Structure and Properties of Stereocomplex‐Type Poly(Lactic Acid)

Hirata, Masayuki; Kimura, Yoshiharu

doi:10.1002/9780470649848.ch5

Cited by 9 publications

(4 citation statements)

References 42 publications

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“…This behavior could not be attributed solely to the crystallinity of the hydrophobic core as isotactic stereopure copolymer 1 had a higher degree of crystallinity than the isotactic stereoblock 7 (Δ H m and X c , Table ) and, in fact, little differences were noted between the crystallinity of all samples with an isotactic bias. To further confirm this, we investigated the micellization of a copolymer with a stereocomplex (sc) ,− PLA core with the pyrene probe, blending stereopure poly( l -lactic acid) and poly( d -lactic acid) prior to micellization. The desired sc-PLA- b -PEG was prepared via room temperature mixing of equal volumes of 2 mg/mL solutions of isotactic stereopure P( l -LA)- b -PEG ( 1 ) and P( d -LA)- b -PEG ( 9 , Table ) and allowing the mixture to stand overnight .…”

Section: Resultsmentioning

confidence: 97%

“…Catalyst B afforded a copolymer, 7 , with long, alternating blocks of l - and d -lactide to give a sb-PLA that had 80% isotactic enchainment, similar to the isotactic enchainment found in copolymer 2 . Structurally, the isotactic copolymers 2 and 7 thus differ significantly as the PLA block in 7 contains semicrystalline stereoblocks of both poly( l -lactic acid) and poly( d -lactic acid) linked by short amorphous atactic stereoerrors, while 2 is predominantly homochiral poly( l -lactic acid) with atactic segments from rac -lactide inclusion . In linear and star macrostructures, these differences can lead to altered polymer properties, especially in their crystallinity. ,, …”

Section: Resultsmentioning

confidence: 99%

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Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Agatemor

Shaver²

2013

Biomacromolecules

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Poly(lactic acid)-block-poly(ethylene glycol) copolymers (PLA-b-PEG) featuring varying tacticities (atactic, heterotactic, isotactic) in the PLA block were synthesized and investigated for their micellar stability, degradation, and thermal properties. Utilizing tin(II) bis(2-ethylhexanoate), aluminum salan, and aluminum salen catalysts, the copolymers were synthesized through the ring-opening polymerization of d-, l-, rac-, or a blend of l- and rac-lactide using monomethoxy-poly(ethylene glycol) as a macroinitiator. The critical micelle concentration, which reflects the micellar stability, was probed using a fluorescence spectroscopic method with pyrene as the probe. The copolymers were degraded in a methanolic solution of 1,5,7-triaza-bicyclo[4.4.0]dec-5-ene and the degradation was measured by (1)H NMR spectroscopic and gel permeation chromatographic analyses. Differential scanning calorimetry and thermogravimetric analysis provided information on the thermal properties of the copolymers. Atactic and heterotactic microstructures in the PLA block resulted in lower micellar stability, as well as faster degradation and shorter erosion time compared to polymers with high isotactic enchainment (Pm). By modification of the Pm, micellar stability, degradation, and erosion rates of the copolymers can be tuned to specific biomedical applications. Interestingly, while tin(II) bis(2-ethylhexanoate) and aluminum salan-catalyzed PLA-b-PEG copolymers exhibited similar micellization behavior, the aluminum salen-catalyzed PLA-b-PEG exhibited unique behavior at high micelle concentration in the presence of the pyrene probe. This unique behavior can be attributed to the disintegration of the micelles through the interactions of long isotactic stereoblock segments.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Agatemor

Shaver²

2013

Biomacromolecules

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“…Increased crystallization, and thus improved mechanical performance and heat resistance of PLA, can be achieved, e.g. by nucleation, strain-induced crystallization through orientation or stereocomplex blends [39][40][41].…”

Section: Introductionmentioning

confidence: 99%

Printed and hybrid integrated electronics using bio-based and recycled materials—increasing sustainability with greener materials and technologies

