Propene copolymerization with

The chain-end stereocontrol for olefin polymerizations leads generally to lower stereoselectivities (differences in activation energy for insertion of the two enantiofaces generally lower than 2 kcal/mol) than the chiral site stereo-control.18131132 For this reason, the corresponding catalytic systems have not reached industrial relevance for propene homopolymerization. However, some of them are widely used for propene copolymerization with ethene. 

A) Monomer feed and copolymer composition for ethylene/propene copolymerization with the catalyst VCl4/AlEt2Cl at —78°C have been shown to fit accurately empirical relationships [322]... 

Galimberti, M., Piemontesi, F., Fusco, O., Camurati, L, and Destro, M., Ethene/ Propene Copolymerization with High Product of Reactivity Ratios from a Single Center, Metallocene-Based Catalytic System, Macromolecules, 31, 3409 (1998). 

Leclerc, M. K. Waymouth, R. M. Alternating ethene/propene copolymerization with a metallocene catalyst. Angew. Chem., Int. Ed. Engl. 1998, 37, 922-925. 

Schneider, M. J. Mulhaupt, R. Influence of indenyl ligand substitution pattern on metallocene-catalyzed propene copolymerization with 1-octene. Macromol. Chem. Phys. 1997,198, 1121-1129. 

The ranges of the reactivity ratios obtained at the lowest [N]/[E] feed ratio are ri = 2.34-4.99 and r2 = 0.0-0.062. The r2 values are in general smaller than those obtained for propene copolymerization. The highest r x 2 values found for the copolymers prepared with catalyst 1-4 confirmed its tendency to give more random copolymers. The values of ri, r2, and ri x r2 for the E-N copolymers obtained with catalysts IV-1 and 1-5 are comparable with those of alternating ethene-propene copolymers with metallocene catalysts. The results of the second-order Markov model also showed that all rn values, as r, are similar to those found for ethene and propene copolymerization with metallocene catalysts with low reactivity ratios. Differences in ri2 and in r22 are illuminating, since they clearly show the preference of the insertion of ethene or norbomene into E-N-Mt (Mt = Metal) and N-N-Mt, respectively. Parameter ri2 increases in the order IV-1 < 1-5 I-l < 1-2, opposite to the tendency to alternate the two comonomers [88]. 

The copolymerization of carbonyl monomes with alkenes has been even less studied than that between different carbonhyl monomers. The radiation-initiated copolymerization of styrene with formaldehyde proceeds by a cationic mechanism with a trend toward ideal behavior, r = 52 and r2 = 0 at —78°C [Castille and Stannett, 1966]. Hexafluoroacetone undergoes radiation-initiated copolymerization with ethylene, propene, and other a-olefins [Watanabe et al., 1979]. Anionic copolymerizations of aldehydes with isocyanates have also been reported [Odian and Hiraoka, 1972]. 

Coordination copolymerization of ethylene with small amounts of an a-olefin such as 1-butene, 1-hexene, or 1-octene results in the equivalent of the branched, low-density polyethylene produced by radical polymerization. The polyethylene, referred to as linear low-density polyethylene (LLDPE), has controlled amounts of ethyl, n-butyl, and n-hexyl branches, respectively. Copolymerization with propene, 4-methyl-1-pentene, and cycloalk-enes is also practiced. There was little effort to commercialize linear low-density polyethylene (LLDPE) until 1978, when gas-phase technology made the economics of the process very competitive with the high-pressure radical polymerization process [James, 1986]. The expansion of this technology was rapid. The utility of the LLDPE process Emits the need to build new high-pressure plants. New capacity for LDPE has usually involved new plants for the low-pressure gas-phase process, which allows the production of HDPE and LLDPE as well as polypropene. The production of LLDPE in the United States in 2001 was about 8 billion pounds, the same as the production of LDPE. Overall, HDPE and LLDPE, produced by coordination polymerization, comprise two-thirds of all polyethylenes. 

