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Inkinen S.,Tate and Lyle Finland Oy | Inkinen S.,Abo Akademi University | Nobes G.A.,Tate and Lyle | Sodergard A.,Tate and Lyle Finland Oy
Journal of Applied Polymer Science | Year: 2011

The suitability of different types of telechelic poly(lactic acid) (PLA) copolymers for dilactide production and prepolymer products was evaluated. L-lactic acid (L-LA) was copolymerized with 1,4-butanediol, pentaerythritol, adipic acid, or 1,2,3,4-butanetetracarboxylic acid (1,2,3,4-BTCA). The influence of branching, the choice of catalyst, and the type of terminal groups on the properties and the thermal stability of the end product was determined. Carboxyl-termination of PLA was shown to lead to higher molar masses than hydroxyl-termination. The observed differences in the molar masses were explained by the lower thermal stability of the hydroxyl-terminated PLA, as evidenced by the faster depolymerization rate of the hydroxyl-terminated polymers and their higher tendency to undergo racemization. Sn(Oct) 2 was found to be a more effective copolymerization catalyst than Fe(OAc) 2 in terms of the final molar masses obtained. It was additionally found that the amount of chains not attached to the comonomers decreased toward longer polymerization times and was typically higher for the hydroxyl-terminated copolymers. The results suggest that predominant carboxyl-termination would increase the thermal stability of PLA polymers, whereas hydroxyl-termination could be utilized to increase the production speed and efficiency of dilactide. © 2010 Wiley Periodicals, Inc. Source

Andersson S.R.,KTH Royal Institute of Technology | Hakkarainen M.,KTH Royal Institute of Technology | Inkinen S.,Tate and Lyle Finland Oy | Sodergard A.,Tate and Lyle Finland Oy | Albertsson A.-C.,KTH Royal Institute of Technology
Biomacromolecules | Year: 2010

Poly-l-lactide/poly-d-lactide (PLLA/PDLA) stereocomplex had much higher hydrolytic stability compared to plain PLLA, but at the same time shorter and more acidic degradation products were formed. Both materials were subjected to hydrolytic degradation in water and in phosphate buffer at 37 and 60 °C, and the degradation processes were monitored by following mass loss, water uptake, thermal properties, surface changes, and pH of the aging medium. The degradation product patterns were determined by electrospray ionization-mass spectrometry (ESI-MS). The high crystallinity and strong secondary interactions in the stereocomplex prevented water uptake and resulted in lower mass loss and degradation rate. However, somewhat surprisingly, the pH of the aging medium decreased much faster in the case of PLLA/PDLA stereocomplex. In accordance, the ESI-MS results showed that hydrolysis of PLLA/PDLA resulted in shorter and more acidic degradation products. This could be explained by the increased intermolecular crystallization due to stereocomplexation, which results in an increased number of tie chains. Because mainly these short tie chains are susceptible to hydrolysis this leads to formation of shorter oligomers compared to hydrolysis of regular PLLA. © 2010 American Chemical Society. Source

Inkinen S.,Tate and Lyle Finland Oy | Inkinen S.,Abo Akademi University | Stolt M.,Tate and Lyle Finland Oy | Sodergard A.,Tate and Lyle Finland Oy | Sodergard A.,Abo Akademi University
Biomacromolecules | Year: 2010

Poly(lactic acid) (PLA) copolymers having a significantly higher glass transition temperature (Tg) than that of high molar mass PLA homopolymers (typically 60 ± 5 °C) were prepared. Lactic acid was copolymerized with 1,4:3,6-dianhydro-d-glucitol (isosorbide, ISB) and succinic acid (SA-2), 1,2,3,4-butanetetracarboxylic acid (BTCA-4) or 1,2,3,4,5,6- cyclohexanehexacarboxylic acid (HCA-6). The highest Tgs obtained for the copolymers containing BTCA-4 and HCA-6 were 80 and 86 °C, respectively. The polymers were prepared by step-growth polymerization in the melt phase, which is an easily operable and simple PLA production method in comparison to the ring-opening polymerization (ROP) route. It was shown that the Tg and the cross-linking induced by the polyfunctional carboxylic acid comonomers could be readily controlled by choosing a suitable polymerization time and temperature. Similar improvement in the Tg as achieved for the copolymers of BTCA-4 and HCA-6 was not observed for linear copolymers containing ISB and SA-2. © 2010 American Chemical Society. Source

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