Synthesis of copolymers

The type of copolymer formed during step growth polymerization depends on the reactivity of the functional groups and the time of introduction of the comonomer. A random copolymer forms when equal concentrations of equally reactive monomers polymerize. The composition of the copolymer, then, will be the same as the composition of the reactants prior to polymerization. When the reactivities of the monomers-differ, the more highly reactive monomer reacts first, creating a block consisting predominantly of one monomer in the chain the lower reactivity monomer is added later. This assumes that there is no chain transfer and no monofrmctional monomer present. If either of these conditions were to exist. 

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The synthesis of copolymers of olefins with carbon monoxide (eq. 3) or ketones (eq. 4) leads to backbone or side-chain carbonyl functionaUty,... 

The synthesis of copolymers from AN and isoprene (ISP) is one of the most promising and effective methods of modifying the properties of PAN to obtain fibres with improved practical properties40. This fibre-forming AN copolymer can, in principle, be also used to spin fibres without using a solvent. 

This feature of the interfacial preparation of poIy(iminocarbon-ates) has an important consequence for the synthesis of copolymers if the dicyanate component is structurally different from the diphenol, partial hydrolysis of the dicyanate will lead to the presence of two structurally different diphenol components that will compete for the reaction with the remaining dicyanate. The interfacial copolymerization will therefore result in a random copolymer. On the other hand, during solution polymerization no hydrolysis can occur. Since the dicyanates can only react with diphenols and vice versa, solution polymerization results in the formation of a strictly alternating copolymer. 

Further work related to the synthesis of copolymers with either P2VP or P4VP blocks has been reported in the literature. Triblock terpolymers PS-fc-P2VP-fo-PEO were synthesized in THF at - 78 °C by sequential polymerization of styrene and 2VP, initiated by s-BuLi in the presence of IiCl [25]. The living polymer was terminated with EO. The end-hydroxyl group was... 

Synthesis of Copolymers with Complex Macromolecular Architectures... 

Finally, it should be mentioned that there exist two other routes for the synthesis of copolymers. First the partial chemical conversion of homopolymers (see Sect. 5.1), for example, the partial hydrolysis of poly(vinyl acetate). Secondly, by homopolymerization of correspondingly built monomers. An example for these macromolecular compounds, sometimes called pseudo-copolymers, is the alternating copolymer of formaldehyde and ethylene oxide synthesized by ringopening polymerization of 1,3-dioxolane. 

Production of materials in which the daughter polymer and the template together form a final product seems to be the most promising application of template polymerization because the template synthesis of polymers requiring further separation of the product from the template is not acceptable for industry at the present stage. Possible method of production of commonly known polymers by template polymerization can be based on a template covalently bonded to a support and used as a stationary phase in columns. Preparation of such columns with isotactic poly(methyl methacrylate) covalently bonded to the microparticulate silica was suggested by Schomaker. The template process can be applied in order to produce a set of new materials having ladder-type structure, properties of which are not yet well known. A similar method can be applied to synthesis of copolymers with unconventional structure. 

Template copolymerization seems to be applied to the synthesis of copolymers with unconventional sequences of units. As it was shown, by copolymerization of styrene with oligomers prepared from p-cresyl-formaldehyde resin esterified by methacrylic or acrylic acid - short ladder-type blocks can be introduced to the macromolecule. After hydrolysis, copolymer with blocks of acrylic or methacrylic acid groups can be obtained. Number of groups in the block corresponds to the number of units in oligomeric multimonomer. Such copolymers cannot be obtained by the conventional copolymerization. 

Research Focus Synthesis of copolymers containing cyclopentadithiazole and dithiophene... 

The low efficiency of the steric control of the propagation, in radical polymerization, by the asymmetric groups present in the monomer has been indirectly confirmed by the synthesis of copolymers containing carbon atoms that are asymmetric owing to the different chemical nature of all the 4 groups directly bound to each of them. 

One of the prospective pathways for the synthesis of HCP involves copolymerization of neutral monomers with a basic ionogenic one. This procedure was used for synthesis of copolymers of acrylonitrile and dimethylaminoethyl methacrylate used for production of dialysis membranes67). Prior to use, the membranes were quater-nized with HC1 and subsequently treated with heparin. The reported high stability of the heparin-polymer complex (the loss of heparin on washing the polymer with distilled water for 70 hours was less than 1 %) does not obviously ensure that the HCP will perform properly when contacted with solutions of proteins and blood. 

In a copolymerization system in which the product rxrz would exceed unity, the copolymer would contain sequences of like units in greater abundance than in a random copolymer of the same composition, and this tendency should be greater the larger the product rxrz (79). However to our knowledge no example of this case is known therefore the synthesis of copolymers with long uninterrupted stretches of a same monomer must be carried out by other methods than by direct copolymerization. In feet such copolymers have been synthesized their properties are more similar to those of a mechanical mixture of both homopolymers and differ markedly from those of a random copolymer. 

Presently the main technique for the synthesis of copolymers are free-radical polymerization methods [11-17]. For a limited range of comonomers, anionic and cationic polymerizations are also used [236,237]. 

A) Synthesis of Copolymers with a Polyvinyl Block and a Hydrophobic... 

Not all monomers are anionically polymerizable. Nevertheless, one can take advantage of the activity of the living ends to introduce reactive end groups at the extremity of homopolymers and then use such end groups to initiate the polymerization of anionically non polymerizable monomers. This method has been applied to the synthesis of copolymers with polyvinyl and polylactone blocks19 and of copolymers with polyvinyl and polypeptide blocks20-2S). One can at last use both anionic and cationic polymerization to prepare block copolymers of tetrahydrofuran with styrene or methylstyrene2. ... 

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