Multilength Scale Studies of the Confined Crystallization in Poly(l-lactide)-block-Poly(ethylene glycol) Copolymer

Abstract

In this work, we investigated the structure and morphology formation in crystalline–crystalline diblock copolymer of poly(l-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) on different length scales with optical microscopy (OM), atomic force microscopy (AFM), synchrotron time-resolved small-angle X-ray scattering (TR-SAXS) and wide-angle X-ray scattering (WAXS) methods. The PLLA-b-PEG copolymer with 5000 of number-average of molecular weight of PLLA and PEG blocks was used in this work. The structure and morphology of PLLA-b-PEG copolymers were formatted by a two-step crystallization process: i.e., the PLLA block crystallized fully at 110 °C in the first step, and then the PEG block crystallized fully at 30 °C in the second step. The OM, AFM, and SAXS results indicated that the PEG block crystallized in the multilength scales amorphous regions confined by PLLA crystals. The PEG block crystallized not only in the interlamellar regions of PLLA crystals, but also in the interfibrillar regions of PLLA. However, the subsequent crystallization of PEG block did not alter the foregoing spherulitic morphology of PLLA on the micrometer scale.

Preparation and characterization of polylactide/poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) hybrid fibers for potential application in bone tissue engineering

“…This might be due to the intrinsic properties of PLA solution, such as surface tension and viscosity. 44 Interestingly, the electrospun fiber surface of PLA exhibited nanoscale pores, as also reported by Bognitzki et al, who rationalized that the rapid phase separation induced by the evaporation of the solvent and the subsequent rapid solidification during electrospinning might have accounted for this surface structure. 22 With increasing PCEC concentration, the process of electrospinning became smooth, with no spindle-shaped structures formed.…”

“…The reason might be ABA triblock copolymer show capable of forming a stereocomplex with the PLA matrix, which was used as the sole strengthening agent to modify the physi cal strength of PLA. 44,45 On the other hand, we speculated that the increase of fiber crystallinity might play an effective role in improvement of mechanical properties of PLA/PCEC hybrid scaffolds.…”

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

“…Moreover, the crystalline superstructures observed in both AB and ABA-type triblock copolymers have been extensively reviewed and include mixed spherulites, concentric spherulites, dendrites, axialites and eutectic crystals. 2,10,[39][40] Recently, Yang et al 39 reported that the subsequent crystallization of PEG blocks in PLLA-b-PEG diblock copolymers could change the crystalline structure of PLLA crystals, and the extent of this change is determined by the crystallization temperature of the PLLA block. Attempts to achieve a fully triple crystalline triblock terpolymer have been done in the past.…”

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.…”

“…PLLA-b-PEO diblock copolymers could form spherulites with banded textures and single crystals with an abundance of screw dislocations. Yang et al [122] have studied the confined crystallization behavior of PLLA-b-PEO copolymers. They crystallized the block copolymers by two steps: the PLLA block crystallized fully at 110 • C in the first step; then the PEO block crystallized by cooling to 30 • C in the next step.…”