Highly Responsive Hydrogel Prepared Using Poly(N-isopropylacrylamide)-Grafted Polyrotaxane as a Building Block Designed by Reversible Deactivation Radical Polymerization and Click Chemistry

Abstract

We prepared building blocks with the ability to form a polymer network, a polyrotaxane (PR) structure that enhances the flexibility of the polymer network, and thermosensitive dangling chains that impart the polymer network with rapid sensitivity. First, thermosensitive poly­(N-isopropyl­acrylamide) (PNIPA) was grafted from α-cyclodextrin, a cyclic molecule of PR, via controlled radical polymerization. The terminal chlorinated alkyl group of the grafted PNIPA was then modified with azide or alkyne. As a result, we obtained two types of PNIPA-grafted PR molecules with different terminations of PNIPA as building blocks. We then prepared a polymer network in which PR molecules with several dangling PNIPA chains were connected by PNIPA chains using a click reaction. Because of the presence of the dangling PNIPA chains, the obtained hydrogel exhibits rapid responses to changes in water temperature; it also exhibits flexibility due to the presence of the PR structure.

A Guiding Principle for Strengthening Crosslinked Polymers: Synthesis and Application of Mobility‐Controlling Rotaxane Crosslinkers

“…have reported that cyclodextrin‐based polyrotaxane hydrogels with rotaxane crosslinks show excellent swelling ability and extensibility . Related studies on such crosslinked cyclodextrin‐based polyrotaxanes also revealed intriguing properties that cannot be attained by crosslinked polymers using covalent crosslinkers . Meanwhile, our group has reported a synthetic route to rotaxane‐crosslinked vinyl polymers using supramolecular crosslinkers that consist of cyclodextrins and macromonomers.…”

An Ultrastrong and Highly Stretchable Polyurethane Elastomer Enabled by a Zipper‐Like Ring‐Sliding Effect

“…[ 32 ] They further studied various CD‐based stimuli‐sensitive ring‐sliding materials with improved mechanical properties and revealed unique features such as their sliding dynamics and viscoelastic relaxation. [ 33–36 ] Takata's group reported the synthesis of CD‐based rotaxane‐crosslinked vinyl polymers in view of the general use of vinyl polymers. [ 37,38 ] They also synthesized various rotaxane‐crosslinked polymers using crown‐ether‐containing vinylic rotaxane crosslinkers in nonaqueous systems.…”

Coil-globule transitions drive discontinuous volume conserving deformation in locally restrained gels

“…The dynamics of the volume phase transition is very slow, typically in the order of hours (for a gel of ~1 mm size) 15 – 17 . The dynamics is accelerated for gels with heterogeneous structures 18 , 19 , dangling bonds 20 , amphiphilic conetwork 21 , and mobile crosslinks 22 , 23 . However, the response time of the volume phase transition is not shorter than the order of minutes (for a gel of ~1 mm size) 21 , because to change the volume of the gel, solvent molecules must travel by the length scale of the size of the gel through the fine mesh of the polymer network 1 – 3 .…”