title: Customizing the hydrolytic degradation rate of stereocomplex PLA through different PDLA architectures.
abstract: 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.
authors.affiliation: Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden.
authors.forename: Sofia Regnell
authors.initials: SR
authors.lastname: Andersson
authors.forename: Minna
authors.initials: M
authors.lastname: Hakkarainen
authors.forename: Saara
authors.initials: S
authors.lastname: Inkinen
authors.forename: Anders
authors.initials: A
authors.lastname: Södergård
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Albertsson
mesh_terms: D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D019344:Lactic Acid / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism; D013499:Surface Properties
chemical_list: D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)