Adsorption of acrylic acid copolymers with hydrophobic chain substituents on polystyrene latex

Awad, Nagi M.; Morawetz, Herbert

doi:10.1002/pol.1981.180190206

Cited by 3 publications

(3 citation statements)

References 29 publications

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“…Our data clearly show the complexity of this binary polyelectrolyte. Several factors are known to govern both polyelectrolyte adsorption on charged surfaces and the interaction of polyelectrolytes, for example, the effect of both pH and ionic strength. − Unfortunately, many of the parameters involved in the theoretical calculations, such as segment-surface free energy and polymer chain flexibility, are not known quantitatively for most systems. The same holds for the entropic and enthalpic contributions that govern the interaction between polyectrolytes in aqueous media, parameters that are strongly dependent on the particular system.…”

Section: Discussionmentioning

confidence: 99%

“…Several factors are known to govern both polyelectrolyte adsorption on charged surfaces and the interaction of polyelectrolytes, for example, the effect of both pH and ionic strength. [49][50][51] Unfortunately, many of the parameters involved in the theoretical calculations, (42) Decher, G. Comprehensive Supramolecular Chemistry; Pergamon Press: New York, 1996, Vol. 9, p 507. such as segment-surface free energy and polymer chain flexibility, are not known quantitatively for most systems.…”

Section: A(t) )mentioning

confidence: 99%

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Photoisomerization of Polyionic Layer-by-Layer Films Containing Azobenzene

et al. 1998

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In this work we employed the layer-by-layer adsorption technique for deposition on solid substrates of polyionic films containing photoactive azobenzene groups. We investigated two systems, each having the same polyanion but using a different polycation. Poly {1-4[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl sodium salt} (PAZO) was employed as the photoactive polyanion; poly(diallyldimethylammonium chloride) (PDDA) and poly(ethyleneimine) (PEI) were used as the polycations. Our phenomenological data show dramatic differences in the behavior of the two systems, although the same experimental conditions were employed in both cases. The assembly of the multilayers was monitored by ellipsometry and X-ray reflectivity via thickness measurements. We observed a considerable difference in the bilayer thickness in the two systems. An average polycation/polyanion bilayer thickness of 5 Å was measured for PDDA/PAZO, while the PEI-containing system resulted in a 36 Å thick bilayer. We used quartz crystal microbalance (QCM) measurements and UV−visible spectroscopy to monitor the adsorption process. QCM measurements showed an influence of the polycation in the polyanion adsorption process of the PAZO molecules. In particular, PEI appears to promote complexation and aggregation of the negatively charged polyion. Aggregates, mainly in the J form, were detected in both PDDA/PAZO and PEI/PAZO systems by UV−visible spectroscopy. We induced trans-to-cis photoisomerization of the azobenzene groups by UV light (340 nm), and we followed the photoreaction by the decrease in the intensity of the π−π* band, which is associated with the trans form of the azo molecules. The photoreaction apparently did not reach completion because the π−π* band did not completely disappear. We found also that the polycations have a significant influence on the molecular orientation of the azobenzene groups in the film and on the photoisomerization kinetics. The kinetics of photoisomerization were not monoexponential, indicating the coexistence of different processes. We investigated also the cis-to-trans reverse isomerization. In particular, we observed a partial recovery of the π−π* band after thermal relaxation that was more significant in the PDDA-containing system. By contrast, cis-to-trans isomerization induced by blue light (460 nm) was not observed. UV light irradiation was responsible for reversible changes in the optical thickness of the films, defined as n × d, where n is the refractive index and d is the overall thickness of the film.

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Section: Discussionmentioning

confidence: 99%

Section: A(t) )mentioning

confidence: 99%

Photoisomerization of Polyionic Layer-by-Layer Films Containing Azobenzene

et al. 1998

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“…However, the relatively long-range electrostatic repulsions in low-ionic-strength solutions tend to counteract the association between hydrophobic groups. Varying the electrolyte concentration and/or the pH offers an interesting way of tuning the self-associative behavior exhibited by HMPEs. − …”

Section: Introductionmentioning

confidence: 99%

Ellipsometric Study of the Adsorption of Hydrophobically Modified Polyacrylates at Hydrophobic Surfaces

1998

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The adsorption of hydrophobically modified polyelectrolytes (HMPEs) at hydrophobic surfaces was studied by ellipsometry. Both the adsorbed amount of polymer Γ and the layer thickness d were measured as a function of time. The HMPEs are polyacrylates carrying various fractions of grafted dodecyl chains. Hydrophobic interactions are responsible for the adsorption (unmodified polyacrylate does not adsorb at the surface). The surface anchoring of grafted dodecyl groups is coupled with the repulsion of charged acrylate groups. This results in the formation of large loops at the interface, separated by very short trains, since the probability to have two or more successive alkyl groups grafted at the polymer chain is small. As in the case of ordinary polyelectrolytes, the mean thickness of the adsorbed layer decreases with increasing solution ionic strength. Changes of the HMPE chemical composition (molar ratio, X, of alkyl units attached on the polyacrylate backbone) affect the adsorbed layer structure in a complex fashion. HMPEs with relatively few grafted chains form thick dilute adsorbed layers. Increasing the ratio of grafted chains to the number of polyelectrolyte monomers results in a monotonic decrease of the thickness and an increase of the HMPE density. However, the adsorbed amount exhibits a maximum at a relatively small ratio between 5% and 7%, above which the effect of the decrease of Γ caused by the decrease of the average loop size becomes larger than the opposing effect of the increasing surface density of anchors. We also discuss the shape of the adsorption isotherms, experimental evidence for the existence of a depletion layer located outside the adsorbed layer, and the time evolution of adsorption and desorption.

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Adsorption

Robb¹

1989

Comprehensive Polymer Science and Supplements

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Adsorption of acrylic acid copolymers with hydrophobic chain substituents on polystyrene latex

Cited by 3 publications

References 29 publications

Photoisomerization of Polyionic Layer-by-Layer Films Containing Azobenzene

Photoisomerization of Polyionic Layer-by-Layer Films Containing Azobenzene

Ellipsometric Study of the Adsorption of Hydrophobically Modified Polyacrylates at Hydrophobic Surfaces

Adsorption

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