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Publications - 1992


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Self-diffusion and spin-spin relaxation in cyclic and linear polydimethylsiloxane melts

T. Cosgrove, P.C. Griffiths, J. Hollingshurst, R.D.C. Richards and J.A. Semlyen
School of Chemistry, University of Bristol, Bristol, UK

Macromolecules (1992), 25(25), 6761-4

Abstract

Self-diffusion and spin-spin relaxation measurements were performed on narrow fraction linear and cyclic di-Me siloxanes in the melt, by pulsed NMR techniques. The effects of ring and chain mol. wt. were studied. The diffusion and relaxation data showed interesting mol. wt. dependencies, some of which were also found in the bulk viscosity. The relaxation data exhibited a noticeable change in mol. wt. dependence at the crit. mol. wt. for entanglement for both the linear and cyclics polymers. The diffusion data were not, however, sensitive to this crit. mol. wt. effect.

Nuclear magnetic resonance studies of adsorbed polymer layers

T. Cosgrove and P.C. Griffiths
School of Chemistry, University of Bristol, Bristol, UK

Adv. Colloid Interface Sci. (1992), 42 175-204

Abstract

A review with 42 refs. on NMR spectroscopy with a large range of techniques which can probe both the structure and dynamics of materials in detail. In the study of polymer adsorption, NMR is capable of distinguishing adsorbed segments (trains) from free segments (loops and tails) in a quant. way. This may be achieved by a variety of exptl. approaches and the background to these will be discussed.

Solvent relaxation NMR: bound fraction determination for sodium poly(styrenesulfonate) at the solid/solution interface

T. Cosgrove, T.M. Obey and M. Taylor
School of Chemistry, University of Bristol, Bristol, UK

Colloids Surf. (1992), 64(3-4), 311-16

Abstract

The adsorption of Na poly(styrenesulfonate) on cationic polystyrene latex was studied using NMR spectroscopy. The adsorbed amt. and the fraction of adsorbed trains were detd. Results are discussed with ref. to recent exptl. data.

Fourier Transform Infrared Spectroscopy and Monte Carlo studies on the dynamics of physisorbing and chemisorbing polymers

Terence Cosgrove, Clive A. Prestidge, Stephen M. King and Brian Vincent
School of Chemistry, University of Bristol, Bristol, UK

Langmuir (1992), 8(9), 2206-9

Abstract

Dynamic studies on the adsorption of poly(methylsiloxane) onto alumina were carried out as a function of the reaction temp. The relative rates of chemisorption and physisorption were markedly temp. dependent, and it was the balance of these rates that detd. the final surface conformation of the polymer. The exptl. results were compared qual. with a dynamical Monte Carlo simulation.

Volume fraction profiles of terminally attached chains

Terence Cosgrove
School of Chemistry, University of Bristol, Bristol, UK

Macromol. Rep. (1992), A29(Suppl. 2), 125-30

Abstract

The vol. fraction of a terminally attached chain which does not phys. adsorb is well-described by a shifted Gaussian function. This was confirmed by comparing a numerical inversion of the data with a nonlinear least squares fit for a deuterated polystyrene attached to a silica particle. The root-mean-square thicknesses calcd. from the profiles assuming a Gaussian profile shape fit the de Gennes model and showed that the chains are extended normal to the interface.

Depletion layer measurements using nuclear magnetic resonance for silica dispersions with non-adsorbing poly(styrenesulfonate)

T. Cosgrove, T.M. Obey and K. Ryan
School of Chemistry, University of Bristol, Bristol, UK

Colloids Surf. (1992), 65(1), 1-7

Abstract

NMR relaxation times were used to est. the depletion-layer thickness for nonadsorbing polyelectrolytes in silica dispersions. The layer thicknesses were estd. using a simple square-well model for the depletion zone. An increase was found in the depletion layer thickness both with increasing mol. wt. and decreasing equil. polymer concn.

