We investigate the crystallization behavior of isotactic polypropylene (iPP) under the influence of nanoscale confinement templated by the microphase-separated structure of an iPP-based diblock copolymer system, isotactic polypropylene-block-atactic polystyrene (iPP-b-aPS). Three types of iPP microdomains, i.e., lamellae, cylinder, and sphere, were generated by controlling the composition of the diblock. The effect of microdomain morphology on the nucleation mechanism, crystallization kinetics, self-nucleation behavior, the population of the helical sequence of iPP block in the melt state, and crystal orientation have been systematically studied. It was found that the crystallization rate of iPP was predominantly controlled by homogeneous nucleation when the crystallization process was largely confined within the individual cylindrical and spherical microdomains. Such a nucleation mechanism and the highly frustrated crystal growth in the isolated microdomains led to the absence of Domain II and atypical crystallization kinetics in Domain III in the self-nucleation study. The population of the longer helical sequence of iPP block revealed by infrared spectroscopy was found to be affected by temperature but not by the spatial confinement, chain stretching, and junction point constraint imposed by the microdomains. Finally, the orientation of α-form iPP crystals in the lamellae-forming iPP-b-aPS was identified over a broad range of crystallization temperatures (T(c)). Different from other crystalline-amorphous diblocks, a lamellar branching of α-form iPP was observed in the lamellar microdomains at T(c) lying between 15 and 80 °C, where the daughter lamellae developed from the perpendicularly orientated parent iPP crystals with a specific angle of 80° or 100°. Once the sample was crystallized at T(c) ≤ 10 °C, the iPP crystals became randomly oriented.

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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.

Producing zeolite films with controlled preferred orientation on an industrial scale is along-standing challenge. Herein we report on as calable approach to the direct wet deposition of zeolite thin films and membranes while maintaining ah igh degree of control over the preferred crystal orientation. As ap roof of concept, thin films comprising aluminophosphate zeolite AEI were cast on silicon wafer or porous alumina substrates.Electrical properties and separation performance of the zeolite thin films/membranes were engineered through controlling degree of preferred crystal orientation.

Producing zeolite films with controlled preferred orientation on an industrial scale is a long-standing challenge. Herein we report on a scalable approach to the direct wet deposition of zeolite thin films and membranes while maintaining a high degree of control over the preferred crystal orientation. As a proof of concept, thin films comprising aluminophosphate zeolite AEI were cast on silicon wafer or porous alumina substrates. Electrical properties and separation performance of the zeolite thin films/membranes were engineered through controlling degree of preferred crystal orientation.