Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

Abstract

SummaryA thermo-, pH- and cyclodextrin- (CD) responsive poly(N-isopropylacrylamide) (PNIPAM), with a N,N-dimethylaminoazobenzene end group was synthesized. Using 3-mercaptopropionic acid as a chain transfer agent, PNIPAM with a well-defined COOH end group was obtained. The acid end group was transferred to the corresponding acid chloride and then functionalized with N,N-dimethyl[4-(4’-aminophenylazo)phenyl]amine. This dye-end-group-labeled polymer showed acidochromic effects, depending on the pH and the presence of randomly methylated β-cyclodextrin (RAMEB-CD). Also higher cloud-point values for the lower critical solution temperature (LCST) in the presence of RAMEB-CD were observed. Additionally, this azo-dye-end-group-labeled polymer was complexed with hyperbranched polyglycerol (HPG) decorated with β-CD to generate hedgehog-like superstructures.

Supramolecular control over thermoresponsive polymers

“…Amphiphilic host molecules, such as cyclodextrins, featuring a hydrophilic outer shell and a hydrophobic cavity, can complexate with hydrophobic guests present in a thermoresponsive polymer, thereby increasing its hydrophilicity and T CP . Many examples have been reported on complexation of cyclodextrins with endgroup guest-functionalized thermoresponsive polymers, including PNIPAAm-azo dye [83], PNIPAAm-vinylcyclopropane [84], or poly(N,N-diethylacrylamide)-4-alkylphenol with methylated bCDs [85]. As expected, T CP variations were found to be dependent on the excess of cyclodextrin host added, and typically increased by less than 5 K, although a T CP increase of close to 10 K was observed in a tert-butyl phenyl-terminated poly(N,N-diethylacrylamide) (PDEAAm) thermoresponsive polymer in the presence of 2 equiv.…”

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

“…33 The end-functionalization of thermoresponsive polymers with various hydrophobic guest molecules and the interaction of these hydrophobic end-groups with supramolecular hosts has been shown to be an effective way to alter polymer phase transition temperatures. [34][35][36] For example, β-cyclodextrin has been exploited to tune the LCST of end-functionalized PNIPAMs bearing a pyrenyl group by the selective complexation of hydrophobic chain ends, resulting, due to the masking effect of the hydrophilic host molecule, in an increase of the T CP of polymers. 37 Woisel and co-workers have shown that the LCST phase transition temperature of 1,5-dialkoxynaphthalene-terminated PNIPAM could be increased by ca.…”

Polymers and Dyes: Developments and Applications

“…The synthesis of poly(NIPAM) bearing covalently attached azo dye end groups was achieved through a different approach (see Scheme 10) [78]. The polymerization of NIPAM was conducted in presence of 3-mercapropropionic acid as chain transfer agent yielding acid end group functionalized poly(NIPAM).…”

“…Scheme 10. End group functionalization of poly(N-isopropylacrylamide) (PNIPAM) with an azo dye [78]. …”