Dendronized Polymers with Peripheral Oligo(ethylene oxide) Chains: Thermoresponsive Behavior and Shape Anisotropy in Solution

Abstract

A series of dendronized polymers carrying oligo(ethyleneoxy) peripheral branches have been prepared by postpolymerization functionalization of multiallylic dendronized polymers using a radical addition of mercaptans, namely 2-methoxy(ethoxy)ethanethiol (EO2) and {2-(2-methoxyethoxy)ethoxy)}ethanethiol (EO3). The functionalization proved to be quite efficient, leading to up to 6 or 9 EO chains per monomer repeating unit. A constant T g value was observed independently of the material characteristics, indicating that T g is ruled by the sole presence of EO chains. According to the hydrophilic and hydrophobic balance, some polymers exhibited a thermoresponsive behavior in water solution, characterized by a sharp lower critical solution temperature (LCST) transition and a small hysteresis. These LCST showed an unusual increase with DP, which might be correlated to a dilution effect and an increase of polymer hydrophilicity by densification of the dendritic coverage. By SAXS investigations and using a spherocylinder shape model, the polymers in solution (below the LCST) could be satisfactorily described. By increasing the DP, the shape of the macromolecule was found to evolve from a spherical to a spherocylinder shape with a constant cross section of ca. 40 Å.

Thermoresponsive Homopolymer Tunable by pH and CO2

“…23 Second, a previous result indicated that for the same mass concentration a higher molecular weight would result in a lower molar concentration, that is, a more "dilute" polymer solution with less polymer chains. 24 In order to test the dilution effect on the LCST of the homopolymer, the concentration dependence on LCST of homopolymer 3b (M n = 7500 g/mol) ( Figure 2C) and LCSTs of poly(DEAE-NIPAM-AM) 3 with a lower concentration of 0.5 mg/mL ( Figure S5, Supporting Information) were examined. The LCST of 3b was 24.5°C as the concentration was 1.0 mg/mL.…”

Dendronization: A Useful Synthetic Strategy to Prepare Multifunctional Materials

“…Recently, dendronized polymers with peripheral oligo(ethylene oxide) chains show a thermoresponsive behavior and an anisotropic shape in solution [81]. According to the hydrophilic and hydrophobic balance, some polymers exhibited a thermoresponsive behavior in water solution, characterized by a sharp lower critical solution temperature (LCST) transition and a small hysteresis.…”

“…According to the hydrophilic and hydrophobic balance, some polymers exhibited a thermoresponsive behavior in water solution, characterized by a sharp lower critical solution temperature (LCST) transition and a small hysteresis. These LCST showed an unusual increase with dendronized polymers, which might be correlated to a dilution effect and an increase of polymer hydrophilicity by densification of the dendritic coverage [81]. Moreover, Junk et al published an interesting approach highlighting the structure/property relationship given by the peripheral end-groups and the core of dendrons as modifiers in thermoresponsive dendronized polymers [82].…”

Reversible and contrasting changes of the cloud point temperature of pillar[5]arenes with one quinone unit and tri(ethylene oxide) chains induced by redox chemistry and host–guest complexation

“…[18][19][20][21][22][23][24][25][26][27][28] The T cloud values of thermo-responsive materials are determined by their chemical compositions, i.e., the ratio of the hydrophobic and hydrophilic parts. 1-28 Poly(N-isopropylacrylamide) is a well-known thermo-responsive polymer; it has a clouding point (T cloud ) at 32 1C in aqueous solution.…”