Polystyrene precipitability

Depressed rates have been observed in Ziegler-Natta systems with monomers other than 4-methylpentene-l. Bier (7) suggested that the slowly decreasing rates of propylene polymerization under polymer precipitating conditions with the catalyst system a-TiCb-Al HsbCl are caused by diffusion control. In another case Burnett and Tait (3) found depressed rates of styrene polymerization under polymer-precipitating conditions with the catalyst system a-TiCb-Al HsU. At styrene concentrations less than 3.5M in heptane (isotactic polystyrene precipitates in this region of monomer concentration) a plot of polymerization rate vs. styrene concentration falls below the extrapolated linear plot by a factor of 2. 

PS = polystyrene precipitated from benzene into methanol. 

Preformed polystyrene Precipitation of iron oxides within preformed porous polymer beads 2 pm Ugelstad et al. ... 

Heat 20 g. of styrene (Section IX,6) with 0 -2 g. of benzoyl peroxide (Section IV,196) on a water bath for 60-90 minutes. A glass-bke polymer (polystyrene) is produced. The polymer is soluble in benzene and in dioxan and can be precipitated from its solution by alcohol. 

Shultz and Floryf measured the critical temperature for precipitation for polystyrene fractions of different molecular weight in cyclohexane. The following results were obtained ... 

Lake Red C is an example of a pigment that has been made insoluble by a heavy metal. In this case the metal is barium one barium ion precipitates two molecules. Other metals used are calcium, strontium, manganese, and aluminum. This pigment is used in polystyrene. 

Fig. 24.2. A two-phase polymer alloy, mode by co-polymerising styrene and butadiene in polystyrene. The precipitates ore a polystyrene-butadiene copolymer.

When styrene and butadiene are polymerised, the result is a mixture of distinct molecules of polystyrene and of a rubbery copolymer of styrene and butadiene. On cooling, the rubbery copolymer precipitates out, much as CuAlj precipitated out of aluminium alloys, or FejC out of steels (Chapters 10 and 11). The resulting microstruc-... 

The pore size, the pore-size distribution, and the surface area of organic polymeric supports can be controlled easily during production by precipitation processes that take place during the conversion of liquid microdroplets to solid microbeads. For example, polystyrene beads produced without cross-linked agents or diluent are nonporous or contain very small pores. However, by using bigb divinylbenzene (DVB) concentrations and monomer diluents, polymer beads with wide porosities and pore sizes can be produced, depending on the proportion of DVB and monomer diluent. Control of porosity by means of monomer diluent has been extensively studied for polystyrene (3-6) and polymethacrylate (7-10). 

In addition to monomers and the initiator, an inert liquid (diluent) must be added to the monomer phase to influence the pore structure and swelling behavior of the beaded resin. The monomer diluent is usually a hydrophobic liquid such as toluene, heptane, or pentanol. It is noteworthy that the namre and the percentage of the monomer diluent also influence the rate of polymerization. This may be mainly a concentration or precipitation effect, depending on whether the diluent is a solvent or precipitant for the polymer. For example, when the diluent is a good solvent such as toluene to polystyrene, the polymerizations proceed at a correspondingly slow rate, whereas with a nonsolvent such as pentanol to polystyrene the opposite is true. 

A macroporous polystyrene-divinylbenzene copolymer is produced by a suspension polymerization of a mixture of monomers in the presence of water as a precipitant. This is substantially immiscible with the monomer mixture but is solubilized with a monomer mixture by micelle-forming mechanisms in the presence of the surfactant sodium bis(2-ethylhexylsulfosuccinate) (22). The porosity of percentage void volume of macroporous resin particles is related to percentage weight of the composite (50% precipitant, 50% solvent) in the monomer mixture. 

Monosized polystyrene particles in the size range of 2-10 /am have been obtained by dispersion polymerization of styrene in polar solvents such as ethyl alcohol or mixtures of alcohol with water in the presence of a suitable steric stabilizer (59-62). Dispersion polymerization may be looked upon as a special type of precipitation polymerization and was originally meant to be an alternative to emulsion polymerization. The components of a dispersion polymerization include monomers, initiator, steric stabilizer, and the dispersion medium... 

