Copolymers alternate

Alternating copolymers Alternative fuel Althesin Alto... 

PEKEKK. See Poly(arylene ether ketone ether ketone ketone) (PEKEKK) PEKK copolymer, alternating, 334 PEKs. See Poly(arylene ether ketone)s (PEKs)... 

Other common emissive conjugated polymers with aromatic ring backbones are poly(phenylene vinylenes) (PPVs), poly(fluorenes) (PFs) - usually formed as copolymers such as poly(fluorene-co-phenylene)s (PFPs), and, more rarely, poly (p-phenylene)s (PPPs). Hetero-aromatic based polymers and copolymers alternating... 

By the formation of copolymers. Alternate isotactic copolymers. . . M,M2M M2. .. of monomers CHA=CHB with CH2=CH2, or of CHA=CHA or CHA=CHB with CHD=CH2 or CHD=CHE are chiral (38, 268, 269). Several examples arc reported in 82-89 (Scheme 18). Chiral copolymers with more complex structure such as. .. M,M,M2M MiM2. . . may be obtained even from two vinyl monomers, as recently demonstrated by WulfF and Hohn (see 53) (93). The copolymers formed by monomer units, which (vide supra) themselves produce chiral homopolymers (270) are also chiral, unless accidental compensation occurs. 

Continuation of this process, with monomer produced by redistribution and then removed by coupling, would lead to a random copolymer. Alternatively, if polymer-polymer coupling were to proceed solely by rearrangement, without dissociation at any stage, either of the ketals I or III would produce only block copolymer. 

Analogously to ethylene-carbon monoxide copolymers, alternating copolymers between cycloolefins such as norbornene and carbon monoxide have been synthesised using cationic Pd(II) complexes modified by phosphorus ligands such as [Pd(MeCN)n(PPh)4 J[BF4]2( = 1,2,3) [27]. General requirements for the... 

The polymerization described so far is homo-polymerization based on single monomers. Some polymers used in pharmaceutical applications are copolymers. They have properties that each homo-polymer does not exhibit. For example, the copolymer of hydroxyethyl methacrylate and methyl methacrylate is synthesized in order to obtain a polymer exhibiting a hydrophilic/hydrophobic balance. A variety of copolymers (alternating, block, random) can be formed from two different monomers. Special processes produce alternating and block copolymers, while random copolymers are produced by free-radical copolymerization of two monomers. The polymerization steps, such as initiation, propagation, and termination, are the same as in free-radical homo-polymerization. Copolymerization kinetics are depicted as follows ... 

Toughened polypropylene may be prepared by block copolymerization in which ethylene monomer is added during the final stages of the polymerization of propylene (4). Thus, some polypropylene chains would contain an end block of rubbery ethylene-propylene copolymer. Alternatively, a blend of an elastomeric copolymer of ethylene and propylene (EPR or EPDM) with isotactic polypropylene (PP) can produce an impact-resistant polymer (5). 

In general, an alternating eopolymer is formed over a wide range of monomer compositions. It has been reported that little chain transfer occurs, and in some cases, conventional free radical retarders are ineffective. Reaction occurs with some combinations, like styrene-acrylonitrile, when the monomers are mixed with a Lewis acid, but addition of a free-radical source will increase the rate of polymerization without changing the alternating nature of the copolymer. Alternating copolymerizations can also be initialed photochemically and electrochemically. The copolymerization is often accompanied by a cationic polymerization of the donor monomer. 

Random Copolymers Alternating Copolymers Graft Polymers Block Copolymers... 

A polymer resulting from polymerisation of two or more different monomers i.e., ter-polymer, tetra-polymer for two- and three monomers, respectively. (see also RANDON COPOLYMER, ALTERNATING COPOLYMER, GRAFT COPOLYMER, BLOCK COPOLYMER.)... 

Aromatic oxadiazoles. See Oxadiazole-based polymers Arylene-vinylene copolymers alternating and random copolymerization, 346-348... 

A large portion of all styrene polymers produced commercially are copolymers. Therefore, the understanding of the Q-e schemeof Alliey and Price (18,19) is important in designing copolymers for specific end uses. The Q-e scheme is a way to correlate structure and reactivity of comonomers. In Equations 2 and 3, Q, and Qj are measures of the resonance stabilization of M, radical and Mj monomer, respectively. The terms e, and e represent measures of the polar properties of the comonomers. In Table 5, styrene s Q-e values are Q=-0.80 and e=l. 00. By selecting comonomers with proper Q-e values, copolymerizations of styrene can give random copolymers, alternating copolymers, or block copolymers. 

In the star-like macromolecules, three and more chains originate in the central locus whereas all chains can have the same chemical stracture (for example homopolymers or statistical copolymers). Alternatively, each arm has a distinct composition - miktoarm star copolymers. 

The traditional linear copolymers can be divided into three categories, that is, random copolymers, alternating copolymers, and statistical copolymers. The first two categories can be seen... 

While some s)uithetic copolymers - alternating, di-, tri-, and mirltiblock copolymers - possess an ordered-sequence distribution of monomeric units along the chain backbone, random copolymers (RCPs) represent a special class of macromolecules, which possess a disordered monomer sequence distribution. A series of papers have been published which established that tuning the copolymer chemical composition and comonomer sequence distribution profoundly afferts the characteristics of RCPs. " Of those characteristics intrinsic to the polymeric materials, most work performed to date addressed the role of the chemical composition. By judiciously... 

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