Imperial College London

Professor DameJuliaHiggins

Faculty of EngineeringDepartment of Chemical Engineering

Senior Research Investigator
 
 
 
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Contact

 

+44 (0)20 7594 5565j.higgins

 
 
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Assistant

 

Mrs Sarah Payne +44 (0)20 7594 5567

 
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Location

 

510ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

247 results found

Aoki Y, Wang H, Sharratt W, Dalgliesh R, Higgins J, Cabral Jet al., Small angle neutron scattering study of the thermodynamics of highly interacting PαMSAN/dPMMA blends, Macromolecules, ISSN: 0024-9297

Poly(methyl methacrylate) (PMMA) and poly(α-methyl styrene-co-acrylonitrile) (PαMSAN) form partially miscible blends with lower critical solution temperature (LCST) behaviour. We revisit this system using small angle neutron scattering (SANS), examining the effect of molecular weight (Mw) of deuterated PMMA (dPMMA), blend composition (φ) and temperature (T) in the homogeneous region. All data are well described by the Random Phase Approximation (RPA) theory, enabling us to determine thermodynamic and structural parameters, including the correlation length ξ, G00 (the second derivative of the free energy of mixing with respect to composition), and the statistical segment length a of each component. Phase boundaries are computed by extrapolation of G00 with temperature, to yield the spinodal, and inspection of Kratky plots to yield the binodal. For PαMSAN, a is determined to be 10.1±0.4 ˚A. Unsurprisingly, this system deviates strongly from Flory-Huggins expectations, exhibiting a minimal Mw dependence of the phase boundaries and φ-dependence of effective interaction parameter (˜χ). Comparison of G00 with values for other blend systems places PαMSAN/dPMMA in a class of highly interacting blends, expected from Cahn-Hilliard theory to yield small initial phase sizes upon spinodal demixing. This is confirmed experimentally, with an illustrative temperature jump resulting in an initial phase size of ' 30 nm.

JOURNAL ARTICLE

Arrighi V, Gagliardi S, Ganazzoli F, Higgins JS, Raffaini G, Tanchawanich J, Taylor J, Telling MTFet al., 2018, Effect of chain length and topological constraints on segmental relaxation in cyclic PDMS, Macromolecules, Vol: 51, Pages: 7209-7223, ISSN: 0024-9297

We present a detailed investigation of local dynamics of linear and cyclic poly(dimethylsiloxane) (PDMS) covering a wide range of molar masses. To aid interpretation of the experimental data, QENS measurements in the time scale from 2 to 200 ps and at Q = 0.3 to 1.8 Å–1 are complemented by theoretical calculations. These make use of a methodology developed by us elsewhere applicable to both simple chain models and real chains and applied here, for the first time, to cyclic PDMS. Analysis of the incoherent dynamic structure factor at T < Tm shows that the rotational motion of the methyl groups is unaffected by polymer topology. At higher temperatures, the QENS data are described by a model that consists of two dynamic contributions: methyl group rotation and segmental motion, the latter described by a stretched exponential function. Relaxation times of both linear and cyclic PDMS increase with increasing molar mass. Several features predicted by theory are also reproduced by the experimental data. We show, unambiguously, that rings have higher relaxation times for the segmental motion compared to linear chains of the same number of monomer units. Theoretical calculations support the idea that such slowing down of local dynamics is due to the topological constraint imposed by the ring closure, a constraint which becomes negligible for very large molar masses. Our calculations suggest that due to its albeit small conformational rigidity, cyclic PDMS undergoes an additional constraint which further increases the relaxation time, producing a shallow maximum for N ≈ 50 repeat units. A similar feature is also observed in the experimental QENS data. Values of activation energy, Ea, are derived from analysis of the temperature dependence of the quasi-elastic broadening and are found to be in agreement with viscosity measurements reported in the literature. Although the pronounced molar mass dependence of Ea for linear PDMS is certainly linked to the pres

JOURNAL ARTICLE

Cabral JP, Higgins JS, 2018, Spinodal nanostructures in polymer blends: on the validity of the Cahn-Hilliard length scale prediction, Progress in Polymer Science, Vol: 81, Pages: 1-21, ISSN: 0079-6700

