Thermal properties of di- and triblock copolymers of poly(l-lactide) with poly(oxyethylene) or poly(ε-caprolactone)

Maglio, Giovanni; Migliozzi, Anna; Palumbo, Rosario

doi:10.1016/s0032-3861(02)00764-4

Cited by 109 publications

(99 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular they discovered that both copolymer blocks are partially miscible depending on their molecular weight, decreasing the nucleation rate and the melting temperature of PLLA block by increasing the percentage of PCL. Maglio et al investigated on PLLA-PCL-PLLA tri-block copolymers with high molecular weight and they concluded that the two blocks can be considered immiscible [24]. The degradation rate of PLLA-PCL copolymers has been reported by Zhao and col., who have developed materials with adjustable degradation time depending on the composition of the copolymer [5].…”

Section: Introductionmentioning

confidence: 96%

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

Peponi

Navarro-Baena

Báez

et al. 2012

Polymer

View full text Add to dashboard Cite

A systematic study on the synthesis and characterization of di-block copolymers based on aliphatic polyesters such as poly(L-lactic acid) (PLLA) and poly(-caprolactone) (PCL), performed varying both the length of the blocks as well as the relative content of each block in the copolymers, is reported. The block-length and the molecular weight of each synthesized PCL-b-PLLA di-block copolymer were analyzed by nuclear magnetic resonance spectroscopy. The influence of the block length and of the amount of each block on the thermal properties and the morphology, was evaluated by differential scanning calorimetry and by small angle X-Ray scattering experiments. In particular, the correlation between the molecular weight of each block and its amorphous and/or crystalline structure was obtained, evidencing that the crystallization of the PLLA block was not influenced by the presence of PCL and depends mainly on its molecular weight but the crystallization of PCL is strongly interfered by the crystallization of PLLA. In particular PLLA blocks are amorphous for short lengths (≤ 672 g/mol, that means ≤ 9.3 LA repeat units) and start to crystallize for molecular weight ≥ 964 g/mol, that means ≥ 13.4 LA repeat units.

show abstract

Section: Introductionmentioning

confidence: 96%

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

Peponi

Navarro-Baena

Báez

et al. 2012

Polymer

View full text Add to dashboard Cite

show abstract

“…Block copolymers, consisting of both crystalline and amorphous segments were widely recognized that their crystallization processes and the resulting crystal morphologies can be significantly influenced by microphase separation in melt [6,7]. However, block copolymers, consisting of different crystalline segments such as the double crystalline block copolymers, usually exhibit much more complicated crystallization behaviors [8,9], including confined crystallization [10][11][12][13], competitive or interactive crystallization and so on [14][15][16]. For these block copolymers, the overall crystallization behavior is influenced by block ratios, nucleation types, crystallization kinetics and characteristics of the individually folded chains [5,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Poly(ethylene glycol)-poly(tetrahydrofuran)-poly(ethylene glycol) triblock copolymer : Synthesis, crystallization behavior and novel morphology

Wang¹,

Fan²,

Tian³

et al. 2013

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. Poly(ethylene glycol)-poly(tetrahydrofuran)-poly(ethylene glycol) (PEG-PTHF-PEG) triblock copolymer was synthesized by ring-opening polymerization of ethylene oxide using sodium alcoholate of PTHF as the macroinitiator. Its crystallization behavior and formation mechanisms of different crystal structures were studied. The study showed that the molecular weight of PEG-PTHF-PEG exhibited a significant effect on its crystallization: that is, with the increase of the copolymer's molecular weight, the crystallizability of PTHF blocks decreased gradually, which led to the transition of copolymer from crystalline-crystalline to crystalline-amorphous. By adjusting the total molecular weight of triblock copolymer, the crystallization process can be effectively controlled, and as a result, different spherulite structures were obtained. Particularly, when PTHF blocks became amorphous, novel double concentric spherulites were observed. The morphological structures were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), polarized optical microscopy (POM), and its crystalline process was investigated.

