Protein resistance of (ethylene oxide)n monolayers at the air/water interface: effects of packing density and chain length

2007 ◽  
Vol 9 (46) ◽  
pp. 6073 ◽  
Author(s):  
Guangming Liu ◽  
Yijian Chen ◽  
Guangzhao Zhang ◽  
Shihe Yang
Keyword(s):  
Ethylene Oxide ◽  
Chain Length ◽  
Packing Density ◽  
Water Interface ◽  
Protein Resistance ◽  
Air Water Interface ◽  
Interface Effects

Interfacial rheology and aggregation behaviour of amphiphilic CBABC-type pentablock copolymers at the air–water interface: effects of block ratio and chain length

RSC Advances ◽  
2015 ◽  
Vol 5 (101) ◽  
pp. 82869-82878 ◽  
Author(s):  
Zhiguang Li ◽  
Xiaoyan Ma ◽  
Duyang Zang ◽  
Xinghua Guan ◽  
Lin Zhu ◽  
...  
Keyword(s):  
Chain Length ◽  
Structure Evolution ◽  
Interfacial Rheology ◽  
Water Interface ◽  
Packing Model ◽  
Aggregation Behaviour ◽  
Air Water Interface ◽  
Pentablock Copolymers ◽  
Interface Effects

The interfacial rheology, aggregation behaviour and packing model of the structure evolution of three amphiphilic CBABC-type pentablock copolymers were investigated at the air–water interface.

scholarly journals Nighttime oxidation of surfactants at the air–water interface: effects of chain length, head group and saturation

2018 ◽  
Vol 18 (5) ◽  
pp. 3249-3268 ◽  
Author(s):  
Federica Sebastiani ◽  
Richard A. Campbell ◽  
Kunal Rastogi ◽  
Christian Pfrang
Keyword(s):  
Oleic Acid ◽  
Double Bond ◽  
Methyl Ester ◽  
Reaction Kinetics ◽  
Chain Length ◽  
Rate Coefficients ◽  
Head Group ◽  
Water Interface ◽  
Organic Monolayers ◽  
Air Water Interface

Abstract. Reactions of the key atmospheric nighttime oxidant NO3 with organic monolayers at the air–water interface are used as proxies for the ageing of organic-coated aqueous aerosols. The surfactant molecules chosen for this study are oleic acid (OA), palmitoleic acid (POA), methyl oleate (MO) and stearic acid (SA) to investigate the effects of chain length, head group and degree of unsaturation on the reaction kinetics and products formed. Fully and partially deuterated surfactants were studied using neutron reflectometry (NR) to determine the reaction kinetics of organic monolayers with NO3 at the air–water interface for the first time. Kinetic modelling allowed us to determine the rate coefficients for the oxidation of OA, POA and MO monolayers to be (2.8±0.7) × 10−8, (2.4±0.5) × 10−8and (3.3±0.6) × 10−8 cm2 molecule−1 s−1 for fitted initial desorption lifetimes of NO3 at the closely packed organic monolayers, τd, NO3, 1, of 8.1±4.0, 16±4.0 and 8.1±3.0 ns, respectively. The approximately doubled desorption lifetime found in the best fit for POA compared to OA and MO is consistent with a more accessible double bond associated with the shorter alkyl chain of POA facilitating initial NO3 attack at the double bond in a closely packed monolayer. The corresponding uptake coefficients for OA, POA and MO were found to be (2.1±0.5) × 10−3, (1.7±0.3) × 10−3 and (2.1±0.4) × 10−3, respectively. For the much slower NO3-initiated oxidation of the saturated surfactant SA we estimated a loss rate of approximately (5±1) × 10−12 cm2 molecule−1 s−1, which we consider to be an upper limit for the reactive loss, and estimated an uptake coefficient of ca. (5±1) × 10−7. Our investigations demonstrate that NO3 will contribute substantially to the processing of unsaturated surfactants at the air–water interface during nighttime given its reactivity is ca. 2 orders of magnitude higher than that of O3. Furthermore, the relative contributions of NO3 and O3 to the oxidative losses vary massively between species that are closely related in structure: NO3 reacts ca. 400 times faster than O3 with the common model surfactant oleic acid, but only ca. 60 times faster with its methyl ester MO. It is therefore necessary to perform a case-by-case assessment of the relative contributions of the different degradation routes for any specific surfactant. The overall impact of NO3 on the fate of saturated surfactants is slightly less clear given the lack of prior kinetic data for comparison, but NO3 is likely to contribute significantly to the loss of saturated species and dominate their loss during nighttime. The retention of the organic character at the air–water interface differs fundamentally between the different surfactant species: the fatty acids studied (OA and POA) form products with a yield of  ∼ 20 % that are stable at the interface while NO3-initiated oxidation of the methyl ester MO rapidly and effectively removes the organic character ( ≤ 3 % surface-active products). The film-forming potential of reaction products in real aerosol is thus likely to depend on the relative proportions of saturated and unsaturated surfactants as well as the head group properties. Atmospheric lifetimes of unsaturated species are much longer than those determined with respect to their reactions at the air–water interface, so they must be protected from oxidative attack, for example, by incorporation into a complex aerosol matrix or in mixed surface films with yet unexplored kinetic behaviour.

Surface activity of perfluorodecanoyl end-capped poly(ethylene oxide) and associated adsorption behavior to the air–water interface

Polymer ◽  
1998 ◽  
Vol 39 (19) ◽  
pp. 4655-4664 ◽  
Author(s):  
Zhaohui Su ◽  
Thomas J McCarthy ◽  
Shaw ling Hsu ◽  
Howard D Stidham ◽  
Zhongyong Fan ◽  
...  
Keyword(s):  
Ethylene Oxide ◽  
Surface Activity ◽  
Adsorption Behavior ◽  
Water Interface ◽  
Air Water Interface ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene
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