Abstract
In this work, we prepared color-changing colloids by using the electrostatic self-assembly approach. The supramolecular structures are composed of a pH-responsive polymeric surfactant and the water-soluble porphyrin 5,10,15,20-tetrakis-(sulfonatophenyl)porphyrin (TPPS). The pH-responsive surfactant polymer was achieved by the chemical modification of an alternating aliphatic polyketone (PK) via the Paal–Knorr reaction with N-(2-hydroxyethyl)ethylenediamine (HEDA). The resulting polymer/dye supramolecular systems form colloids at the submicron level displaying negative zeta potential at neutral and basic pH, and, at acidic pH, flocculation is observed. Remarkably, the colloids showed a gradual color change from green to pinky-red due to the protonation/deprotonation process of TPPS from pH 2 to pH 12, revealing different aggregation behavior.
Highlights
Supramolecular chemistry is an effective approach to obtain functional structures from building blocks linked together by noncovalent interactions [1,2,3,4,5]
Aliphatic polyketones composed of ethylene, propylene, and carbon monoxide were synthesized according to a reported procedure [85], yielding a polyketone with an aliphatic synthesized according to a reported procedure [85], yielding a polyketone with an aliphatic part part comprised by the 50 mol% ethylene and 50 mol% propylene (PK, Mw = 3640 g mol−1 )
The successful grafting of pendant groups on the PK was confirmed by 1 H-NMR (Figures S6–S8) and Attenuated Total Reflectance (ATR)–FTIR (Figure S9) spectroscopies; the material has been successfully characterized with the help of a model compound
Summary
Supramolecular chemistry is an effective approach to obtain functional structures from building blocks linked together by noncovalent (and reversible) interactions [1,2,3,4,5]. Among several approaches to fabricate supramolecular systems, electrostatic self-assembly is one of the most attractive due to its easiness, low cost, and versatility in terms of building block choices [5,6,15,16] An alternative is represented by the chemical modification of alternating aliphatic polyketones with primary amine compounds via the Paal–Knorr reaction [38,39,40,41,42,43,44] Throughout this method, hydrophilic/hydrophobic functional groups are grafted randomly on the polyketone backbone as pendant groups, producing random amphiphilic polymers [38,45]. Paal–Knorr reaction on polyketone the polyketone (PK) N-(2with hydroxyethyl)ethylenediamine [84]. [84]
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