Abstract
A study of the morphology of diblock copolymers composed of two crystalline blocks of isotactic polypropylene (iPP) and polyethylene (PE) is shown. The samples form phase-separated structures in th...
Highlights
Semicrystalline block copolymers (BCPs) combining crystallizable blocks of isotactic polypropylene and polyethylene (PE) have recently received considerable attention thanks to the possibility to use them as compatibilizers in poorly miscible iPP/PE blends, opening new opportunities for recycling polyolefins into equal- or higher-value materials with lower sorting costs.[1−3] The preparation of iPP−PE BCPs with precise control over block length and architecture offers the possibility to tailor the final properties of the material, further expanding the already enormous range of applications of iPP and PE homopolymers in packaging, textile, and cutting edge automotive and aircraft markets.[4,5]
Semicrystalline iPP−PE BCPs with a high molecular mass and with precise control over block length and architecture have been recently obtained by using a pyridylamidohafnium precatalyst activated with B(C6F5)[3,1,2,9] which follows the extensive effort in obtaining living iPP with this class of catalysts.[10−12] The obtained materials, consisting of semicrystalline stereoregular iPP and linear PE blocks, display superior interfacial activity, effectively compatibilizing PE/iPP blends and dramatically improving the tensile properties of blends for certain combinations of block molecular masses and molecular architectures.[1,2]
We report the characterization of the microstructure of crystalline−crystalline diblock copolymers (CC-BCP) constituted by blocks of iPP and PE of different molecular masses
Summary
Semicrystalline block copolymers (BCPs) combining crystallizable blocks of isotactic polypropylene (iPP) and polyethylene (PE) have recently received considerable attention thanks to the possibility to use them as compatibilizers in poorly miscible iPP/PE blends, opening new opportunities for recycling polyolefins into equal- or higher-value materials with lower sorting costs.[1−3] The preparation of iPP−PE BCPs with precise control over block length and architecture offers the possibility to tailor the final properties of the material, further expanding the already enormous range of applications of iPP and PE homopolymers in packaging, textile, and cutting edge automotive and aircraft markets.[4,5] Despite the tremendous applicative potential of these materials, the synthesis of iPP−PE BCPs6 has been very challenging because of the difficulties concerning the evolution of living polymerization methods[7,8] that guarantee obtaining high-molecular mass polymers with a high control of the stereochemistry and high level of stereoregularity. Epitaxial crystallizations were performed using as substrate crystals of BA (melting temperature equal to 123 °C), following procedures described in the literature.[39] In particular, the iPP and iPP−PE films, prepared onto microscope glass slides, were melted along with BA at temperatures above the melting temperatures of the BCP samples (Table 1), and the mixtures were crystallized by moving the glass slide slowly down the temperature gradient of a hot bar (cooling rate 10−15 °C/min). The slowly crystallized samples were obtained by melting the iPP−PE thin films, prepared by casting onto microscope glass slides, at ≈220 °C for 5 min and cooled by moving the slides slowly down the temperature gradient of the hot bar (cooling rate 10−15 °C/min). The measurements were confirmed by repeating the analysis on images of independent samples
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