Polymerization of acrylic monomers

A novel transformation reaction of living poly(tetrahydrofuran) from cationic into anionic propagation species has been published. This species was formed by end-capping of living poly(THF) with potassium iodide followed by the reduction with bis(pentamethylcyclopentadienyl)samarium (Cp 2Sm). The formed terminal anionic carbanion is 

The synthesis of link-functionalized (LFP) poly(methyl methacrylate) (PMMA), and poly( -caprolactone) (PCL), using bimetallic complexes of the type Cp 2Sm-R-SmCp 2 has been reported. Bis-initiated polymerization 

The dimeric yttrium and samarium hydride complexes are converted into monomers in the first step of the reaction. The preparation of block-co-polymers of 1-hexene or 1-pentene with MMA and e-caprolactone, respectively, has also been reported. The polymerization of ethylene with MMA, e-caprolactone and 2,2-dimethyltri-methylenecarbonate was studied in detail racemic Me2Si(CsH2-2-SiMe3-4-But)2Sm(THF)2 or meso-Me2Si(Me2SiOSiMe2)(CsH2-3-But)Sm(THF) were active in the ABA-type triblock-co-polymerization.986 

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Usually, free-radical initiators such as azo compounds or peroxides are used to initiate the polymerization of acrylic monomers. Photochemical (72—74) and radiation-initiated (75) polymerizations are also well known. At a constant temperature, the initial rate of the bulk or solution radical polymerization of acrylic monomers is first order with respect to monomer concentration and one-half order with respect to the initiator concentration. Rate data for polymerization of several common acrylic monomers initiated with 2,2 -azobisisobutyronittile (AIBN) [78-67-1] have been determined and are shown in Table 6. The table also includes heats of polymerization and volume percent shrinkage data. 

The free-radical polymerization of acrylic monomers follows a classical chain mechanism in which the chain-propagation step entails the head-to-tail growth of the polymeric free radical by attack on the double bond of the monomer. 

Group-Transfer Polymerization. Living polymerization of acrylic monomers has been carried out using ketene silyl acetals as initiators. This chemistry can be used to make random, block, or graft copolymers of polar monomers. The following scheme demonstrates the synthesis of a methyl methacrylate—lauryl methacrylate (MMA—LMA) AB block copolymer (38). LMA is CH2=C(CH2)COO(CH2) CH2. 

Group of plastics based on resins generated from the polymerization of acrylic monomers (e.g., ethyl acrylate and methyl methacrylate). 

A substantial number of photo-induced charge transfer polymerizations have been known to proceed through N-vinylcarbazole (VCZ) as an electron-donor monomer, but much less attention was paid to the polymerization of acrylic monomer as an electron receptor in the presence of amine as donor. The photo-induced charge-transfer polymerization of electron-attracting monomers, such as methyl acrylate(MA) and acrylonitrile (AN), have been recently studied [4]. In this paper, some results of our research on the reaction mechanism of vinyl polymerization with amine in redox and photo-induced charge transfer initiation systems are reviewed. 

ENGAGE is an ethylene-octene copolymer. Ray and Bhowmick [70] have prepared nanocomposites based on this copolymer. In this study, the nanoclay was modified in situ by polymerization of acrylate monomer inside the gallery gap of nanoclay. ENGAGE was then intercalated inside the increased gallery gap of the modified nanoclay. The nanocomposites prepared by this method have improved mechanical properties compared to that of the conventional counterparts. Preparation and properties of organically modified nanoclay and its nanocomposites with ethylene-octene copolymer were reported by Maiti et al. [71]. Excellent improvement in mechanical properties and storage modulus was noticed by the workers. The results were explained with the help of morphology, dispersion of the nanofiller, and its interaction with the mbber. 

Webster OW (2004) Group transfer polymerization mechanism and comparison with other methods for controlled polymerization of acrylic monomers. In New synthetic methods. Advances in polymer science, vol 167. Springer, Berlin, pp 1-34... 

Polymerization employing Co complexes as catalysts or else polymers incorporating functionality that includes Co ions represent aspects of polymerization reactions of interest here. Cobalt-mediated free-radical polymerization of acrylic monomers has been reviewed.55 Co11 porphyrins act as traps for dialkylcyanomethyl radicals.1098 Alkyl complexes of Co(TMesP)... 

