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SUMMARY:Melville Lecture 1: Stimuli-Responsive Smart Soft Materials abrica
 ted under Nonequilibrated Conditions - Professor Takuzo Aida\, University 
 of Tokyo 
DTSTART:20170207T160000Z
DTEND:20170207T170000Z
UID:TALK70763@talks.cam.ac.uk
CONTACT:Sharon Connor
DESCRIPTION:Machine technology frequently puts magnetic or electrostatic r
 epulsive forces to practical use\, as in maglev trains\, vehicle suspensio
 ns or non-contact bearings. In contrast\, materials design overwhelmingly 
 focuses on attractive interactions\, such as in the many advanced polymer-
 based composites\, where inorganic fillers interact with a polymer matrix 
 to improve mechanical properties. However\, articular cartilage strikingly
  illustrates how electrostatic repulsion can be harnessed to achieve unpar
 alleled functional efficiency: it permits virtually frictionless mechanica
 l motion within joints\, even under high compression. Here we describe a c
 omposite hydrogel with anisotropic mechanical properties dominated by elec
 trostatic repulsion between negatively charged unilamellar titanate nanosh
 eets embedded within it. Crucial to the behaviour of this hydrogel is the 
 serendipitous discovery of cofacial nanosheet alignment in aqueous colloid
 al dispersions subjected to a strong magnetic field\, which maximizes elec
 trostatic repulsion6 and thereby induces a quasi-crystalline structural or
 dering over macroscopic length scales and with uniformly large face-to-fac
 e nanosheet separation. We fix this transiently induced structural order b
 y transforming the dispersion into a hydrogel using lighttriggered in situ
  vinyl polymerization. The resultant hydrogel\, containing charged inorgan
 ic structures that align cofacially in a magnetic flux\, deforms easily un
 der shear forces applied parallel to the embedded nanosheets yet resists c
 ompressive forces applied orthogonally. We anticipate that the concept of 
 embedding anisotropic repulsive electrostatics within a composite material
 \, inspired by articular cartilage\, will open up new possibilities for de
 veloping soft materials with unusual functions. More recently\, we reporte
 d a highly oriented thin film of a carbon nitride polymer\, which shows an
 omalous mechanical responses to minute fluctuations in the ambient humidit
 y. \n \nReferences [1] Q. Wang\, J. L. Mynar\, M. Yoshida\, E. Lee\, M. Le
 e\, K. Okuro\, K. Kinbara\, and T. Aida\, Nature 2010\, 463\, 339–343. [
 2] M. Liu\, Y. Ishida\, Y. Ebina\, T. Sasaki\, and T. Aida\, Nature Commun
 . 2013\, 4\, 2029 [3] M. Liu\, Y. Ishida\, Y. Ebina\, T. Sasaki\, T. Hikim
 a\, M. Takata\, and T. Aida\, Nature 2015\, 517\, 68–72. [4] Y.-S. Kim\,
  M. Liu\, Y. Ishida\, Y. Ebina\, T. Sasaki\, T. Hikima\, M. Takata\, and T
 . Aida\, Nature Mat. 2015\, 14\, 1002–1007. [5] H. Arazoe\, D. Miyajima\
 , K. Akaike\, F. Araoka\, E. Sato\, T. Hikima\, M. Kawamoto\, T. Aida\, Na
 ture Mat. 2016
LOCATION:Wolfson Lecture Theatre\,  Department of Chemistry
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