymer chains. To overcome these drawbacks. 

Copolymerization of lactones allows the tuning of polymer properties while introducing new challenges to enzyme-catalyzed ROP such as understanding relationships between comonomer reactivity ratios, transesterification and copolymer microstructure (Scheme 4.20). 

During batch copolymerization, composition may drift with conversion because of differences in comonomer reactivity and can result in less valuable... 

Uses Monomer for creating and modifying polymers, acrylic resins, urethane methacryiates marine antifouling paint resin comonomer reactive comonomer for acryiic and S/B resins rubber modifier binder for textiies/paper adhesives, nonwoven fabrics, enamels, adhesives grafting of textiie fibers scaie inhibitors adhesion promoter for polymers hydrophilic polymers It.-curing polymer systems reactive thinner for radiation curing food-pkg. adhesives, polymers Manuf./Distrib. Acros Org. Aldrich Allchem Ind. Ashland BP Amoco Electron Microscopy Sciences Fluka ICN Biomed. Research Prods. Kessler Lancaster Synthesis Laporte Perf. Chems. Monomer-Polymer Dajac Labs Pfaltz Bauer Rohm Haas Rohm Tech San Esters Scientific Polymer Prods. Sigma TCI Am. Ubichem pic Whyte Chems. Ltd... 

N- Vlnyl-2-pyrrolldone comonomer, reactive acrylate resins... 

Hydroxyethyl acrylate, Itaconic acid comonomer, reactive S/B resins 2-Hydroxyelhyl methacrylate comonomer, reactive vinyl acetate 2-Hydroxyethyl acrvlate comonomer, refinisning paints Mhoromer AM 414 Mhoromer AM 438 comonomer, specialty coatings 1,4-Cycbhexanedlmethanol dMnyl ether, Cycbhexyl i/lnyl ether, 2-Ethythexyl i/lnyl ether Hydroxyhutyl vinyl ether, Rapl-Cure CHVE Rapl-Cure CVE Rapl-Cure DDVE Rapl-Cure DVE-2 Rapl-Cure DVE-3 Rapl-Cure EHVE Rapl-Cure HBVE Rapl-Cure PEPC comonomer, styrene polymerization Velsicol DOM... 

An interesting trend is the increasing use of in situ NMR to study polymerization kinetics, curing reactions, or to determine the comonomer reactivity ratios (127). High-pressurCy high resolution NMR has been employed to study polymer/solvent interactions in poly(l,l-hydroperfluorooctyl acrylate) and its copolymer with styrene (128). 

Synonyms 2-Methyl-2-propene-1-sulfonic acid sodium salt Empiricai C4H7NaO S Formuia H2C=C(CH3)CH2S03Na Properties M.w. 158.15 m.p. > 300 C anionic Uses Dye improver reactive comonomer for acrylic fibers polymerization dyeable polyacrylonitrile/polyvinyl acetate comonomer reactive emulsifier or coemulsifier Manuf./Distrib. Aldrich http //www.sigma-aidrich.com, Monomer-Polymer Dajac Labs Trade Name Synonyms Geropon MLS/A [Rhodia HPCII http //www.rhodia-hpcii.com]... 

The Phillips and Ziegler-Natta catalyst systems are actually believed to possess more than one type of catalyst "site," with each site having distinct ratios of chain-transfer to propagation rates and different comonomer reactivity ratios. 

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