Preformed end-functionalized polymer

Many block and graft copolymer syntheses involving transformation reactions have been described. These involve preparation of polymeric species by a mechanism that leaves a terminal functionality that allows polymerization to be continued by another mechanism. Such processes are discussed in Section 7.6.2 for cases where one of the steps involves conventional radical polymerization. In this section, we consider cases where at least one of the steps involves living radical polymerization. Numerous examples of converting a preformed end-functional polymer to a macroinitiator for NMP or ATRP or a macro-RAFT agent have been reported.554 The overall process, when it involves RAFT polymerization, is shown in Scheme 9.60. 

The grafting-to approach is based on the attachment of already preformed end-functionalized polymer molecules to fimctional groups on the nanotube surface via appropriate chemical reactions. An advantage of this method is that commercially available polymers containing reactive fimctional groups can be utilized. However, the main limitation of grafting-to technique is that initial binding of polymer chains sterically prevents diffusion of additional macro-... 

Figure 6 Formation of miktoarm polymer using the hybrid approach by attaching an end-functional polymer to the juncture point of a preformed AB diblock copolymer. ...

The grafting through strategy means the preparation of cylindrical brushes by the polymerization of preformed MMs. This was the first method in the synthesis of cylindrical brushes. For the first time, Tsukahara et al. [108] successfully obtained cylindrical brushes by the radical polymerization of MMs. Short polymer chains with a polymerizable vinyl chain end were first made by anionic polymerization and sequential end-functionalization. Further radical polymerizations of the premade MMs yielded cylindrical brushes with uniform side chains. This method was then further employed by Schmidt et al. [109, 119-121] and Ishizu et al. [122-127] to... 

Monomers with Different Functionalities Introduction of other functionalities into monomer structure is a versatile approach to increase the reactivity, provide wavelength tunability, and improve the properties of the networks formed. Monomers attached to preformed polymers [2] or equipped with photosentizers [119], hydroxyl groups [108-110], and groups polymerizable by other modes [2,120,121] were readily prepared. For example, epoxy end functionalized poly (e-caprolactone)... 

One of the major drawbacks of CRPs is the inability to prepare block copolymers of monomers with widely differing reactivities, such as styrene and vinyl acetate, by sequential monomer addition. Thus, the use of chemistries that permit effective coupling between suitably end-functionalized preformed polymer chains is clearly an attractive alternative. Quemener et al. designed two novel RAFT agents that could be used to polymerize styrene and vinyl acetate independently [36] one RAFT agent installed an azide unit at the end of the polyvinyl... 

Copolymers. There are two forms of copolymers, block and random. A nylon block copolymer can be made by combining two or more homopolymers in the melt, by reaction of a preformed polymer with diacid or diamine monomer by reaction of a complex molecule, eg, a bisoxazolone, with a diamine to produce a wide range of multiple amide sequences along the chain and by reaction of a diisocyanate and a dicarboxybc acid (193). In all routes, the composition of the melt is a function of temperature and more so of time. Two homopolyamides in a moisture-equiUbrated molten state undergo amide interchange where amine ends react with the amide groups. 

There is a current drive in microlithography to define submicron features in bilevel resist structures. The introduction of organometallic components, most notably organosilicon substituents, into conventional resists is one promising approach. To this end, organosilicon moieties have been primarily utilized in starting monomers (1-4) or in post-polymerization functionalization reactions on the polymer (5,6). Little work has been done on the reaction of preformed reactive oligomers to synthesize block copolymer systems. 

The effective complexation of CD was also used for the preparation of side-chain polyrotaxanes [96-102], All of these side-chain systems are based on Method 4 or Method 5 (Figure 9) and were reported by Ritter and coworkers. For Method 4, the CD was threaded on to a small molecule bearing a functional group Y and with one end blocked, i.e., a hemirotaxane. The reaction of Y with X, a pendant functional group in a preformed polymer, gives thermally stable... 

The direct synthesis of block copoljmiers by radical polymerization is an alternative to using preformed blocks with functional endgroups. Polymers with initiator end-groups (3a,3b), with end groups accessible to radical activation polyinitiators (6, 7.)... 

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