posted on 2024-01-04, 13:05authored byMyoeum Kim, Shifeng Nian, Daniel A. Rau, Baiqiang Huang, Jinchang Zhu, Guillaume Freychet, Mikhail Zhernenkov, Li-Heng Cai
Three-dimensional (3D) printing of elastomers enables
the fabrication
of many technologically important structures and devices. However,
there remains a critical need for the development of reprocessable,
solvent-free, soft elastomers that can be printed without the need
for post-treatment. Herein, we report modular soft elastomers suitable
for direct ink writing (DIW) printing by physically cross-linking
associative polymers with a high fraction of reversible bonds. We
designed and synthesized linear-associative-linear (LAL) triblock
copolymers; the middle block is an associative polymer carrying amide
groups that form double hydrogen bonding, and the end blocks aggregate
to hard glassy domains that effectively act as physical cross-links.
The amide groups do not aggregate to nanoscale clusters and only slow
down polymer dynamics without changing the shape of the linear viscoelastic
spectra; this enables molecular control over energy dissipation by
varying the fraction of the associative groups. Increasing the volume
fraction of the end linear blocks increases the network stiffness
by more than 100 times without significantly compromising the extensibility.
We created elastomers with Young’s moduli ranging from 8 kPa
to 8 MPa while maintaining the tensile breaking strain around 150%.
Using a high-temperature DIW printing platform, we transformed our
elastomers to complex, highly deformable 3D structures without involving
any solvent or post-print processing. Our elastomers represent the
softest melt reprocessable materials for DIW printing. The developed
LAL polymers synergize emerging homogeneous associative polymers with
a high fraction of reversible bonds and classical block copolymer
self-assembly to form a dual-cross-linked network, providing a versatile
platform for the modular design and development of soft melt reprocessable
elastomeric materials for practical applications.