Oligomers styrenes

There are different reasons to discard a column a column can be damaged by irreversible adsorption of reactive polymer samples. Small amounts of styrene oligomers are known to permanently elute from styrene-divinylbenzene materials with tetrahydrofuran as the eluent, which means a continuous shear degradation of the separation material and consequently a decrease of the packing quality this observation is very important if fractions are collected and used for further analyses, e.g., for the determination of infrared (IR) spectra. One can presume that similar effects are present with other organic materials too. 

Figure 12.3 Clrromatogr-ams of an ignition-resistant high-impact polystyrene sample (a) Microcolumn SEC fi ace (b) capillary GC trace of peak x . Peak identification is as follows 1, ionol 2, benzophenone 3, styrene dimer 4, palmitic acid 5, stearic acid 6, styrene trimers 7, styrene trimer 8, styrene oligomer 9, Irganox 1076 and Irganox 168 10, styrene oligomer 11, nonabromodiphenyl oxide and 12, decabromodiphenyl oxide. Reprinted with permission from Ref. (12).

Polymer films can be made antistatic with a-sulfonated fatty acid salts and esters [94]. For example, an antistatic additive for polypropylene manufacture can be prepared from potassium methyl a-sulfopalmitate, styrene oligomer, and 2-propanol [95]. The treatment of synthetic fibers and fabrics with a-sulfo-... 

Figure 6.9 Separation of a poly(styrene) oligomer mixture of 2000 average molecular weight by open tubular column SFC using a linear density program (A) and an asymptotic density progreua in (B) with carbon dioxide as the mobile phase. (Reproduced with permission from ref. 115. Copyright Preston Publication, Inc.)...

The oligomer distribution is highly dependent on the method of isolation of the oligomers (TLC, Soxhlet or dissolution/precipitation). Jung and Lee [513] have determined a dimer of 2-phenylbenzoxazole in a polyester resin by means of TLC. A comparative study of the separation of styrene oligomers (up to dodecamers) by TLC and OPLC has appeared [514]. 

Apart from styrene oligomers [514], it appears that OPLC analysis of polymer additives has not been reported. However, the technique has been used for analysis of food antioxidants (BHA, BHT, NDGA and propyl, octyl, and dodecyl gallate) on silica with five different solvent mixtures and densitometric detection [479],... 

We have shown [1, 2] that, in the polymerisation of styrene by perchloric acid under the conditions reported here, the initiation reaction does not produce carbonium ions and that the monomer is polymerised by non-ionic chain carriers. Since the most likely nonionic reaction product formed from perchloric acid and styrene is the ester 1-phenylethyl perchlorate we attempted its preparation in order to try it as catalyst for the polymerisation of styrene. However, we found this ester to be unstable in methylene dichloride solution. It forms styrene oligomers, polystyryl ions, and perchloric acid, and the preparative technique and the mechanism of the reactions involved will be discussed in a paper dealing with the spectroscopic behaviour of polymerising and polymerised systems. 

Examples of the separation of styrene oligomers by HPLC on reversed-phase oc-tadecylsilica columns in a gradient of the mobile phase follow the expected tendency for reversed-phase chromatography of small molecules [120]. Their re-... 

Fig. 12. Separation of styrene oligomers by reversed-phase (left) and size-exclusion chromatography (right) (Reprinted with permission from [121]. Copyright 1996 American Chemical Society). Conditions (left) column, molded poly(styrene-co-divinylbenzene) monolith, 50 mm x 8 mm i.d., mobile phase, linear gradient from 60 to 30% water in tetrahydrofuran within 20 min, flow rate 1 ml/min, injection volume 20 pi UV detection, 254 nm (right) series of four 300 mm x 7.5 mm i.d. PL Gel columns (100 A, 500 A, 105 A, and Mixed C), mobile phase tetrahydrofuran, flow rate, 1 ml/min injection volume 100 pi, toluene added as a flow marker, UV detection, 254 nm temperature 25 °C,peak numbers correspond to the number of styrene units in the oligomers...

Fig. 10 A simple PML document showing the construction of a styrene oligomer...

Styrene undergoes polymerisation with the cationic organonickel(II) complex / 3-methallyl ( /4-cycloocta-l,5-diene)nickel hexafluorophosphate [(MeAll) (Co<7)/W]+[PF]6 combined in situ with tricyclohexylphosphine. The product of such polymerisation is a styrene oligomer with Mn = 1900, characterised by a... 

