Vinyl ethers graft polymers

El-S.A. Hegazy, A.M. Dessouuki, A.M. Rabie and I. Ishigaki, Membranes obtained by preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene-perfluoro-vinyl ether), J. Polym. Sci., Polym. Chem. Ed. 1984, 22, 3673-3685. 

A series of graft polymers on polychloroprene were made with isobutjiene, /-butyl vinyl ether, and a-methylstyrene by cationic polymerization in solution. The efficiency of the grafting reaction was improved by use of a proton trap, eg, 2,6-di-/-butylpyridine (68). 

Carbon blacks have been reported to be capable of initiating the cationic polymerization of vinyl monomers such as vinyl ethers, indene, and acenaphthylene. The grafting sites of the polymer were based on carboxyl groups present on the surface [88]. The polymerization was inhibited by treatment of the carbon blacks with NaHCOs, CH2N2, pyridine, and DMF. Also, the degree of conversion was found to be dependent on temperature and time of polymerization [89]. 

Recently, Spange et al. (19,20) have successfully achieved cationic graft polymerizations of vinyl ethers, vinyl furan, and cyclopentadiene onto silica, initiated by a stable ion pair formed from silanol and aiylmethyl halide, such as di(p-methoxy-phenyl)methyl chloride. The grafting of the polymer onto silica is proposed to take place via the propagation based on olefin insertion to a cation center being in a rapid equilibrium with the ion pair, as shown in Scheme 12.1.3. 

Block copolymers that consist of hydrophilic and hydrophobic segments are typical amphiphilic polymers, a variety of which have been synthesized by living cationic polymerization. Figure 9 schematically illustrates the structures of some of these amphiphilic polymers thus far obtained though the examples therein are based on poly(vinyl ether) segments, any other appropriate segments may be incorporated. As seen in the illustrations, macromolecular amphiphiles are not necessarily linear AB- and ABA-type block copolymers but may be graft, multiarmed, and network polymers, where the basic components are amphiphilic block copolymers. 

A class of end-functionalized polymers with polymerizable terminal groups are generally called macromonomers. By both functional initiator and terminator methods, a variety of macromonomers have been synthesized in living cationic polymerization of vinyl ethers, styrenes, and isobutene, as summarized in Table 3 [16,31,147,149-151,155,158-171]. Some of these macromonomers are used in the synthesis of graft polymers (Section VI.C). 

The macromonomer method (C) has also been adopted in cationic polymerization. For instance, amphiphilic graft polymers of vinyl ethers are synthesized by the cationic polymerization of a vinyl ether-capped macromonomer (26) with a block copolymer chain consisting of IBVE and AcOVE segments, followed by alkaline hydrolysis of the latter part into the HOVE units [165], This graft polymer also undergoes a host-guest interaction similar to those with amphiphilic star block copolymers [220]. 

Several examples of cationic grafting have been reported in the literature [40, 41]. Polymer chains having labile halogen atoms in combination with various Lewis acids have been used. Examples are polychloroprene, poly(vinyl chloride), chlorinated styrene-butadiene rubber, chlorinated PB, etc. The monomers involved in the grafting reaction include isobutylene, styrenes, THF, alkyl vinyl ethers, etc. 

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