Copolymers with long grafts

Another macromonomer has been made by reacting the terminal hydroxyl groups of poly(oxy-2,6-dimethyl-l, 4-phenylene) (MW = 2000-7000) with norbom-5-ene-2-carbonyl chloride. When this macromonomer is reacted with the 

7 Copolymers by ROMP in conjunction with radicai reactions 

The ROMP of cyclooctene-5-methacrylate and its copolymerization with cyclooctadiene is catalyzed by Ru(=CHCH=CPh2)(Cl)2(PCy3)2 in the presence of p-methoxyphenol as radical inhibitor. The double bonds in the methacrylate groups are inert towards metathesis. After chain transfer with ethyl vinyl ether to release the polymer from the ruthenium centre, it can be cross-linked by radical polymerization through the methacrylate side-chains (Maughon 1995). 

The simultaneous ROMP of norbomene or dicyclopentadiene on the one hand, and the radical polymerization of styrene or methyl methacrylate on the other, gives a polymer blend (Sjardijn 1990b). 

Studies of this kind fall broadly into two groups as indicated in Table 15.1. Those labelled P are mainly concerned with the effect of small quantities of acyclic olefin M2 on the MW, yield, and cis content of the polymer produced from the cyclic olefin Mi in this case the ratio [M2]/[Mi] is usually 0-0.05. Those labelled T involve the use of much higher proportions of M2 (with [M2]/[Mi] 0.5-2), with the object of producing telomers with well-defined end-groups, in some cases for synthetic purposes. For example, highly substituted cyclopentane and tetrahydro-fiiran derivatives can be readily made by the cross-metathesis of substituted norbomenes or 7-oxanorbomenes with hex-3-ene or l,4-dimethoxybut-2-ene catalyzed by ruthenium carbene complexes (Schneider, M.F. 1996). If the acyclic olefin is unsymmetrical and represented by Q Q, where Q and are the alkylidene moieties, three series of telomers may be produced, Q (Mi) Q, Q (Mi) Q, Q (Mi) Q, where ti is the number of Mi units. The lowest members of the series (n= 1) are dienes, and it is sometimes possible to deteet, separate, and identify the cc, ct, and tt isomers. 

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The term graft copolymer is used to describe copolymers with long sequences of another monomer (comonomer) as branches on the main polymer chain. Most commercial varieties of high-impact polystyrene (HIP) and copolymers of acrylonitrile, butadiene, and styrene (ABS) are graft copolymen in which the main polymer chain is polybutadiene and the branches are styrene, or styrene and acrylonitrile. Figure 1.12 shows various types of copolymers. 

In contrast, thermoplastic elastomers vulcanize by a physical cross-linking, that is, by formation of hard domains in a soft matrix. Here, hard and soft refer to glass transition temperatures relative to application temperatures. The properties of these thermoplastic elastomers follow directly from their structures. All thermoplastic elastomers (TPEs, plastomers) are copolymers with long sequences of hard and soft blocks. They can be block polymers, segment polymers, or graft polymers. 

Grafting provides a convenient means for modifying the properties of numerous polymers. It is often required that a polymer possess a number of properties. Such diverse properties may not be easily achieved by the synthesis of homopolymers alone but can be achieved through the formation of copolymers or even terpoly-mers. The formation of graft copolymer with sufficiently long polymeric sequences of diverse chemical composition opens the way to afford speciality polymeric materials. 

PDMS macromonomer was used as a component of block segment to obtain a graft block copolymer with PMMA (Scheme 1) [51-53]. This graft block copolymer is characteristic of surface water repellence, easy peeling, and weatherability superior to simple graft copolymers of the same members. PDMS-b-PVC film also shows long life surface water repellency with weatherability and very low coefficiency of abrasion [18,54]. 

For a graft copolymer with a backbone derived from monomer A and the graft B what often occurs when B is long ... 

Block and graft copolymers differ from the other copolymers in that there are long sequences of each monomer in the copolymer chain. A block copolymer is a linear copolymer with one or more long uninterrupted sequences of each polymeric species,... 

The third possibility to prepare graft copolymers is termed grafting onto . This means that a growing chain B attacks the polymer backbone A with formation of a long branch. This attack can be a chain-transfer reaction or a copolymerization with unsaturated groups, for example, in polydienes. These reactions play an important role in the preparation of high impact polystyrene (see... 

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