Such process is described as resusdtable free radical polymerization [204]. It has been applied to the synthesis of poly(a-Me styrene)-b-poly(methyl methacrylate) copolymers from a-methyl styrene oligomers [206] and of amphiphilic copolymers containing polymethacrylic acid and PS sequences [205]. However, macroinitiation from styrene oligomers failed as a probable consequence of the too high stability of the end-groups. 

Step 4 and Step 5 products were used by the author to prepare low molecular weight three-arm star styrene oligomers and are described in the current invention. 

In order to prevent the formation of the red layer observed by De Brouwer and Tsavalas, Vosloo et al. performed SDS-stabilized miniemulsion polymerizations of styrene using pre-formed dithiobenzoate-end-capped styrene oligomers, formed in bulk [297]. Two types of cosurfactant (hexadecane and cetyl alcohol) and two oligomers with different molecular weights were used. Red layer formation was not observed in any of the miniemulsion polymerizations, and the results were better - lower polydispersities, and molecular weights that were closer to the theoretical values - when hexadecane and the lower molecular weight oligomers were used. 

In a study recently carried out in Hong Kong on disposable plastic containers for take-away meals the migration of styrene oligomers, heavy metals and the overall migration from plastic containers and, where present, their lids were determined into food simulants under different test conditions. Results showed that all the disposable plastic container samples met the safety standards for heavy metals and residual styrene monomers. Hence, with the proper use of disposable plastic containers, they would be unlikely to cause a food... 

Figure 2.2 Reactions during styrene oligomer formation in the chain initiation phase...

In GPPS systems, these peroxides mainly supplemented the free radicals generated by thermal initiation, whereas in the HIPS process, it was found that they could enhance the grafting of styrene to unsaturated rubbers, such as polybutadiene. Additional benefits of organic peroxide initiators were increased production per unit reactor volume, reduction of styrene oligomers and lower reactor temperatures. The instantaneous removal of peroxide feed to a runaway reactor also provides a safety mechanism. Peroxide-initiated systems have higher reaction rates owing to shorter reactor residence times, so the ability to remove one source of radical initiation quickly is important. 

In Japan, the production of polystyrene (PS) is fairly high for example, 115 00001 were produced in 1999, involving one of the four major general-purpose type resins. It has been reported that some kinds of styrene oligomers, which are by-products of polymerization, remained in PS products [1]. In the Wingspread statement announced by Colborn et al. in 1996, it was reported that certain synthetic chemicals have endocrine-disrupting effects on humans or animals. Most of these chemicals are pesticides, but styrene dimers (SDs) and trimers (STs) are listed in this statement along with plasticizers and antioxidants [2]. 

GPC analysis of the solid products is needed to elucidate whether or not they contain partially degraded styrene oligomers. 

Other main liquid components are dimeric, trimeric, and other oligomeric styrene components. The content reaches 14 wt% of these oligomers. Other components formed by the pyrolysis of polystyrene are toluene, a-methylstyrene, diphenylethane/propane, and other aromatics. The styrene oligomers show secondary isomerization reactions. These make it difficult to pyrolyze them in a following step into higher amounts of styrene. Mainly, other aromatics are obtained by the degradation of the styrene oligomers. This means that the optimum recovery of styrene from PS is about 77 wt% in an uncatalyzed fluidized-bed process. 

The effect of termination in aqueous-phase on particle formation will depend on whether the terminated and usually doubly charged molecules stay in solution, are absorbed on existipg particles, or form the nucleus for a new particle. It seems unlikely that doubh charged styrene oligomers with... 

The influence of reciprocal miscibility between the methacrylic copolymer containing cyclic anhydride groups and the styrenic oligomers was investigated in the case of monohydroxylated oligomers, which were also prepared by anionic polymerisation of styrene and further deactivation with ethyleneoxide. 

Figure 15.2 Size-exclusion chromatogram of styrene oligomers, with n= 1-14 [reproduced with permission from W. Heitz, Fresenius Z. Anal. Chem., 277, 324 (1975)]. Conditions column, 100cm x 2 mm i.d. (coiled) stationary phase, Merckogel 6000 mobile phase, dimethylformamide.

A chromatogram for styrene oligomers, with = 1-14, may be taken as an example (Figure 15.2). The peak on the far right may be derived from styrene. This is the smallest molecule (next to those of the mobile phase) and is eluted last. The void volume, Vo, is its relevant elution volume. The hrst small peak on the left is produced by excluded molecules, the relevant volume being the interstitial volume, V) (liquid found between the individual particles of the stationary phase)." ... 

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