Neutron reflection from polymers adsorbed at the solid/liquid interface

T. Cosgrove, J.S. Phipps and R.M. Richardson
School of Chemistry, University of Bristol, Bristol, UK

Springer Proc. Phys. (1992), 61(Surf. X-Ray Neutron Scattering), 169-72

Abstract

Neutron reflection measurements were made on block copolymers adsorbed onto single crystal quartz. The effect of solvent quality on the segment d. distribution of the adsorbed polymer layer was clearly obsd. The presence of a layer of bound water at the quartz surface was also obsd.

Neutron reflection from liquid/liquid interfaces

T. Cosgrove, A. Eaglesham, D. Horne, J.S. Phipps and R.M. Richardson
School of Chemistry, University of Bristol, Bristol, UK

Springer Proc. Phys. (1992), 61(Surf. X-Ray Neutron Scattering), 159-65

Abstract

An exptl. method for the measurement of neutron reflection from liq./liq. interfaces is described. The strengths and limitations of the technique are described and its application to the study of adsorbed layers is discussed. Results are given for the protein b-casein and a block copolymer of polydimethylsiloxane-polyvinylpyridine oxide.

Adsorption of block copolymers from nonselective solvent

D. Guzonas, M.L. Hair and T. Cosgrove
Xerox Res. Cent. Canada, Mississauga, ON, Canada

Macromolecules (1992), 25(10), 2777-9

Abstract

The scaling model of C. M. Marques and J. F. Joanny (1989) for diblock copolymer adsorption from a nonselective solvent was used to explain the results of D. T. Wu et al. (1991). The results of Wu et al. and the authors' work with block copolymers (1991) were used to illustrate the validity of the model and point out its utility in the design of diblock copolymers for optimum stabilizing power. The model predicted a max. in the adsorbed amt. and the adsorbed layer thickness and gave a simple expression for the compn. of the copolymer at this max. for a given total d.p.

Adsorption of PEO-PPO-PEO block copolymers at silica

Martin Malmsten, Per Linse and Terence Cosgrove
Chem. Cent., Univ. Lund, Lund, Sweden

Macromolecules (1992), 25(9), 2474-81

Abstract

The adsorption on silica of ethylene oxide (I)-propylene oxide (II)-I triblock copolymers (III) as well as that of I homopolymer (IV) is studied. For a no. of III of total mol. wt. apprx. 15,000, the adsorbed amt. is rather low (0.35-0.40 mg/m2), independent of the II content in the range 0-30% II. For III of total mol. wt. 4000 and II content 50%, the adsorbed amt. is .apprx.0.20 mg/m2. All polymers investigated form thin adsorbed layers, with hydrodynamic thickness .apprx.2-5 nm. The pH dependence of the adsorbed amt. and the hydrodynamic thickness is similar to that displayed by IV. Ellipsometry expts. on silica surfaces show good agreement with the expt. on silica dispersions. Both adsorption and desorption are fast processes in these systems, occurring over minutes. Ellipsometry expts. show that, just prior to soln. micellization, an abrupt increase in the adsorbed amt. occurs. At temps. above the crit. micellization temp., the adsorbed amt. remains independent of temp. at 15-50°. At all temps., the hydrodynamic thickness is much smaller than the hydrodynamic diam. of the soln. micelles. On hydrophobic surfaces, no abrupt increase in the adsorbed amt. is obsd. The exptl. findings are interpreted with a modified mean-field theory.

Neutron reflection from a liquid/liquid interface

T. Cosgrove, J.S. Phipps and R.M. Richardson
School of Chemistry, University of Bristol, Bristol, UK

Colloids Surf. (1992), 62(3), 199-206

Abstract

The structure of 2 fatty acids (hexadecanoic and docosanoic) and a triblock copolymer of poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) were measured at the liq./liq. interface for the first time by neutron reflection. The measurement is made possible by the formation of a layer of n-hexane (a few microns thick) on the surface of water, which permits acceptable transmission of the neutron beam. The results are described in terms of simple models of the interfacial structure, and the limitations and advantages of this novel method are discussed.

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