C—polymerization

I. I-dichli)rt)ethene, I. l-dichloroethylene, asymmetric dichloroethene, CH2=CCl2, colourless liquid, b.p. 37 C. Prepared by heating 1,1,1- or 1,1,2-trichloroethene with excess lime at 70-80 C. Polymerizes readily to an insoluble solid. 

PVDE is manufactured using radical initiated batch polymerization processes in aqueous emulsion or suspension operating pressures may range from 1 to 20 MPa (10—200 atm) and temperatures from 10 to 130°C. Polymerization method, temperature, pressure, recipe ingredients, the manner in which they are added to the reactor, the reactor design, and post-reactor processing are variables that influence product characteristics and quaUty. 

The ethynylation reaction takes place at 10—40°C and 2 MPa (20 atm) and hquid ammonia is the solvent. The methylbutynol is converted into methylbutenol by selective hydrogenation and then is dehydrated over alumina at 250—300°C. Polymerization-grade isoprene is obtained. 

Polymerization in Solution or Slurry. Many hydrocarbon solvents dissolve PE at elevated temperatures of 120—150°C. Polymerization reactions in solution requite, as theit last step, the stripping of solvent. A variety of catalysts can be used in these processes. 

The rate of ion propagation, is independent of the counterion and has been found to be about 46 X 10 in all cases for CF SO", AsF, SbF, SbCFg, PF g, and BF/ counterions. Conditions were the same for all counterions, ie, 8.0 M of monomer in CCI4 solvent and 25°C polymerization temperature. With less stable counterions such as SbCF and BF at most temperatures, the influence of transfer and termination reactions must be taken into account (71). 

Fig. 1. Examples of the kinetic curves during ethylene polymerization by chromium oxide catalysts. Support—SiOs temperature—80°C polymerization at constant ethylene pressure in perfect mixing reactor. Curve 1—catalyst reduced by CO at 300°C. Curve 2— catalyst activated in vacuum (400°C) polymerization in the case of (1) and (2) in solvent (heptane) ethylene pressure 10 kg/cm2 02 content in ethylene 1 ppm, HsO 3 ppm. Curves 3, 4, 5, 6—catalyst activated in vacuum (400°C) polymerization without solvent ethylene pressure 19 (curve 3), 13 (curve 4), 4 (curve 5), and 2 (curve 6) kg/cm2 02 content in ethylene 1 ppm, HsO = 12 ppm.

If the dissolving of a portion of the polymer takes place, diffusional restriction may occur as a result. Such a case was observed in (98) where a decrease of the polymerization rate (slurry process in cyclohexane) with temperature rise from 75° to 90°C was found despite the increase in the number of propagation centers. At a further increase of the polymerization temperature (>115°C) polymerization becomes a solution process that may also proceed with no diffusional restrictions (94). 

These processes compete with radiation-induced crosslinking, scission and, for case (c), polymerization. 

C. Polymeric Garbodiimide. The polymeric urea prepared above (9.09 g.) is combined with 100 ini. of dichloromethane in a 300-ml., thrce-ncckcd, round-bottomed flask equipped with a magnetic stirrer, a condenser fitted with a gas-inlet tube, and a stopper. Under a blanket of nitrogen, 5.76 g. (0.057 mole) of triethylamine [Ethanamine, N,N-... 

Monomer Formula Explosion Causing Environment Explosion Prevention Techniques Heat of Polymerization in kcal/mole Ignition Temp,°C Polymerization Techniques... 

The temperature of die oil badi in die initial stages and throughout die course of die polymerization is monomer and catalyst dependent. As a general rule, low-boiling, volatile monomers are started at room temperature (20-25°C), whereas higher boiling substrates may be started at 30-40°C. Polymerizations using catalyst 14 should be started at lower temperatures (20-30°C) compared to reactions... 

According to the data, f-BuCl and f-BuBr were equally reactive initiators. Comparable yields were obtained using MeCl and MeBr solvents, particularly at high f-BuX concentration (4.8 x 10-4M). At lower f-BuX concentration (1.2 x 10 4 and 2.4 x 10-4 M), yields were generally lower with f-BuBr than with f-BuCl, and for a given initiator with MeBr than MeCl. Interestingly, f-BuI in conjunction with Et2 AlBr initiated polymerization at —40 °C and —50 °C. However, below —50 °C, polymerization did not take place. Polymerization did not occur also using Mel solvent. 

