The ethers themselves are quite hydrophilic; for instance, the solubility of diethyl ether in water is of 69 g/L, so no surprise that polymeric ethers can be hydrophilic as well. The hydrophobicity of ethers is due to hydrocarbon parts of the molecule, thus the key parameter is the ratio of carbons to oxygen. Poly(propylene glycol) is much less hydrophilic, and this leads to variety of PEG-PPG polymeric surfactants.

The OH, at the terminus make it hydrophilic. More over ether oxygen can hydrogen bond with water. This makes it stretch out and make it soluble.

The ethers themselves are quite hydrophilic; for instance, the solubility of diethyl ether in water is of 69 g/L, so no surprise that polymeric ethers can be hydrophilic as well. The hydrophobicity of ethers is due to hydrocarbon parts of the molecule, thus the key parameter is the ratio of carbons to oxygen. Poly(propylene glycol) is much less hydrophilic, and this leads to variety of PEG-PPG polymeric surfactants.

All PEGs are not hydrophobicity materials. PEG is poly ether, a lot of ether oxygen make it hydrophilic!!!

The hydrogen bonding makes PEG hydrophilic, I think.

Hi friends thanks for trying to help, there are some issues that are need clarification.

1) Diethyl ether is not water soluble. at room temperature it forms an organic layer and is used to extract hydrophobic compounds from water.

2)its true that poly propylen glycol is more hydrophobic BUT poly methylen glycol which is one less carbon is also MORE hydrophobic than PEG.

3) ether is the least polar/hydrophylic oxygen containing functional group, less polar than ketones,aldehydes,alcohols and acids so why is it like the most used polymer for hydrophylic blocks.

im not saying PEG is not hydrophylic im just want to understand why....

thanks

Hi i have found this very good paper in PNAS talking about this exact same issue:

http://www.pnas.org/content/94/16/8378.full

Thanks, Shamay Yosi, the paper seems interesting! Will have a closer look when I have time... However, the mistake in the very abstract (PPG structure holds the name of poly(butylene glycol)) shows that is should be carefully read!

And just a small note following the previous post: the diethyl ether IS soluble in water (69 g/l is quite a lot). That it is used for organic compounds extraction, means that it IS NOT fully miscible with water. This is a small remark on the terms, otherwise I agree that the question is more intriguing than could seem at the first glance. However, I would still be more excited about the hydrophobicity of PMG rather than too much hydrophilic PEG ;)

Just a short remark on that topic:

I like the explanation of Evgeny Karpushkin above about the behaviour of PEG and PPG. Its really about the carbon chain and the unpolar part of the polymer.

Oh and by the way OF COURSE ether is soluble in water. Did you ever think about the fact that you have to dry ether or other organic solvents like DCM???? All of the dissolve partly in water as well as water dissolves partly in them.

PMG (poly methylen glycol) has to be excluded from the explanation, because it forms a helical structure which can not be broken from the hydrogen bonds in water. That's why it doesn't dissolve in water.

And to your thrid point, aldehydes and ketons might be more polar because the have a higher dipol moment, but they cannot form as stable hydrogen bonds as ethers. I guess it has something to do with HOMO energy. And of cours ethers like PEG are extremly simple to synthesize. Polymeric ketons, aldehydes and ester always have a hugh carbon chain connected with them which makes it les hydrophilic.

Cheers