@article {867,
	title = {Attractive bridging interactions in dense polymer brushes in good solvent measured by atomic force microscopy},
	journal = {Langmuir},
	volume = {20},
	number = {6},
	year = {2004},
	note = {ISI Document Delivery No.: 802JMTimes Cited: 25Cited Reference Count: 56},
	month = {Mar},
	pages = {2333-2340},
	type = {Article},
	abstract = {Using an atomic force microscope (AFM), we have investigated the interaction forces exerted by latex particles bearing densely grafted polymer brushes consisting of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA), poly(N-isopropylacrylamide) (PNIPAM), and PMEA-b-PNIPAM in aqueous media (good solvent). The brushes were prepared by controlled surface-initiated atom transfer radical polymerization, and the hydrodynamic thicknesses were measured by dynamic light scattering. The molecular weight (M-n), grafting density (sigma), and polydispersity (PDI) of the brushes were determined by gel permeation chromatography and multiangle laser light scattering after cleaving the polymer from the latex surface by hydrolysis. Force profiles of PDMA (0.017 nm(-2) less than or equal to sigma less than or equal to 0.17 nm(-2)) and PMEA (sigma = 0.054 nm(-2)) brushes were purely repulsive upon compression, with forces increasing with M-n and sigma, as expected, due to excluded volume interactions. At a sufficiently low grafting density (sigma = 0.012 nm(-2)), PDMA exhibited a long-range exponentially increasing attractive force followed by repulsion upon further compression. The long-range attractive force is believed to be due to bridging between the free chain ends and the AFM tip. The PNIPAM brush exhibited a bridging force at a grafting density of 0.037 nm(-2), a value lower than the sigma needed to induce bridging in the PDMA brush. Bridging was therefore found to depend on grafting density as well as on the nature of the monomer. The grafting densities of these polymers were larger than those typically associated with bridging. Bridging interactions were used to confirm the presence of PNIPAM in a block copolymer PMEA-b-PNIPAMA brush given that the original PMEA homopolymer brush produced a purely repulsive force. The attractive force was first detected in the block copolymer brush at a separation that increased with the length of the PNIPAM block.},
	keywords = {ADSORBED POLYMERS, CHAIN, COPOLYMERS, IONIC-STRENGTH, LAYERS, LIGHT-SCATTERING, MICA, POLYELECTROLYTE, POOR SOLVENT, SURFACE INTERACTION FORCES},
	isbn = {0743-7463},
	url = {<Go to ISI>://000220159800048},
	author = {Goodman, D. and Kizhakkedathu, J. N. and Brooks, D. E.}
}
@article {6959,
	title = {CONTINUUM ELECTROSTATIC INTERACTIONS BETWEEN PLANAR LATTICES OF DIPOLES AND THE POSSIBLE RELEVANCE TO THE HYDRATION FORCE},
	journal = {Physical Review A},
	volume = {43},
	number = {6},
	year = {1991},
	note = {ISI Document Delivery No.: FD045Times Cited: 11Cited Reference Count: 37},
	month = {Mar},
	pages = {2953-2962},
	type = {Article},
	abstract = {The electrostatic interaction between two planar dipolar lattices in dielectric continua is investigated. If there are no dielectric images, the pressure is equally likely to be attractive or repulsive, depending upon the relative lateral displacement of the two lattices. In addition to perfect dipolar lattices, we consider the effects of real dipoles, of disorder, and of finite-sized domains. When the surfaces constitute the boundary between dielectric media, and when there are no correlations between the two surfaces, then there occurs a strong exponentially decaying repulsion due to the interaction between a lattice and its dielectric images. The relevance of this repulsion to the hydration force is discussed, and an experimental test that should discriminate between different theories for that force is proposed.},
	keywords = {BILAYER SYSTEMS, DEPENDENCE, DOUBLE-LAYER, ELECTROLYTE-SOLUTIONS, MICA, MOBILE, MODEL, ORIENTABLE DIPOLES, polarization, SURFACES, WATER},
	isbn = {1050-2947},
	url = {<Go to ISI>://A1991FD04500037},
	author = {Attard, P. and Patey, G. N.}
}
