Control of Nanostructural Dimension by Crystallization in a Double-Crystalline Syndiotactic Poly(4-methyl-1-pentene)-block-poly(l-lactide) Block Copolymer

Abstract

The control of nanostructural dimension by crystallization-induced chain stretching was investigated in a novel double-crystalline block copolymer, syndiotactic poly(4-methyl-1-pentene)-block-poly(L-lactide) (sPMP−PLLA), featuring a lamellar phase. Because of the similar glass transition temperatures of sPMP and PLLA, their blocks could crystallize under soft confinement (i.e., a crystallization temperature higher than the glass transition temperatures of the constituent blocks) in sPMP−PLLA. With the strong segregation of sPMP−PLLA, the first-crystallized sPMP block was templated by microphase separation to form confined crystalline sPMP lamellae within the microphase-separated lamellar texture. Most interestingly, the first-crystallized sPMP block may also induce significant stretching of the PLLA chains from the lamellar interface, resulting in the increase of microdomain thickness of the PLLA block. With the increase of crystallization temperature, this chain stretching may become more significant, resulting in a large increase (∼34%) of the lamellar long period. The double-crystalline lamellar morphologies having homeotropic orientation for both sPMP and PLLA crystals can be acquired in the shear-aligned sPMP−PLLA as evidenced by simultaneous 2D small-angle X-ray scattering and wide-angle X-ray diffraction, giving uniform birefringence under polarized light microscope with thermal reversibility. As a result, the switchable lamellar nanostructures having significant dimensional change can be carried out by simply controlling crystallization or melting of the crystallizable blocks.

Hierarchical Structures with Double Lower Disorder-to-Order Transition and Closed-Loop Phase Behaviors in Charged Block Copolymers Bearing Long Alkyl Side Groups

“…In our experiment mode, it is expected that the LAM-1 structure should exhibit no scattering pattern. Similar phenomena are widely reported in the literature for the sheared LAM structure when the X-ray passes through the sample along the gradient direction. ,− However, in this work, a perfect orientation of the LAM-1 structure is difficult to achieve since we just used a flat spoon to scrap the sample unidirectionally. Therefore, very few lamellae in the LAM-1 structure are still edge-on arranged, leading to the weak scattering arcs along the equatorial direction in Figure a.…”

Crystallization of polymer chains confined in nanodomains

“…4), where the growth direction of PCL crystals controls the final crystal orientation at each d PCL . It is also reported using other crystalline-crystalline diblock copolymers that the existing crystalline lamellar morphology significantly affects the subsequent crystallization of block chains with T c,2 [57,59,60,64,66,67,[70][71][72]. In addition, it is reasonable to suppose that the crystallization behavior and crystal orientation of block chains with T c,2 depend significantly on the hardness of pre-existing crystalline lamellar morphology, because the crystallization of block chains confined in hard nanolamellae is extremely different from that in soft nanolamellae (Figs.…”

“…The sequential crystallization has been examined using several crystalline-crystalline diblock copolymers with sufficiently separate crystallizable temperatures [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72]. We examined the crystallization behavior and crystal orientation of PCL blocks in PCL-block-polyethylene (PCL-b-PE) diblock copolymers [56,58,[61][62][63]65,69], where the PCL blocks (with T c,2 $ 40°C) were accommodated between the crystalline lamellar morphology provided by the advance crystallization of PE blocks (with T c,1 $ 100°C), and started to crystallize there.…”

Cold Crystallization of PDMS and PLLA in Poly(l-lactide-b-dimethylsiloxane-b-l-lactide) Triblock Copolymer and Their Effect on Nanostructure Morphology

“…The crystallization behavior of several crystalline−crystalline (di-and triblock) copolymers has been studied. 24,25,43,44 It has been reported that if the melting temperatures for both blocks in a double-crystalline polymer are similar, both blocks can crystallize together from the melt for symmetric block ratios. As a consequence, the final morphologies of the block copolymer are more complicated due to the interactive effect of the microphase separation, crystallization, vitrification, and sequence of crystallization.…”