Webster, O. IV Group Transfer Polymerization Mechanism and Comparison with Other Methods of Controlled Polymerization of Acrylic Monomers. Vol. 167, pp. 1-34. 

Much work on the preparation of nonaqueous polymer dispersions has involved the radical polymerization of acrylic monomers in the presence of copolymers having the A block the same as the acrylic polymer in the particle core 2). The preparation of polymer dispersions other than polystyrene in the presence of a PS-PDMS diblock copolymer is of interest because effective anchoring of the copolymer may be influenced by the degree of compatibility between the PS anchor block and the polymer molecules in the particle core. The present paper describes the interpretation of experimental studies performed with the aim of determining the mode of anchoring of PS blocks to polystyrene, poly(methyl methacrylate), and poly(vinyl acetate) (PVA) particles. 

A value for the polymerization enthalpy of 21.5 kcal/mole can be used to estimate percent conversion and rates for N-substituted maleimide/vinyl ether and maleic anhydride/vinyl ether copolymerizations. A value of 18.6 kcal/mole can be used for the enthalpy of polymerization of acrylate monomers to convert heat evolution data to percent conversion. Since the molar heats of polymerization for N-substituted maleimide vinyl ether copolymerization and acrylates vary by less than 20 percent, the exotherm data in the text are compared directly. 

In 1981 we reported (2, 3) the first examples of free radical polymerizations under phase transfer conditions. Utilizing potassium persulfate and a phase transfer catalyst (e.g. a crown ether or quaternary ammonium salt), we found the solution polymerization of acrylic monomers to be much more facile than when common organic-soluble initiators were used. Somewhat earlier, Voronkov and coworkers had reported (4) that the 1 2 potassium persulfate/18-crown-6 complex could be used to polymerize styrene and methyl methacrylate in methanol. These relatively inefficient polymerizations were apparently conducted under homogeneous conditions, although exact details were somewhat unclear. We subsequently described (5) the... 

In the polymerization of acrylic monomers by bulk, suspension, or in organic solution, the most common initiators are diacyl peroxide (e.g., dibenzoyl peroxide supplied as a paste in water) or azo compounds (e.g., 2,2 -azobisisobutyronitrile). For emulsion or aqueous solution polymerizations, sodium persulfate by itself or in combination with bisulfites or a host of other reducing agents may be used. 

Emulsion Polymerization of Acrylic Monomers, Bull. CM-104 A/cf Rohm and Haas Company, Philadelphia, PA. 

Both the benzoyl and the methyl radicals react with the double bond of the monomer and thus initiate the polymerization. Other types of photoinitiators, like 1-benzoylcyclohexanol or 2,2-dimethyl-2-hydroxyacetophenone, were shown to be as efficient as DMPA in initiating the polymerization of acrylate monomers (15,16) however, their absorption in the near UV is less pronounced so that the overall rate of the laser-induced polymerization is substantially... 

Triphenylphosphine sensitizes the radical polymerization of acrylic monomers, such as methyl acrylate or methyl methacrylate (MMA), whereas styrene and vinyl acetate are not photosensitized. Complex formation between MMA and (C6H6)3P was spectroscopically observed. 

Usually, free-radical initiators such as azo compounds or peroxides are used to initiate the polymerization of acrylic monomers. Photochemical and radiation-initiated polymerizations are also well known. Methods of radical polymerization include bulk, solution, emulsion, suspension, graft copolymerization, radiation-induced, and ionic with emulsion being the most important. 

Inoue [56] has developed a method similar to GTP for polymerization of acrylic monomers. A methylaluminum porphyrin (MeAlTPP) is converted to a ketene acetal by in situ reaction of MMA and used to polymerize MMA (Scheme 24). A hindered Lewis acid catalyst is needed to activate the MMA. 

Ballard et al. [64] found that bulky dialkyl aluminum phenolate additives would improve the anionic polymerization of acrylic monomers. They called their method Screened Anionic Polymerization (Scheme 28). 

Controlled Free Radical Polymerization of Acrylic Monomers... 

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