Interest in thermoresponsive polymers has steadily grown over many decades, and a great deal of work has been dedicated to developing temperature sensitive macromolecules that can be crafted into new smart materials. However, the overwhelming majority of previously reported temperature-responsive polymers are based on poly(N-isopropylacrylamide) (PNIPAM), despite the fact that a wide range of other thermoresponsive polymers have demonstrated similar promise for the preparation of adaptive materials. Herein, we aim to highlight recent results that involve thermoresponsive systems that have not yet been as fully considered. Many of these (co)polymers represent clear opportunities for advancements in emerging biomedical and materials fields due to their increased biocompatibility and tuneable response. By highlighting recent examples of newly developed thermoresponsive polymer systems, we hope to promote the development of new generations of smart materials.
The
classical division of polymeric materials into thermoplastics
and thermosets based on covalent network structure often implies that
these categories are distinct and irreconcilable. Yet, the past two
decades have seen extensive development of materials that bridge this
gap through incorporation of dynamic crosslinks, enabling them to
behave as both robust networks and moldable plastics. Although their
potential utility is significant, the growth of covalent adaptable
networks (CANs) has obscured the line between “thermoplastic”
and “thermoset” and erected a conceptual barrier to
the growing number of new researchers entering this discipline. This
Perspective aims to both outline the fundamental theory of CANs and
provide a critical assessment of their current status. We emphasize
throughout that the unique properties of CANs emerge from the network
chemistry, and particularly highlight the role that the crosslink
exchange mechanism (i.e., dissociative exchange or associative exchange)
plays in the resultant material properties under processing conditions.
Predominant focus will be on thermally induced dynamic behavior, as
the majority of presently employed exchange chemistries rely on thermal
stimulus, and it is simple to apply to bulk materials. Lastly, this
Perspective aims to identify current issues and address possible solutions
for better fundamental understanding within this field.
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