Postpolymerization

Postpolymerization Reactions. Copolymers can also be formed by postpolymetization reactions on polymers. A well-known example is the partial hydrolysis of polyacrjiamide (PAM) to hydrolyzed polyacrylamide (HPAM). The product becomes a random copolymer of acrylamide and acryUc acid (44) (see Acrylamide polya rs). 

Solid-state postpolycondensation, 99, 108 Solid-state postpolymerization, 72, 105-106... 

Ethylene-acrylic acid copolymers are converted to ethylene ionomers in a separate, postpolymerization reaction. 

Figure 5.18 shows the relationship between the resistivity and phosphorus concentration of the initial solution for the film formed from various solutions and heated under the same polycrystallizing RTA conditions (750 °C for 5min). As the initial phosphorus concentration increases, the resistivity decreases down to 2.1mQcm. The film formed from a l-wt% postpolymerization addition solution and the film formed from a 0.01-wt% copolymerized solution exhibit almost the same resistivity, which is reasonable since the two films have almost the same amount of phosphorus atoms, as shown in Fig. 5.16. To apply these doped-silicon films to the source and drain regions of poly-Si TFTs, the initial concentration of 0.1-1 wt% will be sufficient in the case of the copolymerized solution for this heating condition.

It is not practical to stir all reaction systems, for example, bulk polymerizations, postpolymerization reactions, fixed-bed catalytic reactors, and plug-flow reactors. Although multipoint temperature sensing is often used as a key solution to determine a runaway in nonagitated vessels, the occurrence of hot spots may not always be detected. 

Fang and Yamamoto [351] reported on postpolymerization functionalization of triarylamine-fluorene copolymer 253, resulting in copolymers 254a,b with stilbene pendant groups. Whereas in the solid-state absorption and PL maxima of both polymers are essentially the same, PL in solution is strongly influenced by solvent (from 433 nm in toluene to 466 nm in jY-methylpyrrolidone). Copolymer 254a showed d>PL in the solid state of 51%, comparable to that of poly(9,9-dialkylfluorenes) (Chart 2.66). 

Polychlorotrifluoroethylene (PCTFE) is ordinarily prepared by emulsion polymerization. A polymer suitable for thermal processing requires coagulation, extensive washing, and postpolymerization workup. Coagulation to provide a filterable and washable solid is a slow, difficult process and removal of surfactant is an important part of it. Complete removal may be extremely difficult depending on the extent of adsorption to the polymer particles. Consequently we set out to develop a suspension polymerization process, which would be surfactant-free and afford an easily isolated product requiring a minimum of postreaction workup. 

Polysilanes with functionalities Z directly attached to the silicon main chain are generally more difficult to synthesize and less stable, due to the reactivity of both the Si-Z and Si-Si linkages. Such polymers are usually not accessible via the Wurtz-type coupling reaction, and alternative synthetic strategies (see Sections 3.11.4.1 and subsequent) or postpolymerization techniques have to be employed. 

Postpolymerization of difunctional monomers to effect star branching has been successfully applied in cationic polymerization, e.g. in the case of polyisobutylene initiated with 2-chloro-2,4,4,-trimethylpentane/TiCl4. Addition of divinylbenzene leads to star polymers [104], Vinyl ethers, when polymerized with HI/ZnI2 in toluene at — 40°C, can be copolymerized with divinylether... 

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. 

Note 2 Physical aging, crystallization, physical crosslinking and postpolymerization reactions are sometimes referred to as curing . Use of the term curing to describe such... 

Depending on the postpolymerization derivatization procedure, silica-based monolithic columns have been employed for NPC [95] (see also Merck KGaA Darmstadt, Germany), RPC [189-193,196,197,200] (see also Merck KGaA Darmstadt, Germany), lEX [194], and HILIC [84,194,198] application. Additionally, their use as efficient bioreactors has recently been reported [86,195]. 

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. 

Unfortunately, the polymerizations of charged monomers are mostly uncontrolled, preventing the easy formation of block copolymers. Fang and Kennedy (2002) circumvented this problem by using a postpolymerization method to introduce the charge species onto one or more blocks of block copolymers that were synthesized using ATRP (Fig. 5.4c and d). 

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