Poly(2‐oxazoline)s as Smart Bioinspired Polymers

Abstract

Poly(2-alkyl-2-oxazoline)s can be regarded as pseudo-peptides or bioinspired polymers, which are available through living/controlled cationic polymerization and polymer ("click") modification procedures. Materials and solution properties may be adjusted via the nature of the side chain (hydrophilic-hydrophobic, chiral, bio-functional, etc.), opening the way to stimulus-responsive materials and complex colloidal structures in aqueous environments. Herein, we give an overview over the macromolecular engineering of polyoxazolines, including the synthesis of biohybrids, and the "smart"/bioinspired aggregation behavior in solution.

Bioinspired Poly(2-oxazoline)s

“…It was proposed that hydrophobic interactions and oriented dipolar interactions promote a slow crystallization of the PiPrOx chains to form nanoribbons, which then fuse together to form nanofibers (Figure 7(b), left). These nanofibers can further assemble into microspheres (vide infra), which is prevented by the presence of small amounts of a co-solvent (e.g., ethanol or tetrahydrofuran) (Figure 7(b), right) [98] or a surfactant (e.g., sodium dodecylsulfate) [11]. Likewise, Winnik et al observed formation of microfibers by heat-induced phase transition and crystallization of an octadecyl end-capped PiPrOx in water (Figure 7(c)) [99].…”

“…PiPrOx, however, may even crystallize in hot aqueous solution to yield a coagulate of uniform microspheres built of crystalline nanofibers (Figure 8) [11]. Crystalline nanofibers could always be observed, but the morphology on the micrometer length scale was found to depend strongly on the environmental conditions, like for instance temperature [102], presence of a co-solvent, surfactant or salt and polymer end group charges.…”

“…Aspects of advanced macromolecular engineering of polyoxazolines, including side-and end-chain functionalization, synthesis and properties of block and random copolymers, etc., have very recently been assorted by Hoogenboom [9,10], Schlaad et al [11], and Makino and Kobayashi [12]. The use of fatty acid based monomers for the preparation of sustainable poly(2-oxazoline)s was also recently highlighted by Hoogenboom [13].…”

“…Not considered are other emerging applications of poly(2-oxazoline)s, for instance in the fields of biomedicine and life sciences, where POXylation is being successfully introduced as an alternative to PEGylation [14], which has very recently been reviewed elsewhere [15]. Rather than trying to present a comprehensive overview of the literature as was done in other recent articles [9][10][11][12][13], it is aimed to introduce the importance and potential of bioinspired poly(2-oxazoline)s based on selected key references from the last decade.…”

Hydrophilization by coating of silylated polyoxazoline using sol–gel process

“…They have allowed the synthesis of a wide range of functionalized polymers [9][10][11][12]. Functionalities can be introduced into the polymer through the initiation [13,14] and/or the termination steps [15] giving head and/or end groups.…”