Effect of Arrangement of <scp>L</scp>‐Lactide and <scp>D</scp>‐Lactide in Poly[(<scp>L</scp>‐lactide)‐<i>co</i>‐(<scp>D</scp>‐lactide)] on its Resistance to Hydrolysis Studied by Molecular Modeling

Karst, David; Yang, Yiqi

doi:10.1002/macp.200700283

Cited by 34 publications

(21 citation statements)

References 26 publications

(44 reference statements)

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“…The M n values were higher for the P(L-2HB)/P(D-2HB) blend than for pure P(L-2HB) and P(D-2HB), when compared for the same degradation periods. The remaining weight percentages and M n values reflect that the P(L-2HB)/P(D-2HB) blend has a superior hydrolytic degradation resistance as compared with pure P(L-2HB) and P(D-2HB); this is in agreement with the experimental results of hydrolytic degradation [16][17][18][19] and theoretical calculations 34 for a PLLA/PDLA stereocomplex relative to pure PLLA and PDLA. The value of M w /M n of pure P(L-2HB), P(D-2HB) and their blend increased in the first 8 days, followed by a decrease or plateau.…”

Section: Hydrolytic Degradationsupporting

confidence: 87%

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

Tsuji

Okumura

2010

Polym J

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The maximum radial growth rate of spherulites of the novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) (P(L-2HB)) and poly(D-2-hydroxybutyrate) (P(D-2HB)) was observed to be substantially higher than those of pure P(L-2HB) and P(D-2HB). The hydrolytic degradation rate of the P(L-2HB)/P(D-2HB) blend traced by gravimetry and gel permeation chromatography was significantly lower than those of pure P(L-2HB) and P(D-2HB); this indicated that the blend had higher resistance to hydrolytic degradation. Further, the thermal degradation rate of the P(L-2HB)/P(D-2HB) blend was retarded as compared with those of pure P(L-2HB) and P(D-2HB). The results obtained in the present study indicate that the intermolecular interaction between P(L-2HB) and P(D-2HB) chains having opposite configurations in the amorphous regions or in the molten state was higher than that between P(L-2HB) or P(D-2HB) chains with the same configurations. The information obtained in the present study should be very useful for designing and processing pure, biodegradable materials of P(L-2HB), P(D-2HB) and their blends for biomedical, pharmaceutical and environmental applications. Keywords: crystallization; hydrolytic degradation; poly(hydroxybutanoic acid); poly(hydroxybutyric acid); stereocomplex; thermal degradation INTRODUCTION Poly(L-lactide) (that is, poly(L-lactic acid) or PLLA) is a biodegradable polymer produced from plant-derived renewable resources and is now used for biomedical, pharmaceutical, environmental, industrial and commercial applications. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Stereocomplexation between PLLA and its enantiomer poly(D-lactide) (that is, poly(D-lactic acid) or PDLA) can yield biodegradable materials having superior mechanical performance and resistance to hydrolytic and thermal degradation relative to pure PLLA and PDLA. [16][17][18][19][20] Poly(2-hydroxybutyrate) (that is, poly(2-hydroxybutanoic acid) or P(2HB)) is a biodegradable polymer with the structure of a poly(lactide) (that is, poly(lactic acid) or PLA) in which methyl groups are substituted with ethyl groups. A stereocomplex can also be formed by blending substituted enantiomeric PLAs, that is, poly(L-2-hydroxybutyrate) [P(L-2HB)] and poly(D-2-hydroxybutyrate) (P (D-2HB)). 21 The melting temperature (T m ) of the P(L-2HB)/P(D-2HB) stereocomplex (ca. 200 1C) is higher than those of pure P(L-2HB) and P(D-2HB) (ca. 100 1C). The spherulite growth or crystallization of the P(L-2HB)/ P(D-2HB) stereocomplex is completed in a substantially shorter period of time as compared with those of pure P(L-2HB) and P(D-2HB). From the results reported for PLLA/PDLA blends, [16][17][18][19][20] it is expected that the resistance of P(L-2HB)/P(D-2HB) blends to hydrolytic and

