Differential Dynamic Microscopy: Diffusion Measurements Where You Want Them

Abstract

Differential dynamic microscopy (DDM) is an emerging tool for the measurement of diffusion coefficients of macromolecules, especially in the form of particles or aggregates. It combines the benefits of microscopy�versatile modes of imaging, ability to locate regions of interest in structured systems, conventional light sources that do not require laser training, very small samples, and easy sample preparation�with many of the traditional benefits of dynamic light scattering (DLS). After introducing the method in terms that will be familiar to DLS users, examples are presented in ascending order of complexity. Reflecting the learning process of newcomers to DDM, the progression goes from simple latex spheres in free solution to the exquisite capabilities of DDM to explore specific regions of structured, inhomogeneous samples and work efficiently in challenging situations, such as encapsulated particles or colored solutions of conjugated backbone polymers in aggressive solvents at high temperatures. The very different user experiences provided by DDM and DLS are described and compared to multiple particle tracking (MPT). The Perspective closes with a glimpse into DDM's bright future.

Isoporous Membranes by the Symmetric Triblock Copolymer: A Strategy to Improve the Mechanical Strength without Sharply Changing the Pore Size and Permselectivity

“…The successful conversion of the triblock copolymer into a diblock copolymer is also demonstrated by the GPC analysis, which shows that the molecular weight of PS4VP is about half that of PS4VPS, proving the successful removal of CTA from the center joint of the symmetrical copolymer (Table ). The successful transition of the triblock copolymer into a diblock copolymer is further demonstrated by diffusion-ordered spectroscopy (DOSY-NMR), which can precisely determine the polymers' diffusion coefficients ( D s ) that are closely related to the MW and hydraulic diameter of synthesized copolymers. , The DOSY results indicate that the extrapolated D s to 0 mg/mL for the triblock copolymer (PS4VPS) and diblock copolymer (PS4VP) are 0.92 and 1.25 (10 –10 m 2 /s), respectively, which correspond to the MWs of 138,000 and 83,910 g/mol. It should be noted that CDCl 3 used in DOSY determination is not a strictly neutral solvent for the block copolymer, and segments are not equally solvated.…”