_ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ SOFT CONDENSED MATTER COMPLEX MOLECULES AT MESOSCOPIC SCALES Juan Colmenero Departamento de Fsica de Materiales UPV/EHU Unidad de Fsica de Materiales CSIC-UPV/EHU Donostia International Physics Center eman ta zabal zazu UPV/EHU _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ What is Soft Condensed Matter? Neutron Scattering & Soft Matter Past & Present: Key Neutron Scattering Contributions to Soft Matter Why Neutrons? SOFT CONDENSED MATTER COMPLEX MOLECULES AT MESOSCOPIC SCALES _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Future: ESS New Opportunities for Soft Matter SOFT CONDENSED MATTER COMPLEX MOLECULES AT MESOSCOPIC SCALES Neutron Scattering & Soft Matter What is Soft Condensed Matter? _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ What is Soft Condensed Matter? _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Soft Condensed Matter Polymers Thermotropic liquid crystals Micellar solutions Microemulsions Colloidal suspensions Substances in biology: membranes, vesicles,... The concept of soft matter subsumes a large class of molecular materials: _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Structural and packaging materials Foams and adhesives Detergents and cosmetics Paints Food additives Lubricants and fuel additives Rubber in tires... Wide range of Applications: Soft Condensed Matter _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ very different properties common physicochemical causes weak interaction between the structural units entropyenthalpy delicate balance entropic enthalpic contrib. to free energy large number of internal degrees of freedom (( Soft Condensed Matter _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ BIOLOGICAL SYSTEMS POLYMER LIQUID CRYSTALS MEMBRANES Structural units: large molecules or aggregates of molecules SURFACTANTS MICELLAR SOLUTIONS AMPHIPHILICS Different length scales: different structural & dynamical properties Soft Condensed Matter BIOLOGICAL SYSTEMS MEMBRANES SURFACTANTS MICELLAR SOLUTIONS AMPHIPHILICS POLYMER LIQUID CRYSTALS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ POLYMER MACROMOLECULES Repetition of N Monomers C C C C C H H H H H H H H _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ POLYMER RANDOM COIL STRUCTURE 300 ATOMIC STRUCTURE 25 _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Polymers Large Scale Dynamics Chain Diffusion Reptation Rouse Dynamics... C C O C H H H H H H Dynamics Static Intermolecular Range - Relaxation Length scale 1 1000 Time scale 1 ps 1 ms Molecular Length Scale Vibrations Side Groups - Relaxation... GLASSY BEHAVIOUR P(Q) Q( -1 ) Q( -1 ) 0 12 S(Q) _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Polymers Large Scale Dynamics Chain Diffusion Reptation Rouse Dynamics... C C O C H H H H H H Dynamics Intermolecular Range - Relaxation Time scale 1 ps 1 ms Molecular Length Scale Vibrations Side Groups - Relaxation... Timescales log (s) 1/T /T g E a 0.5eV E a 0.1eV CH 3 end to-end (M w ) GLASSY BEHAVIOUR _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutrons & Soft Matter Why Neutrons? _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutrons & Soft Matter Unique role: Q Q Q Q Suitability of length and time scales accessed, especially SANS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Decipher structure & dynamics in complex systems b H =-3.74 fm b D =+6.67 fm Selectivity varying contrast: H D Suitability of length and time scales accessed, especially SANS Neutrons & Soft Matter Unique role: _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Decipher structure & dynamics in complex systems Suitability of length and time scales accessed, especially SANS Unique role of neutron reflectometry Surface and interfaces in soft matter Neutrons & Soft Matter Unique role: Selectivity varying contrast: H D _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ High penetration: Influence of external fields/parameters Space-time resolution Molecular motions Viscoelastic/mechanical properties e.g. Fabrication conditionsTailor made materials Unique role of neutron reflectometry Surface and interfaces in soft matter Neutrons & Soft Matter Unique role: Decipher structure & dynamics in complex systems Suitability of length and time scales accessed, especially SANS Selectivity varying contrast: H D _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutrons & Soft Matter Techniques _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Large Scale Dynamics Chain Diffusion Reptation Rouse Dynamics... C C O C H H H H H H Intermolecular Range - Relaxation Length scale 1 1000 Time scale 1 ps 1 ms Molecular Length Scale Vibrations Side Groups - Relaxation... P(Q) Q( -1 ) Q( -1 ) 0 12 S(Q) NEUTRON SCATTERING TECHNIQUES SANS Liquid Diffractometer Polarised Diffuse Scattering NSE WA-NSE BS TOF _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Length scale 1 1000 Time scale 1 ps 1 ms NEUTRON SCATTERING TECHNIQUES SANS Liquid Diffractometer Polarised Diffuse Scattering NSE Complex Materials: Interfaces Reflectometry WA-NSE BS TOF _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutrons & Soft Matter Past and Present: Key Contributions (some examples) _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Conformation of Polymer Chains in the Melt and the Amorphous State _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Conformation of Polymer Chains in the Melt and the Amorphous State Random Coil Model Flory 50s First experimental evidences by neutron scattering (70s) Kirste et al., Jlich Benoit et al., Grenoble ReRe RgRg _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ SANS Conformation of Polymer Chains in the Melt and the Amorphous State _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ P(Q) = [ Q e (-Q 2 ) ] 2 Q 4 2 Kirste et al. (1975) PMMA Conformation of Polymer Chains in the Melt and the Amorphous State _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Conformation of Polymer Chains in the Melt and the Amorphous State M W PS Benoit et al. (1974) 2 _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Linear Chain Dynamics in the Melt _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Linear Chain Dynamics in the Melt N n f n (t) Gaussian Chain in a Heat Bath Entropic springs Rouse Model _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Rouse t 1/2 Rouse Model Diffusion t log t log NSE Linear Chain Dynamics in the Melt _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Rouse Model MwMw Increasing Molecular Weight Spatial ConfinementEntanglements Long time plateaus NSE REPTATION Linear Chain Dynamics in the Melt _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ tete tRtR t 1/4 Local Reptation Rouse Diffusion t 1/2 t log t log Rouse Model Reptation Model (Edwards, deGennes) t 1/2 Reptation tdtd t Diffusion Linear Chain Dynamics in the Melt M. Monkenbusch et al. (unpublished) Jlich _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Dynamics in Miscible Polymer Blends _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ 100% Dynamics in Miscible Polymer Blends DYNAMIC HETEROGENEITY Different segmental dynamics ( -relaxation) for each component in the blend log 1/T 50/50 _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ PI 100% PVE 100% Blend PVE/PI 50/50 Dielectric Spectroscopy Dynamics in Miscible Polymer Blends DYNAMIC HETEROGENEITY _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ PVE 100% Instrumental resolution PI 100% in blend: PI & PVE Quasielastic Neutron Scattering Q: -1 (Backscattering) Dynamics in Miscible Polymer Blends DYNAMIC HETEROGENEITY _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ PI 100% PVE 100% Is there any relevant length scale for miscibility? Q-dependence of the characteristic relaxation time NEUTRON SCATTERING PVE & blend PI 1/Q~ K Homogeneous Heterogeneous Crossover at ~ K Dynamics in Miscible Polymer Blends PRL 85, 772 (2000) _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Future Opportunities _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Future Trends in Soft Matter (by definition ) Scientific and Technological development is unpredictable but... E.g., Heavier-than-air flying machines are impossible Lord Kelvin, president, Royal Society, 1895 I think there is a world market for maybe five computers Thomas Watson, chairman of IBM, 1943 640K ought to be enough for anybody Bill Gates, 1981 _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Multi-component soft & soft/hard materials tailor made for industrial applications Future Trends in Soft Matter Increasing structural & dynamical complexity at different length and time scales _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times Increasing structural & dynamical complexity at different length and time scales Future Trends in Soft Matter _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering: decisive role... in combination with Computer Simulations and Modellisation Advanced Chemistry Current limitation: INTENSITY _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ How can the ESS further contribute to the development? more intensity at the detector higher resolution in frequency Fourier time and real time Neutron Scattering: decisive role _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ ESS Contribution Performance gain factor calculated for Soft Matter instruments: InstrumentTotal gain High intensity SANS ~ 100 High intensity reflectometer ~ 40 Liquids diffractometer ~ 20 Polarised diffuse scattering ~ 300 High resolution NSE ~100 Wide angle NSE ~ 300 Backscattering ~ 50 Variable chopper cold TOF ~ 800 Structure Dynamics _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times Increasing structural & dynamical complexity