Confinement Effects on the Crystallization Kinetics and Self‐Nucleation of Double Crystalline Poly(p‐dioxanone)‐b‐poly(ϵ‐caprolactone) Diblock Copolymers

Abstract

The morphology, crystallization and self nucleation behavior of double crystalline diblock copolymers of poly(p‐dioxanone) (PPDX) and poly(ϵ‐caprolactone) (PCL) with different compositions have been studied by different techniques, including optical microscopy (OM), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). The two blocks crystallize in a single coincident exotherm when cooled from the melt. The self‐nucleation technique is able to separate into two exotherms the crystallization of each block. We have gathered evidences indicating that the PPDX block can nucleate the PCL block within the copolymers regardless of the composition. This effect is responsible for the lack of homogeneous nucleation or fractionated crystallization of the PCL block even when it constitutes a minor phase within the copolymer (25% or less). Nevertheless, we were able to show that decreasing amounts of PCL within the diblock copolymer still produces confinement effects that retard the crystallization kinetics of the PCL component and decrease the Avrami index. On the other hand evidence for confinement was also obtained for the PPDX block, since as its content is reduced within the copolymer, a depression in its self‐nucleation and annealing temperatures were observed.

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

“…In block copolymers, factors such as the volumetric fraction and the degree of segregation affect the type of confinement and, as a consequence, influence the SN behavior. Several works dealing with the crystallization of semicrystalline block copolymers have reported the SN of crystallizable block(s) [3,[94][95][96][97][98][108][109][110][111][112][113][114][115][116][117][118][119]. In these studies, three kinds of behavior have been reported: 1.…”

Crystalline and Spherulitic Morphology of Polymers Crystallized in Confined Systems

“…This makes the crystallizable block copolymers representative systems having confined crystallization behavior, especially in the strong segregation regime [52]. Confined crystallization has been widely observed in the diblock copolymers having double crystalline blocks, such as PEO-b-PCL [112][113][114][115][116], PLLA-b-PEO [117][118][119][120][121][122], PLLA-b-PCL [123][124][125], poly(p-dioxanone) (PPDX)-b-PCL [126][127][128], polyolefin-based block copolymers [129][130][131][132][133][134][135], and so on. The confined crystallization kinetics and crystalline morphology of such block copolymers have been extensively studied.…”

Melt Structure and its Transformation by Sequential Crystallization of the Two Blocks within Poly(L‐lactide)‐block‐Poly(ε‐caprolactone) Double Crystalline Diblock Copolymers

“…[2][3][4] Although there have been a number of prior reports on double crystalline diblock copolymer systems, the understanding of their complicated properties is still at a nascent stage. [5][6][7][8][9][10][11][12][13][14][15][16] Poly(L-lactide) (PLLA) has been widely employed in the medical field because of its biodegradability. However the applications of PLLA to commercial products are limited principally by its brittleness.…”