Tuning temperature responsive poly(2-alkyl-2-oxazoline)s by supramolecular host–guest interactions

Abstract

A poly[(2-ethyl-2-oxazoline)-ran-(2-nonyl-2-oxazoline)] random copolymer was synthesized and its thermoresponsive behavior in aqueous solution modulated by the addition of different supramolecular host molecules. The macrocycles formed inclusion complexes with the nonyl aliphatic side-chains present in the copolymer, increasing its cloud point temperature. The extent of this temperature shift was found to depend on the cavitand concentration and on the strength of the host-guest complexation. The cloud point temperature could be tuned in an unprecedented wide range of 30 K by supramolecular interactions. Since the temperature-induced breakage of the inclusion complexes constitutes the driving force for the copolymer phase transition, the shift in cloud point temperature could be utilized to estimate the association constant of the nonyl side chains with the cavitands.

Supramolecular control over thermoresponsive polymers

“…Adapted from Ref. [95] Copyright (2014) Wiley-VCH Verlag GmbH & Co. [92,93]. In particular, the combination of a thermoresponsive PEtOx-ran-PNonOx copolymer containing 12 mol% nonyl sidechains with a range of cyclodextrins and cucurbit [7]uril (CB7) hosts resulted in an unprecedented increase of the T CP of 30 K with stoichiometric amounts of the cavitands (Fig.…”

“…In particular, the combination of a thermoresponsive PEtOx-ran-PNonOx copolymer containing 12 mol% nonyl sidechains with a range of cyclodextrins and cucurbit [7]uril (CB7) hosts resulted in an unprecedented increase of the T CP of 30 K with stoichiometric amounts of the cavitands (Fig. 6) [92]. The broad tunability of the T CP achieved in this study is in line with the intuitive assumption that a higher content of hydrophobic guest units across the copolymer chain allow the incorporation of a larger number of cavitands therefore expanding the T CP tunability of the copolymer.…”

Complexation of thermoresponsive dialkoxynaphthalene end-functionalized poly(oligoethylene glycol acrylate)s with CBPQT4+in water

“…The extent of this increase was found to be dependent on the concentration of the host molecule added and the strength of the complexation between nonyl side-chains and the host molecule. 42 It is clear that the combination of supramolecular hosts with thermoresponsive polymers displaying complementary and specific recognition properties represents a straightforward strategy to finely modulate the solution behavior of thermoresponsive polymers. 33 Nonetheless, there are surprisingly few studies focusing on the fundamental aspects of how thermoresponsive polymers can influence host-guest complexation as the majority of reports are proof of concept studies showing that the host-guest interactions can influence the T CP .…”

Synthesis, binding and self-assembly properties of a well-defined pillar[5]arene end functionalised polydimethylacrylamide

“…Furthermore, the non-covalent modification of polymers has allowed their solubility and correspondingly their processability to be greatly improved. 8,9 The development of this field has largely gone hand-in-hand with the enormous progress that has been made in the development of well-defined polymers synthesised using controlled radical polymerisation (CRP) techniques that feature specific recognition motifs (hydrogen acceptor/donor, 10,11 ionic unit, 12,13 metal/ligand, 14,15 host/guest [16][17][18] molecules) attached in specific locations (end or side chain) to polymer backbones. Pillar[n]arenes (n = 5, 6, 7, 8…) have emerged as important host units for the construction of supramolecular assemblies with applications spanning materials, 19,20 medicine [21][22][23] and sensing.…”