Doctoral students seminar (May 26, 2020)

Crystallization of polymers at the air-water interface
by Nazmul Hasan

From single chains to aggregates: How conjugated polymers behave in solution
by Sayed Mohammad Fahimi

Location: Online, via MLUconf
Time: 3.20pm-5.00pm


Crystallization of polymers at the air-water interface
Nazmul Hasan

Polymer crystallization on solid supports in quasi-2D environment has been studied in last decade. Using Langmuir trough experiments, an alternative approach is available having several advantages:  film thickness can be varied from Å – range to several nm, pseudo-dewetting observed on the surface of solid supports can be prevented and crystallization progress can be controlled by compression, expansion, and temperature variation. In this study, several homo and block copolymers are crystallized on the water surface of a Langmuir trough. The crystallization is directly visualized using Brewster angle and epifluorescence microscopy. The final confirmation of crystallization and the crystal orientation are determined using infrared reflection absorption spectroscopy (IRRAS) and grazing incident wide-angle X-ray scattering (GI-WAXS) techniques in both Langmuir and Langmuir-Blodgett (LB) film [1-4].


[1] Hasan N, et al (2020) Crystallization of poly(ε-caprolactone) at the air-water interface studied by IRRAS and GI-WAXS. Polymer 196:122468–122477
[2] Hasan N, et al (2018) Crystallization of a polyphosphoester at the air-water interface. Eur Polym J 101:350–357
[3] Karsten Busse, Fuchs C, Hasan N, et al (2018) Crystallization of poly(ethylene oxide) on the surface of aqueous salt solutions studied by grazing incidence wide-angle X‑ray scattering. Langmuir 34:12759–12763
[4] Hasan N, et al (2019) Langmuir film formation of amphiphilic hybrid block copolymers based on poly(ethylene glycol) and poly(methacrylo polyhedral oligomeric silsesquioxane). Colloid Polym Sci 297:1149–1159


From single chains to aggregates: How conjugated polymers behave in solution
Sayed Mohammad Fahimi

Conjugated polymers are emerging as an important class of materials due to their potential applications in electronic devices such as light emitting diodes, photovoltaics, and field effect transistors. In general, π-conjugated polymers have a very strong tendency for aromatic π- stacking via inter- or intra-chain interactions, which leads to the formation of micrometer- to sub- nanometer-sized aggregated species.
Fluorescence correlation spectroscopy (FCS) is a powerful single molecule technique to trace the diffusion dynamics of a single or few polymer chains in dilution at nano-molar concentrations. FCS determines the rate kinetics as well as the diffusion dynamics using fluctuations in the intensity at thermal equilibrium. Such deviations occur due to both the motion of particles or chains as well as inter- or intra-molecular interactions.
in this research PNDI2OD-T2 aggregate formation is investigated by FCS technique.


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