A joint experimental and computational DFT/MM study [56, 57] on the copolymerization of ethene and 2-butene provided further proof of the validity of the growing chain control of stereoselectivity mentioned above. The idea is that, if the same steric interactions postulated for propene hold for 2-butene, insertion of Z-butene should be favored with C2-symmetric metallocenes like Zr(Me2Si(l-indenyl)2CH3+, while E-butene should be favored with Cs-symmetric metallocenes like Zr(Me2Si(cyclopentadienyl-9-fluorenyl) CH3+. DFT/MM calculations confirmed this qualitative view, predicting the barrier for Z-butene to be 1.6 kcal/mol lower in the case of C2-symmetric complexes, and the barrier for E-butene to be 1.8 kcal/mol lower in the case of Cs-symmetric complexes. These results were corroborated by experiments, which showed molar compositions of 14% and 25% when the appropriate 2-butene isomer was copolymerized with ethene, while the molar percent was in the range of 1% when the wrong isomer was used. 

The highest productivity of 4400 kg polymer/g Zr resulted in the homopolymerization of ethylene. It was found lower in the copolymerization with propene, 1-hexene and 1,5-hexadiene. With increasing concentration of the comonomer in the feed the productivity decreased and was only 50 to 600 kg polymer/g Zr in the homopolymerization of the pure comonomers. The lowest productivity was observed with 1,5-hexadiene. 

An interesting effect is observed for the polymerization with ethylene(bisin-denyl) zirconium dichloride and some other metallocenes (Fig. 5). Although the activity of the homopolymerization of ethene is very high, it increases when copolymerizing with propene [66]. 

Uncomplexed acrylates do not copolymerize with ethylene only polyacryla-les (e.g. polyethyl acrylate) are formed. BF2 is a strong Lewis acid used as an initiator in cationic polymerizations. With acrylic monomers it forms a complex which can be relatively easily copolymerized with ethylene and propene. This process is similar to radical reactions it requires an initiator [96],... 

With the VCl4/Al(Hex)3 catalyst the ratio of the rates of polymerization of ethylene and propene is ca. 1800, considerably larger than that found for more active catalysts for propene polymerization, such as TiCl4 /AIR3. The lai e ratio for the vanadium catalysts is because most of the catalyst sites cannot initiate the polymerization of propene, although once they have added a molecule of ethylene they can subsequently add either ethylene or propene. In conformity with this view it is found that the soluble portion of the catalyst will polymerize ethylene but not propene. The overall activation energy for copolymerization with VCI4 /Al(Hex)3 was found to be 6.5 kcal mole and to be the same as for the two individual monomers [194]. 

Homogeneous vanadium-based catalysts formed by the reaction of vanadium compounds and reducing agents such as organoaluminum compounds [10-12] are used industrially for the production of elastomers by ethylene/propene copolymerization (EP rubber) and ethylene/propene/diene terpolymerization (EPDM rubber). The dienes are usually derivatives of cyclopentadiene such as ethylidene norbomene or dicyclopentadiene. Examples of catalysts are Structures 1-4. Third components such as anisole or halocarbons are used to prevent a decrease in catalyst activity with time which is observed in the simple systems. 

A conventional approach to fhe controlled formation of short-chain branches is ethene copolymerization wifh co-monomers such as propene, butene(l), 4-mefhyl-pentene(l), hexene(l) or octene(l). In the ethene/propene copolymerization example given below an increased number of methyl groups compared with vinyl end groups is consistent wifh a propene incorporation of approximately 6 mol% [Eq. (13)], fhe observed lower DSC melt temperatures and lower densities are typical for medium density (MDPE) and hnear low density polyethylene (LLDPE). 

The development of bifunctional catalysts for specific catalytic sequences of reactions in which the product of the first reaction can serve as substrate for the second is of great importance. There are many examples of such reactions. They are, for instance, the monomer-isomerizing polymerization of heptene-2, heptene-3 and 4-methyl-2-pentene and the combination of propene disproportionation with oligomerization, etc. Bifunctional catalysts are most widely used for ethylene copolymerization with a-butene in situ in the production of so-called low-density linear polyethylene (LDLPE). All general methods for LDLPE production are based on incorporation into a PE backbone of short-chain branches, which can be made by catalytic copolymerization of ethylene with a-olefins C3-C10. A macromolecnlar ligand offers wide possibilities of joining the different types of active site in the same matrix (see also Section 12.5.2). 

