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    Improving polylactide toughness by plasticizing with low molecular weight polylactide-poly(Butylene succinate) copolymer
    (2021-01-01)
    Srithep, Yottha
    ;
    Veang-In, Onpreeya
    ;
    Pholharn, Dutchanee
    ;
    Turng, Lih Sheng
    ;
    Morris, John
    A low-molecular-weight polylactide-poly(butylene succinate) (PLA-PBS) copolymer was synthesized and incor-porated into polylactide (PLA) as a novel toughening agent by solvent casting. The copolymer had the same chemical structure and function as PLA and it was used as a plasticizer to PLA. The copolymer was blended with PLA at a weight ratio from 2 to 10 wt%. Phase separation between PLA and PLA-PBS was not observed from their scanning electron microscopy (SEM) images and the crystal structure of PLA almost remained unchanged based on the X-ray diffraction (XRD) measurement. The melt flow index (MFI) of the blends was higher as the amount of PLA-PBS increased, indicating that the block copolymer did improve the mobility of the PLA chains. Moreover, tensile tests revealed that PLA with greater PLA-PBS copolymer exhibited higher elongation at break and it reached the maximum at 8 wt% of PLA-PBS in PLA, which was around 6 times higher than that of pure PLA. Furthermore, the glass transition temperature, measured by differential scanning calorimetry (DSC), mark-edly decreased with an increasing amount of the copolymer as it decreased from 61.2°C for pure PLA to 41.3°C when it was blended with 10 wt% PLA-PBS copolymer. Therefore, the PLA-PBS copolymer was shown to be a promising plasticizer for fully biobased and toughened PLA.
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    TMPMgnBu(L), where L = THF, 2-MeTHF, pyridine and dimethylaminopyridine and TMP = 1,5,9-trimesityldipyrromethene: Reaction with lactide and ε-caprolactone
    (2017-01-01)
    Balasanthiran, Vagulejan
    ;
    Chisholm, Malcolm H.
    ;
    Choojun, Kittisak
    ;
    Durr, Christopher B.
    ;
    Jing, Stanley
    The compounds TMPMg<sup>n</sup>Bu(L), where L = THF, 2-MeTHF, pyridine (py) and dimethylaminopyridine (DMAP) and TMP = 1,5,9-trimesityldipyrromethene, have been synthesized and allowed to initiate polymerization with rac-lactide (rac-LA) and ε-caprolactone (ε – CL). Both the rate of rac-LA polymerization and the tacticity were found to be solvent dependent, with CH<inf>2</inf>Cl<inf>2</inf> being faster than THF and yielding heterotactic polylactic acid with P<inf>r</inf> ∼70% and 95%, respectively. For ε-CL, rates of polymerization were in the inverse order with THF being faster than CH<inf>2</inf>Cl<inf>2</inf>. In CH<inf>2</inf>Cl<inf>2</inf> the reactions showed a dependence on the coordinating ligand with rates, 2-MeTHF > THF > py > DMAP in the polymerization of rac-LA and ε-CL. The molecular structure of TMPMg<sup>n</sup>Bu(2-MeTHF) was shown to contain a trigonally distorted tetrahedron of TMPMg(<sup>n</sup>Bu) with a weak axial Mg—-2-MeTHF bond.