Publications - 2006
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Effects of Electrolytes on Adsorbed Polymer Layers: Poly(ethylene oxide)-Silica System
Charlie Flood, Terence Cosgrove, Ian Howell and Patricia Revell
School of Chemistry, University of Bristol, Bristol, UK
Langmuir (2006), 22(16), 6923-6930
Abstract
The effects of various electrolytes on the adsorption of poly(ethylene oxide) onto silica have been studied. The salts were the chlorides of Na+, Mg2+, Ca2+, and La3+. The methods used were adsorption isotherms, found using a depletion method with phosphomolibdic acid, photon correlation spectroscopy, and solvent relaxation NMR. All the salts increased the particle-polymer affinity and adsorbed amt. according to the adsorption isotherms, and a linear relationship was found between the initial slope of the isotherms and the ionic strength of the soln. Final adsorbed amts. were approx. 0.4-0.5 mg m-2. The polymer layer thicknesses as found by PCS were of the same order as the radius of gyration of the polymer and increased with both the concn. and the valency of the salt due to increased adsorption. Solvent relaxation NMR showed that NaCl is too weak to have a noticeable effect on the polymer train layer, but the divalent salts clearly did increase both the strength of solvent binding close to the silica surface and the amt. of PEO required to reach the max. train d.
Small-Angle Neutron Scattering Study of Concentrated Colloidal Dispersions: The Electrostatic/Steric Composite Interactions between Colloidal Particles
Dong Qiu, Terence Cosgrove and Andrew M. Howe
School of Chemistry, University of Bristol, Bristol, UK
Langmuir (2006), 22(14), 6060-6067
Abstract
Small-angle neutron scattering was used to investigate the interactions in concd. colloidal dispersions contg. silica or polystyrene latex with adsorbed polyethyleneoxide (PEO). In these dispersions of charged particles, both electrostatic and steric repulsions are present. The PEO layer was made invisible to neutrons through contrast matching. The effect of the interparticle repulsion was clearly shown in the scattering spectra by the appearance of a peak at low Q. The effective potentials can be well described by the Hayter-Penfold/Yukawa (HPY) potential. In the silica dispersions studied, the layer thickness is small, hence the electrostatic potential dominates and the potential has a lower concn. dependence. In the dispersions of polystyrene latex, the adsorbed layer is thicker; consequently, the electrostatic potential dominates at low vol. fraction (the potential has a lower concn. dependence), and the steric potential dominates at higher vol. fraction (the potential has a higher concn. dependence). This study also suggests that when more than one potential is present the stronger one has a dominant influence in detg. the structure factor. This finding makes it possible to describe the multicomponential interactions by a single function.
Polymeric materials having reduced tack, methods of making the materials and chewing gum compositions containing such materials
Terence Cosgrove, Henry Craik-White, Erol Ahmed Hasan and Voss Moore Gibson
The University of Bristol, UK
PCT Int. Appl. (2006), 47 pp. CODEN: PIXXD2 WO 2006016179 A1 20060216 Designated States W: AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BW, BY, BZ, CA, CH, CN, CO, CR, CU, CZ, DE, DK, DM, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ, NA, NG, NI, NO, NZ, OM, PG, PH, PL, PT, RO, RU, SC, SD, SE, SG, SK, SL, SM, SY, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, YU, ZA, ZM, ZW. Designated States RW: AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IS, IT, LU, MC, NL, PT, SE, TR, BF, BJ, CF, CG, CI, CM, GA, ML, MR, NE, SN, TD, TG. Patent written in English. Application: WO 2005-GB3176 20050812. Priority: GB 2004-17938 20040812. AN 2006:152707 CAPLUS
Abstract
A polymeric material having low tack which has a straight or branched chain carbon-carbon polymer backbone and a multiplicity of side chains attached to the backbone wherein the side chains, which are attached directly to carbon atoms of the polymer backbone, have the formula (I) or have the formula (II) wherein R1 is H, -C(O)OR4 or -C(O)Q and R2 is -C(O)OR4 or -C(O)Q provided that at least one of R1 and R2 is the group -C(O)Q; R3 is H or -CH3 ; R4 is H or an alkyl group having from 1 to 6 carbon atoms; Q is a group having the formula -O-(YO)b-(ZO)c-R5, wherein each of Y and Z is, independently, an alkylene group having from 2 to 4 carbon atoms and R5 is H or an alkyl group having from 1 to 4 carbon atoms; a is 3 or 4 and each of b and c is, independently, 0 or an integer of from 1 to 125 provided that the sum b + c has a value in the range of from 10 to 250, preferably from 10 to 120. The polymeric material may be used to replace at least part of a water-insol. gum base in a chewing gum compn. to give a compn. exhibiting reduced adhesion to surfaces.
