I have a standard (i.e. not functionalised) PEO molecule with a Mw of 4E6. I would like to be able to attach one end to a surface (density doesn't need to be that high). This surface needs to be hydrophobic. I have considered using a film of carboxy terminated PS and refluxing this in sulphuric with the PEO to try and form an ester but my chemistry is a bit weak and am not sure whether this is reasonable. I don't seem to be able to buy functionalised PEO of a sufficiently high Mw so many of the usual brush techniques are out unless I can functionalise the PEO myself. So, I need some chemistry advice! Is there a way to make a silanated version of my polymer which could be used with glass or silicon? Any advice or pointers?
Boiling of PEO in sulphuric acid is definitely a bad idea since the polymer is prone to acid-catalyzed degradation. You should try alternative methods that proceed under milder conditions, for instance by using direct coupling agents (e.g. carbodiimides) or spacers (e.g. diisocyanates). You must, however, keep in mind that the reactivity of high-molecular-weight PEO, regardless of the chemical nature of the polymer's terminals (OH, NH2, COOH), will be very low - this is due to extremely low concentration of chain-end reactive groups.
For chemical surface grafting, I would suggest you considering PET (instead of PS), which is also hydrophobic but insoluble and unswellable in common organic solvents. Moreover, the polyester can be easily modified in order to generate reactive functional groups on its surface.
Thanks for both your answers. Pawel I think that the roughness of PET may affect my droplet but I'll look into the coupling agents you mention. Rongyue could you spell out the chemistry for me. How do I sulfate a PS surface and when you say react with PEO would you simply have a solution of PEO in the presence of the sufated surface or is something more required? Heat? Catalyst? Sorry to be so basic but chemistry is really not my strong point.
please refer to "European Polymer Journal 39 (2003) 327–331", I hope this reference can help you.
Michael, what is the purpose that you are going to use PEO of such extremely high molecular weight? As I pointed out, the reactivity of this polyether will be very low and, in consequence, grafting the polymer onto the PS surface will be difficult, if at all possible. If you replaced high-MW PEO with amine-terminated PEO monoether (commercialy available mPEO-NH2 with a wide range of MW: 0.4-40k), the surface of polystyrene could be effectively grafted via a simple synthetic route using carbodiimide chemistry. If this is convenient for you, I can provide you with a detailed protocol for doing so.
PEO-N2 or PEO-NH2, How to use carbodiimide chemistry, could you please send me the detailed protocol for doing so? My email: [email protected], thank you very much.
I'm studying a problem in dilute polymer solutions (see a previous paper of mine Phys Rev Letts 104 (2010) 154502) Usually the polymers are free in solution but I'd like to try attaching them to the surface. The effect only works with very high molecular weight polymers. Any protocols that are simple enough to be attempted by someone with little chemistry experience would be very useful.
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