First Poly(2‐oxazoline)s with Pendant Amino Groups

Abstract

Summary: A new 2‐oxazoline monomer with a Boc protected amino function, 2‐[N‐Boc‐5‐aminopentyl]‐2‐oxazoline; (Boc‐AmOx), was synthesized from commercially available compounds. With an initiator salt system (N‐methyl‐2‐methyl‐2‐oxazolinium triflate; MeOxOTf), the monomer could be converted via living cationic ring‐opening polymerization to well‐defined homopolymers with narrow molar mass distributions and targeted polymer chain length. After a quantitative deprotection, poly(2‐oxazoline)s with pendant amino functions were obtained. In order to vary the polymer functional group density and solubility of the polymer, copolymerization with different monomer ratios of Boc‐AmOx and 2‐ethyl‐2‐oxazoline (EtOx) was performed. Ex‐situ NMR spectroscopy studies verified the randomness of the cationic copolymerization. The accessibility of the pendant amino side functions was confirmed in polymer analog thiourea formation with different isothiocyanates, such as benzyl isothiocyanate (BzNCS), or a fluorescence dye, tetramethyl rhodamine isothiocyanate (TRITC). A cross‐linking reaction with a bifunctional isothiocyanate (Ph(NCS)2) resulted in poly(2‐oxazoline) hydrogels. magnified image

UV-Induced Crosslinking of Poly[2-(2’-Norbornenyl)-2-Oxazoline]s

“…NbOx was added to the freshly prepared solution of the macroinitiator maintaining inert conditions, and, due to the significantly lower reactivity compared to methyl cations, the sterically more demanding macroinitiator preferentially attacked the nitrogen atom of the 2-oxazoline rings and yielded soluble pNbOx (Scheme 1). Similar findings were reported for the polymerization of a 2-oxazoline monomer with a pendant amino group [11]. According to 1 H-NMR analyses of the polymerization of NbOx, no residual monomer was present in the polymerization mixture after reaction times of 1 h; the polymerization was quenched with water.…”

Design Strategies for Functionalized Poly(2-oxazoline)s and Derived Materials

“…While pMeOx and pEtOx enabled single-point attachment only in the copper-catalyzed reaction, the other two copolymers allowed multiple-point attachment (because of the p n Pe ≡ Ox units) and yielded fully crosslinked core-shell structures of high thermal stability. n PeOx-stat-pEtOx that was obtained from the CROP of (NHBoc) n PeOx (and EtOx) and deprotection of the copolymer [197]. The amino groups were subsequently reacted with various isothiocyanates, yielding crosslinked hydrogels in the case of bifunctional isothiocyanates.…”

Kinetic Investigations on the Polymerization of 2‐Oxazolines Using Pluritriflate Initators

“…Furthermore, numerous functional monomers allow the introduction of pendant functional side chains. Among others, carboxylic acid, [3,4] hydroxyl [3,5] and, more recently, amine, [6] thiol, [7] aldehyde [8] and alkyne [9] side chains are of particular interest for preparation of poly-and multifunctional polymer carriers for biomedical applications. Furthermore, the CROP of 2-oxazolines allows for the preparation of telechelics, [9,10] (multi)block-copolymers [11] or surface reactive lipopolymers.…”