Polymerization of MMA

Table 7.3-2 Free radical polymerization of MMA in the ionic liquid [BMIM][PFg] [44].

Figure 7.4-3 SEC traces for the Cu(l)Br-mediated living radical polymerization of MMA in the...

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

Studies in the photoinitiation of polymerization by transition metal chelates probably stem from the original observations of Bamford and Ferrar [33]. These workers have shown that Mn(III) tris-(acety]acetonate) (Mn(a-cac)3) and Mn (III) tris-(l,l,l-trifluoroacetyl acetonate) (Mn(facac)3) can photosensitize the free radical polymerization of MMA and styrene (in bulk and in solution) when irradiated with light of A = 365 at 25°C and also abstract hydrogen atom from hydrocarbon solvents in the absence of monomer. The initiation of polymerization is not dependant on the nature of the monomer and the rate of photodecomposition of Mn(acac)3 exceeds the rate of initiation and the initiation species is the acac radical. The mechanism shown in Scheme (14) is proposed according to the kinetics and spectral observations ... 

Photoinitiation of polymerization of MMA and styrene by Mn(facac)3 was also investigated, and it was shown that the mechanism of photoinitiation is different [33] from that of Mn(acac)3 and is subject to the marked solvent effect, being less efficient in benzene than in ethyl acetate solutions. The mechanism shown in Schemes (15) and (16) illustrate the photodecomposition scheme of Mn(facac)3 in monomer-ethyl acetate and monomer-benzene solutions, respectively. (C = manganese chelate complex.)... 

Kaeriyama and Shimura [34] have reported the photoinitiation of polymerization of MMA and styrene by 12 metal acetylacetonate complex. These are Mn(acac)3, Mo02(acac)2, Al(acac)3, Cu(bzac)2, Mg(acac)2, Co(a-cac)2, Co(acac)3, Cr(acac)3, Zn(acac)2, Fe(acac)3, Ni(a-cac)2, and (Ti(acac)2) - TiCU. It was found that Mn(a-cac)3 and Co(acac)3 are the most efficient initiators. The intraredox reaction with production of acac radicals is proposed as a general route for the photodecomposition of these chelates. 

The polymerization of MMA photoinitiated by al-koxo-oxo-bis(8-quinolyloxo) vanadium (V) complex [VOQ2 OR] has also been studied [38,39]. The alkyloxo radical ( OR) formed from the photodecomposition of the chelate (A = 365) nm at 25°C) was found to be the initiating species ... 

The ion-pair complex formed by the interaction of hydroxobis(8-quinolyloxo) vanadium (V) [VOQ2OH] and /i-butyl amine is also effective in photoinitiation of polymerization of MMA in bulk and in solution [40]. The quantum yield of initiation and polymerization determined are equal to 0.166 and 35.0, respectively. Hydroxyl radical ( OH) is reported to be the initiating radical and the following photoreaction is suggested ... 

Several vanadium (V) complexes were also studied by Aliwi [41] in 1988 as possible photoinitiators for the radical polymerization of MMA. These complexes are oxo-tris(ethoxo) vanadium (V), VO(OC2H5)3, oxo-tris-(triphenylsiloxy) vanadium (V), VO(Si(C6Hs)3)3,... 

Okimato and coworkers [51] have introduced a new multicomponent photoinitiating system composed of the metal-ion-amine CCU for the polymerization of MMA (A > 300 nm). The most active system is FeS04-7H20/... 

We have also used j3-picolinium-p-chlorophenacylide ()3-PCPY) [15], a cycloimmonium ylide, as the radical initiator for the polymerization of MMA [18,19] at 60-70°C. (See also Table 1.) The kinetics of the system has been studied. 

In continuation of this series, Saini et al. [24] studied the initiation effect of a-PCPY on the polymerization of MMA [28] and MA [29]. The systems followed nonideal kinetics in both cases, which was explained in terms of... 

Previously, the same author [52] reported that compounds containing the tricoordinated sulfur cation, such as the triphenylsulfonium salt, worked as effective initiators in the free radical polymerization of MMA and styrene [52]. Because of the structural similarity of sulfonium salt and ylide, diphenyloxosulfonium bis-(me-thoxycarbonyl) methylide (POSY) (Scheme 28), which contains a tetracoordinated sulfur cation, was used as a photoinitiator by Kondo et al. [63] for the polymerization of MMA and styrene. The photopolymerization was carried out with a high-pressure mercury lamp the orders of reaction with respect to [POSY] and [MMA] were 0.5 and 1.0, respectively, as expected for radical polymerization. 

