Dynamic light scattering advantages and disadvantages

SCIENCE 296 104 ( 2002)Дilute solutions Semi-dilute solutions f* 2xh Entangled dynamics 2Rg Brownian motion Polymer Dynamics Multiple Glassy States in a Simple Model System Sterically stabilized PMMA-particles in cis-decalin. Glass-to-glass transitions copolymer micellar system SCIENCE 300, 619 (2003) 0,2 221 K 0 -6 -4 -2 0 2 4 10 10 10 10 10 10 Time (s) Poly(propylene glycol)ДЄrrhenius Plot 4 Polymer Dimer (n=69) (n=2) 0 Oligomer (n=7) Monomer -4 log (n=1) -8 -12 2 2.5 3 3.5 4 4.5 5 5.5 6 1000/T (1/K) Arrhenius Plot Conclusion: Shorter polymer chains relax faster than long chains.Дў00 - 500 Г… Glass Transition dynamics in Free-standing Polymer Films Polystyrene Tg=369 K DLS can be used to probe the dynamics of thin free-standing polymer films

Determination of size on complex systems: ДЎ.0 0.8 0.6 correlation 0.4 t 0.2 0.0 -2 -1 0 1 2 log Glass transition dynamics log пЃґ glass liquid пЃЎ-relaxation.

The influence of pH on Insulin Amplitude Diameter (nm) Size Distribution of Insulin Intensity Diameter (nm) Difficult!Д®xamples Some examples of sub-micron systems: Д¬alculated ellipitic shape Lysozome Hydrodynamic size Calculated hard sphere Estimation of Ellipsodial objects Can be used for estimation of ellipticity of the particles. Shape: Ellipsodial particles results in a small fraction depolarized scattered light. These small random jumps are what make up Brownian motion.ДЄpplications of DLS Size: Using Stoke-Einstein equation DLS can be used to easy, fast and accurate determination of the hydrodynamic radius of particles. If the particle is very small, the number of hits it takes from one side at a given time will be stronger than the bumps from other side. Stoke-Einstein relation: Brownian Motion Explanation: A suspended particle is constantly and randomly bombarded from all sides by molecules of the liquid.

Jean-Baptiste Perrin verified Einstein's analysis (Nobel Prize 1926).

The mathematical theory of Brownian motion was developed by Einstein in 1905.

Desaulx in 1877: 'In my way of thinking the phenomenon is a result of thermal molecular motion in the liquid environment (of the particles).вЂќ.

He was looking at pollen grains under a microscope.

First observed in 1827 by the botanist Robert Brown.

Sensitive for mechanical disturbances +.

Wide time range Cheap Simple experimental set-up Advantages and Disadvantages Time range of DLS DLS QENS NMR Raman Brillouin Dielectric -14 -10 -6 -2 2 LOG(TIME (s)) DLS covers a very large time range! Typically: 10-7 - 103 s! => 10 decades in time!Д®xperimentally accessible wave vectors Q-range: typically 0.6 вЂ“ 2Г—10-3 Г…-1 DLS is therefore suitable for diffusional studies of macromolecules, such as polymers and large biomolecules!

Size and shape of sub-micron objects Research.

Accessible time- and length-scales Applications.

Introduction toDYNAMIC LIGHT SCATTERING (DLS) or PHOTON CORRELATION SPECTROSCOPY (PCS) Christer Svanberg

Dynamic light scattering advantages and disadvantages