Spinodal decomposition of partially miscible polymer blends has the potential to generate well-defined polymeric nanostructured materials, with precise control of length scale and connectivity, and applications ranging from membranes and scaffolds to photovoltaics. In this review, we briefly summarize the theoretical basis for describing spinodal decomposition in binary polymer blends, and the parameters that determine the accessible demixing length scales and the timescales over which they develop. We then examine experimentally the validity of the classical Cahn-Hilliard (CH) theory prediction for the initial spinodal length scale, where G′′ is the second derivative of the free energy of mixing with respect to composition, and k is the ‘square gradient’ parameter, accounting for changes in free energy arising from concentration gradients. Benefitting from the perspective of over 40 years of neutron and light scattering data, and noting (remaining) misconceptions in the literature when analyzing phase separation, we examine a large collection of Λ measurements, and independent -G′′(T) and k experimental estimates. Overall, we find the CH prediction for Λ to be remarkably accurate for all blends and self-consistent conditions examined. We then summarize design considerations for generating polymeric materials via spinodal decomposition, bound by thermodynamics of available polymer systems, coarsening kinetics governed by rheology, as well as by engineering constraints. The fulfillment of the potential of this approach in the development of real functional materials demands, however, improved thermodynamic theories for polymer blends, able to quantitatively predict G′′(T) and k in terms of molecular structure and interactions.

JOURNAL ARTICLE

DeFelice J, Higgins JS, Lipson JEG, 2017, The effects of branching and deuterium labeling on blend miscibility, POLYMER, Vol: 114, Pages: 149-160, ISSN: 0032-3861

JOURNAL ARTICLE

Higgins JS, 2016, Neutron Scattering from Polymers: Five Decades of Developing Possibilities, ANNUAL REVIEW OF CHEMICAL AND BIOMOLECULAR ENGINEERING, VOL 7, Vol: 7, Pages: 1-28, ISSN: 1947-5438

JOURNAL ARTICLE

White RP, Lipson JEG, Higgins JS, 2012, How Pure Components Control Polymer Blend Miscibility, MACROMOLECULES, Vol: 45, Pages: 8861-8871, ISSN: 0024-9297

JOURNAL ARTICLE

White RP, Lipson JEG, Higgins JS, 2012, New Correlations in Polymer Blend Miscibility, MACROMOLECULES, Vol: 45, Pages: 1076-1084, ISSN: 0024-9297

JOURNAL ARTICLE

Chua Y-C, Chan A, Wong H-C, Higgins JS, Cabral JTet al., 2010, Thermodynamics of TMPC/PSd/Fullerene Nanocomposites SANS Study, MACROMOLECULES, Vol: 43, Pages: 9578-9582, ISSN: 0024-9297

JOURNAL ARTICLE

Higgins JS, Lipson JEG, White RP, 2010, Neutron scattering as an insight to polymer mixtures, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol: 240, ISSN: 0065-7727

JOURNAL ARTICLE

White RP, Lipson JEG, Higgins JS, 2010, Effect of Deuterium Substitution on the Physical Properties of Polymer Melts and Blends, MACROMOLECULES, Vol: 43, Pages: 4287-4293, ISSN: 0024-9297

JOURNAL ARTICLE

Higgins JS, Lipson JEG, White RP, 2010, A simple approach to polymer mixture miscibility, PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 368, Pages: 1009-1025, ISSN: 1364-503X

JOURNAL ARTICLE

Cabral JT, Higgins JS, 2009, Small Angle Neutron Scattering from the Highly Interacting Polymer Mixture TMPC/PSd: No Evidence of Spatially Dependent chi Parameter, MACROMOLECULES, Vol: 42, Pages: 9528-9536, ISSN: 0024-9297

JOURNAL ARTICLE

Saiani A, Novak A, Rodier L, Eeckhaut G, Leenslag J-W, Higgins JSet al., 2007, Origin of multiple melting endotherms in a high hard block content polyurethane: Effect of annealing temperature, MACROMOLECULES, Vol: 40, Pages: 7252-7262, ISSN: 0024-9297

JOURNAL ARTICLE

Tambasco M, Lipson JEG, Higgins JS, 2006, Blend miscibility and the Flory-Huggins interaction parameter: A critical examination, MACROMOLECULES, Vol: 39, Pages: 4860-4868, ISSN: 0024-9297

JOURNAL ARTICLE

Sakai VG, Higgins JS, Trusler JPM, 2006, Cloud curves of polystyrene or poly(methyl methacrylate) or poly(styrene-co-methyl methacrylate) in cyclohexanol determined with a thermo-optical apparatus, JOURNAL OF CHEMICAL AND ENGINEERING DATA, Vol: 51, Pages: 743-748, ISSN: 0021-9568