Recently, in connection with the use of sulfur ylides in polymerization, Kondo and his coworkers [64] attempted to use diphenylsulfonium bis(methoxycarbo-nyl)methylide (DPSY) (Schemes 27, 29) methylphen-ylsulfonium bis-(methoxycarbonyl)methylide (MPSY) (Scheme 30) and dimethylsulfonium bis (methoxycar-bonyl) methylide (DMSY) (Scheme 31) as photoinitiators for the polymerization of MMA and styrene. They concluded that DPSY and MPSY are effective photoini-... 

Various acrylates, methacrylates and related compounds have been reported to undergo spontaneous polymerization. 110 A complication in studying thermal polymerization of MMA is the difficulty in eliminating impurity initiated polymerization. The monomer is extremely difficult to purify or retain in a "pure" state. These problems have led some to question whether there is any true spontaneous initiation.323 It is, in any event, clear that the rate of thermal polymerization of MMA is substantially less than that of S at the same temperature (at least 70-fold less at 90 °C).310324... 

Dimer and trimer byproducts have been isolated from MMA polymerizations and these are suggestive of 1,4-diradical intermediates.323 28 Lingnau and Mcycrhoff523 found that rates of spontaneous polymerization of MMA were substantially higher in the presence of transfer agents (RH). They were able to isolate the compound (98) that might come from trapping of the biradical intermediate (Scheme 3.65). 

Feldman et a .210 211 and Wulff et ul v have examined other forms of template controlled oligomerization of acrylic monomers. The template (23) has initiator and transfer agent groups attached to a rigid template of precisely defined structure.210 "11 Polymerization of MMA in the presence of 23 gave a 3 unit oligo(MMA) as ca 66% of the polymeric product. The stereochemistry of the oligomer was reported to be different" from that of atactic PMMA. 

Dithiocarbamatc 16 has been used to prepare low dispersity PMAA ( Mw 1 Mn-1.2).52 Photopolymerization of S in the presence of dithiocarbamate 16 also displays some living characteristics (molecular weights that increase with conversion, ability to make block copolymer). However, 17 appears to behave as a conventional initiator in S polymerization.53 The difference in behavior was attributed to the relatively poor leaving group ability of the 2-carboxyprop-2-yI radical. This hypothesis is supported by MO calculations. Dithiocarbamatc 17 was used to control polymerizations of MMA,54 HEMA54 and NIPAM.5... 

Fig. 5. Arrhenius diagram of the ion pair rate constant in the anionic polymerization of MMA in 1-2-dimethoxyethane. (R. Kraft, A. H. E. Muller, H. Hocker, G. V. Schulz, Ref. 39))...

Fig. 7. Calculated time/conversion curves and experimental data points in the anionic polymerization of MMA (C0 = 0.1 mol/1) initiated by methyl-a-lithioisobutyate (C0 = 0.05 mol/1) at 25 °C in THF (Products higher than the tetramer are omitted) (A. H. E. Muller, L. Lochmann, J. Trekoval, Ref.S0))...

A new rate model for free radical homopolymerization which accounts for diffusion-controlled termination and propagation, and which gives a limiting conversion, has been developed based on ft ee-volume theory concepts. The model gives excellent agreement with measured rate data for bulk and solution polymerization of MMA over wide ranges of temperature and initiator and solvent concentrations. 

The My, D and conversions observed for the free-radically initiated polymerization of MMA produced in a periodically operated CSTR... 

Experimental conversion-time data, obtained from the literature, on the bulk free radical polymerization of MMA initiated by AIBN at several temperatures and initiator concentrations, were described by the model. However, the expressions for the rate of conversion and gel effect index were first simplified and rearranged. ... 

Model Description of the Bulk Polymerization of MMA with Chain Transfer to Monomer... 

The hydrophilic/hydrophobic SIN composition of PDMS with poly(HEMA) and poly(AAC) were proposed as a potential apphcation for high-permeability soft contact lenses. Other sUicone-containing IPNs for contact lenses include polymerization of MMA in the presence of polymerized methacryloxypropyl trimethoxysilane, the cross-linking of a polymeric hydrogel of a copolymer of NVP during the final compression or injection-moulding process. 

Free radical polymerization of MMA is a well understood process. The kinetic mechanism neglecting the chain transfer reactions is given as follows (Odian (1970), Rudin (1982)). 

A series of simulations were performed to study the effect of variables such as initiator concentration, initiator half-life and activation energy on the optimum temperature and optimum time. It was assumed that initially the polymerization mixture contained S volume percent monomer, the rest of the mixture being solvent and polymer formed earlier. It was required to reduce the monomer concentration from S volume percent to 0.S volume percent in the minimum possible time. The kinetic and tbeimodyamnic parameters used are similar to those of free radical polymerization of MMA. The parameter values are given in Appendix B. 

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