which one is more polar?
I work on nanaoprticles ,included in microparticles like PEG 4000 and PEG 1000.
After analyzing their size, PEG 4000 had minimum size.
but I dont know exaclty why?
be cause Idont know the differences between PEG1000 and PEG 4000.
Can some one help me?
The short answer is they have similar (low) polarity. Pure PEG 4000 is a solid and PEG 1000 is a liquid at room temperature. The both self associate, but the PEG 4000 has long enough chains to solidify at room temperature.
The difference between PEG 4000 and PEG 1000 (and all of the PEG and PEO's) is the length of the polymer chain. The number of each PEG (e.g. 10,000, 4000, 1000, 400, 200, etc) refers to the molecular weight and the monomer is H−O−CH2−CH2. When polymerized they are linked together--head to tail--and the chemical structure is: H−(O−CH2−CH2)n−OH. The "n" in the chemical formula represents the number of monomer units. So PEG 4000 chains have an average of 90 monomer units and PEG 1000 has an average of 22 monomers.
None of the PEG's and PEO's have strong polar groups so none are very polar. You could make the case that they are slightly polarizable and the longer the chain will have more opportunity to be more polarizable--but the difference between PEG 4000 and PEG 1000 is small. The main feature is PEG and PEO is its hydrophilicity--the longer the chain the greater the effect. So PEG 4000 is more hydrophilic than PEG 1000 and will impart greater effect if attached to something.
PEG 4000 and PEG 1000 are both solid at room temperature (20°C). Their respective melting ranges (as PEGs contain several polymer chain lengths centered on the nominal value - in a Gaussian manner) are 53-58°C and 33-40°C, respectively.
Both PEG have low polarity. PEG 1000 is slightly more polar than PEG 4000 as their respective dielectric constants are 10.74 and 9.53 (at liquid state, 60°C). Reference can be found here (table 2): https://core.ac.uk/download/pdf/39208567.pdf
How did you measure their sizes, is it in solutions.
If that is the case. Did you have same concentrations as both polymers have different Mwts . I think it might be down to miceller formation issues in the case of PEG 4000. Also, its ability to relatively further reducing surface tension of water.
Dear Haneih Moghadasi.. PEG or we can say polyethylene glycol are both hydrophilic but their differ in their characteristic as PEG 4000 is solid (crystalline form) while PEG 1000 is liquid in nature.. PEG 4000 as we work on it could increase solubility of different materials and it may absorb water in it's structure then dissolve so it could be more hydrophilic.
As described by Vincent Jannin, PEG 1000 is more polar than PEG 4000. Higher is the Polarity (PEG 1000), more is the solubility in water. Hence, it will attract more water molecule which increases the film thickness of the hydration layer. Hence, PEG 1000 nanoparticles might be showing a higher size (hydrodynamic diameter as measured by DLS). Whereas, actually, the core size might be less for PEG 1000 nanoparticles. For this, you can carry out, SANS to identify the core diameter and differentiate between the DLS size (hydrodynamic diameter) and SANS size (Core diameter).
Ref: Solubilization of vardenafil HCl in lipid-based formulations enhances its
oral bioavailability in vivo: A comparative study using Tween - 20 and
Cremophor - EL, Journal of Molecular Liquids, 2019.
Presumably, PEG 4000, has higher molecular weight, so it is more molar than PEG 1000.
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