Dear Samar Khattab, do have an idea about the CMC of the diblock copolymer you are working with, if not try to determine it, it will make you decide on the possible occurence and the form of the self-assembly of the copolymer. My Regards

Samar Khattab

Your micelles are classified as hydrogel micelles. They self-assemble and contain a lot of hydration water inside and outside the micelles. Self-assembly involves the nuclear quantum effect. The proton of water in the picosecond range migrates along the chains of water connected by hydrogen bonds. This increases the energy of this connection. The effect is quantum in nature.

Article Structure of Micelles of Sodium Dodecyl Sulphate in Water: a...

Preprint Nuclear quantum effect in aqueous micellar surfactant solutions

Preprint Supplementary information for Nuclear quantum effect in aque...

See also the answer to a similar question

https://www.researchgate.net/post/How_to_measure_DLS_of_mesoporous_silica_coated_nanoparticles

Dear Samar Khattab,

besides what has already been mentioned, I would also focus on the data quality. 1000 nm is 1 micron; your micelles would scatter light and give your sample a hazy appearance. However, that's also the size of common contaminants like dust. The scattering intensity scales with the 6th power of the size. In other words, a 10 times larger particle provides a million times stronger signal in DLS. The contaminants often mask the signal of your actual sample. For comparison, dissolved PMMA coils with Mw=100000 are around 10 nm, yielding one trillion times weaker scattering.Article Bulk Polymer Nanocomposites with Preparation Protocol Govern...

Is your result based on the intensity data, or is it recalculated to the number/weight average? You may also consider filtering or centrifuging your sample to see if there is another population hidden behind these large scatterers.

The most probable answer is non-optimal sample preparation, I'm afraid. "Dust" is your enemy in DLS measurements.

What filter are you using? Do you centrifuge the samples before measurement?

Alan Parker

i use syringe filter nylon 0.45 micrometer.

no centrfuge.

Petr Lepcio

yes ,the result is based on the intensity data i got from DLS .

obviously, it is something related to the contamination, generally, i will reconsider the sample preparation and filtration again!

thanks all for your answers. it was really helpful

here is an update for my results for anyone in the future facing the same situation, i repeat the sample preparation and take care of dust very well and the size diameter was 100 nm.

so in DLS TAKE CARE of sample preparation!

Thank you for the update, I am glad we could help you.

Samar Khattab , if you do not mind sharing, what precautions did you take this time? Back then, what was the percentage of 1000 nm particles? I do ask these questions as I'm facing something similar but with higher particle size.

Thanks!

Matheus Augusto de Castro

The general precautions are:

- purify your raw materials (filtration, centrifuging, distillation, sedimentation, etc.)

- wash/wipe all equipment just before use

- work in a clean area; a certified cleanroom is good but not necessary; if necessary, wipe the dust and let the rest settle before you start work; try to reduce air streams in the lab while you work

- cover your skin and hair - humans are strong pollutants when it comes to unwanted particles

- wear a clean lab coat made from synthetic fabric - cotton clothes produce a lot of particles

- wear powder-free gloves

- store your samples in clean jars/plastic bags

By the way, don't forget to check the purity of the measuring cuvette on toluene.

We have a certified cleanroom at our facility, but usually, you don't have to be that strict for DLS measurement. Any measures will help. If you keep struggling, you can still consider filtering or centrifuging. We use disposable PTFE syringe filters, usually 200-400 microns, but I have made many DLS samples in a regular "dirty" (= not in a cleanroom) lab which didn't need to be filtered.

Thanks Petr Lepcio , these tips are very useful, especially the toluene one, which I was not aware of. Definitely cleaning can be tricky depending on sample nature.