Synthesis, Sequential Crystallization and Morphological Evolution of Well‐Defined Star‐Shaped Poly(<i>ε</i>‐caprolactone)‐<i>b</i>‐poly(<scp>L</scp>‐lactide) Block Copolymer

Wang, Jing‐Liang; Dong, Chang‐Ming

doi:10.1002/macp.200500546

Cited by 74 publications

(76 citation statements)

References 33 publications

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“…Another interesting observation is the absence of the typical cold crystallization peak of PLLA block during heating, which has been usually reported for PLLA block copolymers. [20][21][53][54] The appearance of this peak depends on the length of the PLLA block, copolymer composition and cooling conditions. Since the cooling rate employed here was very low (1 ºC min -1 ), the PLLA block is able to crystallize until saturation under this condition and additional crystallization does not occur during the heating scan.…”

Section: Saxs Characterization Of the Peo-b-pcl-b-plla Triblock Terpomentioning

confidence: 99%

“…2,7,10,47 In many PEO-b-PCL, PCL-b-PLLA and PEO-b-PLLA diblocks copolymers, morphological changes with temperature and composition have been observed: from well-defined Maltese cross spherulites and concentric spherulites to spherulites with continuous banding extinction patterns. 29,33,47,51,53 For instance, PEO-b-PLLA diblock copolymers with PLLA content between 71 and 32 % exhibit PLLA banded spherulites. 52 However, based on the observations of Huang et al 51 in the same diblock copolymers, the branching morphology developed as PLLA content in the terpolymers is lower (see Fig 8a, left) might be a result of the richer PCL-PEO amorphous phase that surrounds the proximity of the PLLA lamellae and disturbs further growth in their immediate vicinity.…”

Section: Morphology Of the Peo-b-pcl-b-plla Triblock Terpolymersmentioning

confidence: 99%

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Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

et al. 2016

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The sequential crystallization of poly(ethylene oxide)-b-poly(e-caprolactone)-b-poly(L-lactide) (PEO-b-PCL-b-PLLA) triblock terpolymers, in which the three blocks are able to crystallize separately and sequentially from the melt, is presented. Two terpolymers with identical PEO and PCL block lengths and two different PLLA block lengths were prepared, thus the effect of increasing PLLA content on the crystallization behavior and morphology was evaluated. Wide angle X-Ray scattering (WAXS) experiments performed on cooling from the melt confirmed the triple crystalline nature of these terpolymers and revealed that they crystallize in sequence: the PLLA block crystallizes first, then the PCL block, and finally the PEO block. Differential scanning calorimetry (DSC) analysis further demonstrated that the three blocks can crystallize from the melt when a low cooling rate is employed. The crystallization process takes place from a homogenous melt as indicated by small angle X-Ray scattering (SAXS) experiments. The crystallization and melting enthalpies and temperatures of both PEO and PCL blocks decrease as PLLA content in the terpolymer increases. Polarized light optical microscopy (PLOM) demonstrated that the PLLA block templates the morphology of the terpolymer, as it forms spherulites upon cooling from the melt. The subsequent crystallization of PCL and PEO blocks occurs inside the interlamellar regions of the previously formed PLLA block spherulites. In this way, unique triple crystalline mixed spherulitic superstructures have been observed for the first time. As the PLLA content in the terpolymer is reduced the superstructural morphology changes from spherulites to a more axialitic-like structure.

