Hello.
I'm trying to make a film using Polycaprolactone(PCL) by solution casting method
at first, I used PCL (Mw ; 70000) but it crystallized too fast and became really hard film when i dissolved PCL in the condition of 10% w/v (10g of PCL/ 100ml of Chloroform)
So i bought PCL-diol (Mw : 2000). It was solid and waxy.
I dissolved it in solvent and dried for 24hr. but it didn't became film.
does PCL-diol have a film making property?
Yes, you should be able to make films with PCL. You may need to add some catalyst (Dabco 33LV or DBTDL) to get it to polymerize. If the conditions allow it, drying in an oven at 50 or 70C will improve your chances of getting a good film as well.
PCL at low molecular weight is really an oligomer used to make other higher molecular weight polymers like polyurethanes or other polyesters. If you do make a polyurethane and control the composition you can make films from solution casting.
Usually, we can get PCL membrane with good mechanical properties if its molecular weight > ~50000g/mol. Because Chloroform volatilizes quickly and PCL is easy to crystallize, the membrane surface always appears wrinkled and the membrane intuitively looks hard (I think here the main reason why it is hard is the high thicknees). If you decrease the thickness of the PCL film, it will be very soft. As to the diol, molecular weight (~2000 g/mol) is too small to make sure the entanglemrent between molecular chains. Therefore the obtained materials are with extreamly poor mechanical properties, even you can not obtain a whole membrane.
I Individually do not recommend using chain extention method, because comparing with direct casting method, the chain extention is relatively complex, and the catalyst is not environmental-friendly. You can control the process with relatively slow solvent evaporation rate (such as using butyl acetate or Inhibiting the surface air flow) and decrease the concentration to some extent (to make sure the low thickness). Thus you can obtain a relatively smooth, soft membrane. In addition, because of the low melting point of PCL, you can also use thermo-pressing method. It is quite convenient. By controlling the pressure, you can control the thickness of a membrane.
To see if PCL-diol polymer has film-forming properties, there is any easy method:
You need to have a metallic ring "the size of a small hand bracelet" which contains little mercury placed inside a glass dish. Pour the polymer's solution over mercury & let the solvent evaporate without heating in a fume cupboard. After that, try to take the film by means of tweezers. If you cannot pull a circular film & you see that it has crumbled, then the polymer does not have fiber-forming properties. Conversely, a film formed is indicative of success, of course.
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