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Customizing the Hydrolytic Degradation Rate of Stereocomplex PLA through Different PDLA Architectures
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-7790-8987
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2012 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 4, 1212-1222 p.Article in journal (Refereed) Published
Abstract [en]

Stereocomplexation of poly(L-lactide) (PLLA) with star shaped D-lactic acid (D-LA) oligomers with different, architectures and end-groups clearly altered the degradation rate and affected the degradation product patterns. Altogether, nine materials were studied: standard PLLA and eight blends of PLLA with either 30 or 50 wt % of four different D-LA. oligomers. The influence of several factors, including temperature, degradation time, and amount and type of D-LA oligomer, on the hydrolytic degradation process was investigated using a fractional factorial experimental design. Stereocomplexes containing star shaped D-LA oligomers with four alcoholic end-groups underwent a rather slow hydrolytic degradation with low release of degradation products. Materials with linear D-LA oligomers exhibited similar mass loss but released higher concentrations of shorter acidic degradation products. Increasing the fraction of D-LA oligomers with a linear structure or with four alcoholic end-groups resulted in slower mass loss due to higher degree of stereocomplexation. The opposite results were obtained after addition of D-LA oligomers with carboxylic chain-ends. These materials demonstrated lower degree of stereocomplexation and larger mass and molar mass loss, and also the release of degradation products increased. Increasing the number of alcoholic chain-ends from four to six decreased the degree of stereocomplexation, leading to faster mass loss. The degree of stereocomplexation and degradation rate were customized by changing the architecture and end-groups of the D-LA oligomers.

Place, publisher, year, edition, pages
2012. Vol. 13, no 4, 1212-1222 p.
Keyword [en]
Enantiomeric Poly(Lactic Acid)S, Bio-Based Polymers, Polylactide Stereocomplex, Crystallization Behavior, Poly(L-Lactic Acid), Spherulite Growth, Product Patterns, End-Group, Melt, Hydrophilicity
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:kth:diva-95108DOI: 10.1021/bm300196hISI: 000303076200032PubMedID: 22394150ScopusID: 2-s2.0-84860711835OAI: diva2:527755
EU, European Research Council, NMP2-CT-2007-026515
QC 20120522Available from: 2012-05-22 Created: 2012-05-14 Last updated: 2013-04-03Bibliographically approved
In thesis
1. Controlling Polylactide Degradation through Stereocomplexation and Lactic Acid Based Additives
Open this publication in new window or tab >>Controlling Polylactide Degradation through Stereocomplexation and Lactic Acid Based Additives
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The successful use of degradable materials in new applications depends on our ability to control the degradation process. A number of aspects need to be evaluated including degradation rate, the onset of degradation and the nature, formation and release of degradation products. In this study, the possibility of tuning the properties and degradation of polylactide (PLA) through stereocomplexation between the L- and D-enantiomers of PLA was investigated. The influence of the oligo(D-lactic acid) architecture on the stereocomplexation and subsequent degradation rate was evaluated. The dependence of stereocomplex formation on the structure of the side-group and the effect of oligo(L-lactide) additives on hydrolytic degradation and thermal aging were also investigated. One advantage of these additives is that no foreign migrants are introduced into the degradation product pattern. This reduces the risk of a harmful impact on the environment. The degradation process was monitored through analyses of the remaining material and the released degradation products. Depending on the modification, both increased and decreased degradation rates could be obtained. Resistance against degradation was increased by stereocomplexation, which is explained by the strong interactions between the complementary L- and D- chain structures. On the other hand, even though the mass loss was low, larger amounts of short hydroxy acids were released from the stereocomplex materials, resulting in a faster decrease in the pH. This can be explained by an increase in the amount of intermolecular stereocomplex crystallites resulting in a large number of tie-chains connecting the crystallites. These chains are more exposed to hydrolysis, and hence short degradation products are released. The architecture of the added oligo(D-lactic acid) had a considerable impact on material properties such as crystallinity and degradation. Acidic end-groups increased the degradation rate, while alcoholic end-groups had the opposite effect. The addition of hydrophilic linear oligo(L-lactide) to poly(L-lactide) (PLLA) resulted in a rapid migration of additives from the material during hydrolytic aging and a faster loss of mass and molar mass than from a material containing cyclic analogues. During thermal aging, however, the opposite effect was observed as the linear oligo(L-lactide) additives interacted more strongly with PLLA, which resulted in smaller mass loss. Stereocomplexation was also revealed to take place between oligomers of the two enantiomers of the lactic acid-like monomer α-hydroxyisovaleric acid.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 53 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2013:14
Polylactide, stereocomplex, plasticizer, degradation, degradation products, ESI-MS
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-120120 (URN)978-91-7501-687-0 (ISBN)
Public defence
2013-04-26, K2, Teknikringen 28, Stockholm, 10:00 (English)

QC 20130403

Available from: 2013-04-03 Created: 2013-03-28 Last updated: 2013-04-03Bibliographically approved

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Regnell Andersson, Sofia RegnellHakkarainen, MinnaAlbertsson, Ann-Christine
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