Simulation of Volumetric Swelling of Degradable Poly[(Rac-Lactide)-Co-Glycolide] Based Polyesterurethanes Containing Different Urethane-Linkers

Ghobadi, Ehsan; Heuchel, Matthias; Kratz, Karl; Lendlein, Andreas

doi:10.5301/jabfm.2012.10432

Cited by 6 publications

(13 citation statements)

References 28 publications

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“…Furthermore, the materials stiffness was modified by incorporating urethane linkers, whereby in the dry‐state pure PLGA and PLGA‐TMDI exhibited a similar stretching behavior reaching ε m values above 75% while for PLGA‐HDI and PLGA‐LDI significant lower values of ε m ≤ 20% could be achieved (Table ). The plasticization effect documented by the increase of the extension values of water‐containing models can be related to an overall increase of the accessible free volume in the wet models compared with their dry counterparts . However as depicted in Figure , the comparison of free volume properties of the here investigated PLGA showed no clear relation to the observed ε x ‐values.…”

Section: Resultsmentioning

confidence: 75%

“…We have previously reported the influence of water on several material properties of (unstretched) PLGA‐PU models at T = 310 K, such as density, free volume, chain mobilities, and radial distribution function of nitrogen atoms of urethane linker units . It was reported that the incorporation of water molecules, for example, leads to an increase in chain mobilities, which can be clearly observed through mean square displacement of backbone atoms.…”

Section: Resultsmentioning

confidence: 99%

“…Distribution of free volume elements accessible for water (hard sphere radius ≈ 1.5 Å) for PLGA and PLGA‐PUs in a) dry and b) wet state with 2 wt% water content. Data from ref …”

Section: Resultsmentioning

confidence: 99%

“…The PLGA‐PU packing models are constructed according to the Theodorou–Suter method under periodic boundary conditions in a pre‐defined cubic volume element (simulation cell). The construction of the dry and wet PLGA packing models was performed according to a method we described recently . Table contains characteristic properties of all the PLGA and PLGA‐PU packing models at room temperature ( T = 310 K) and ambient pressure condition.…”

Section: Methodsmentioning

confidence: 99%

“…In this work, we explored the shape‐memory behavior of amorphous domains in poly[( rac ‐lactide)‐ co ‐glycolide] (PLGA) and PLGA‐based polyester urethanes (PLGA‐PUs), containing three different urethane linker units in dry and wet state (with 2 wt% H 2 O) based on recently introduced atomistic simulation methods . The constructed dry and wet packing models are subjected to a simulated cyclic thermomechanical tensile test, which comprises uniaxial stretching at T high = 500 K, cooling to T low = 250 K under constant stress, unloading at T low = 250 K, and stress free recovery at T high = 500 K. Furthermore, the effect of addition of water on the T g of PLGA and PLGA‐PU models was examined.…”

Section: Introductionmentioning

confidence: 99%

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Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Ghobadi

Heuchel

Kratz

et al. 2013

Macro Chemistry & Physics

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An atomistic molecular dynamics simulation approach is applied to model the influence of urethane linker units as well as the addition of water molecules on the simulated shape‐memory properties of poly[(rac‐lactide)‐co‐glycolide] (PLGA) and PLGA‐based copolyester urethanes comprising different urethane linkers. The shape‐memory performance of these amorphous packing models is explored in a simulated heating–deformation–cooling–heating procedure. Depending on the type of incorporated urethane linker, the mechanical properties of the dry copolyester urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the urethane units. Good shape‐memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated.

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Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

“…Distribution of free volume elements accessible for water (hard sphere radius ≈ 1.5 Å) for PLGA and PLGA‐PUs in a) dry and b) wet state with 2 wt% water content. Data from ref …”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Ghobadi

Heuchel

Kratz

et al. 2013

Macro Chemistry & Physics

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Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices

Mathew

Baudis

Neffe

et al. 2015

European Journal of Pharmaceutics and Biopharmaceutics

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In this study, the effect of three aliphatic diisocyanate linkers, L-lysine diisocyanate ethyl ester (LDI), hexamethylene diisocyanate (HDI), and racemic 2,2,4-/2,4,4-trimethyl hexamethylene diisocyanate (TMDI), on the degradation of oligo[(rac-lactide)-co-glycolide] (64:36 mol%) based polyester urethanes (PEU) was examined. Samples were characterized for their molecular weight, mass loss, water uptake, sequence structure, and thermal and mechanical properties. Compared to non-segmented PLGA, the PEU showed higher water uptake and generally degraded faster. Interestingly, the rate of degradation was not directly correlating with the hydrophilicity of the diisocyanate moieties; instead, competing intra-/intermolecular hydrogen bonds in between urethane moieties appear to substantially decrease the rate of degradation for LDI-derived PEU. By comparing microparticles (μm) and films (mm) as matrices of different dimensions, it was shown that autocatalysis remains a contributor to degradation of the larger-sized PEU matrices as it is typical for non-segmented lactide/glycolide copolymers. The shown capacity of lactide/glycolide-based multiblock copolymers to degrade faster than PLGA and exhibit improved elastic properties could be of interest for medical implants and drug release systems.

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Influence of the addition of water to amorphous switching domains on the simulated shape-memory properties of poly(l-lactide)

Ghobadi

Heuchel

Kratz

et al. 2013

Polymer

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a b s t r a c tIt is well known that the environmental conditions e.g. humidity can alter the shape-memory properties of polymers. In this work we applied an atomistic molecular dynamics simulation approach to model the influence of the addition of 1 wt% and 2 wt% water on the simulated shape-memory behavior of the amorphous switching domains of poly(L-lactide) (PLLA) with a molecular weight of M n ¼ 52,000 g mol À1 .For the dry as well as the water swollen PLLA-models, two subsequent uniaxial thermomechanical test cycles have been calculated, whereby the applied uniaxial deformation ε m was varied between 50% and 150%.All simulated PLLA models showed high shape fixity ratio of R f ! 84%. The shape-memory properties obtained at ε m ¼ 100% for the dry PLLA and the models containing 1 wt% water were almost identical with a shape recovery ratio in the first and second test cycle around R r ¼ 61%e64%. In contrast PLLA with 2 wt% water exhibited higher values of R r ¼ 76% during the first test cycle, but a lower R r ¼ 52% in the subsequent second cycle. Furthermore, increasing the applied ε m resulted in a decrease of R r from 82% to 42% for the dry PLLA, whereas PLLA with 2 wt% water did not show a dependence of R r on ε m . We anticipate that these observations can be attributed to differences in the initial structure of the various simulated PLLA models e.g. the different distribution of the free volume elements.

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Simulation of Volumetric Swelling of Degradable Poly[(Rac-Lactide)-Co-Glycolide] Based Polyesterurethanes Containing Different Urethane-Linkers

Abstract: It can be anticipated that the incorporation of urethane linkers might be a helpful tool to adjust the degradation behavior of polyesters.

Cited by 6 publications

References 28 publications

Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Atomistic Simulation of the Shape‐Memory Effect in Dry and Water Swollen Poly[(rac‐lactide)‐co‐glycolide] and Copolyester Urethanes Thereof

Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices

Influence of the addition of water to amorphous switching domains on the simulated shape-memory properties of poly(l-lactide)

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