Paine et al. [99] tried different stabilizers [i.e., hydroxy propylcellulose, poly(N-vinylpyrollidone), and poly(acrylic acid)] in the dispersion polymerization of styrene initiated with AIBN in the ethanol medium. The direct observation of the stained thin sections of the particles by transmission electron microscopy showed the existence of stabilizer layer in 10-20 nm thickness on the surface of the polystyrene particles. When the polystyrene latexes were dissolved in dioxane and precipitated with methanol, new latex particles with a similar surface stabilizer morphology were obtained. These results supported the grafting mechanism of stabilization during dispersion polymerization of styrene in polar solvents. 

Addition of styrene to a green solution of naphthalene" Na+ in tetrahydrofuran leads to an instantaneous change of color from green to red. Styrene polymerizes rapidly and quantitatively within a few seconds, and when the reaction is completed, addition of water converts the red solution of polystyryl carbanions into colorless solution of polystyrene. After precipitation of the polymer it was shown spectroscopically25 that the residual solution contains an amount of naphthalene equal to that used in the preparation of the initiating catalyst. This observation confirms the proposed mechanism of initiation of the polymerization. 

Los Alamos is processing a wide variety of residues, including Pu-Be neutron sources, polystyrene-Pu02-U02 blocks, incinerator ash, Pu-U alloys and oxides, Pu-Zr alloys and oxides, Pu-Np alloys and oxides, Pu-Th alloys and oxides, etc. Processes have been developed for these scrap items (see Figure 2), but we need to know more about Pu-Np separations Pu-Th separations oxalate precipitations for both plus 3 and plus 4 valences valence stabilization dissolution methods for high-fired impure oxides in-line alpha monitors to measure extremely low concentrations of Pu and Am in HNO3 solutions and solubility of various mixtures of Pu02 and UO2 under a variety of conditions. 

Under nitrogen, anhydrous DMF (10 mL) was added to a mixture of 83 (0.240 g, 0.5 mmol), 84 (0.063 g, 0.5 mmol), and Et3N (1 mL). Pd(PPh3)4 (0.027 g, 0.025 mmol) and Cul (0.005 g, 0.025 mmol) were then added and the reaction mixture was stirred at 100°C for 48 h. After being cooled to room temperature, die reaction mixture was poured into MeOH and filtered. The solid was washed with MeOH and dried under vacuum. The repetition of the precipitation procedure gave polymer 85 as orange powder in 96% yield (0.212 g). GPC (polystyrene standards) Mn — 15.100. 

Under nitrogen, a mixture of 97 (2 eq.), 2,6-dibromo-l-dedocyloxy-4-methylbenzene 98 (1 eq.), and Pd(PPli3)2Cl2 in THF was stirred at reflux for 24 h. Polymer 99 was purified by repetitive precipitation-centrifugation using THF and MeOH. GPC (polystyrene standards) Mn = 1700, PDI = 1.4. 

To a mixture of 1,3-dibromobenzene (4.36 g, 18.49 mmol), 1,3-phenylene diamine 111 (2.00 g, 18.49 mmol), NaO-t-Bu (3.73 g, 38.84 mmol), Pd2(dba)3 (0.339 g, 0.37 mmol), and BINAP (0.691 g, 1.11 mmol) in a heavy-walled flask equipped with a Teflon valve was added THF (15 mL) under inert atmosphere. The flask was sealed and heated to 90°C. After 24 h, die reaction mixture was cooled to room temperature and neutralized using 0.2 mol equivalents of 2.4 N HC1 in MeOH. The polymer was precipitated from hexanes, filtered, and dried under vacuum. The dried polymer was redissolved in THF, filtered through Celite, and reprecipitated. The solid was collected by filtration and dien purified by Soxlilet extraction with CH2C12 overnight. After drying under vacuum, a green-tan solid was obtain in 106% yield. GPC (NMP, polystyrene standards) Mw = 39,000 ... 

Under nitrogen, 115( 1 eq.) was reacted with BuLi (2 eq.) at 0°C for 1 h followed by treatment with trimethyltin chloride (2.5 eq.) in THF at room temperature for 30 min. Then a solution of 116 (1 eq.) and PdCl2(Ph3As)2 (0.02 eq.) in THF was combined and the mixture was stirred at reflux overnight. The polymer was precipitated with MeOH followed by filtration and dried under vacuum. GPC (polystyrene standards) Mn = 2000. 

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