Suspension copolymerization

Suspension Polymerization. At very low levels of stabilizer, eg, 0.1 wt %, the polymer does not form a creamy dispersion that stays indefinitely suspended in the aqueous phase but forms small beads that setde and may be easily separated by filtration (qv) (69). This suspension or pearl polymerization process has been used to prepare polymers for adhesive and coating appHcations and for conversion to poly(vinyl alcohol). Products in bead form are available from several commercial suppHers of PVAc resins. Suspension polymerizations are carried out with monomer-soluble initiators predominantly, with low levels of stabilizers. Suspension copolymerization processes for the production of vinyl acetate—ethylene bead products have been described and the properties of the copolymers determined (70). Continuous tubular polymerization of vinyl acetate in suspension (71,72) yields stable dispersions of beads with narrow particle size distributions at high yields. 

Sedimentation systems with the particle size of 0.1-1.0 pm were obtained by mechanical dispersion of the copolymers with subsequent washing, fractionation, and separation of fractions. Micrograin forms (gr.) were synthesized by suspension copolymerization and fractionated. For the description of properties of weakly swelling and weakly dissociating gels, Katchalsky [36] has proposed an equation which contains the electrostatic potential eip... 

Vinyl chloride/2-ethylhexyl acrylate copolymers were prepared by suspension copolymerization (1). 

D. Seebach, Preparation of dendritic and non-dendritic styryl-substituted Salens for cross-linking suspension copolymerization with styrene and multiple use of the corresponding Mn and Cr complexes in enantioselective epoxidations and hetero-Diels-Alder reactions, Chem - Eur.J. 2001, 7, 2873-2887. 

Suspension copolymerization of 1-butene and sulfur dioxide can lead to expandable beads. The cellular material obtained has improved properties with respect to expanded polystyrene. The manufacture of expandable beads by suspension copolymerization is covered by a patent... 

Porous methacrylic acid-DVB resin having excellent sorptive-desorptive properties and suitable for the pharmaceutical isolation of polymyxin E can be prepared by the suspension copolymerization method... 

The suspension copolymerization of acrylic esters, acrylonitrile, and DVB in presence of a free radical catalyst followed by the hydrolysis of the bead copolymer with alkali gives a carboxylic add cation-exchange resin with exchange capadty of... 

Dendritic and nondendritic polystyrene-boimd manganese-salen complexes were described by Seebach and coworkers [30]. The supported catalysts were prepared by suspension copolymerization of styrene with the vinyl-substituted complexes and employed in the epoxidation of phenyl-substituted alkenes by m-CPBA/NMO. Activities and selectivities were similar to those obtained with the monomeric complexes. High catalyst stabilities were observed and it was demonstrated that the immobilized catalysts can be recycled up to 10 times without loss of performance. Laser ablation inductively coupled plasma mass spectrometry was used to monitor the manganese content in repeatedly used polystyrene beads and a correlation between metal leaching from the support and catalytic activity was disclosed [31]. 

Table b. Examples of activated resin intermediates (8) produced by suspension copolymerization of styrene with 2,4,5-trichlorophenyl acrylate and a crosslinking monomer [46]... 

Fig. 9. Scanning electron micrographs of surface and cross-sections of beaded resins obtained by suspension copolymerization of AOTcp with styrene and divinylbenzene (see Table 6)...

Acenaphthalene 119-122, 128, 134 Acrylates, activated 1, 3 -, reactivity ratios 7 -, -, suspension copolymerization 13 Acrylic groups 49, 53 A-Acryloxy derivatives 37 Active ester method, graft copolymers 29 Alkyl esters, aminolysis 14 Aminolysis, alkyl esters 14 Amphigels, polymer-solvent compatibility 24... 

Surface-bound reactive polymers Surfactants, conventional 51 Suspension copolymerization 13 Swelling behavior 26... 

Scheme 12. TADDOL Precursors for Grafting (on Merrifield resin or on controlled-pore glass) and for Cross-Linking Suspension Copolymerization with Styrene. These TADDOL derivatives are prepared in the usual way from (suitably protected) components [21][78-81]. The zero- and first-generation Frechet-type [82] branches were attached by reaction of branch benzyl bromides with a TADDOL bearing four phenohc OH groups [22] [78] [79]. The cross-linked polymer beads we used had a diameter of ca. 400 pm. To keep the styryl derivatives from uncontroUed polymerization, they should be kept in the dark and in the cold.