The effect of f-BuX, Et2 A1X and MeX on PIB yield and polymerization rate was studied (Sections V, VI, VII). Relative initiator reactivities were determined based on yields, initiator efficiencies at —60 °C, polymerization rates and floor temperatures. Initiator reactivity orders can be summarized as follows ... 

Sekiguchi, H., and Clarisse, C., Polymerization of e-caprolac-tone with boron derivatives as catalysts, Makromol. Chem., ... 

FIGURE 1 Schematic representation of the use of trifunctional amino acids as monomeric starting materials for the synthesis of pseudopoly-(amino acids), (a) Polymerization via the C terminus and the side chain R. (b) Polymerization via the N terminus and the side chain R. (c) Polymerization via the C terminus and the N terminus. The wavy line symbolizes any suitable nonamide bond. See text for details. ... 

Freezing point 14°C Polymerizes readily with oxygen... 

Phosphorus vapor consists of tetrahedral P4 molecules, and at higher temperatures also of P2 molecules (P=Pbond length 190 pm). White phosphorus forms by condensation of the vapor it also consists of P4 molecules. Liquid phosphorus normally consists of P4 molecules, but at a pressure of 1 GPa and 100 °C polymeric liquid phosphorus is formed which is not miscible with liquid P4. 

Acrylic acid (Propenoic acid, propene acid) CH2 CHCOOH 54 - 1.1 2.5 140 Colourless, Water soluble liquid Freezing point 14°C Polymerizes readily with oxygen Must be inhibited... 

C. Polymeric Precursors Derived from tris(Borylamino)borazines 112... 

In general, syndiotacticity (rr%) increases with a reduction of the polymerization temperature. In the case of SmH(C5Me5)2, it increased from 78 to 95.2% as the polymerization temperature was reduced from 25 to — 95 °C, but the polydispersity index remained low [3]. Extrapolating the data suggests that syndiotacticity over 97% may be obtained at — 115°C. Polymerization of MMA in both THF and toluene using the organolanthanide initiators produced syndiotactic polymers, despite the fact that the RMgX initiator in toluene led to isotactic polymers [15]. 

Solution of comonomers and initiator in 10% aqueous DMSO (1 step) 65°C Polymerization... 

When (NPC12)3 is heated to 250 °C, polymerization occurs, giving polymers that contain up to 15,000 monomer units. 

With MAO activation, Zr- and Hf-FI catalysts 1 and 3 exhibit fairly high reactivity toward propylene and produce propylene oligomers [64, 65], Conversely, the corresponding Ti-FI catalyst/MAO 2 forms semicrystalline PP (1 °C polymerization), which displays a peak melting temperature of 97 °C, indicative of the formation of a stereoregular polymer. To our surprise, microstructural analysis by 13C NMR indicates that the resultant polymer is syndiotactic (rr 19%), and that a chain-end control mechanism is responsible for the observed stereocontrol, regardless of the C2 symmetric catalyst ([28] for the first report on syndiospecific propylene... 

Figure 3. Possible preparation of polymeric model membranes (X = polymerizable group). (a)-(c) Polymerization preserving head group properties, (d) Polymerization preserving chain mobility (30). Corresponding monomers see Table 1.

Fig. 3. Effect of dodecanol in the porogenic solvent on the differential pore size distribution of molded poly(glycidyl methacrylate-co-ethylene dimethacrylate) monoliths (Reprinted with permission from [62]. Copyright 1996 American Chemical Society). Conditions polymerization time 24 h, temperature 70 °C, polymerization mixture glycidyl methacrylate 24%, ethylene dimethacrylate 16%, cyclohexanol and dodecanol contents in mixtures 60/0 (curve 1), 57/3 (curve 2), 54/6 (curve 3), and 45/15 vol.% (4)...

Conditions polymerization mixture 20 wt% ethylene dimethacrylate, 20% vinyl azlac-tone+acrylamide, 60% porogenic solvent, and azobisisobutyronitrile (1% with respect to monomers), temperature 65 °C polymerization time 24 h. b Percentage of vinyl azlactone (VAL) and acrylamide (AA) in polymerization mixture. c Median of the pore size distribution profile. d Total pore volume. 

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