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de Paula FH, de Freitas FA, Nunes DG, Iglauer S, Gramatges AP, Nascimento RS, Lachter ER. Alkyl glyceryl ethers as water-based lubricant additives in mixtures with xanthan gum. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2021.127881] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Slastanova A, Campbell RA, Islas L, Welbourn RJL, R P Webster J, Vaccaro M, Chen M, Robles E, Briscoe WH. Interfacial complexation of a neutral amphiphilic 'tardigrade' co-polymer with a cationic surfactant: Transition from synergy to competition. J Colloid Interface Sci 2022; 606:1064-1076. [PMID: 34487929 DOI: 10.1016/j.jcis.2021.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Revised: 07/22/2021] [Accepted: 08/02/2021] [Indexed: 11/24/2022]
Abstract
HYPOTHESIS Neutral amphiphilic PEG-g-PVAc co-polymer (a "tardigrade" polymer consisting of a hydrophilic polyethylene glycol, PEG, backbone with hydrophobic polyvinyl acetate, PVAc, grafts) can form complexes at the air-water interface with cationic dodecyltrimethylammonium bromide (DTAB) via self-assembly. Compared to anionic SDS, cationic DTAB headgroups are expected to interact strongly with the negatively charged OH- groups from the partial dissociation of the PVAc grafts. We anticipate a transition from synergistic to competitive behaviour, which is expected to be dependent on the surfactant structural characteristics and concentration. EXPERIMENTS DTAB/PEG-g-PVAc mixtures were investigated using a combination of dynamic and equilibrium surface tension measurements, neutron reflectivity (NR) at the air-water interface, and foaming tests. We varied the concentrations of both the DTAB (0.05 to 5 critical micelle concentration, cmc) and that of PEG-g-PVAc (0.2 and 2 critical aggregation concentration, cac). FINDINGS Our results show that the interfacial interactions between DTAB and PEG-g-PVAc were both synergistic and antagonistic, depending sensitively on the surfactant concentration. At DTAB concentrations below its cmc, a pronounced cooperative adsorption behaviour was likely driven by the hydrophobic interactions between the DTAB tail and the PVAc grafts and the attraction between the DTAB headgroups and the partially dissociated -O- groups in the partially hydrolysed PVAc grafts, forming a mixed layer. This synergistic adsorption behaviour transitioned to a competitive adsorption behaviour at DTAB concentrations above its cmc, leading to polymer-surfactant partition, forming a "hanging" polymer layer underlying a surfactant monolayer at the interface. We postulate that DTAB/PEG-g-PVAc complexation in the bulk contributed to partial depletion of the mixture from the interface. We therefore consider this polymer/surfactant system to be a moderately interacting system at the air-water interface. No discernible differences in the foaming behaviour were observed between the DTAB/PEG-g-PVAc systems and the pure surfactant. Our results suggest that surfactant headgroup characteristics (particularly charges) were crucial in determining the structure and composition of polymer-surfactant complexes at the air-water interface, as well as the foamability and foam stability, whilst the coexistence of the synergistic and competitive adsorption behaviour is attributed to the unique architecture of the tardigrade polymer with amphiphilicity and partial charge, facilitating different surfactant-polymer interactions at different DTAB concentrations.
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Affiliation(s)
- Anna Slastanova
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Richard A Campbell
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK; Institut Laue-Langevin, 71 Avenue des Martyrs, CS20156, Grenoble 38042, France
| | - Luisa Islas
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
| | - Rebecca J L Welbourn
- ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| | - John R P Webster
- ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Mauro Vaccaro
- Procter & Gamble, Temselaan 100, 1853 Strombeek-Bever, Brussels, Belgium
| | - Meng Chen
- Procter & Gamble Beijing Innovation Centre, 35 Yu'an Rd, Shunyi District, Beijing, China
| | - Eric Robles
- Household Care Analytical, Procter & Gamble Newcastle Innovation Centre, Whitley Road, Longbenton, Newcastle NE12 9TS, UK
| | - Wuge H Briscoe
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
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Synergy, competition, and the "hanging" polymer layer: Interactions between a neutral amphiphilic 'tardigrade' comb co-polymer with an anionic surfactant at the air-water interface. J Colloid Interface Sci 2019; 561:181-194. [PMID: 31830734 DOI: 10.1016/j.jcis.2019.11.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 11/03/2019] [Accepted: 11/05/2019] [Indexed: 12/21/2022]
Abstract
Understanding the structure of polymer/surfactant mixtures at the air-water interface is of fundamental importance and also of relevance to a variety of practical applications. Here, the complexation between a neutral 'tardigrade' comb co-polymer (consisting of a hydrophilic polyethylene glycol backbone with hydrophobic polyvinyl acetate grafts, PEG-g-PVAc) with an anionic surfactant (sodium dodecyl sulfate, SDS) at the air-water interface has been studied. Contrast-matched neutron reflectivity (NR) complemented by surface tension measurements allowed elucidation of the interfacial composition and structure of these mixed systems, as well as providing physical insights into the polymer/surfactant interactions at the air-water interface. For both polymer concentrations studied, below and above its critical aggregation concentration, cac, (0.2 cac and 2 cac, corresponding to 0.0002 wt% or 0.013 mM and 0.002 wt% or 0.13 mM respectively), we observed a synergistic cooperative behaviour at low surfactant concentrations with a 1-2 nm mixed interfacial layer; a competitive adsorption behaviour at higher surfactant concentrations was observed where the polymer was depleted from the air-water interface, with an overall interfacial layer thickness ~1.6 nm independent of the polymer concentration. The weakly associated polymer layer "hanging" proximally to the interface, however, played a role in enhancing foam stability, thus was relevant to the detergency efficacy in such polymer/surfactant mixtures in industrial formulations.
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