Macromonomers step growth polymerization

Scheme 5. Structural and chronological overview of the macromonomers used for synthesis of dendronized polymers chain growth (a) and step growth polymerizations (b)...

A macromonomer is a macromolecule with a reactive end group that can be homopolymerized or copolymerized with a small monomer by cationic, anionic, free-radical, or coordination polymerization (macromonomers for step-growth polymerization will not be considered here). The resulting species may be a star-like polymer (homopolymerization of the macromonomer), a comblike polymer (copolymerization with the same monomer), or a graft polymer (copolymerization with a different monomer) in which the branches are the macromonomer chains. 

In an approach combining step growth polymerization with ring opening polymerization, Uchida and coworkers prepared a linear polyurethane capped with isocyanate groups on both ends [40]. This macromonomer was then mixed with NCA and hydrazine initiator, which was designed to... 

Alkene-functionalized linear polymers, such as the polyether-thioether described in Figure 3.9, was prepared by thiol-ene click step-growth polymerization using a fast, efficient, and green approach for the synthesis of macromonomers with a variety of functionalities. 

Another kind of macromonomer has gained interest recently polymers having two functions capable of participating in step growth polymerization reactions at one end of their chain. Such species are synthesized by free radical polymerization carried out in the presence of a bifunctional transfer agent, such as thiomalic acid or thioglycerol. Yamashita has prepared a number of... 

Another advantage of the DPE functionalization methodology is that it can be used to prepare condensation macromonomers, 34, which are polymers with two polymerizable ftmctional groups at one chain end. This type of macromonomer can participate in step-growth (condensation) polymerization with other diftmctional monomers to form model comb-type, branched condensation copolymers. 

A different approach of modeling ethylene-based copolymers is presented using acyclic diene metathesis (ADMEl) polymerization. Monomer s)mtiiesis dictates final polymer structure due to step-growth chemistry yielding only to olefin metathesis. While copolymerization of ethylene with a-olefins produces random distribution of alkyl branches along the PE backbone, polymerization of one kind of symmetric macromonomer produces PE with a perfectly known primary structure, as seen in Figure 1. 

This type of macromonomer can participate in step-growth (condensation) polymerization with other difunctional monomers to form model comb-type. 

In order to circumvent such phenomena, unique low molecular weight PPE telechelic copolymers were prepared. These PPE macromonomers (PPE-MM) were tailored with functionality to co-polymerize via step-growth or chain-growth polymerization in a variety of thermosetting resins. They exhibit very high solubility in solvents and monomers, and exhibit single-phase morphology in the final fully cured material. 

Figure 13. Shematic model in several steps for the particle nucleation and growth of sterically stabilized particles in dispersion polymerization using macromonomer technique [117].

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