For practical purposes, styrene—DVB copolymers have commonly been obtained by the suspension polymerization method,[53, 54] which is well known to consist of heating and agitating a solution of initiator in monomers with an excess of water containing a stabilizer of the oil-in-water emulsion. Polymerization proceeds in suspended monomer droplets and, in this way, a beaded copolymer is obtained. While looking very simple, this procedure can provide many complications that significantly change the properties of the beaded product as compared to the properties of materials prepared by bulk copolymerization. AU parameters of the suspension copolymerization have to be strictly controlled, since even small deviations from optimal conditions of the synthesis can serve as an additional source of heterogeneity in the copolymer beads. [55]... 

As far back as in the late 1940s to the early 1950s, it was noticed that if the suspension copolymerization of mono- and divinyl monomers is carried out in the presence of an inert solvent, it wiU yield beads that are opaque in appearance and much more resistant to osmotic shock compared with the known gel-type copolymers. It soon became evident that the improved physical properties of the new resins are caused by their special internal structure, which, in its turn, results from the phase separation of the initially homogeneous comonomer—diluent solution. This finding opened the door to a new generation of polymeric adsorbents, the so-called macroporous resins that exhibit stable porosity in both the dry and the solvated states. 

The above approach of using a diluent of an intermediate thermodynamic quahty during the polymerization of DVB has been intensively examined and, indeed, resulted in materials with enhanced proportions of mesopores. In order to create a rigid polymer of desired porosity, DVB (usually more than 30% in its mixture with styrenic co-monomers) must be copolymerized in the presence of a sufficient amount of a poor diluent (usually 100% or more of the volume of the co-monomers). Of crucial importance is the nature of the poor solvent. Besides cyclohexane, mixtures of a thermodynamically good solvent (ethylene dichloride, toluene, etc.) with precipitating media (hexane, octane, isooctane, higher aliphatic alcohols, etc.), taken in an appropriate proportion, can be applied. Microphase separation during the suspension copolymerization of such a mixture should take place when the major part of the co-monomers has converted into polymer. 

In Figure 11.1 the MMCCD of a commercial copolymer of styroie and acrylonitrile prepared by suspension copolymerization is shown, and was obtained by a combination of GPC and HPLC measurements [116]. 

The use of polymeric carriers as immobilizing media has been described. Spherical macroporous reactive carriers capable of forming covalent bonds with amino-acids and proteins have been prepared by suspension copolymerization of 2-hydroxyethyl methacrylate, ethylene dimethaciylate, and 4-nitrophenyl esters of methacrylic acid, and by suspension copolymerization of methacryloyl derivatives of glycine, /3-alanine, and 6-aminohexanoic acid. The carriers were reported to be suitable for enzyme immobilization. 

Reaction with polymers obtained by suspension copolymerization of methacrylate and methacryloyl type monomers... 

In suspension polymerization, inorganic solids such as hydroxyapatite [3 Ca3 (P04)2 Ca(OH)2] are often used in conjunction with (polymeric) surfactants. Des-landes [92] reported in 1987 a study in which he investigated the morphology of the beads obtained in the suspension copolymerization of styrene and butadiene. A thin layer composed of very uniformly distributed hydroxyapatite particles was adhered to the surface of the polymer bead, and surrounded by a thicker and flakier layer of loosely packed agglomerates of hydroxyapatite and small polymer beads, which were also covered by a monolayer of inorganic matter. Despite this paper, studies on the use of solid particles in suspension polymerization remained focused on their effective use as stabilizers. 

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

The ATR probe has been used successfully for the monitoring of emulsion (unpublished data) and suspension polymerization processes. The copolymerization of IB with isoprene (IP) initiated by AICI3 is such a suspension copolymerization. In this system, the polymer precipitates in the form of a fine slurry. Upon addition of the AICI3 - MeCl solution to the comonomer charge, the appearance of a fine slurry was observed. Polymerization was evidenced by the depletion of IB as shown by the progressive disappearance of the characteristic signal of IB at 1655 cm" (I in Figure 13). 

Itsuno synthesized supported aminoalcohols 111-113 (Scheme 57) [104] and N-suUbnylamino acid 114 [105-107] (Scheme 58) by radical suspension copolymerization of the corresponding monomer chiral styryl aminoalcohols and styryl sulfonylamino acid derivatives with styrene and eventually with a crosslinker. 

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