Conformations of Short-Chain Poly(ethylene oxide) Lipopolymers at the Air−Water Interface:  A Combined Film Balance and Surface Tension Study

Abstract

The interfacial behavior of a short-chain poly(ethylene oxide) (PEO) lipopolymer, PEO (molecular weight 2000) grafted distearoylphosphatidylethanolamine (PEO2K-DSPE), and its mixtures with distearoylphosphatidylcholine (DSPC) have been studied using Langmuir film balance and surface tension methods. Surface pressure-area isotherms for pure PEO2K-DSPE and PEO2K-DSPE/DSPC mixtures (with 2, 5, 10, 15, or 20 mol % of PEO2K-DSPE) revealed two phase transitions. The simple additivity in the molecular area of lipid mixtures with increasing incorporation of PEO lipopolymer below the low-pressure transition indicates the existence of a two-dimensional thin layer of PEO and lipid. The low-pressure transition is interpreted as desorption of surface-adsorbed PEO molecules into the aqueous subphase. Correlation of film balance experiments with PEO lipopolymer and surface tension experiments with PEO aqueous solutions suggests dehydration of the PEO in the lipopolymer film by expulsion of PEO-associated water molecules as surface pressure increases. Theoretical models, based on scaling theories of polymers at interfaces, fit the observed isotherms well in the low-pressure regime below the first transition but poorly in the high-pressure regime above the first transition. The high-pressure transition is interpreted as ordering of lipid tails in lipopolymers, as driven by the enthalpic gain from lipid alignment and balanced by the entropic loss for lipid ordering and most importantly by dehydration of the PEO chains.

Poly(ethylene oxide)s hydrophobically modified. Adsorption and spreading at the air–water interface

“…These values are in agreement with the tendency reported by Xu and co-workers [23]. The collapse condition was corroborated by means of repeating of the isotherms before and after the collapse point.…”

Effects of nanoencapsulation and PEGylation on biodistribution of indocyanine green in healthy mice: quantitative fluorescence imaging and analysis of organs

“…49 The higher flexibility and mobility of low MW PEG chains result in higher entropic repulsion between proteins and the surface. 50,51 Our in vitro studies confirmed the choice of PEG 5 kDa for passivation coatings of ICG-NCs and for impeding their uptake by macrophages. 10 Conversely, reduced flexibility of high MW PEG chains, due to the entrapment submit your manuscript | www.dovepress.com of long chains, induces low protein resistivity.…”

Temperature-dependent interfacial properties of hydrophobically end-modified poly(2-isopropyl-2-oxazoline)s assemblies at the air/water interface and on solid substrates

“…Most fundamental studies on telechelic HM-polymers focus on the ''bulk" properties of their aqueous solutions, rather than on their interfacial characteristics. A number of reports demonstrate that PEO chains modified with hydrophobic substituents, such as n-alkyl [10], perfluoro [11], polyhedral oligomeric silsesquioxanes [12], or double-chained lipids [13] are able adsorb at the A/W interface upon end-group modification. Endmodified HM-poly(N-isopropylacrylamide) (PNIPAM) derivatives [14] also form Langmuir films at the A/W interface.…”