Cation grafted

A Cationic Graft Copolymer of Lignin. The applications of the anionic graft copolymers described above are many but the negative charge on the polymer or the behavior of the anionic polymer under application conditions often limit the utility of these materials. 

Lignin has been reacted with 4N,4N - dimethyl-4-ammoniumhept-1,6 -diene chloride monomer to make a cationic graft copolymer. The structure of the copolymer is illustrated by the formula ... 

More recently, the scope of using hyperbranched polymers as soluble supports in catalysis has been extended by the synthesis of amphiphilic star polymers bearing a hyperbranched core and amphiphilic diblock graft arms. This approach is based on previous work, where the authors reported the synthesis of a hyperbranched macroinitiator and its successful application in a cationic grafting-from reaction of 2-methyl-2-oxazoline to obtain water-soluble, amphiphilic star polymers [73]. Based on this approach, Nuyken et al. prepared catalyticaUy active star polymers where the transition metal catalysts are located at the core-shell interface. The synthesis is outlined in Scheme 6.10. 

Pan et al recently reported the preparation and characterization of polystyrene/graphite composites prepared by cationic grafting polymerization. Graphite/polystyrene composites were produced with cationic grafting... 

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. 

Fig. 13. Cationic grafting of phosphine oxide onto polystyrene...

J. P Kennedy, Ed., Cationic Graft Copolymerization, Wiley, New York, 1977. 

Similarly, in the case of cationic method, the initiation reaction between labile alkyl halide [68] and Lewis acid have been utilised for cationic grafting onto halogenated polymers as shown in Scheme 3. 

Scheme 3 Cationic grafting onto halogenated polymers can be brought about using the...

Even though some techniques of cationic grafting 125) and of free-radical grafting4 have been developed 126,127), the number of systems that can actually be used is very small, and the search for new and more general methods, applicable to systems that cannot respond to ionic techniques, has been one of the determining factors for research in the field of macromonomers. 

Kennedy, J. P. Cationic Graft Copolymerization, Appl. Polym. Symp., J. Appl. Polym. Sci. 30,(1977)... 

Table 6 Synthesis and Application Data for Cationic Graft Copolymer A Synthesis Data...

The original idea of cationic grafting produced by initiation from a polymer containing cocatalytic moieties was proposed by Plesch in 1958 Basically, the principle of this branching reaction relies on activation of a C—X bond of the polymer by a Lewis acid in a process thought to proceed by halide ion abstraction ... 

Kennedy and coworkers improved considerably the degree of grafting by using di-ethylaluminium chloride at low temperature and claimed that this achievement was due to the essential absence of transfer reactions in the branching pdymerisation. The work of this prolific group has recently been the object of an entire issue of Applied Polymer Symposium and the interested reader will find in those papers a general introduction to cationic grafting and the ecific contributions and applications achieved at Akron. 

We have omitted from the above brief survQ tho studies dealing with the cationic grafting of a polymer onto another since these Friedel-Crafts alkylation reactions, although proceeding via carbenium ion intermediates, do not initiate any polymerisation and fall therefore outside the realm of the present review. Kennedy has recently summarised this type of work ° ... 

Initiation mechanisms are everywhere elucidated by their integration into the complex overall rate behaviour of cationic polymerisation. Propagation rates determine yields and convenfently multiply the measurable effects of initiation. Termination steps contribute their effects to the jigsaw of cationic polymerisation, and even various kinds of cationic grafting reactions are covered. There can be few reviews punctuated by so many specific proposals for timely research, not only by academics, but also sometimes for possible industrial development. 

In addition to a better understanding of the effect of reaction variables on products, rates and molecular weights, this work has also led to new mechanistic concepts such as termination by hydridation and to the optimization of cationic graft-copolymer synthesis. 

The high rate of termination that occurs with EtjAl could be exploited in cationic graft copolymerizations (20). The use of EtgAl coinitiator could minimize chain transfer due to faster termination, thereby reduce homopolymerization and con quently increase grafting efficiency. 

Photolithography on the basis of the cationic graft-polymerization uses an inert polymer film containing a PAQ coated onto a wafer. Exposing the photoresist to the UV radiation generates acid on its surface, to which a vapor-phase silicon-containing monomer is grafted. RIE in O2 is used as a final step. ° ... 

An objective in synthesizing poly (butadiene-g-styrene) by cationic grafting onto was to study the morphology of such grafts by transmission electron microscopy and the effect of composition on graft morphology. The unsaturated nature of the backbone permitted such a study. 

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