Styrene-methyl methacrylate alternating

More quantitative studies have shown that, although some hypochromism effects exist, they are small. For example, Monnerie I9) examined the integrated molar extinction coefficient of atactic PS in chloroform and found only a 2 % decrease for the polymer relative to ethyl benzene. In addition, Vala and Rice 15 reported a 10% decrease in absorption for the 260 nm band of isotactic PS relative to atactic PS, which was qualitatively confirmed by Longworth18>. Similarly, Cantow 8> observed a 4% hypochromism of the 261.5 nm band of isotactic PS in dioxane relative to atactic PS. Finally, Cantow 8) observed strong hypochromism (relative to atactic PS) ranging from 19% at 262 nm to 32% at 269 nm for an alternating styrene-methyl methacrylate copolymer and for random copolymers having a low styrene content. 

Vinyl monomers, such as styrene, methyl methacrylate, vinyl acetate, vinyl chloride or acrylonitrile are preferably polymerized by chain polymerization techniques initiated by free radicals. Suitable free radicals can be handily achieved from unstable chemicals like peroxides (benzoyl peroxide, dicumil peroxide) or di-azo reagents (e.g. 2,2 -azo-bis-isobutyronitrile, AIBN) which are dissolved in monomer and usually thermally decompose at temperature range of 40-120 °C. Alternatively, suitable radicals for polymerization can also be activated without addition of external initiators, by just applying ultraviolet light (wave length 200-350 nm) or ultrasound (15,33,34) onto monomer. 

Zeng W and Shirota Y (1989) Studies on alternating radical copolymerization analysis of microstructures of styrene-maleic anhydride, styrene-acrylonitrile, and styrene-methyl methacrylate copolymers by fluorescence spectroscopy. Macromolecules 22 4204-8. 

In addition to these irregularities, Winey et al. (1996) have found that in random and alternating copolymers of styrene and methyl methacrylate, the sequence distribution of monomers along the backbone of the polymer strongly affects its miscibility with polystyrene and polymethylmethacrylate homopolymers, even when the overall ratio of styrene/methyl methacrylate in the copolymer chain is held constant. A strictly alternating sequence of monomers in the copolymer was found to be more miscible with the ho-miopolymers than is a copolymer with a random sequence distribution. These results... 

Structure and Properties of Random, Alternating, and Block Copolymers The UV Spectra of Styrene-Methyl Methacrylate Copolymers... 

Diethyl vinyl phosphate can be co-polymerised with styrene, methyl methacrylate or acrylonitrile monomers by free radical addition, using benzoyl peroxide (12.84). Alternating or block-type polymers are presumably possible. 

Complexation with Lewis acids has also been used to alter sequences in copolymerization and prepare alternating copolymers in systems which usually provide very small tendency for alternation like styrene/methyl methacrylate (rs mma 0.5) (130,131). 

With compositions close to the preferred styrene polyester ratio, the overall rate of conversion depends on the reactivity of styrene with maleate and fumarate, the ratio of maleate to fumarate in the polyester, and the reactivity of styrene with itself. Data from the literature on relevant reactivity ratios are conflicting, but the consensus of evidence is that styrene is more reactive with fumarate than with maleate and is more reactive with either than with itself. Similarly, maleate/fumarate is more reactive with styrene than with itself, hence the tendency to form alternating copolymers from styrene and maleate/fumarate unsaturation. Methyl methacrylate is sometimes used as a component in unsaturated polyesters to reduce refractive index and thereby derive aesthetic variations when the polymers are filled with particulates or glass. However, methyl methacrylate could not wholly replace styrene in polyester resins because, unlike styrene, methyl methacrylate is much more reactive with itself than... 

Ihe procedure has been applied to the copolymer series 1-vinyl-naphthalene-methyl methacrylate [17], 1-vinylnaphthalene-methyl acrylate [71], acenaphthylene-methyl methacrylate [26] and styrene-methyl methacrylate [72]. The consistency of the data derived from alternative extrapolations are good as exemplified for the 1-vinylnaphthalene-methyl methacrylate copolymer series in Table (III)... 

Rana D, Mounach H, Halary JL, Monnerie L. Differences in the mechanical behaviour between alternating and random styrene-methyl methacrylate copolymers. J Mater Sci 2005 40(4) 943-953. 

Polymers containing oxazoline groups are obtained either by grafting the 2-oxazoline onto a suitable existing polymer such as polyethylene or polyphenylene oxide or alternatively by copolymerising a monomer such as styrene or methyl methacrylate with a small quantity (<1%) of a 2-oxazoline. The grafting reaction may be carried out very rapidly (3-5 min) in an extruder at temperatures of about 200°C in the presence of a peroxide such as di-t-butyl peroxide Figure 7.13). 

Notable among the alternative materials are the MBS polymers, in which methyl methacrylate and styrene are grafted on to the polybutadiene backbone. This has resulted in two clear-cut advantages over ABS. The polymers could be made with high clarity and they had better resistance to discolouration in the presence of ultraviolet light. Disadvantages of MBS systems are that they have lower tensile strength and heat deflection temperature under load. 

Preparation and Reactions of S-b-MM. As mentioned in the introduction, we were interested in block copolymers of styrene and alkali metal methacrylates with overall molecular weights of about 20,000 and methacrylate contents on the order of 10 mol%. The preparation of such copolymers by the usual anionic techniques is not feasible. An alternative is to prepare block copolymers of styrene and methacrylic esters by sequential anionic polymerization, followed by a post-polymerization reaction to produce the desired block copolymers. The obvious first choice of methacrylic esters is methyl methacrylate. It is inexpensive, readily available, and its block copolymers with styrene are well-known. In fact, Brown and White have reported the preparation and hydrolyses of a series of S-b-MM copolymers of varying MM content using p-toluenesulfonic acid (TsOH) (6). The resulting methacrylic acid copolymers were easily converted to their sodium carboxylates by neutralization with sodium hydroxide. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

Using the r and tz values from Table 6-2, construct plots showing the initial copolymer composition as a function of the comonomer feed composition for the radical copolymerizations of methyl acrylate-methyl methacrylate and styrene-maleic anhydride. Are these examples of ideal or alternating copolymerization ... 

Bevington has continued his studies of the initiation reaction and of the reactivities of monomers towards reference radicals (69—71). A study of the polymerization of substituted styrenes was recorded (72). In methyl methacrylate polymerization by ammonium trichloroacetate in the presence of copper derivatives, the complexities of the initiation and termination reactions were elegantly unravelled by Bamford and Robinson using two differently labelled trichloroacetates (73). Apparently cyclic processes involving alternate oxidation and reduction of copper may arise. 

One of the first detailed studies on these systems was that of Beaman (26), who showed that methacrylonitrile polymerizes by an anionic chain mechanism when treated with various bases, including Na in liquid ammonia at —75° C. He noted also that low molecular weight polymers are obtained from reaction of acrylonitrile with butylmagnesium bromide. Foster (56) extended the liquid ammonia method to copolymerization studies in which acrylonitrile was combined with styrene, with methyl methacrylate and with vinyl butyl sulfone. Satisfactory data were obtained only with the sulfone, in which case there was some tendency for alternation. 

The infrared spectograms were obtained on a Beckman IR-10 instrument. Solutions of the styrene-maleic anhydride alternating copolymer and styrene block copolymer were used. A KBr pellet was used for the spectogram of the methyl methacrylate block copolymer. 

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