The 3 factors controlling scattering intensity (other than the power of the impinging radiation) are:

• Size of the scattering centers
• Concentration
• Optical contrast i.e the relative refractive index of the particle in relation to the environment it is in

So, unless your change in viscosity is caused by a change in concentration, for example, then no, viscosity has no effect on the scattering. However, viscosity is inherent in the Stokes-Einstein equation and thus would be relevant if you were wanting to size the polymer, for example, by dynamic light scattering (DLS).

Thank you Sir for your answer. Yes. The concentration does change and this has an effect on the refractive index. What would be the the case in case of monomer solution which I cure via UV irradiation?

I do not understand what you mean by 'what would be the case......'.

Please explain. If the concentration changes then the scattering will change.

They are inter-related in the sense that both internal viscosity and light scattering an be used for determining average moleular mass BUT: they are different averages, and both methods require measurements at several concentrations and extrapolation to infinite dilution

https://www.wyatt.com/solutions/properties/molar-mass-by-multi-angle-light-scattering-sec-mals.html

Obviously dilute solution viscometry (DSV) can be explored to measure molecular mass as Gyorgy has correctly explained. This relies on interpolation of known molecular masses via such empirical methods as the Mark-Houwink equation. The viscosity isn't related to the light scattering in a direct way - but they are different routes to the same end. The Mark-Houwink plot may need calibration values obtained by light scattering. The Zimm plot can be used in static light scattering to the same ends as well - extrapolation to zero concentration and zero angle.

Thanks everyone for your valuable comments.

Dr. Rawle, I meant if the solution is the mixture of two monomer solution (bulk) and after laser irradiation the polymer is formed via photo-polymerization like in case of stereolithography. In such case scattering of UV laser becomes an issue when we change monomer ratio resulting in polymer with bigger dimension which I expected is due to light scattering.

Without more details, it's hard to answer. How much bigger are you're structures than expected? Are you focusing the laser to a diffraction limited spot (trying to raster and write structures)? Or is this directly exposed? Big difference in size then. Either case, you're in the Mie scattering regime, and the mathematics aren't as simple as Rayleigh. Regardless, could diffusion of the excited monomers be causing the larger structures? Try reducing laser intensity so you don't overexpose?

This conversation is getting very confused now - or is it just me?

Yeah. This was posted as a scattering question, but I have a feeling this is really about photolithography... cryptically posed.

Yes kind of photolithography. Will try reducing laser intensity. Anyway thanks everyone

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