@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 {865,
	title = {Evaluation of an atomic force microscopy pull-off method for measuring molecular weight and polydispersity of polymer brushes: Effect of grafting density},
	journal = {Langmuir},
	volume = {20},
	number = {15},
	year = {2004},
	note = {ISI Document Delivery No.: 837VSTimes Cited: 16Cited Reference Count: 31},
	month = {Jul},
	pages = {6238-6245},
	type = {Article},
	abstract = {The accuracy of the molecular weights M-n and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(NN-dimethylacrvlamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with a ranging between 0.17 and 0.0059 chains/nm(2) and constant M-n. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a M-n of 30 600 and polydispersity (PDI) of 1.35. The M-n determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, which explains the discrepancy between the two methods at low sigma. The PDI was typically higher than that obtained by GPC, suggesting that sampling of chains with above average contour length occurs at sigma frequency that is greater than their spatial distribution.},
	keywords = {CHAIN, DETACHMENT, DIBLOCK COPOLYMER MONOLAYERS, DYNAMICS, INTERFACE, LAYERS, NEUTRON REFLECTIVITY, SURFACE},
	isbn = {0743-7463},
	url = {<Go to ISI>://000222669800025},
	author = {Goodman, D. and Kizhakkedathu, J. N. and Brooks, D. E.}
}
@article {1040,
	title = {Laser-light-scattering study of internal motions of polymer chains grafted on spherical latex particles},
	journal = {Journal of Physical Chemistry B},
	volume = {108},
	number = {48},
	year = {2004},
	note = {ISI Document Delivery No.: 875JUTimes Cited: 6Cited Reference Count: 35},
	month = {Dec},
	pages = {18479-18484},
	type = {Article},
	abstract = {Using atom-transfer radical polymerization, we have prepared core-shell particles by grafting thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) chains on a spherical polystyrene latex core (with a radius of similar to287 nm) via the "grafting-from" approach. As the temperature increases from 25 degreesC to 35 degreesC, the PNIPAM shell shrinks from a thickness of 625 nm to 110 nm and the chain density near the core increases from 7.3 x 10(-3) g/cm(3) to 7.2 x 10(-2) g/cm(3). Using such core-shell particles, we have, for the first time, been able to study dynamics of long chains anchored on a particle in dilute dispersion by laser-light scattering. Our results showed that, besides the translational diffusion of the particle as a whole, there also exists an additional slow relaxation mode that is only observable at larger scattering vectors (q),which are presumably related to internal motions of the shell. In the fully swollen state, the relaxation rate of the slow motion (<Gamma>(slow)) is insensitive to the observation length (1/q); however, its contribution to the scattering intensity (A(slow)) increases as q increases. In the shrunken state, <Gamma>(slow) slightly decreases as q increases. <Gamma>(slow) can be scaled to the shell thickness (<L>(brush)) as <Gamma>(slow) proportional to <L>(alpha)(brush), with alpha = -2.5 +/- 0.2, which is smaller than the predicated value of 3.},
	keywords = {AQUEOUS ATRP, BRUSHES, CONFORMATION, DYNAMICS, GLOBULE TYPE TRANSITIONS, INTERFACE, LAYERS, MODEL, POLY(N-ISOPROPYLACRYLAMIDE), SIMULATION},
	isbn = {1520-6106},
	url = {<Go to ISI>://000225417200015},
	author = {Yang, C. and Kizhakkedathu, J. N. and Brooks, D. E. and Jin, F. and Wu, C.}
}
@article {4655,
	title = {Tensor LEED analysis for the Cu(111)-(root x root 7)R19.1 degrees-S surface structure},
	journal = {Surface Science},
	volume = {441},
	number = {2-3},
	year = {1999},
	note = {ISI Document Delivery No.: 253RWTimes Cited: 11Cited Reference Count: 36},
	month = {Nov},
	pages = {425-435},
	type = {Article},
	abstract = {A tensor LEED analysis is reported for the (root 7 x root 7)R19.1 degrees structure formed by S at the Cu(lll)surface. A new structural model is found which corresponds to a modified version of the copper sulphide overlayer model first proposed by Domange and Oudar. In that model, the topmost layer has 3/7 monolayer each of Cu and S atoms, but the modification involves one S atom per unit mesh moving down to displace a Cu atom from the second metal layer. Relaxations among the topmost Cu atoms result in one S atom being effectively three-fold coordinate while the other two are sixfold coordinate and 12-fold coordinate: the averaged S-Cu bond lengths are indicated to equal 2.19, 2.47 and 2.62 Angstrom respectively. Some discussion is included of factors that may influence this choice of surface structure. (C) 1999 Elsevier Science B.V. All rights reserved.},
	keywords = {ADSORPTION, chemisorption, copper, ENERGY-ELECTRON-DIFFRACTION, LAYERS, low energy electron diffraction, LOW INDEX SINGLE CRYSTAL, METAL-SURFACES, MOLECULE, RAY STANDING-WAVE, RECONSTRUCTION, RU(0001), SUBSTRATE, SULFUR, sulphur, SURFACE, surface reconstruction},
	isbn = {0039-6028},
	url = {<Go to ISI>://000083570400024},
	author = {Saidy, M. and Mitchell, K. A. R.}
}
