Ring-opening polymerizations 2-oxazolines

One product is poly(2-ethyl-2-oxa2oline) (PEOX). It is prepared by the ring-opening polymerization of 2-ethyl-2-oxazoline (19) with a cationic initiator (48) (eq. 6). 

Ring-opening polymerization of 2-methyl-2-oxazoline produces poly( V-acetyl-ethylenimine) (Scheme 2) [24-27], The resulting polymer can be regarded as a... 

Thus, the ring-opening polymerization of 2-methyl-2-oxazoline followed by the treatment of the resulting oxazolinium propagating end group with 3-aminopropyltriethoxysilane produced successfully triethoxysilyl-terminated poly-oxazoline as shown in Scheme 3 [29]. 

Polyamines can also be synthesized by cationic ring-opening polymerization of ethyleneimines (aziridines), trimethyleneimines (azetidines), and 2-oxazolines. 

Although the first examples of hyperbranched polymers proposed by Flory involved condensation-type polymerization strategies, the first well-characterized hyperbranched example involved the ring-opening polymerization of 2-carboxylic-2-oxazoline derivatives. As early as 1988, Odian and Tomalia [2] reported the ring-opening polymerization of these derivatives to form random... 

The living cationic ring opening polymerization (CROP) of 2-oxazolines was first reported in the 1960s [61, 62]. The polymerization can be initiated by an electrophile such as benzyl halides, acetyl halides, and tosylate or triflate derivatives. The typical polymerization mechanism for 2-alkyl-2-oxazoline initiated by methyl tosylate is shown in Scheme 6. 

Paulus RM, Becer CR, Hoogenboom R et al. (2008) Acetyl halide initiator screening for the cationic ring opening polymerization of 2-ethyl-2-oxazoline. Macromol Chem Phys 209 794-800... 

Becer CR, Paulus RM, Hoppener S et al. (2008) Synthesis of poly(2-ethyl-2-oxazoline)-h-poly(styrene) copolymers via a dual initiator route combining cationic ring opening polymerization and atom transfer radical polymerization. Macromolecules 41 5210-5215... 

Hoogenboom, R. and U.S. Schubert, Microwave-Assisted Cationic Ring-Opening Polymerization of a Soy-Based 2-Oxazoline Monomer, Green Chemistry, 8, 895-899 (2006). 

Linear PEI can be obtained by cationic ring-opening polymerization of 2-oxazoline, followed by alkaline hydrolysis of the resulting poly(N-formylethyleneimine)9). 

Carlos, G.S., Richard, H., and Ulrich, S.S. 2006. Fast and green living cationic ring opening polymerization of 2-ethyl-2-oxazoline in ionic liquids under microwave irradiation. 

In addition, there may be an equilibrium in ring-opening polymerizations between onium ions and covalent species. This equilibrium has been observed in the polymerizations of cyclic ethers [29], oxazolines [68], and phosphorus-containing monomers [69], The position of the equilibrium and its dynamics depend on the relative nucleophilicities of the monomer and the counteranion, as well as on the nucleofugacity ot the leaving group. 

All the approaches described have been used to prepare functional polymers by cationic ring-opening polymerization. From this point of view, groups of monomers that have been investigated most are cyclic ethers (tetrahydrofuran), cyclic acetals (1,3-dioxolane), cyclic imines (N-f-butylaziridine), and oxazolines, i.e., these monomers for which the living conditions can be approached. 

The last system to be discussed in this introductory article is the interesting ring opening polymerization of 2-oxazolines as outlined briefly in Scheme XVI. This area has been pioneered by a number of people, including Professor Litt who contributes an additional article in this book. The polymerizations were also... 

Based on the same idea, of using alkyl halides as initiators for the ring opening polymerization of 2-alkyl oxazolines, Schulz and Dworak partially hydrolyzed... 

Polymerization of macromonomers by cationic ring-opening polymerization Macromonomer has been prepared from 2-(p-hydroxyphenyl)-2-oxazoline and ethylene oxide using n-butyl lithium to initiate the anionic polymerization of EO 16I). The living chains were terminated with CH3I or H20 yielding macromonomers with Mn = 1,010 and M = 1,930, respectively ... 

Commercial polyethyleneimine 1 is prepared by ring-opening polymerization of ethyleneimine [Eq. (6—1)]. This polymer is a highly branched, relatively compact, water-soluble macromolecule, and approximately contains 25% primary, 50% secondary, and 25% tertiary nitrogen atoms 112). The averse structure is therefore represented as i ven below. Recently, Saegusa et al. succeeded in preparing linear, crystalline polyethyleneimine by polymerization of 2-oxazoline and subsequent hydrolysis [Eq. (6-2)] (ii5). 

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