Copolymerization, propylene conversion

Tan C-S, Chang C-F, Hsu T-J (2002) Copolymerization of carbon dioxide, propylene oxide and cyclohexene oxide by a yttrium-metal coordination catalyst system. In CO2 conversion and utilization. ACS Symp Ser 809 102-111... 

Another important use of BC13 is as a Friedel-Crafts catalyst in various polymerization, alkylation, and acylation reactions, and in other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cydophosphazenes to polymers (81,82) polymerization of olefins such as ethylene (75,83—88) graft polymerization of vinyl chloride and isobutylene (89) stereospecific polymerization of propylene (90) copolymerization of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerization of norbomene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Ashikari, Kanemitsu, Yanagisawa, Nakagawa, Okomoto, Ko-bayashi and Nishioko (59) have studied the copolymerization of propylene and styrene. They found decreasing styrene content and conversion of the copolymer by increasing aluminum to titanium ratios with triisobutyl aluminum and titanium trichloride catalysts. The trialkylaluminum titanium tetrachloride catalyst had relatively low steric control on the polymerization while trialkylaluminum-titanium trichloride had higher steric control. The ionicity which is required for atactic polymerization is more cationic for styrene than for propylene which is more cationic than that for ethylene. Some of the catalyst systems for these three monomers are shown on the ionicity chart in Fig. 9. 

The first enantiomer-selective polymerization was performed with propylene oxide (172) as a monomer [245], The polymerization was carried out with a ZnEt2/(+)-bor-neol or ZnEt2/(-)-menthol initiator system. The obtained polymer was optically active and the unreacted monomer was rich in (S)-isomer. Various examples are known concerning the polymerization and copolymerization of 172 [246-251 ]. A Schiff base complex 173 has been shown to be an effective catalyst In the polymerization at 60°C, the enantiopurity of the remaining monomer was 9% ee at 50% monomer conversion [250],... 

Finally, we reported a di-iron(III) catalyst 24 and the corresponding copolymerization activity [147]. This system was able to produce copolymer with CHO/C02 and demonstrated a TOF of 53 h 1, at 80°C, lObar and aCHO/Fe ratio of 10,000 1. The system did not yield copolymer with PO, but addition of one equivalent of [PPN]C1, per Fe centre, allowed the conversion of PO into cyclic propylene carbonate with TOFs around 10 h 1. Previously, some heterobimetallic iron tert-butoxide complexes ( (7-BuO)5FeLa] and [(f-BuO)4FeZn]) had been reported for the copolymerization of PO and C02 [153]. This catalyst was the first use of an iron complex for the homogeneous copolymerization of CHO and C02. Rieger and coworkers recently reported a mononuclear Fe system that showed similar behaviour towards PO [154] and some copolymer formation with CHO/C02 strongly dependent on the co-catalyst system [98]. 

Manufacture. Propylene oxide is copolymerized with allyl glycidyl ether in an aliphatic, aromatic, or chlorinated hydrocarbon solution using Vandenberg-type catalysts. A complete conversion and a uniform copolymer is obtained containing about 6% of AGE. 

Methacrylates with pendant oxyethylene units (FM-19) were polymerized in a controlled way with metal catalysts in the bulk or in water. The catalytic systems include a bromide initiator coupled with Ni-2 for n = 2 (bulk, 80 °C)319 and CuCl for n = 7-8.246-320 The latter polymerization proceeded very fast in aqueous media at 20 °C to reach 95% conversion in 30 min and gave very narrow MWDs (MJMn =1.1 — 1.3). The fast reaction is attributed to the formation of a highly active, monomeric copper species com-plexed by the oxyethylene units. A statistical copolymerization of FM-19 (n = 7—8) and FM-20, a methacrylate with a oligo (propylene oxide) pendant group, led to hydrophilic/hydrophobic copolymers with narrow MWDs (MwIMn = 1.2).320... 

Figure 6. The influence of conversion on molecular weight in the alternating copolymerization of propylene oxide and phthalie anhydride catalyzed by the TPPAlCl-EtSPhPBr system.

Copolymerization of Propylene with Hexafluoroacetone. The conversion curves of the copolymerization are shown in Figure 12 as a function of irradiation time for equimolar monomer mixtures at 0°, —35°, and — 78°C. The copolymerization rate is much slower than that of the copolymerization of ethylene and hexafluoroacetone. We have data at... 

Figure 12. Conversions as a function of irradiation time at different temperatures in the copolymerization of propylene-hexafluoro-...

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

Unlike molecules containing electron-rich heteroatoms, boron compounds do not poison Ziegler-Natta or metallocene polymerization catalysts. Borane-containing olefin comonomers are therefore well suited to produce olefin copolymers while retaining good catalyst activity. The resulting polymers are suitable for subsequent conversion into a variety of functional groups. In principle, two approaches are possible (1) hydroboration of the terminal double bond (formed by typical chain transfer processes) of a preformed polyolefin, and (2) direct copolymerization of propylene or a 1-alkene with an alkenyl borane (Scheme 11.4). 

As applied to copolymerization with Ziegler catalysis, tubular reactors are limited in conversion for two principal reasons. The reaction is highly exothermic and high temperatures are detrimental to the catalyst. In addition, since the monomers have differing reactivity, polymer of varying composition is obtained as the monomers are depleted. Useful EPDM elastomers have a restricted compositional range. The material produced in these studies have compositions of 55 to 70% ethylene, 30 to 45% propylene and about 3% hexadlene by weight. 

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