Postpolymerization approach

The use of Si-H coatings to chemically modify the surface of c-Si is an alternative postpolymerization approach for the introduction of functional groups and a means to provide stability with respect to the contact of water and air at the c-Si surface. The c-Si surface offers ideal 2D Si-skeleton lattices or Si-Si bond nanosheets with puckered hexagonal lattices. Various functional groups are successfully employed. A coating of Si-H on c-Si is formed using aqueous HF to treat c-Si and remove Si02 layers. 

The incorporation of comonomers into PET and other polyesters, with the intent that these comonomers would then serve as the site for additional, postpolymerization reactions, has not been widely explored. A potential difficulty in such an approach is that the reactive comonomer cannot react under PET synthesis conditions of ca. 285 °C/2h/Lewis acid catalyst if the modification is to be effective. Two such systems, stable under PET synthesis, and then subjected to post-polymerization reactions, have been recently reported. 

Side chain functionalization of covalently functionalized pol5mers can take place either by prepolymerization functionalization, which is the functionality that has been bestowed to the monomer, or by postpolymerization functionalization, which is after the polymerization, when the polymer backbone is subsequently functionalized with the desired moiety (Pollino and Week 2005). Although both approaches have been employed successfully in covalent pol5mer chemistry, the first approach can be synthetically more demanding but always yields 100% functionalization, which is not the case for most postpolymerization functionalization strategies. 

The book contains 22 chapters, logically organized into an overview chapter with three other subsections Part one The synthesis of functional polymers by direct methods, such as anionic, cationic, free radical and coordination polymerization. Part two The synthesis of functional polymers by postpolymerization functionalization. Part three Novel approaches and structures. Special emphasis is given to more modem techniques Aat allow for controlled and directed functionalization via living polymerization. 

Suzuki-Miyaura cross-coupling polymerization of 1,4-bis((Z)-2-bromovinyl)benzenes with aryl-bis-boronic acids. The interest has been in an alternative approach, where rather than building a PPV with a pre-ordained stereochemistry, a postpolymerization yyn-selective reduction on a poly(phenylene ethynylene) (PPE) is used [125]. This scheme has the advantage that high molecular weight PPEs can be synthesized using either Pd-catalysis or alkyne metathesis. This route could also potentially allow for the access to an additional array of PPVs that are uniquely accessible from PPEs. The transformation of the triple bonds in PPEs and other acetylene building blocks to alkenes has considerable potential. 

As an alternate intermediate, adiponitrile is employed to react with hexamethylene diamine and steam in a multistage distillation column to prepare nylon-6,6 [194]. The process is carried out in the presence of an oxygen-containing phosphorous catalyst at an elevated temperature and pressure. Nylon-6,6 of high molecular weight can be produced by the postpolymerization of lower molecular weight polymer in the molten state in the presence of a phosphonic acid catalyst [195] or in the solid state [196]. In a different approach, a prepolymer is formed in a reactor system. 

A new class of water soluble polypyrrole has been prepared by selfdoping of the polymer. These self-doped polypyrroles can be prepared electrochemically or chemically, using various dopant anions covalently bound to the polymer backbone. The self-doped sulfonated polypyrrole is most commonly synthesized electrochemically in nonaqueous media. Electrochemical synthesis in aqueous media and chemical synthesis are not typically used, presumably due to issues with overoxidation. The postpolymerization modification of polypyrrole, in a manner similar to that used to form sulfonated polyaniline is rare [41]. The various synthetic approaches and properties of the polymer are discussed in the following sections. 

The approaches for the description of the postpolymerization kinetics considered above do not take into account the composition changes in a polymerization system composition and its phase state that is why such approaches are formal. However, they are interesting because it has been shown that the kinetic models involving active radicals with one characteristic life time (mono- or bimolecular chain termination) correspond considerably worse to experimental data in comparison with the kinetic model characterized by two characteristic life times (mixed mono- and bimolecular chain termination). The same technique of widening the characteristic life times of active radicals from the position of a microheteiogeneous model and monomolecular chain termination is proposed in Rel. [55]. 

Molecularly imprinted polymers and CPs are the most common examples of polymers used as biosensors. Both of these polymers are facile to be synthesized and modified as described above. Of particular interest is the postpolymerization modifications that have been used to functionalize the side chains of CPs because this approach allows for facile and diverse functionalization from a single starting material, that is, the CP. MIPs are good recognition motifs in sensors, creating binding sites for analytes through... 

Two basic approaches that can be used to prepare random or non-segmented acetylene copolymers are (1) using mix monomers during synthesis and (2) postpolymerization chemical modification. The earliest method used to prepare random copolymers of... 

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