Colloidal behavior of polystyrene-based copolymer microgels composed of a hydrophilic hydrogel layer
Kong Soo Kim, Brian Vincent and Terence Cosgrove
Department of Chemical Engineering, Chung-buk University Cheong ju, Chung buk, South Korea
Journal of Industrial and Engineering Chemistry (Seoul, Republic of Korea) (2006), 12(1), 91-97 (Journal written in English)
Abstract
Polystyrene (PSt)-based copolymer colloidal microgels consisting of a hydrophilic hydrogel layer, such as poly(methacrylic acid) (PMAA) or poly(N-iso-Pr acrylamide) (PNIPAM), were synthesized through emulsifier-free polymn. The morphol. and particle size of the microgel particles were characterized using a combination of TEM and photon correlation spectroscopy (PCS). The microgel particles consisted of a hydrophobic PSt-core and a hydrophilic PMAA and PNIPAM shell. When the microgels were characterized for their pH- and temp.-responsive behaviors by PCS, the hydrodynamic diam. of the microgel particles composed of St/MAA/NIPAM gradually increased below pH 4.5 and above pH 7. LCSTs of PNIPAM in the microgels were barely affected by different molar ratios of St/MAA/NIPAM; in addn., the shrinking transition of the microgels, which were composed of St/MAA/NIPAM, shifted to higher region than did the LCST of PNIPAM. The electrophoretic mobility and zeta potential for the microgel particles were found to be neg., and a marked max. neg. value occurred at around pH 5. The colloidal stability of the microgel particles was very sensitive to the concn. of the KCl soln. and to the temp.
On the absolute calibration of bench-top small-angle X-ray scattering instruments: a comparison of different standard methods
Cécile A. Dreiss, Kevin S. Jack and Andrew P. Parker
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
and Centre for Nanotechnology and Biomaterials, School of Molecular and Microbial Sciences, The University of Queensland, QLD 4072, Australia
and Bristol Colloid Centre, University of Bristol, University
Gate, Park Row, Bristol BS1 5UB, UK
Journal of Applied Crystallography, (2006). 39, 32–38
Abstract
Absolute calibration relates the measured (arbitrary) intensity to the differential scattering cross section of the sample, which contains all of the quantitative information specific to the material. The importance of absolute calibration in small-angle scattering experiments has long been recognized. This work details the absolute calibration procedure of a small-angle X-ray scattering instrument from Bruker AXS. The absolute calibration presented here was achieved by using a number of different types of primary and secondary standards. The samples were: a glassy carbon specimen, which had been independently calibrated from neutron radiation; a range of pure liquids, which can be used as primary standards as their differential scattering cross section is directly related to their isothermal compressibility; and a suspension of monodisperse silica particles for which the differential scattering cross section is obtained from Porod's law. Good agreement was obtained between the different standard samples, provided that care was taken to obtain significant signal averaging and all sources of background scattering were accounted for. The specimen best suited for routine calibration was the glassy carbon sample, due to its relatively intense scattering and stability over time; however, initial calibration from a primary source is necessary. Pure liquids can be used as primary calibration standards, but the measurements take significantly longer and are, therefore, less suited for frequent use.
A Small-Angle X-ray Scattering Study of the Interactions in Concentrated Silica Colloidal Dispersions
Dong Qiu, Terence Cosgrove, Andrew M Howe and Cecile A Dreiss
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
and Kodak European R&D, Headstone Drive, Harrow, Middlesex HA1 4TY, U.K
Langmuir : the ACS journal of surfaces and colloids (2006), 22(2), 546-52
Abstract
The structure factors of colloidal silica dispersions at rather high volume fractions (from 0.055 to 0.22) were measured by small-angle X-ray scattering and fitted with both the equivalent hard-sphere potential model (EHS) and the Hayter-Penfold/Yukawa potential model (HPY). Both of these models described the interactions in these dispersions successfully, and the results were in reasonable agreement. The strength and range of the interaction potentials decreased with increasing particle volume fractions, which suggests shrinkage of the electrical double layer arising from an increase in the counterion concentration in the bulk solution. However, the interactions at the average interparticle separation increased as the volume fraction increased. The interaction ranges (delta) determined by the two models were very similar. Structure factors were also used to determine the size and volume fraction of the particles. The values of the size obtained from the structure factors were slightly larger than those obtained from the form factors; this difference is ascribed to the nonspherical shape and polydispersity of the colloidal particles. The volume fractions measured by these two methods were very similar and are both in good agreement with the independently measured results.
Solubility of cyclomaltooligosaccharides (cyclodextrins) in H2O and D2O: a comparative study
Edvaldo Sabadini, Terence Cosgrove and Fernanda do Carmo Egidio
School of Chemistry, The University of Bristol, Cantock's Close, Bristol, UK
Carbohydrate Research (2006), 341(2), 270-274
Abstract
Cyclomaltooligosaccharides (cyclodextrins, CDs) are cyclic oligomers having six, seven, or eight units of α-glucose, named as cyclomaltohexaose (α-CD), cyclomaltoheptaose (β-CD) and cyclomaltooctaose (γ-CD), resp. The mol. of CD has a cavity in which the interior is hydrophobic relative to its outer surface. The soly. of cyclodextrins in water is unusual, as an irregular trend is obsd. in the series of the cyclic oligomers of glucose. β-CD is at least nine times less sol. than the others CDs. This intriguing behavior has been investigated, and some interesting explanations in terms of the effect caused by CD on the water lattice structure have been proposed. In this work a comparative study on the soly. of α, β, and γ-cyclodextrins was carried out in H2O and D2O and reveals a much lower soly. of the three CDs in D2O. The solid-phase structure of the CDs in equil. with the soln. is quite similar with both solvents. The results are discussed in terms of the CD mol. structure and the differences in the hydrogen bonds formed between H2O and D2O.
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