PLA with high elongation induced by multi-branched poly(ethylene imine) (mPEI) containing poly(l-lactic acid) (PLLA) terminals

- mPEI with PLLA terminals was synthesized via lactide ring opening polymerization.
- mPEI provides free volume whereas PLLA terminals enhances crystallization of PLA.
- mPEI-PLLA was an effective plasticizer to improve the elongation of PLA for 280%.
- mPEI-PLLA was miscible to PLA as evidenced by a single Tg of the PLA blend.

The present work demonstrates the function of multi-branched poly(l-lactide) based on polyethylenimine cores (mPEI-PLLA) as an additive to drastically enhance the elongation of PLA resin. By simply applying mPEI as the core molecule with a catalytic amount of tin octoate, LLA ring-opening polymerization is accomplished to result in multi-branched PLLA, i.e. mPEI-PLLA. The blend of mPEI-PLLA with PLA in the film form represents the significant increase of elongation at break for as high as 280% without significant changes in Tg, indicating the role of branching PLLA to induce amorphous phase in the packing structure of PLA. The ease of mPEI-PLLA preparation and the superb elongation at break provided to PLA convince us that mPEI-PLLA is a practical miscible additive to solve the brittleness of PLA.

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