I was polymerizing Poly(L-lysine) and when I precipitate in Ethyl Acetate/Hexane (followed a procedure) it turns out to be sticky precipitates instead of solid.
I was wondering what is the cause? I was under the assumption that it's because of Ethyl Acetate and I should just use pure hexane instead although I did not try this yet.
Sticky or gummy nature of your polymer is its consistency. The degree of polymerization influences it. Sticky product means size of polymeric molecules is comparatively low and to get solid you have to ensure by controlling the polymerization conditions such that you get long chain polymeric molecules. It requires a proper stoichiometry among monomer, initiator, chain arrestor etc. In concentration terms.
When first prepared, polymers may emerge as viscous liquid or as sticky product or as a wax or as a powder or as flakes or similar to fluffy wool or cotton... several possibilities.
Drying your polymer may end this tacky appearance. If stickiness persists, then there are 2 probabilities: either the polymer has adhesive properties or the polymer is oligomeric (i.e. it is polymeric but has low average molecular mass). Example: When phenol is reacted with formaldehyde, a fast ending of the reaction gives a polymer that is used as an adhesive in sandwich wood. Upon continuation of the reaction "in which heating is applied", the end product is a very rigid solid polymer which is used as the black handles of a pressure cooker.
Polymer may have very long non-polar chain segments with few highly hydrophilic blocks.
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