Among the various
ordered morphologies self-assembled from block
copolymers, the spherical packing phases are particularly interesting
because they resemble the familiar atomic crystals. The commonly observed
spherical morphology of block copolymers is the body-centered-cubic
phase. Recently, a number of novel spherical packing phases, i.e.,
the complex Frank–Kasper phases originally obtained in metallic
alloys, have been observed in block copolymer melts. Theoretical studies
have revealed that conformational asymmetry of the different blocks
provides a key mechanism to stabilize the Frank–Kasper phases.
Furthermore, local segregation of different copolymers in blends of
diblock copolymers and copolymer architectures provides additional
mechanisms to enhance the stability of the complex ordered phases.
In this Viewpoint we summarize recent advances in our understanding
of the formation of the nonclassical spherical packing phases in AB-type
block copolymers, emphasizing the formation mechanisms of these fascinating
complex ordered structures.
A new
kind of biobased material named lignin-containing polyhydroxyurethane
(LPHU) is prepared from bis(6-membered cyclic carbonate) (BCC), dimer
fatty diamine, and lignin for the first time. The preparation strategy
is isocyanate-free, solvent-free, and catalyst-free, representing
a green and environmentally friendly method to access polyurethane
(PU)/lignin composites. The resultant LPHUs possess dual networks:
a dynamic covalent network and a hydrogen bonding network, exhibiting
superior mechanical strength, high thermal stability, excellent reprocessability/recyclability,
and smart properties such as shape memory and self-healing. Potential
application investigations indicate that the resultant LPHUs can be
not only used for smart packaging label fabrication for heat-sensitive
commodities but also further combined with natural cellulose paper
to prepare paper-based electromagnetic shielding materials with high
mechanical performance.
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