The surface of a triblock copolymer, containing a solid-phase drug, was investigated using 15 keV Ga+ and 20 keV C60+ ion beams. Overall, the results illustrate the successful use of a cluster ion beam for greatly enhancing the molecular ion and high-mass fragment ion intensities from the surface and bulk of the polymer system. The use of C60+ also established the ability to see through common overlayers like poly(dimethyl siloxane) which was not possible using atomic ion sources. Moreover, the use of C60+ allowed depth profiles to be obtained using primary ion dose densities in excess of 6 × 1014 C60+/cm2. Resulting sputter craters possess relatively flat bottoms without the need for sample rotation and reached depths of ca. 2 μm. AFM results illustrate the more gentile removal of surface species using cluster ions. Specifically, phase contrast and topographic images suggest the relatively high ion doses do not significantly alter the phase distribution or surface topography of the polymer. However, a slight increase in rms roughness was noticed.

Colloidal processing offers a way to minimize undesired heterogeneities in the fabrication of advanced ceramics. Stable dispersions can be created by manipulation of interparticle potential. Adsorption of diblock copolymer amphiphiles provides a way to obtain long range repulsive interactions between particles, at comparatively low polymer coverage, thereby enabling suspension stabilization. In this study we investigate the relationship between copolymer structure and adsorbed layer characteristics, and specifically, the nature and range of interactions. We find that the surface density and interaction range are governed by a characteristic measure of the copolymer asymmetry. In the case of copolymers where one of the blocks is ionic, and therefore water soluble, we find a hysteresis in the interaction forces, indicating a meta-stable state of the polymer layer.

We have studied the adsorption of diblock copolymers of poly(2-vinylpyridine) (PVP)-poly-(styrene) (PS) from toluene solutions onto oxidized silicon and mica substrates. Adsorbed amounts for copolymers of various molecular weight and composition were measured by scintillation counting from tritium-labeled adsorbed layers and by X-ray photoemission spectroscopy. We find a dimensionless surface density sigma* to be a unique function of a copolymer block size asymmetry ratio. Within this correlation, we see two regimes of behavior. For copolymers of moderate asymmetry, the surface density sigma is influenced more strongly by the molecular weight of the adsorbing PVP block. These results agree well with a model by Marques et al. For copolymers with large PS blocks (high asymmetry), the surface density is determined primarily by the molecular weight of the PS block. Angle-resolved XPS measurements on dry adsorbed layers indicate a layered structure with PS segments preferentially located at the top surface. These results are supported by contact angle measurements on the dry adsorbed layers.

Surface-enhanced Raman scattering (SERS) was used to determine the conformation of 2-vinylpyridine/styrene (2VP/S) block copolymers adsorbed onto silver surfaces. The SERS spectra were also obtained from polystyrene (PS) and poly(2-vinylpyridine) (P2VP) to confirm band assignments of 2VP/S diblock copolymers. The bands near 1615 and 1041 cm-1 related to the styrene block were only weakly observed in the SERS spectra of 2VP/S diblock copolymers and the bands due to the 2VP block observed near 1073, 1161, 1336, and 1585 cm-1 were relatively strong in intensity in the SERS spectra, indicating that the SERS spectra observed for 2VP/S diblock copolymers were mostly contributed by the 2VP block. Since SERS has previously been shown to be a surface-selective effect, the results obtained here confirmed that the 2VP block preferentially adsorbed to the surfaces while the styrene block was positioned away from the surfaces. The results obtained from angle-resolved X-ray photoelectron spectroscopy (XPS) were consistent with those obtained from SERS. The ratio of nitrogen to carbon (N/C) in the interface region of the adsorbed copolymer was larger than in the bulk copolymer. The N/C ratio was also found to increase with increasing "takeoff" angle in the near-interface region. Since nitrogen is a characteristic element of the 2VP block and the N/C ratio can be used to determine the composition profiles, it was again confirmed that the 2VP block preferentially adsorbed onto the silver surface and that the 2VP layers were enriched in the interface region. Differences in the relative intensities and frequencies of several bands in the normal Raman and SERS spectra of P2VP adsorbed onto the silver surfaces were related to orientation effects. It was concluded that P2VP and the 2VP block of diblock copolymers were adsorbed by sigma-bonding through the pyridine nitrogen atoms with a vertical conformation.

Measurements have been made of the forces of interaction between pairs of adsorbed layers of diblock copolymers. These have been made on layers of 2-vinylpyridine-styrene and 2-vinylpyridine-isoprene copolymers. From toluene solution, the vinylpyridine block adsorbs strongly and the other blocks adsorb negligibly. This paper discusses the adsorption process itself and ways in which the interactions between two such layers can be tailored for particular purposes.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTComment on a paper by Hurung-Rern Lee, Tsai-An Yu, and Yu-Der LeePing I. Lee, Edward Parsonage, and Nicholas A. PeppasCite this: Macromolecules 1990, 23, 16, 3868Publication Date (Print):August 1, 1990Publication History Published online1 May 2002Published inissue 1 August 1990https://pubs.acs.org/doi/10.1021/ma00218a025https://doi.org/10.1021/ma00218a025research-articleACS PublicationsRequest reuse permissionsArticle Views54Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts