2-Alkyl-2-oxazoline

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. 

Addition of 2-Alkyl-2-Oxazolines All of the above mentioned reactions of nucleophilic addition of nitrones give the corresponding hydroxylamines. In this chapter, the reactions of nitrones and nucleophiles and their conversions to compounds of other structures are considered. 

The reaction of lithiated 2-alkyl-2-oxazolines with nitrones enables stereoselective and enantioselective syntheses of 5-isoxazolidinones, which are used as precursors of 3-amino acids. Highly enantiomerically enriched 5-izoxazolido-nones and 3-amino acids of inverse configuration can be generated by simply changing the chirality of the initial 2- . sopropyl-2-oxazoline (600). 

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. 

Scheme 3 Synthesis of chitin-gra/t-poly(2-alkyl-2-oxazoline) [35]...

Gaertner FC, Luxenhofer R et al (2007) Synthesis, biodistribution and excretion of radiolabeled poly(2-alkyl-2-oxazoline)s. J Control Release 119 291-300... 

Currently, Z. -bipyridine derivatives figure prominently in supramolecular assembly,9 in bioinorganic contexts,10 in studies of redox electrocatalysis43 and in polymeric materials.11 Halomethyl bpys and their various metal complexes have also been used as initiators for controlled polymerizations of several different monomers including styrene and 2-alkyl-2-oxazolines.12... 

Alkyl-2-oxazoline macromonomers were prepared by termination of the living polymers with diethanolamine [ 181 ] as illustrated in the following reactions (Scheme 49). 

These macromonomers were used for the preparation of polyurethane-g-poly(2-alkyl-2-oxazoline) graft copolymers. Initially a prepolymer was formed by the reaction of poly( -caprolactone) having 2-OH end groups with 4-4/meth-ylenedi(phenylisocyanate). Copolyaddition of this product with the macromonomers provided the graft copolymers. The reaction is outlined in the following Scheme 50. 

HUB Huber, S. and Jordan, R., Modulation of the lower critieal solution temperature of 2-alkyl-2-oxazoline copolymers. Coll. Polym. Sci., 286,695,2008. 

Glycogen- f(/t-poly(2-alkyl-2-oxazolines) were easily prepared by CROP of 2-alkyl-2-oxazolines followed by termination of the living cationic ends with sodium glycogenate as new versatile biopolymer-based thermorespon-sive polymers (14RSCA61580). 

Oxazolines. Cationic polymerization of 2-alkyl-2-oxazolines provides an excellent methodology for the easy introdnction of fimctional end gronps (376). Polymerization proceeds via oxazolininm species and fimctional gronps can be incorporated at both initiation and termination steps by nsing functional initiator and nucleophile, respectively. 

Concerning block copolymers with non-ionic hydrophilic block other than PEO, typical examples are those reported by Binder and Gruber [175] for poly(2-methyl-2-oxazoline)-b-poly(2-alkyl-2-oxazoline) and by Cho et al. [176] for poly(N-isopropylacrylamide)-b-poly(7-benzyl L-glutamate). These PNIPAM-based copolymers, are typical for the preparation of thermosensitive micelles, with a coil-globule transition of the PNIPAM fringe at around 31-32°C [177]. 

Bonne TB, Liidtke K, Jordan R, Stepanek P, Papadakis CM (2004) Aggregation behavior of amphiphilic poly(2-alkyl-2-oxazoline) diblock copolymers in aqueous solution studied by fluorescence correlation spectroscopy (vol 282, pg 833, 2004). Colloid Polym Sci 282 (12) 1425-1425... 

Park, J.-S. and Kataoka, K. (2007) Comprehensive and accurate control of thermo-sensitivity of poly(2-alkyl-2-oxazoline)s via well-defined gradient or random copolymerization. Macromolecules, 40,3599-3609, doi 10.1021/ma0701181. 

Christova, D., Velichkova, R., and Goethals, E.J. (1997) Bis-macromonomeis of 2-alkyl-2-oxazolines - synthesis and polymerization. Macromolecular Rapid Communications, 18,1067 1073. 

Guinot, P., Bryant, L., Chow, T.Y., and Saegusa, T. (1996) Random and block 2-alkyl-2-oxazolines telecheUc macromonomers. Macromolecular Chemistry and Physics, 197,1-17. 

The synthesis of poly(2-alkyl-2-oxazoline)s, qttasi-diblock and diblock copoly (2-oxazoline)s with improved microwave-assisted polymerization was reported (Hoogenboom et al., 2005, 2007 Wiesbrock et al., 2005a). 

The most commonly studied thermo-responsive polymers are poly (N-isopropylacrylamide), poly(2-alkyl-2-oxazoline)s, poly(vinyl methyl ether), poly(N-vinyl caprolactam), and polymers of oligoethylene glycol (meth)acrylates. Each of them is characterized with specific LCST, mechanism of heat-driven phase transition, structure and properties of the resulting mesoglobules, as well as with varying extents of reversibility and reproducibility of the process of mesoglobule formation [58]. The most preferable characteristics of the thermo-responsive polymers and mesoglobules used as templates for nanocapsule preparation have been formulated below [58] ... 

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