Grafting onto the Chains

This method of grafting requires the addition of a living cationic polymer to a preformed polymer having several nucleophilic centers in the chain. An example is epoxidized butyl rubber (see above). It was observed that the model of the reactive unit, namely the trisubstituted epoxide 2,3-epoxy-2,4,4-trimethylpentane, terminates THF polymerization 153)  

Formation of similar units in the chains occurs when butyl rubber containing some epoxy groups is mixed with living polyTHF. Some gel is also formed, indicating that grafting from , onto and through proceed simultaneously. 

With more nucleophilic active sites only grafting onto is possible. In this way Franta et al. grafted polyTHF onto poly(N,N-dimethylaminostyrene) and poly(2-vinylpyridine)154). The grafting process was in both cases quantitative, yielding polymeric quaternary ammonium salts  

Random copolymerization of styrene and N,N-dimethylaminostyrene is less effective because some homopolymer of THF was also found among the products. 

In a similar way Richards et al. have grafted polyTHF onto poly(4-vinyl pyridine) 

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In both water-reducible coatings and wata-soluble polymers, the polymer chain, which is naturally hydrophobic, is altaed hydrophilic segments such as carboxylic acid groups, sulphonic acid groups, and tertiary amines are grafted onto the chain to confer a degree of water solubility. 

The first drugs in this class to be introduced into clinical practice are simple derivatives of 5-nitrofurfural (18). Thus, the oxime is known as nitrofuroxime (19) while the semicarbazone is called nitrofurazone (20). In order to maintain better control over the distribution and metabolism of these antibacterial agents, increasingly complex side chains and rings have been grafted onto the hydrazone. 

It has also been found a certain level of reactivity between C60 and C70 with the unsaturated fatty acids. The electronic absorption spectra show evidences that C60 or C70 are grafted onto the fatty chains when the fullerene solutions in vegetable oils are left for days in air, by heating the solutions under N2, Ar and air, or by UV irradiation of the solutions in inert atmosphere. 

During the polymerization of the styrene, the poly(butadiene) or butadiene copolymer is grafted onto the styrene polymer chain. To increase the grafting efficiency of the poly(butadiene), it is desirable for the poly(butadiene) to have end segments having a high vinyl content rather than cis- or trans-configurations. 

Figure 39 represents schematically such a process in the case of two-site (ditopic) complementary components Te 2 and Ts2. The resulting supramolecular polymeric material ((Te 2, T32) may present liquid-crystalline properties if suitable chains are grafted onto the components. One may note that the mixed site species e Tsrepre-... 

This model shows that the radius of polymer particle follows simple scaling relationships with the key parameters in the system x1/3, [comonomer]02/3, [macromonomer]01/2, and [initiator]0 1/2, where [ ]0 means initial concentration. These equations also predict that the particle size and stabilization are determined by the magnitude of In addition the surface area occupied by a hydrophilic (PEO) chain follows x 1/3 in the case of azeotropic copolymerization, x=Xj. This means that the PEO chain conformation for chains grafted onto the polymer particles change with grafting density. 

An interesting aspect related to the design of these ensembles is the fine-tuning of the polarity of the inner pores. In this respect, Inumaru et al. reported the adsorption behavior of alkylphenols and alkylanilines by MCM-41 -type solids doped with different degrees of Al3+ and equipped with alkyl chains of different length grafted onto the surface.24,25 The authors found two well defined trends (1) lipophilic guests were... 

The surface area per sterically-stabilized particle is determined by the surface area (S) occupied by a macromonomer chain times the number (n ) of these chains grafted onto the surface. 

The rubber particles were examined with an electron microscope after the sample was treated with osmium tetroxide (27). The micrograph (Figure 7) clearly indicates the porous nature of the rubber phase and the occlusion of polystyrene. We therefore classify this type of rubber phase as filled graft rubber. Since grafting takes place before and after the rubber chain is coiled, therefore, for this case, the monomer is grafted onto the rubber both within and without the rubber phase. Polybutadiene is thus made more compatible to the polymer matrix surrounding the rubber phase and the polymer filling the rubber phase. Here we have an... 

A variety of specific reactions are performed on polymeric amidic Mannich bases for instance, poly(maleimide), after aminomclhylation with aromatic amine, is subjected to a coupling reaction with a diazo derivative in order to obtain azo dyes, grafted onto the polymeric chain 439, which arc able to give colored chelates." ... 

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