Hydrocarbon-Based Statistical Copolymers Outperform Block Copolymers for Stabilization of Ethanol–Water Foams

Abstract

Well-defined block copolymers have been widely used as emulsifiers, stabilizers, and dispersants in the chemical industry for at least 50 years. In contrast, nature employs amphiphilic proteins as polymeric surfactants whereby the spatial distribution of hydrophilic and hydrophobic amino acids within the polypeptide chains is optimized for surface activity. Herein, we report that polydisperse statistical copolymers prepared by conventional free-radical copolymerization can provide superior foaming performance compared to the analogous diblock copolymers. A series of predominantly (meth)acrylic comonomers are screened to identify optimal surface activity for foam stabilization of aqueous ethanol solutions. In particular, all-acrylic statistical copolymers comprising trimethylhexyl acrylate and poly(ethylene glycol) acrylate, P(TMHA-stat-PEGA), confer strong foamability and also lower the surface tension of a range of ethanol−water mixtures to a greater extent than the analogous block copolymers. For ethanol-rich hand sanitizer formulations, foam stabilization is normally achieved using environmentally persistent silicone-based copolymers or fluorinated surfactants. Herein, the best-performing fully hydrocarbon-based copolymer surfactants effectively stabilize ethanol-rich foams by a mechanism that resembles that of naturally-occurring proteins. This ability to reduce the surface tension of low-surface-energy liquids suggests a wide range of potential commercial applications.

Thermoresponsive Reversible Unimer Micelles of Amphiphilic Fluorinated Copolymers

“…The crude product was purified by filtration on basic alumina and repeated precipitations from chloroform solutions into a large excess of n-hexane. The final product (yield 83%) was characterized by 1 H and 19 F NMR spectroscopies.…”

“…The same procedure was used for all the copolymers with the conditions summarized in Table 4. 1 Characterizations: 1 H and 19 F NMR measurements were carried out on a Bruker Avance 400 (400 MHz) spectrometer in deuterated solvent solutions (≈30 g L −1 ) at room temperature. T 1 and T 2 * were measured with a JEOL CZR 500 MHz spectrometer in D 2 O and HFB (with a capillary of benzene-d 6 ) copolymer solutions (20 g L −1 ) at 18 °C.…”

“…In particular, the local mobility of hydrophilic oxyethylene and hydrophobic perfluorinated side chains was evaluated in D 2 O and HFB for copolymers PEGMA85-co-FA15, TEGMA76-co-FA24 and TEGMA65-co-FA35, the former two being below their T c and the latter above its T c at the analysis temperature. 1 H and 19 F NMR spectra of the selected copolymers are reported in Figure 8.…”

“…The signals at ≈0.7 and ≈4 ppm of the CH 3 and COOCH 2 , respectively, were selected as references for the (meth)acrylic main chain in the 1 H NMR spectra. The peaks at ≈2.5 ppm of CH 2 CF 2 and ≈−5.5 ppm of CF 3 were selected as references for the hydrophobic perfluorinated segments in the 1 H NMR and 19 F NMR spectra, respectively. Longitudinal spin-lattice relaxation time (T 1 ), half-height linewidth (w 1/2 ), and observed trans-verse spin-spin relaxation time (T 2 * ) were evaluated for these peaks and the values are collected in Tables S2 and S3, Supporting Information.…”

“…Therefore, the field has experienced remarkable growth in the last two decades. [ 4–6 ] Practical application of such artificial single‐chain nanostructures may be enormous, and several examples are already present in the scientific literature, especially in the fields of, but not limited to, catalytic nanoreactors, [ 7,8 ] nanoprobes, [ 9 ] environmental remediation, [ 10,11 ] vectors for contrast agents, [ 12–14 ] encapsulation and delivery carriers, [ 15–18 ] surfactants, [ 19,20 ] and anti(bio)fouling systems. [ 21 ]…”