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Section: Saxs Characterization Of the Peo-b-pcl-b-plla Triblock Terpomentioning

confidence: 99%

Section: Morphology Of the Peo-b-pcl-b-plla Triblock Terpolymersmentioning

confidence: 99%

Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

et al. 2016

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“…[23][24][25] However, in the system of block copolymers, 17,26,27 the formation of banded texture of PLLA become quite complicated because of the strong molecular interaction, microphase separation and constrained geometry of each block, which make the investigations on banded spherulites of the block copolymers consisting of PLLA blocks are still under discussion and not yet claried up to now. Moreover, considering the structural diversity of the block copolymers and the above literature review, there is still lack of intuitive cognition about the banded spherulites of PLLA-PCL copolymers, and no results have been reported on the block length ratio and crystallization temperature on crystalline morphology of PLLA blocks.…”

Section: Introductionmentioning

confidence: 99%

“…13 Aerward, Castillo et al investigated the crystallization kinetics and morphology of PLLA and PCL blocks within a series of PLLA-PCL double crystalline diblock copolymers and found that the reorganization ability of the PLLA block increased with PCL content. 16 Wang et al synthesized well-dened star-shaped PCL-PLLA copolymers and founded that the band spherulites with no obvious Maltese cross patterns were formed, 17 but the detailed formation mechanism of the banded texture of PLLA within the star-shaped PCL-PLLA copolymer was not analyzed.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and morphological transition of poly(l-lactide)–poly(ε-caprolactone) diblock copolymers with different block length ratios

et al. 2017

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The crystallization behavior, banded spherulite and morphological transition of poly(L-lactide) (PLLA) phases within the block copolymers were investigated. All experimental results showed that the structure and thermal properties of PLLA-PCL copolymers could be adjusted by varying the ratios of the chain length of the two blocks. Morphological results indicated that the banded spherulites of PLLA formed when PLLArich copolymers crystallized. PCL segments introduced unbalanced stresses around PLLA lamellar crystals, which resulted in a bending moment responsible for twisting of PLLA lamellar crystals. As the block length ratio of PCL to PLLA increased, an over accumulation of PCL segments influenced the twisting of PLLA lamellae. In addition, it was interesting to find that the banded spherulite morphology changed with increasing the crystallization temperature. The crystallization temperature has an effect on the relationship between the sense of lamellar twisting and the morphological transition of PLLA, which is reflected in the fact that the band spacing of banded spherulites showed strong temperature dependence when the crystallization temperature exceeds 115 C, while it exhibited weak temperature dependence below 115 C. In particular, above 125 C the band spacing disappeared and nonbanded spherulites formed.

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“…Stannous octanoate [Sn(Oct) 2 ] is the most widely used catalyst for SPCLs. [12][13][14][15][16][17] Nevertheless, high temperature (around 120 C) is always needed for the polymerization. Furthermore, Sn(Oct) 2 is extremely air and moisture sensitive.…”

Section: Introductionmentioning

confidence: 99%

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

Zhu

Tong

Xie

et al. 2010

J of Applied Polymer Sci

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ABSTRACT:The rare earth compound, scandium trifluoromethanesulfonate [Sc(OTf) 3 ], has been used as a water-tolerant catalyst for the synthesis of star-shaped poly(e-caprolactone)s (SPCLs) with trimethylol propane as trifunctional initiator in solvent at 40 C. Triarm SPCLs have been successfully prepared. The molar mass of SPCLs were determined by end-group 1 H NMR analyses, which could be well controlled by the molar ratio of the monomer to the initiator, and were independent of the amount of Sc(OTf) 3 used. Differential scanning calorimetry analyses suggested that the maximal melting point, the cold crystallization temperature, and the degree of crystallinities of SPCLs increased with the increasing of the molar mass and were lower than the linear poly (e-caprolactone) (LPCL) with similar molar mass. Furthermore, polarized optical microscopy indicated that LPCL showed fast crystallization rate and good spherulitic morphology with apparent Maltese cross pattern, whereas SPCLs exhibit much lower crystallization rate and poor spherulitic morphology.

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Synthesis, Sequential Crystallization and Morphological Evolution of Well‐Defined Star‐Shaped Poly(ε‐caprolactone)‐b‐poly(L‐lactide) Block Copolymer

Cited by 74 publications

References 33 publications

Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

Crystallization and morphological transition of poly(l-lactide)–poly(ε-caprolactone) diblock copolymers with different block length ratios

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

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