Aromatic vinyl homopolymers

Electronic Energy Relaxation in Aromatic Vinyl Homopolymers... 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

Examples of homopolymers are given. Poly(4-vinylphenol) was prepared as a prepolymer for the subsequent alkylation [55]. Poly[2-(4-vinylbenzyl)hydroqui-none] 65 is an example of the unhindered phenolic antioxidant for rubbers. Many homopolymers bear a hindered phenolic moiety. Homopolymer 66 was proposed for blending with BR and IR [56]. Other examples are poly[vinyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] [57] (67), poly(3,5-di-/ert-butyl-4-hydroxy-benzyl methacrylate) [58] (68) or poly[iV-3,5-di-tert-butyl-4-hydroxybenzyl) male-imide] [59] (69). Numerous polymeric antioxidants are functionalized with aromatic amine groups. Poly(4-anilinophenyi methacrylate) [53] (70) serves as an example. 

Some 2,6-bis(1,1-dimethylethyl)-4-methyl phenol (BHT) which is added as an inhibitor, can be seen in the pyrogram (at 72.20 min.). The difference between the pyrolysis results for the poly(vinyl acetate) homopolymer and that of the copolymer with polyethylene indicates that the acetate groups are sparsely distributed in the copolymer. The differences in the generation of aromatic compounds are indicated schematically below. The poly(vinyl acetate) homopolymer will undergo during pyrolysis reactions of the following type ... 

Except for the acetic acid peak, the pyrogram of poly(vinyl chloride-co-vinyl acetate) is very similar to that of poly(vinyl chloride). However, this is easily explained by the fact that both poly(vinyl chloride) and poly(vinyl acetate) homopolymers have a similar pyrolysis mechanism, with the elimination of side chain groups and formation of double bonds along the polymeric backbone. After the acetic acid and/or HCI elimination the remaining polymeric structure undergoes the same process of formation of unsaturated and aromatic molecules. This explains the presence of a number of aromatic compounds that are identical in the pyrolysate of the two homopolymers (see Section 6.5 for the pyrolysis of poly(vinyl acetate)). 

The NMR spectra of the homopolymers obtained from the endo and exo adducts at temperatures below 200 C indicated that the polymers retained the configuration of the monomeric adducts. The spectrum of the endo adduct homopolymer contained a peak centered at 6,8 , not present in the spectrum of the exo adduct homopolymer. The endo adduct homopolymer spectrum contained broad peaks at 7.0-7,7 and 7.8-8.6 f , while the exo adduct homopolymer spectrum had a narrow peak at 7.0-7.4T, centered at 7.25 , and a broader peak at 8.3-8.9 . Both spectra had the peaks of aromatic hydrogens at 2.4-3.0 . Neither spectrum contained peaks at about 4.0 attributable to vinylic hydrogens, indicating the absence of unsaturation (Figure 1). 

The molecular and chemical composition of the polymer will influence its solubility characteristics. Park (A) has discussed the solvent-resin relationships in detail in "Advances in Chemistry Series 12A." They can be summarized as follows Aromatics such as toluene and xylene are primary solvents for only the most soluble of the vinyl resins. The homopolymers have very slight aromatic tolerances. Aliphatic-type solvents are not considered good solvents for vinyls. As with the aromatics, the extremely soluble resins will tolerate aliphatic solvents if a strong ketone is present. Only fair aliphatic tolerance is obtained with the low molecular weight high vinyl chloride content solution polymers. Aliphatic tolerance of the homopolymers is practically nil. The alcohol tolerance of vinyl resins is very limited. Recent studies with the high solubility type metal adhesion copolymers indicate that appreciable quantities of 2-propanol may be used, if a strong ketone solvent is used. 

PE would have a low solubility even in hot toluene. In the case of styrene-butadiene copolymer, the uncrosslinked polymer is soluble in aromatic solvents, whilst the highly crosslinked (gel) fraction is completely insoluble and, indeed, this can be used as the basis of a method for separating gel from uncrosslinked polymer. Copolymers usually dissolve in a greater number of solvents than homopolymers. Thus, whilst PVC is only slightly soluble in acetone or methylene chloride, its copolymers with vinyl acetate or acrylates dissolve easily. 

Many studies have focused on catalysts that could potentially copolymerize ethylene and vinyl aromatic monomers, together with the associated polymerization chemistry and chemical analyses of the produced polymers. It is evident from a number of references (eg 12-14) that the catalyst structure and polymerization conditions, such as temperature and monomer feed ratios, have major influences on the reaction product in terms of production efficiency, product composition (copolymer, homopolymer contents), and copolsrmer microstructure, including stereoregularity. 

The term vinyl aromatic polymers refers to low molecular weight homopolymers of vinyl aromatic monomers such as styrene, vinyl toluene, and a-methyl styrene, copolymers of two or more of these monomers with each other, and copolymers containing one or more of these monomers in combination with other monomers such as butadiene and the like. These polymers are distinguished from PRs in that they are prepared from substantially pure monomer. 

Particular studies of the IR spectra of homopolymers include isotactic poly(l-pentane), poly(4-methyl-l-pentene), and atactic poly(4-methyl-pentene) [16], chlorinated polyethylene (PE) [17], aromatic polymers including styrene, terephthalic acid, isophthalic acid [18], polystyrene (PS) [19-21], trans 1,4-polybutadiene [22], polyether-carbonate-silica nanocomposites [23], polyhydroxyalkanoates [24], poly(4-vinyl-n-butyl) [25], polyacetylenes [26], polyester urethanes [27], miscellaneous... 

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