I'm currently trying to polymerize PLA by ring opening bulk polymerization using Sn(Oct)2 as a catalyst and lauryl alcohol as an initiator. The best result I've got was reducing the amount of catalyst by 5.6wt% and initiator by 3.8wt%. Below are the processes of experiment.
1. Melting of D,L - Lactide at 145°C
2. Mixing D,L - Lactide, catalyst, initiator reagents by using magnetic bar at 180°C
Haven't tried nitrogen purging and other processes regarding purification of chemicals, which were used as served. If I lower the amount of catalyst and initiator, I can't see any trace of polymerization while all I get is oligomeric state of lactide. Any advices would be greatly appreciated.
Jeongwon Kim, what molecular characteristics of PLA you are planning to get: high/low molecular weight, narrow/broad MWD, high/low polymerization rate, limited/unlimited discoloration, high/low amount of unreacted monomer?
Pawel P. Sobecki , for now high molecular weight, high polymerization rate and low amount of unreacted monomer is a main goal.
Jeongwon Kim
A purified lactide monomer is essential. Try to purify it thoroughly by recrystallization and/or resublimation.
Reduce the concentration of lauryl alcohol (LA) to 0.2-0.3 mol% with respect to DL-LA. The concentration you inidcated will not produce a high-molecular-weight polymer.
Reduce the concentration of tin octoate further to 10 mol% with respect to LA.
A proposed reaction mixture batch (100 g) will be as follows:
DL-LA: 99.56 g
LA: 0.37 g
SnOct2: 0.07 g
Reaction conditions: 170'C for 0.5 hour, followed by cooling down to 140'C and proceeding for 8 hrs
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