Välimäki

Sokka

Peltola

et al. 2020

Int J Adv Manuf Technol

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Printed and hybrid integrated electronics produced from recycled and renewable materials can reduce the depletion of limited material resources while obtaining energy savings in small electronic applications and their energy storage. In this work, bio-based poly(lactic acid) (PLA) and recycled polyethylene terephthalate (rPET) were fabricated in film extrusion process and utilized as a substrate in ultra-thin organic photovoltaics (OPV). In the device structure, metals and metal oxides were replaced by printing PEDOT:PSS, carbon and amino acid/heterocycles. Scalable, energy-efficient fabrication of solar cells resulted in efficiencies up to 6.9% under indoor light. Furthermore, virgin-PET was replaced with PLA and rPET in printed and hybrid integrated electronics where surface-mount devices (SMD) were die-bonded onto silver-printed PLA and virgin-PET films to prepare LED foils followed by an overmoulding process using the rPET and PLA. As a result, higher relative adhesion of PLA-PLA interface was obtained in comparison with rPET-PET interface. The obtained results are encouraging from the point of utilization of scalable manufacturing technologies and natural/recycled materials in printed and hybrid integrated electronics. Assessment showed a considerable decrease in carbon footprint, about 10–85%, mainly achieved through replacing of silver, virgin-PET and modifying solar cell structure. In outdoor light, the materials with low carbon footprint can decrease energy payback times (EPBT) from ca. 250 days to under 10 days. In indoor energy harvesting, it is possible to achieve EPBT of less than 1 year. The structures produced and studied herein have a high potential of providing sustainable energy solutions for example in IoT-related technologies.

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“…Poly(lactic acid) (PLA) is a biodegradable and biocompatible polymer that can be obtained from renewable resources and represents an interesting alternative for replacing petroleum-based polymers [1]. PLA is usually obtained in the amorphous state after being processed, in view of its slow crystallization rate in comparison to the cooling rates employed during processing.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and Stereocomplexation of PLA-mb-PBS Multi-Block Copolymers

et al. 2017

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Abstract:The crystallization and morphology of PLA-mb-PBS copolymers and their corresponding stereocomplexes were studied. The effect of flexible blocks (i.e., polybutylene succinate, PBS) on the crystallization of the copolymers and stereocomplex formation were investigated using polarized light optical microscopy (PLOM), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and carbon-13 nuclear magnetic resonance spectroscopy ( 13 C-NMR). The PLA and PBS multiple blocks were miscible in the melt and in the glassy state. When the PLA-mb-PBS copolymers are cooled from the melt, the PLA component crystallizes first creating superstructures, such as spherulites or axialites, which constitute a template within which the PBS component has to crystallize when the sample is further cooled down. The Avrami theory was able to fit the overall crystallization kinetics of both semi-crystalline components, and the n values for both blocks in all the samples had a correspondence with the superstructural morphology observed by PLOM. Solution mixtures of PLLA-mb-PBS and PLDA-mb-PBS copolymers were prepared, as well as copolymer/homopolymer blends with the aim to study the stereocomplexation of PLLA and PDLA chain segments. A lower amount of stereocomplex formation was observed in copolymer mixtures as compared to neat L 100 /D 100 stereocomplexes. The results show that PBS chain segments perturb the formation of stereocomplexes and this perturbation increases with the amount of PBS in the samples. However, when relatively low amounts of PBS in the copolymer blends are present, the rate of stereocomplex formation is enhanced. This effect dissappears when higher amounts of PBS are present. The stereocomplexation was confirmed by FTIR and solid state 13 C-NMR analyses.

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Structure and Properties of Stereocomplex‐Type Poly(Lactic Acid)

Cited by 9 publications

References 42 publications

Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Printed and hybrid integrated electronics using bio-based and recycled materials—increasing sustainability with greener materials and technologies

Crystallization and Stereocomplexation of PLA-mb-PBS Multi-Block Copolymers

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