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Effect of blending ratio and oligomer structure on the thermal transitions of stereocomplexes consisting of a D ‐lactic acid oligomer and poly( L ‐lactide)
Author(s) -
Inkinen Saara,
Stolt Mikael,
Södergård Anders
Publication year - 2011
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1654
Subject(s) - oligomer , materials science , lactic acid , lactide , polymerization , molar mass , molar ratio , polymer chemistry , chemical engineering , polymer , thermal stability , composite material , organic chemistry , catalysis , chemistry , biology , bacteria , engineering , genetics
Poly(lactic acid) (PLA) stereocomplexes have high potential as renewable materials for advanced polymer applications, mainly due to their high melting temperature ( T m , typically 230–240°C). The properties of PLA stereocomplexes consisting of linear high molar mass homopolymers have been studied extensively in the past, but the available information about the possibilities to affect the thermal properties of the stereocomplex by varying the structure of the blend components has not been sufficient. Novel stereocomplexes containing linear or star‐shaped D ‐lactic acid ( D ‐LA) oligomers and high molar mass poly( L ‐lactide) ( L‐ PLA) were thus prepared. The T m and melting enthalpy (Δ H m ) of the racemic crystallites were found to depend strongly on both the blending ratio and the arm‐length of the D ‐lactic acid oligomer. The preparation method of the oligomers, i.e. step‐growth polymerization or ring‐opening polymerization (ROP), did not affect the T m or Δ H m of the blends significantly. Slightly higher Δ H m values were, however, obtained, when linear oligomers were used. The results thus indicated that the T m and Δ H m of PLA stereocomplexes could be optimized, simply by selecting a D ‐LA oligomer having a suitable arm‐length and structure as the other blend component. The possibility to adjust the melting behavior of the stereocomplex blend is a significant advantage and could make PLA suitable for a wider range of products used at elevated temperatures. Copyright © 2010 John Wiley & Sons, Ltd.