show abstract

“…Therefore the crystallized morphology formed by high-T m blocks is a kind of spatial confinement for the subsequent crystallization of low-T m blocks, which will be qualitatively different from the confinement imposed by amorphous or glassy microdomains observed in crystallineamorphous diblock copolymers. [9][10][11] There are some studies so far on the morphology formation of double crystalline block copolymers with different T m values, [12][13][14][15][16][17][18][19][20][21][22][23][24] where they are mainly focused on the characteristic morphology finally formed in the system.…”

mentioning

confidence: 99%

Composition Dependence of Crystallization Behavior Observed in Crystalline-Crystalline Diblock Copolymers

Ikeda

Ohguma

Nojima

2008

Polym J

View full text Add to dashboard Cite

The crystallization behavior of poly("-caprolactone) (PCL) blocks starting from a solid morphology formed in advance by the crystallization of polyethylene (PE) blocks (PE-crystallized morphology) in PCL-b-PE diblock copolymers has been investigated by a time-resolved synchrotron small-angle X-ray scattering (SR-SAXS) method as a function of composition (or volume fraction of PE blocks PE in the system). The PE-crystallized morphology and the crystallized state of PCL blocks (i.e., melting temperature and crystallinity of PCL blocks) were examined by static SAXS and differential scanning calorimetry methods, respectively. When PCL-b-PE with PE 0:58 was quenched from a microphase-separated melt into low temperatures T c (30 C T c 45 C), the PE block crystallized first to yield the PE lamellar morphology, an alternating structure consisting of thin PE crystals and amorphous PE + PCL layers, followed by the crystallization of PCL blocks starting from this PE lamellar morphology, where two different crystallization behaviors of PCL blocks were observed depending on T c ; at higher T c (! 40 C) the Avrami index was ca. 3, indicating a heterogeneous crystallization in 3D space. However, it was smaller ($ 2) at lower T c ( 38 C), suggesting a confined crystallization within the PE lamellar morphology. The temperature at which the crystallization mechanism changed was almost independent of PE in these copolymers. The late stage of PCL crystallization (or post-Avrami process) was not significantly dependent on PE and similar to that of crystalline homopolymers. For PCL-b-PE with PE ! 0:73, the PE block crystallized on the basis of molten microdomains to yield the PE-crystallized microdomain, and eventually PCL crystallization was confined within this microdomain for every T c at early and late stages. These results were consistent with our previous conclusions derived from the investigation of resulting morphology.KEY WORDS: Crystalline-Crystalline Diblock Copolymer / Composition / Crystallization Behavior / Synchrotron SAXS / Crystalline-crystalline diblock copolymers show a complicated morphology formation according to the melting temperature T m of constituent blocks when they are quenched from a microphase-separated melt into low temperatures.1 If T m values of two blocks are close enough, we have a simultaneous crystallization of both blocks to result in a complicated morphology formation.2-8 If T m of one block is enough higher than that of the other, we have a two-step crystallization; high-T m blocks crystallize first to form a crystallized morphology and subsequently low-T m blocks start to crystallize from this morphology. Therefore the crystallized morphology formed by high-T m blocks is a kind of spatial confinement for the subsequent crystallization of low-T m blocks, which will be qualitatively different from the confinement imposed by amorphous or glassy microdomains observed in crystallineamorphous diblock copolymers. [9][10][11] There are some studies so far on the morphology formation of double crystall...

show abstract

Thermal properties of di- and triblock copolymers of poly(l-lactide) with poly(oxyethylene) or poly(ε-caprolactone)

Cited by 109 publications

References 20 publications

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

Effect of the molecular weight on the crystallinity of PCL-b-PLLA di-block copolymers

Poly(ethylene glycol)-poly(tetrahydrofuran)-poly(ethylene glycol) triblock copolymer : Synthesis, crystallization behavior and novel morphology

Composition Dependence of Crystallization Behavior Observed in Crystalline-Crystalline Diblock Copolymers

Contact Info

Product

Resources

About