at different length and time scales Future Trends in Soft Matter _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times HIGH INTENSITY ESS Future Trends in Soft Matter _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times New Opportunities for Soft Matter HIGH INTENSITY ESS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ SANS Kinetic studies t Mixing t=0 + Recent example: Micellar exchange kinetics ALWAYS INTENSITY LIMITED _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Real time: exchange kinetics unexpected result: two exchange mechanisms Recent example: Micellar exchange kinetics ALWAYS INTENSITY LIMITED Kinetic studies _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Fast Process: unimer exchange Slow Process: ??? Recent example: Micellar exchange kinetics ALWAYS INTENSITY LIMITED Kinetic studies _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Bu - Li + + M Bu-M - Li + Bu-(M) n -M - Li + [Bu-(M) n - M - Li + ] x=? +n M Observed chain aggregation ( x > 12) contradicts common picture of polymerisation mechanism I raw [cm -1 ] t= 0min. t= 30min. t= 65min initiator Q[ -1 ] Initiation Maximal aggregation after initiation 3x t=69h t=42h t=30h t=21h t=14h t=10h t=7h t=3h t=1h t=12min. (dS/dW)(Q )[cm - 1 ] Q[ -1 ] Chain Growth Chain growth during complete reaction Recent example: In Situ polymerisation ALWAYS INTENSITY LIMITED Kinetic studies to high vacuum line Polymerisation reactor SANS sample light scattering sample _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Pilote experiments : Spinning of fibers Strength Chain Conformation Optimisation of spinning process by in situ SANS studies Small samples Non Equilibrium studies ALWAYS INTENSITY LIMITED _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times New Opportunities for Soft Matter HIGH INTENSITY ESS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Molecular Rheology of Topological Polymer Fluids linear star H- polymer combs trees only a few branches alter processing behaviour completely Industrial processing Macromolecular dynamics Topology of the molecules ALWAYS INTENSITY LIMITED _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ polyethylene Molecular Rheology of Topological Polymer Fluids ALWAYS INTENSITY LIMITED Industrial processing Macromolecular dynamics Topology of the molecules _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Molecular Rheology of Linear Chain Polymers Rouse & Reptation models _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Molecular Rheology of Linear Chain Polymers Rouse & Reptation models Branched polymers?? _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Molecular Rheology of Branched Polymers Rouse & Reptation models Branched polymers?? ? _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Dilute scattering centers INTENSITY!! Neutron Scattering Experiments: Isotopic substitution of branched points Molecular Rheology of Branched Polymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Experiments on inherently small or dilute samples In situ real time kinetic & non equilibrium processes Smaller cross-sections Measurements over shorter times New Opportunities for Soft Matter HIGH INTENSITY ESS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Self-assembling Block-copolymers Unprecedent variety of morphologies _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Nanoscale Morphologies generated by Self-Assembly: Simplest case: Diblock-Copolymers Polymer A N A units Polymer B N B units NANA+ NBNANA+ NB f = Self-assembling Block-copolymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ More than a hundred morphologies were identified Triblock-Copolymers Polymer A Polymer B Polymer C Self-assembling Block-copolymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Mesoporous materials for separation technologies High efficient catalysts Templates for wax-control in diesel fuels Templating of magnetic devices Photonic crystals Applications Self-assembling Block-copolymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ The role of Neutrons A rational design needs a detailed characterisation of all components Neutron Scattering: SANS Reflectometry Selective labeling Polarisation analysis......in combination with: NMR Synchrotron Imaging methods... However... Self-assembling Block-copolymers _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ Structural complexity Extensive sets of experimental data Kinetics of structure formation Time resolved experiments ESS Self-assembling Block-copolymers The role of Neutrons ESS _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ SUMMARY Soft Condensed Matter ESS will open plenty of future opportunities in this field Broad and rich field with close links to applications Neutrons: Key role Proper length and time scales H/D contrast _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _ __ _ _ _ _