Polymer Modification Functionalization and Grafting

Jose Bonilla-Cruz, Mariamne Dehonor, Enrique Saldivar-Guerra, and Alfonso Gonzalez-Montiel 

The synthesis or modification of polymeric substrates in order to produce polymers with polar or functional groups can be carried out by several synthetic pathways. When the process starts from a previously existing nonfunctional polymer, and functional groups are introduced to the chain, the term functionalization is used. The techniques employed for the generation of a functionalized or functional polymer are as follows  

Direct copolymerization [1, 2], In this case, two types of monomers react, one of them having a functional or pendant functional group for instance, the copolymerization of maleic anhydride (MA) and styrene (St) generates the alternating copolymer poly (St-a/t-MA) [1]. Another example is the direct copolymerization of a-olefins (polypropylene, PP, and polyethylene. 

End-functionalization [5], Possible routes are (i) modification of the chain end of preexisting polymers  

Handbook of Polymer Synthesis, Characterization, and Processing, First Edition. Edited by Enrique Saldivar-Guerra and Eduardo Vivaldo-Lima. 2013 John Wiley Sons, Inc. Published 2013 by John Wiley Sons, Inc. 

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A method for extracting cadmium, copper, europium, and nickel metal ions from aqueous solution using modified polyethyleneimine is described. The polymer modification consists of grafting an imide, diol, triol, carboxylic acid, or thiocar-boxylic acid function to poly(ethyleneimine), which then forms stable metal complexes that are readily removed from solution. 

In dentistry, silicones are primarily used as dental-impression materials where chemical- and bioinertness are critical, and, thus, thoroughly evaluated.546 The development of a method for the detection of antibodies to silicones has been reviewed,547 as the search for novel silicone biomaterials continues. Thus, aromatic polyamide-silicone resins have been reviewed as a new class of biomaterials.548 In a short review, the comparison of silicones with their major competitor in biomaterials, polyurethanes, has been conducted.549 But silicones are also used in the modification of polyurethanes and other polymers via co-polymerization, formation of IPNs, blending, or functionalization by grafting, affecting both bulk and surface characteristics of the materials, as discussed in the recent reviews.550-552 A number of papers deal specifically with surface modification of silicones for medical applications, as described in a recent reference.555 The role of silicones in biodegradable polyurethane co-polymers,554 and in other hydrolytically degradable co-polymers,555 was recently studied. 

In many experiments, it appears that such drastic solvent extraction can remove the major part of the synthetic polymer, showing that the grafted polymer presents, in point of fact, a good "adhesive" bondability. However, in the case of surface modification, a heavy grafting is not necessary and the degre of permanence is a function of the insolubility of the homopolymer in the solvents used in the common course of subsequent treatments. So it can be inferred that this notion of grafting may be dependent on the efficiency of the solvent extraction. 

By a similar degradation and graft copolymer formation mechanism block copolymers could be obtained by reactive extrusion. A prerequisite is the presence of functional groups and the interaction of these groups with immiscible polymers during melt processing. Several polyamide block copolymers are synthesised by a melt-modification process. 

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