Polystyrene 4-methylstyrene

OC-Methylstyrene. This compound is not a styrenic monomer in the strict sense. The methyl substitution on the side chain, rather than the aromatic ring, moderates its reactivity in polymerization. It is used as a specialty monomer in ABS resins, coatings, polyester resins, and hot-melt adhesives. As a copolymer in ABS and polystyrene, it increases the heat-distortion resistance of the product. In coatings and resins, it moderates reaction rates and improves clarity. Physical properties of a-methylstyrene [98-83-9] are shown in Table 12. 

Vinyltoluene, comprising a mixture of ca 33% para- and 67% y /i7-methylstyrene, has been marketed for ca 45 yr by Dow Chemical Company and also by Cosden. However, the performance properties of the polymers prepared from the para isomer are not only superior to those of the polymer prepared from the typical mixed isomers, but are generally superior to those of polystyrene (60). This advantage, coupled with a raw material cost advantage over styrene, suggests that i ra-methylstyrene may displace significant amounts of styrene, currendy a 3.2 x 10 t/yr domestic market. 

The acetone supply is strongly influenced by the production of phenol, and so the small difference between total demand and the acetone suppHed by the cumene oxidation process is made up from other sources. The largest use for acetone is in solvents although increasing amounts ate used to make bisphenol A [80-05-7] and methyl methacrylate [80-62-6]. a-Methylstyrene [98-83-9] is produced in controlled quantities from the cleavage of cumene hydroperoxide, or it can be made directly by the dehydrogenation of cumene. About 2% of the cumene produced in 1987 went to a-methylstyrene manufacture for use in poly (a-methylstyrene) and as an ingredient that imparts heat-resistant quaUties to polystyrene plastics. 

Polymers of a-methylstyrene have been marketed for various purposes but have not become of importance for mouldings and extrusions. On the other hand copolymers containing a-methylstyrene are currently marketed. Styrene-a -methylstyrene polymers are transparent, water-white materials with BS softening points of 104-106°C (c.f. 100°C for normal polystyrenes). These materials have melt viscosities slightly higher than that of heat-resistant polystyrene homopolymer. 

It is worth noting that occasionally high Tg compatible additives are incorporated into the polystyrene phase, when the PSA requires higher temperature performance. These additives are usually based on poly-a-methylstyrene. 

S-(a-MeS)B 4 Polystyrene poly(a-methylstyrene) High 1,4-polybutadiene 1,2-polybutadiene Polystyrene (poly-(a-methylpoly-styrene) Polyethylene ... 

S-(a-MeS)-I Polystyrene poly(a-methylstyrene) Polyisoprene Polystyrene poly(a-methylstyrene) Poly(ethylene-co- propylene) ... 

Examples shown in this chapter are for PMMA. Other polymers can be separated as well. The polymers separated so far (1,2) include polystyrene, poly(a-methylstyrene), polycaprolactone, polycarbonate, poly(hexyl isocyanate), polytetrahydrofuran, poly (vinyl methyl ether), and polyvinylpyrrolidone. 

This method was first applied by McCormick27 and by Bywater and Worsfold11 to the system a-methylstyrene/poly-a-methyl-styrene, and the free energy, entropy and heat of polymerization as well as the ceiling temperature were determined. Similar studies concerned with the system styrene/polystyrene are being carried out in our laboratories. 

It is typical, for instance, of syndiotactic polystyrene (s-PS) [7-9] and syndiotactic poly- p-methylstyrene (s-PPMS) [10] to present crystalline forms with a transplant conformation of the chains (shown for s-PS in Fig. 1) as well as crystalline forms with sequences of dihedral angles of the kind TTG+G+ (or the equivalent G G TT), corresponding to a s(2/l)2 helical symmetry of the chains (shown for s-PS in Fig. 1). 

Hyperbranched polymers have also been prepared via living anionic polymerization. The reaction of poly(4-methylstyrene)-fo-polystyrene lithium with a small amount of divinylbenzene, afforded a star-block copolymer with 4-methylstyrene units in the periphery [200]. The methyl groups were subsequently metalated with s-butyllithium/tetramethylethylenediamine. The produced anions initiated the polymerization of a-methylstyrene (Scheme 109). From the radius of gyration to hydrodynamic radius ratio (0.96-1.1) it was concluded that the second generation polymers behaved like soft spheres. 

The precipitated silica (J. Crosfield Sons) was heated in vacuo at 120° for 24h. before use. Two grades of surface areas 186 and 227 m g l (BET,N2), were used during this project. Random copolymers, poly(methyl methacrylates) and polystyrene PS I were prepared by radical polymerization block polymers and the other polystyrenes were made by anionic polymerization with either sodium naphthalene or sodium a methylstyrene tetramer as initiator. The polymer compositions and molecular weights are given in Table I. 

Brominated diphenyl oxides, 77 461 Brominated epoxies, 70 383 Brominated epoxy ohgomers, 77 470 Brominated epoxy resin, 70 456 Brominated poly(isobutylene-co-p-methylstyrene), 4 438 blends with halobutyl, 4 453 copolymers, 4 446 vulcanization, 4 450 Brominated polystyrene(s), 77 470 474 20 65... 

Tg (168°C) of poly(a-methylstyrene) (PMS I ) whereas ST incorporation has a smaller effect due to the lower T of polystyrene (ca. 100°C). In addition, maintaining a high concentration of mcthacrylic acid units in the copolymer by minimizing dehydration helps increase T because of the high f. (228°C) of PMAA. 

The heat distortion temperature of styrene polymers is insufficient for some applications, but can be improved by copolymerization with monomers such as -methylstyrene or maleic anhydride. Maleic anhydride copolymers are excellently suited to the manufacture of foamed articles. The advantages of glass-fiber reinforcement are greater in such copolymers than in polystyrene itself. 

Figure 34. The Polystyrenes. Polystyrene is a low sensitivity negative resist, poly (a-methylstyrene) is a low sensitivity positive resist and the para-substituted analogs listed are all sensitive negative resists.

A study of methods for controlling the grafting sites of polystyrene polymers may serve as an example for the quantitative and structural analysis of the site of lithiation. Trimethylsilyl chloride serves as the quenching agent owing to the low incidence of side reactions besides metal replacement. Thus, on varying the conditions of metallation of low molecular weight polystyrene (409) and poly(4-methylstyrene) (410), aromatic and... 

In the crystal state most stereoregular polymers have helical conformations. Group s(M/N) 1 comprises all the isotactic vinyl polymers [polypropylene, polybutene, polystyrene, etc., M/N = 3/1 poly-o-methylstyrene, etc., 4/1 ... 

Polystyrene and poly(alpha-methylstyrene) Polystyrene and poly(alpha-methylstyrene) Polystyrene and poly(alpha-methylstyrene) Poly(methyl methacrylate)... 

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