Styrene copolymerisation

The greatest use of latex paints for indoor applications is based upon vinyl acetate, which constitutes 85% of the total polymer usage, the remainder being acrylates (e.g., n-butyl acrylate). For outdoors or bathroom usage, acrylates are the major components. For various applications, e.g., wood paints, styrene copolymerised with acrylates are used. Flowever, yellowing of the styrene units occurs. 

Several types of bidentate ligands, different from diphosphines, for example bipyridines and phenantrolines, have been proven to give active catalysts, particularly in the CO-styrene copolymerisation [25], but, particularly with ethene, diphosphines give higher performances. 

Figure 5.11 Schematic presentation of the effect of the kind of penultimate monomeric unit on the formation of a cis-1,4- or trans- 1,4-butadiene unit in butadiene/styrene copolymerisation with a lanthanide-based catalyst...

Figure 5.12 Schematic presentation of the backbiting coordination involving penultimate and pen-penultimate cis- 1,4-butadiene units in butadiene/styrene copolymerisation with transition metal- and rare-earth metal-based catalysts...

For the cure study of radical reactions, such as the unsaturated polyester resin-styrene copolymerisation, a different and more elaborated approach incorporating a molecular weight dependent diffusion coefficient, shouldbe employed to take the Trommsdorff, or gel, effect into account. 

Figure 2.18 Mechanism of viscosity build-up in UPE-styrene coPolymerisation (schematic). Reproduced with permission from S.V. Muzumdar and L.J. Lee, Polymer Engineering Science, 1996, 36, 7, 943 1996. 1996,...

Finally, to complete the picture of natural biopolymers, one can mention the existence of materials produced by lignin/styrene copolymerisation and by lignin/methyl methacrylate copolymerisation. In both cases, the increase of lignin improves the biodegradation of the product by fungi. 

Dow catalysts have a high capabihty to copolymetize linear a-olefias with ethylene. As a result, when these catalysts are used in solution-type polymerisation reactions, they also copolymerise ethylene with polymer molecules containing vinyl double bonds at their ends. This autocopolymerisation reaction is able to produce LLDPE molecules with long-chain branches that exhibit some beneficial processing properties (1,2,38,39). Distinct from other catalyst systems, Dow catalysts can also copolymerise ethylene with styrene and hindered olefins (40). 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

Tetraneopentyltitanium [36945-13-8] Np Ti, forms from the reaction of TiCl and neopentyllithium ia hexane at —80° C ia modest yield only because of extensive reduction of Ti(IV). Tetranorbomyltitanium [36333-76-3] can be prepared similarly. When exposed to oxygen, (NpO)4Ti forms. If it is boiled ia ben2ene, it decomposes to neopentane. When dissolved ia monomers, eg, a-olefins or dienes, styrene, or methyl methacrylate, it initiates a slow polymerisation (211,212). Results from copolymerisation studies iadicate a radical mechanism (212). Ultraviolet light iacreases the rate of dissociation to... 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

The mutual polymerisation of two or more monomers is called copolymerisation. This topic has been comprehensively reviewed (4,5). Monomers frequentiy show a different reactivity toward copolymerisation than toward homopolymerisation. In fact, some monomers that can be bomopolymerised only with great difficulty, can be readily copolymerised. One such monomer is maleic anhydride. It is rather inert to free-radical homopolymerisation yet can be copolymerised convenientiy with styrene and many other monomers under free-radical conditions. 

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). 

Several other elastic materials may be made by copolymerising one of the above monomers with lesser amounts of one or more monomers. Notable amongst these are SBR, a copolymer of butadiene and styrene, and nitrile rubber (NBR), a copolymer of butadiene and acrylonitrile. The natural rubber molecule is structurally a c/i -1,4-polyisoprene so that it is convenient to consider natural rubber in this chapter. Some idea of the relative importance of these materials may be gauged from the data in Table 11.14. 

The common feature of these materials was that all contained a high proportion of acrylonitrile or methacrylonitrile. The Vistron product, Barex 210, for example was said to be produced by radical graft copolymerisation of 73-77 parts acrylonitrile and 23-27 parts by weight of methyl acrylate in the presence of a 8-10 parts of a butadiene-acrylonitrile rubber (Nitrile rubber). The Du Pont product NR-16 was prepared by graft polymerisation of styrene and acrylonitrile in the presence of styrene-butadiene copolymer. The Monsanto polymer Lopac was a copolymer of 28-34 parts styrene and 66-72 parts of a second monomer variously reported as acrylonitrile and methacrylonitrile. This polymer contained no rubbery component. 

Because of its low price, compatibility, low viscosity and ease of use styrene is the preferred reactive diluent in general purpose resins. Methyl methacrylate is sometimes used, but as it does not copolymerise alone with most unsaturated polyesters, usually in conjunction with styrene in resins for translucent sheeting. Vinyl toluene and diallyl phthalate are also occasionally employed. The use of many other monomers is described in the literature. 

This is a linear polyester containing phthalic anhydride to ensure hydrocarbon solubility and maleic anhydride to enable copolymerisation to take place, esterified with 2-propanediol. The ester is dissolved in styrene which initially acts as the solvent and subsequently as film former when it is copolymerised with the double bond in the ester by free radical induced polymerisation. 

A widely used cation exchange resin is that obtained by the copolymerisation of styrene (A) and a small proportion of di vinyl benzene (B), followed by sulphonation it may be represented as (C) ... 

The polymer is based on a simple head-to-tail arrangement of monomer units and is amorphous, since the specific position of the benzene ring is somewhat variable and hence inhibits crystallisation. Despite its generally desirable properties, for many applications it is considered too brittle. Because of this, a number of approaches have been made to modify the mechanical properties of poly (styrene). The most successful of these have been (i) copolymerisation and (ii) the addition of rubbery fillers. 

A variety of ionomers have been described in the research literature, including copolymers of a) styrene with acrylic acid, b) ethyl acrylate with methacrylic acid, and (c) ethylene with methacrylic acid. A relatively recent development has been that of fluorinated sulfonate ionomers known as Nafions, a trade name of the Du Pont company. These ionomers have the general structure illustrated (10.1) and are used commercially as membranes. These ionomers are made by copolymerisation of the hydrocarbon or fluorocarbon monomers with minor amounts of the appropriate acid or ester. Copolymerisation is followed by either neutralisation or hydrolysis with a base, a process that may be carried out either in solution or in the melt. 

IPNs are found in many applications though this is not always recognised. For example conventional crosslinked polyester resins, where the polyester is unsaturated and crosslinks are formed by copolymerisation with styrene, is a material which falls within the definition of an interpenetrating polymer network. Experimental polymers for use as surface coatings have also been prepared from IPNs, such as epoxy-urethane-acrylic networks, and have been found to have promising properties. 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

Graft copolymerisation of styrene on partially carboxymethylated cotton using gamma radiation. 

For radical chain copolymerisation of styrene and MMA, rjxr2different from the monomer... 

However, in the anionic copolymerisation of styrene and MMA, jq r2/l and r < 1 and r2> 1. As it adds slower, the styrene content in the copolymer is always lower than in the monomer mixture. 

An important class of copolymers made by chain copolymerisation is graft copolymers, synthesized in order to toughen brittle materials through inclusion of a rubber phase. Examples are the cases of styrenic copolymers called "HIPS" for High-Impact Polystyrene and ABS for Acrylonitrile-Butadiene-Styrene. Both are synthesized in two steps. 

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