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Section: Hydrolytic Degradationsupporting

confidence: 87%

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

Tsuji

Okumura

2010

Polym J

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“…Similar to this result, P(LLA-co-CL) retained a higher molecular weight than P(DLLA-co-CL) during NHD [155]. Karst and Yang [295] used molecular modeling to explain the fact that resistance of stereocopolymers poly(L-lactideco-D-lactide) P(LLA-DLA) to hydrolysis is affected by the percentages of L-and D-lactyl units and their arrangement (block or random) in the polymer. It was found that among the stereocopolymers with the longest blocks of L-and Dlactyl units, those containing 50% L-lactyl units had greater hydrolysis resistance and were more stable before hydrolytic degradation compared to stereocopolymers with 26% or 74% L-lactyl units.…”

Section: Molecular Structuresupporting

confidence: 70%

“…A similar result was obtained for the alkaline hydrolytic degradation of PLLA/PDLA blend monolayers [233]. Molecular modeling ascribed the high hydrolysis resistance of PLLA/PDLA blends compared to that of stereocopolymers P(LLA-DLA) with the same L-lactyl unit content to the fact that blends can form more stereocomplexes than stereocopolymers [295].…”

Section: Highly Ordered Structuressupporting

confidence: 65%

Hydrolytic Degradation

Tsuji

2010

Poly(Lactic Acid)

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“…Since the gradual left-hand shift of the phase curve means that the critical gelation concentration was decreased due to an increased density of hydrophobic core and decrease in water solubility with increasing amount cross-linked ratio PL(D)LA. This can be related to the structural stability of individual micelles that were closely packed to form a three dimensional gel structure due to an increase in crystallinity or chain packing tendency at critical concentration and temperature [19]. The stereocomplexed crystallites produced from the complexation of enantiomeric copolymer based on PLLA and PDLA should have physically cross-linked copolymers, resulting in more robust and stable Pluronic based sol-gel transition hydrogels.…”

Section: Scheme I Synthesis Of Cross-linked Pl(d)la-pluronic Copolymentioning

confidence: 99%

Preparation of cross-linked biodegradable copolymers based polycarbanion of 3-arm PL(D)LA with brominated pluronic and stereocomplex mediated gelation behavior

Nam

Al-Nahain

et al. 2012

Proceedings of 2012 IEEE-EMBS International Conference on Biomedical and Health Informatics

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We overcome rapidly dissolution properties of Pluronic hydro g els by chemical and physical crosslinkin g synergistic combination of gelation characteristics with polymer thermo-sensitivity. A new class of injectable sol-gel transition hydrogel was successfully prepared using biodegradable cross-linked poly(lactide)-Pluronic copolymers (PL(D)LA-Pluronic) via polycarbanion derived from enantiomeric 3-arm PLA using brominated Pluronic. The presence of enantiomeric PLA segments enables to form intermolecular stereocomplex, resultin g in temperature-responsive injectable hydrogels. In contrast to the Pluronic which exhibits the temperature-dependent sol-gel transition at a concentration of 16% (w/v) or higher, the 3-arm PL(D)LA-Pluronic cross-linked stereocomplex copolymersshowed much lower critical gelation concentration (-10 wt%).The stereocomplex formation was examined by differential scannin g calorimetry (DSC) and X-ray diffraction (XRD). The elegant design of polymeric configurations and the suitable introduction of enantiomeric properties produced a new type of copolymer that can be widely implemented as injectable hydrogels for drug delivery systems.

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Effect of Arrangement of L‐Lactide and D‐Lactide in Poly[(L‐lactide)‐co‐(D‐lactide)] on its Resistance to Hydrolysis Studied by Molecular Modeling

Cited by 34 publications

References 26 publications

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

Crystallization and hydrolytic/thermal degradation of a novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) and poly(D-2-hydroxybutyrate)

Hydrolytic Degradation

Preparation of cross-linked biodegradable copolymers based polycarbanion of 3-arm PL(D)LA with brominated pluronic and stereocomplex mediated gelation behavior

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