Ethyl oxazoline

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). 

These poly(2-alkyl-2-oxazoline) silane coupling agents were copolycondensed with tetraethoxysilane by acid-catalyst to produce poly(2-alkyl-2-oxazoline)-modified silica gel. The composite gel from 2-ethyl-2-oxazoline was also homogeneous and transparent glass. Poly(2-alkyl-2-oxazoline)-modified silica gels, especially gels based on poly(2-ethyl-2-oxazoline) absorbed water and also organic solvents such as DMF or alcohols as shown in Table 7. This result means that the obtained composite gel shows the amphiphilic adsorption property. 

Controlled synthesis of ABA type poly(2-ethyl-2-oxazoline)-b-PDMS block copolymers was obtained by the melt reaction of a,c -benzyl halide terminated PDMS oligomers and the oxazoline monomer 291 as shown in Reaction Scheme XX. 

Synthesis of Poly(2-ethyl-2-oxazoline)-b-PDMS (ABA) Block Copolymers 2911... 

The metal-centered complexes can also be used as multifunctional initiators. For example, Fe2+(4,4 dichloromethyl-2,2 -bipyridine)3 or the Ru2+ complex have been used as initiators for the living cationic polymerization of 2-ethyl-2-oxazoline [120],... 

Interestingly, the Fe2+ ion in the core can be easily removed by base, the complex dissociates and the individual polymer dimers can be analyzed. Block copolymers of 2-ethyl-2-oxazoline with other substituted oxazolines have also been made [121]. Ru2+(4,4 dichloromethyl-2,2 bipyridine)3 has also been used as the multifunctional initiator for the ATRP of styrene at 110°C [122], It is interesting to note that the Cu+ ions necessary for the polymerization reaction are solubilized via complexation with other bipyridine species. 

Fig. 9.27 Reaction scheme for the preparation of amphiphilic poly(2-ethyl-2-oxazoline) brushes by means of LCSIP [272].

Fig. 9.28 Analysis of the CH-stretching region (3000-2800 cm ) and the amide I band around 1650 cm V (a) ER-FTIR spectrum of poly(2-ethyl-2-oxazoline) (PEOx) as grown on the triflate functionalized HUT SAM. (b) ER-FTIR spectrum of HUT SAM. (c) Subtraction result of (a)-(b). (d) Bulk spectrum of PEOx. In the spectrum to the left, a significant shift...

In a similar approach Riihe et al. [279] reported the preparation ofpoly(2-oxazoline) brushes by the grafting onto as well as grafting from method. For LCSIP of 2-ethyl-2-oxazolines silane functionalized undecane tosylate was first prepared and then immobilized on the substrate surface. SIP resulted in PEOx layers with thickness close to 30 nm. PEOx brushes were prepared by chemisorption of PEOx disulfides onto gold substrates. Preliminary static and dynamic swelling experiments are reported for these brushes. However, later observations [243] contradicted these findings. 

Hoogenboom R, Thijs HML, Fijten MWM, Schubert US (2007) Synthesis, characterization, and cross-linking of a library of statistical copolymers based on 2- soy alkyl -2-oxazoline and 2-ethyl-2-oxazoline. J Polym Sci Part A Polym Chem 45 5371-5379... 

Scheme 6 Schematic representation of the CROP of 2-ethyl-2-oxazoline (EtOx) initiated by the methyl tosylate...

Hoogenboom R, Paulus RM, Fijten MWM et al. (2005) Concentration effects in the CROP of 2-ethyl-2-oxazoline in iV,iV-dimethyl acetamide. J Polym Sci Part A Polym Chem 43 1487-1497... 

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... 

Xu S, Zhao H, Tang T, Dong L, Huang B. Effect and mechanism in compatibilization of poly(styrene-l)-2-ethyl-2-oxazoline) diblock copolymer in poly(2,6-dimethyl-1,4-phenylene oxide)/poly(ethylene-ran-acrylic acid) blends. Polymer 1999 40 1537-1545. 

Surface-initiated living cationic polymerization of 2-oxazolines on planar gold substrates has been reported by Jordan et al (Fig. 9). SAMs of initiators on a planar gold substrate have been used to initiate the living cationic ringopening polymerization of 2-ethyl-2-oxazoline. The polymer chain end was functionalized with an alkyl moiety by means of a termination reaction in order to form an amphiphilic brush-type layer. The resulting layers (thickness... 

An interesting extension to this finding resulted when 2-aminoethanol was reacted with propionitrile. Initial formation of amidine 9 occurs, with subsequent ring-closure giving the final product, 2-ethyl-2-oxazoline 10. 

Alkyl substituted 2-oxazolines, for instance 2-methyl-2-oxazoline9), or 2-ethyl-2-oxazoline 10) can be used in the place of unsubstituted 2-oxazoline. In all cases, the molecular weight of the resulting PEI is relatively low, usually in the order of a few thousands. 

Jeong, J.H., Song, S.H., Lim, D.W., Lee, H., and Park, T.G. (2001) DNA transfection using linear poly(ethylenimine) prepared by controlled acid hydrolysis of poly(2-ethyl-2-oxazoline). Journal of Controlled Release 73 391-399. 

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. 

Oxazoline monomers have been commercialized since the mid-1970s and mainly produced by Dow Chemical Co. and Chemisches Werkes Huls. The principal monomer supplied is 2-ethyl-2-oxazoline. 

Asymmetric Aldol Additions. 2-Ethyl-2-oxazoline takes part in aldol condensations as its boron azaenolate. The erythro selectivity for this protocol is excellent (95 5 to 98 2) but the enantios-electivity is only moderate (29-71% ee eq 6). ... 

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