Cloner
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Posts: 150
Registered: 7-12-2004
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Mood: apocalyptic
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polylactic acid separation from lactic acid
The biopolymer polylactic acid is made of lactic acid monomers through a condensation reaction. There are many ways to make this polymer, the better
ones starting with lactide (a cyclic dimer of lactic acid). However, I am keeping it very basic and want to make some sort of polymer from
commercially available lactic acid.
What I am doing is heat lactic acid with tin(II)chloride in a microwave. This process leads to a gel which is probably low weight polymer mixed with
monomer and oligomers.
Is it possible to separate the higher molecular weight polymer from the lower MW stuff?
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Cloner
Hazard to Others
Posts: 150
Registered: 7-12-2004
Member Is Offline
Mood: apocalyptic
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I have performed a polymerization reaction in the microwave. Two samples were run at 2 * 10 minutes at defrost setting (220 W). The first sample was
just rac. lactic acid. The second sample also contained 100mg Sn(II)Cl2, well dissolved in the lactic acid.
After cooling for 24 h, both samples were a tough gel. They were subsequently treated with about 100ml water and stirred well. This was repeated twice
and the samples were stored with water for a night.
The sample without tin catalyst was still partially a tough slimy translucent syrup. The sample with tin catalyst had turned white. It is still a
gellish substance.
It is now hard to remove the water from the white stuff which I assume is prepolymer. It remains a glueish substance. Heating this stuff leads to
decomposition after the water is evaporated (might be lactide?). The material still contains acid.
The route to true PLA would require this lactide for ring opening polymerization, but I want to see if the low molecular weight polymer can be
obtained pure and whether it has some use.
[Edited on 12-4-2011 by Cloner]
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