Stable Dispersions of Highly Anisotropic Nanoparticles Formed by Cocrystallization of Enantiomeric Diblock Copolymers

Portinha, Daniel; Boué, François; Bouteiller, Laurent; Carrot, Géraldine; Chassenieux, Christophe; Pensec, Sandrine; Reiter, Günter

doi:10.1021/ma070467v

Cited by 62 publications

(53 citation statements)

References 38 publications

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“…Portinha et al. observed highly anisotropic nanoparticles, that is, pearl‐necklace structures, formed by 1:1‐mixtures of P l LA‐poly(ε‐caprolactone) and P d LA‐poly(ε‐caprolactone) in THF solution at room temperature . Under these conditions, the individual block copolymers were dissolved as single chains, and aggregation occurred solely through the stereocomplexation between P l LA and P d LA.…”

Section: Methodsmentioning

confidence: 99%

Polylactide‐Based Amphiphilic Block Copolymers: Crystallization‐Induced Self‐Assembly and Stereocomplexation

Noack

Schanzenbach

Koetz

et al. 2018

Macromol. Rapid Commun.

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The aqueous self‐assembly behavior of a series of poly(ethylene glycol)‐poly(l‐/d‐lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm‐like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm‐like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self‐assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular‐shaped clusters of spherical micelles and pearl‐necklace‐like structures.

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Section: Methodsmentioning

confidence: 99%

Polylactide‐Based Amphiphilic Block Copolymers: Crystallization‐Induced Self‐Assembly and Stereocomplexation

Noack

Schanzenbach

Koetz

et al. 2018

Macromol. Rapid Commun.

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“…Bouteiller and coworkers examined the stability of the stereocomplex aggregates formed by enantiomeric PLA block copolymers in THF using small-angle neutron scattering (SANS) and SLS and reported similar findings to ours where the aggregates remained stable over months and are not sensitive to dilution. [54][55][56] However, when similar 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 stability experiments were performed on Sample 3, the R h of the micelles decreases by approximately 20% , i.e., from approximately 76 to 62 nm and 114 to 95 nm, at pH 8 and 4 respectively, when diluted by a dilution factor of 5 as depicted in Figure 4(d). Likewise, the R g, app of micelles formed from Sample 3 also decreases significantly (approximately 25%) when diluted at both pH 8 and 4, further indicating that the stability of the micelle core is susceptible to dilution.…”

Section: Figures 3(a) and (B) Demonstrate The Particle Size Distributmentioning

confidence: 99%

Poly(ethylene glycol) Conjugated Poly(lactide)-Based Polyelectrolytes: Synthesis and Formation of Stable Self-Assemblies Induced by Stereocomplexation

et al. 2015

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A series of pH-responsive amphiphilic poly(N,N-dimethylaminoethyl methacrylate)-block-poly(D-lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) conjugated with poly(ethylene glycol) (D-PDLA-D@PEG) and D-PLLA-D@PEG copolymers were synthesized using a combination of ring-opening polymerization and atom-transfer radical polymerization followed by sequential quaternization of PDMAEMA chains and azide-alkyne click reaction with alkyne-end PEG. Gel permeation chromatography, nuclear magnetic resonance, and Fourier transform infrared spectroscopy results demonstrate the successful synthesis of the copolymers, and the conjugated PEG percentages in the copolymers can be tuned by the feeding ratios in the quaternization reaction. Conjugating PEG onto the PDMAEMA segments also successfully facilitated the D-PDLA-D@PEG, D-PLLA-D@PEG, and its corresponding 1:1 D/L mixtures to be dissolved directly in aqueous solution at the desired concentration range without using any organic solvents unlike the copolymers without PEG conjugation (D-PDLA-D and D-PLLA-D). We demonstrate control over micellar size, charge, and stability via three different preparation pathways, i.e., solution pH, percentages of PEG conjugation in the copolymers, and formation of PLA stereocomplex in micellar core. Static and dynamic light scattering studies demonstrate that the size of the core-shell micelles increases when the solution pH is reduced due to the protonation of the PDMAEMA segments that caused the osmotic pressure within the micelle to increase until the micelles reached a maximum size. It is interesting to note that the micelles formed by 1:1 D/L mixtures have larger swelling ratios as well as aggregation number and hydrodynamic radius that do not change significantly with pH and dilution, respectively, as compared to micelles formed from individual D or L forms of the copolymers. The enhanced stability of the pH-responsive micelles prepared by direct dissolution of the 1:1 D/L mixtures of the PEG conjugated PLA-based polyelectrolytes in aqueous medium is attributed to the stereocomplex formation between PLLA and PDLA in the micellar core as confirmed by wide-angle X-ray scattering measurements.

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“…Since crystallization usually leads to a chain folding stack of the insoluble block, the semicrystalline block copolymers prefer to form platelet micelles containing a thin crystalline lamella with solvent‐swollen coronas of the soluble block protruding from both surfaces, as Vilgis and Halperin predicted 9. Besides the platelet morphology,10–12 other micellar morphologies such as sphere and cylinder were also reported for the semicrystalline micelles of block copolymers 13–21…”

Section: Introductionmentioning

confidence: 93%

Effect of pH on the Micellar Morphology of Semicrystalline PCL‐b‐PEO Block Copolymers in Aqueous Solution

et al. 2012

Macro Chemistry & Physics

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The effect of pH on the micellar morphology of a semicrystalline poly( ε -caprolactone)-blockpoly(ethylene oxide) block copolymer (PCL 66 -b -PEO 44 ) in aqueous solution is investigated. Spherical micelles are formed in neutral and acidic solutions. However, addition of alkali to the neutral micellar solution triggers a sphere-to-cylinder transformation of the micellar morphology. The micelles are stable in both neutral and acidic solutions, but the size of the micelles becomes gradually larger in the alkali solution. This phenomenon is interpreted in terms of the effect of pH value on the reduced tethering density of the corona in the semicrystalline micelles.

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Stable Dispersions of Highly Anisotropic Nanoparticles Formed by Cocrystallization of Enantiomeric Diblock Copolymers

Cited by 62 publications

References 38 publications

Polylactide‐Based Amphiphilic Block Copolymers: Crystallization‐Induced Self‐Assembly and Stereocomplexation

Polylactide‐Based Amphiphilic Block Copolymers: Crystallization‐Induced Self‐Assembly and Stereocomplexation

Poly(ethylene glycol) Conjugated Poly(lactide)-Based Polyelectrolytes: Synthesis and Formation of Stable Self-Assemblies Induced by Stereocomplexation

Effect of pH on the Micellar Morphology of Semicrystalline PCL‐b‐PEO Block Copolymers in Aqueous Solution

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