JOURNAL ARTICLE

Gretton-Watson SP, Alpay E, Steinke JHG, Higgins JSet al., 2006, Multi-functional monomer derived hyperbranched poly(methyl methacrylate): Kinetic modelling and experimental validation, CHEMICAL ENGINEERING SCIENCE, Vol: 61, Pages: 1421-1433, ISSN: 0009-2509

JOURNAL ARTICLE

Immanuel CD, Steinke JHG, Higgins JS, 2006, An integrated model-based analysis of polymer chemistry and polymerisation reactors, MACROMOLECULAR SYMPOSIA, Vol: 243, Pages: 225-232, ISSN: 1022-1360

JOURNAL ARTICLE

Gretton-Watson SP, Alpay E, Steinke JHG, Higgins JSet al., 2005, Hyperbranched polymers. Synthesis, modeling, experimental validation, and rheology of hyperbranched poly(methyl methacrylate) derived from a multifunctional monomer (MFM) route, Industrial & Engineering Chemistry Research, Vol: 44, Pages: 8682-8693, ISSN: 0888-5885

JOURNAL ARTICLE

Higgins JS, Tambasco M, Lipson JEG, 2005, Polymer blends; stretching what we can learn through the combination of experiment and theory, 40th International Symposium on Macromolecules, Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: 832-843, ISSN: 0079-6700

CONFERENCE PAPER

Gagliardi S, Arrighi V, Ferguson R, Dagger AC, Semlyen JA, Higgins JSet al., 2005, On the difference in scattering behavior of cyclic and linear polymers in bulk, JOURNAL OF CHEMICAL PHYSICS, Vol: 122, ISSN: 0021-9606

JOURNAL ARTICLE

Tambasco M, Lipson JEG, Higgins JS, 2004, New routes to the characterization and prediction of polymer blend properties, MACROMOLECULES, Vol: 37, Pages: 9219-9230, ISSN: 0024-9297

JOURNAL ARTICLE

Cereghetti PM, Kind R, Higgins JS, 2004, Tacticity effects on the barriers to rotation of the ester methyl group in poly (methyl methacrylate): A deuteron magnetic resonance study, JOURNAL OF CHEMICAL PHYSICS, Vol: 121, Pages: 8068-8078, ISSN: 0021-9606

JOURNAL ARTICLE

Bucknall DG, Higgins JS, Butler SA, 2004, Real-time neutron reflectivity study of the early stages of diffusion into and dissolution of glassy polymers, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 42, Pages: 3267-3281, ISSN: 0887-6266

JOURNAL ARTICLE

Saiani A, Rochas C, Eeckhaut G, Daunch WA, Leenslag JW, Higgins JSet al., 2004, Origin of multiple melting endotherms in a high hard block content polyurethane. 2. Structural investigation, MACROMOLECULES, Vol: 37, Pages: 1411-1421, ISSN: 0024-9297

JOURNAL ARTICLE

Arrighi V, Higgins JS, 2004, Structural investigation of polymers by neutron scattering, PLASTICS RUBBER AND COMPOSITES, Vol: 33, Pages: 313-329, ISSN: 1465-8011

JOURNAL ARTICLE

Tang P, Arrighi V, Higgins JS, Li GXet al., 2004, Kinetics of phase separation of poly(styrene-co-methyl methacrylate) and poly(styrene-co-acrylonitrile) blends, Polymer International, Vol: 53, Pages: 1686-1692, ISSN: 0959-8103

JOURNAL ARTICLE

Arrighi V, Gagliardi S, Dagger AC, Semlyen JA, Higgins JS, Shenton MJet al., 2004, Conformation of cyclics and linear chain polymers in bulk by SANS, Macromolecules, Vol: 37, Pages: 8057-8065, ISSN: 0024-9297

JOURNAL ARTICLE

Arrighi V, Gagliardi S, Zhang CH, Ganazzoli F, Higgins JS, Ocone R, Telling MTFet al., 2003, A unified picture of the local dynamics of poly(dimethylsiloxane) across the melting point, MACROMOLECULES, Vol: 36, Pages: 8738-8748, ISSN: 0024-9297

JOURNAL ARTICLE

Damrongsakkul S, Sinweeruthai R, Higgins JS, 2003, Processability and chemical resistance of the polymer blend of thermoplastic polyurethane and polydimethylsiloxane, 7th European Symposium on Polymer Blends, Publisher: WILEY-V C H VERLAG GMBH, Pages: 411-419, ISSN: 1022-1360

CONFERENCE PAPER

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