Preparation of copolymers

The successful development of eye contact lenses led in turn to a demand for soft contact lenses. Such a demand was eventually met by the preparation of copolymers using a combination of an acrylic ester monomer such as methyl methacrylate, a cross-linkable monomer such as a dimethacrylate, and a monomer whose homopolymer is soluble or highly swollen in water such as N-vinyl pyrrolidone. Such copolymers swell in water (hence the term hydrophilic), the degree of swelling being controlled by the specific type and amount of the monomers used. In use the lens is swollen to equilibrium in water, a typical soft lens having a water content of about 75%. 

Since the reactivity ratios of ethylene-polar monomer pairs are quite different, the preparation of copolymers with precisely the same comonomer composition can be a challenging endeavor. Earlier in this chapter, we described the synthesis and characterization of precisely placed methyl groups on a polyethylene... 

Figure 4. Synthesis of an indicator dye for amines which exhibits methacrylate groups for preparation of copolymers. The dye shows a reversible change in fluorescence from green to blue upon interaction with amphetamine.

Preparation of Copolymers Containing Both Electrophilic and Nucleophilic Groups. Our first implementation of this reaction scheme involved the preparation of a series of copolymers incorporating both a latent electrophile and an electron-rich aromatic moiety which, being phenolic, also provides access to swelling-free development in aqueous medium. The copolymers are prepared as shown in Figure 1 by copolymerization of 4-t-butyloxycarbonyloxy-styrene with 4-acetyloxymethyl-styrene. Although the reactivity ratios of these two monomers are different [11], our study of this system has confirmed that they copolymerize essentially in random fashion. 

Preparation of Copolymers of Vinvlbenzvlacetate and 4(t-BOOstvrene. 4-Vinylben-zyl acetate was obtained from Eastman Kodak or prepared from 4-chloromethylsty-rene by displacement with acetate under phase transfer conditions. 

Scheme 8.9 Preparation of copolymer of 47 and MMA by atom transfer radical polymerization at 50°C [40],...

Preparation of Copolymers II and III. Using the above general copolymerization scheme, two more copolymers of p-dioxanone/glycolide at 90/10 and 80/20 initial weight composition were prepared. The following amounts of reactants and catalysts were used. 

Research Focus Preparation of copolymers containing perfluorosulfonate functions useful... 

The preparation of copolymers and block copolymers does not make problems. For example, cyclopentadiene can be copolymerized with norbornene using the following procedure. Cyclopentadiene and the norbornene are mixed with benzene and added to the reactor... 

Propylene oxide is one of the raw materials used to manufacture rubbery and crystalline polyepoxides. R. J. Herold and R. A. Livigni describe propylene oxide polymerization with hexacyanometalate salt complexes as catalyst. Polyphenylene oxide is made by copper catalyzed oxidative coupling of 2,6-dimethylphenol. G. D. Cooper, J. G. Bennett, and A. Factor discuss the preparation of copolymers of PPO by oxidative coupling of dimethylphenol with methylphenylphenol and with diphenylphenol. 

Vl/7 e have had a continuing interest in flame retardants, methods of test and mechanisms of action of such materials. Recently, we reported studies involving fire retardant additives, syntheses of monomers, and the preparation of copolymers to achieve flame resistance (41). In addition, considerable synthetic work in phosphorus chemistry has been pursued at our Stamford Research Laboratories. Some of this has been reported by Grayson, Rauhut, Buckler, Wystrach, and co-workers. This chapter and the one following result from this background. 

Preparation of Copolymer of Chloro- and Butyl- -xylylene. Mixtures of dichloro-di-p-xylylene and butyl-di-p-xylylene were prepared and melted to ensure homogeneity. The mixture was placed in the distillation zone, and the reaction was carried out in the usual fashion. The copolymers formed in the initial polymerization zone which was maintained at 90°-100°C. Poly-p-xylylene formed in the final, air-cooled zone. At... 

Table 10. Amounts of components used in the preparation of copolymers and polymer composites...

Examples of preparation of copolymers are scarce. Mun et al. [81, 82] showed that the binary system of cobaltocene/ bis(ethylacetoacetato) copper (II) effectively initiates the living radical polymerizaton of MMA at 25 °C in acetonitrile. The polymerization activity of this initiator system was markedly affected by the solvent used. The synthesis of PMMA-b-PS copolymers with molecular weights reaching 700000 was successfully attempted by adding styrene to the living PMMA. The yield of the copolymers reached 80% when the MMA polymerization was carried out for three days. The same team [91] also synthesized PS-b-PMMA copolymers from the polymerization of MMA with polystyrene obtained in the presence of reduced nickel/halide systems. The yields range from 84 to 91% depending on the halide complex used. 

Finally, these reactions led to a new method of preparation of copolymers based on the interaction of two homopolymers in the presence of a cationic initiators (schematically) ... 

Experimental and analytical data for the preparation of copolymers 6 - 16 are listed in Table 1. It is obvious that the yield increases with the chain length of the starting oligomer 3-5. The degree of polymerization (DP) was calculated by determination of the integral ratios of the signals of siloxy-units versus silanol endgroups in Si NMR analysis. 

The present volume is particularly concerned with the use of the different modes of controlled radical polymerisation for the preparation of copolymers such as random copolymers, linear block copolymers, as well as graft copolymers and star-shaped copolymers. It also presents the combination of controlled radical polymerisation with non-controlled radical copolymerisation, cationic and anionic polymerisation,both of vinyl monomers and cyclic monomers, and ringopening metathesis polymerisation. 

OTHER COMMENTS used during the application of specialty paints and varnishes used during spray applications of vinyl toluene polyester surface coatings chemical intermediate for unsaturated polyester resins useful in the preparation of copolymers with drying oils for surface coatings. 

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