Table 1 Reactivity ratios of ethene and propene in gas-phase and suspension copolymerizations with MgCl2/TiCLt catalyst at 70°C [61]...

Reagents i, IM-NaOH (exact equiv.), then removal of arylamldoxime (ether extraction), acidification (HiSO ) of aqueous layer and ether extraction ii, PhNHg iii, NaOH(aq) iv, 210—280°C, in vflc o tv, boilingKMnOi(aq) vi, unsuccessful attempts were made to homopolymerize or copolymerize (with CF2=CFj or CH =CFa) the propenes where x = 3, Ar = Ph, p-MeCjHi, or m-MeC,Hi using free-radical initiation systems. 

Table 26 Copolymerization of propene (1) with various a-olefins (2). 

Also soluble catalyst based on ethene bis(indenyl)zirconium dichloride/methylalu-minoxane can be used [519]. The C-NMR spectroscopically measured isotacticity is in excess of 97%, the molecular weight low (44 000), and the crystallinity 66.9%. Similar to polypropene poly(l-butene) crystallizes in four different modifications [520]. To influence the crystallinity, 1-butene was copolymerized with ethene or propene [521,522] or compounded [523,524]. Poly(l-butene) shows very good stability against stress, corrosion, cracking and is therefore used for pressure tubes. 

In the addition to homo-PVF2, a large number of copolymers have also been synthesized which allow to optimize the mechanical properties of fluoropolymers. Most common are copolymers with vinyl fluoride, trifluoroethylene, tetrafluoroethylene, hexafiuoropropy-lene, hexafluoroisobutylene, chlorotrifluoroethylene, and pentafiuoro-propene [521,535, 559-562]. Copolymerization with nonfluorinated monomers is possible [563] in principle but has not yet found commercial use. Fluorocarbon monomers that can help to retain or enhance the desirable thermal, chemical, and mechanical properties of the vinylidene structure are more interesting comonomers. Copolymerization with hexafluoropropylene, pentafluoropropylene, and chlorotrifluoroethylene results in elastomeric copolymers [564]. The polymerization conditions are similar to those of homopoly(vinylidene fluoride) [564]. The copolymers have been well characterized by x-ray analysis [535], DSC measurements [565], and NMR spectroscopy [565,566]. 

Indeed TFE can be copolymerized with numerous other monomers under conditions similar to those used for its homopolymerization. It was copolymerized with, e.g., hexafluoropropene (FEP) [627], perfluorinated ethers [628], isobutene [629], ethene [630] and propene [631]. In some cases it is used as a termonomer [632]. It is also used to prepare low molecular weight polyfluorocarbons [633] and carbonyl fluoride [634] as well as to form PTFE coatings in situ on metal surfaces [635]. 

Ethene is frequently copolymerized with other monomers to modify its properties. Propene, alone (PP) or copolymerized with ethene, creates a more rigid polymer that can be heated to higher temperatures. It is therefore widely... 

A selected list of reactivity ratios for vinyl chloride with a number of comonomers are given in Table IV. The copolymerization ratios of 1-chloro-l-propene and 2-chloro-l-propene are of interest. These isomers of allyl chloride, strangely enough, seem to be impurities formed in the manufacture of vinyl chloride by some processes. These compounds could find application in the reduction of the cost of poly(vinyl chloride), if they were copolymerized with vinyl chloride. Also to be noted is that the... 

Norbomene can be copolymerized with olefins such as ethene and propene. Among these new cyclic olefin copolymers, made accessible from metallocenes [22, 28, 38-93], the ethene-norbomene (E-N) copolymers are the most versatile and interesting ones. 

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