Supramolecules: Low & Medium molecular weight - umk

kitteninterestAI and Robotics

Nov 15, 2013 (3 years and 11 months ago)

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Discovery Channel News


MIT Technology Reviews


Materials Research Society Bulletin (USA)


+ several others





March 2010

Why aroused broad interest


Nature shows stiff and strong nanocomposites


Nacre, silk, etc


Drastically exceed the properties of the present day synthetic polymeric nanocomposites



Problem: how to prepare them in
technically relevant methods


Real bottleneck!



Biomimetics


Learn
the essential aspects
of natural materials and realize them
in new ways
that allow
mass production


Not easy



Extensive efforts have been to
mimic nacre


Work in the lab, too slow or expensive for “real life”



We show the first route for practical nacre
-
mimetic materials


Painting, paper
-
making, spraying, doctor
-
blading, etc….


The innovation is conceptual, works for a large set of materials


How?

What could be a daydream engineering material


High modulus


Stiff


High strength


Strong


Tough


Does not break eg. upon
deformations


Cracks do not grow easily


Small density


Light weight construction


Easily processible at large scale


Economic


Safe





Rubber


Tough: elastic and
cracks do not propagate


Not stiff and strong





Porcellain




Stiff and strong


Not tough: cracks
propagate easily




Difficult!

Standard practice: Aim to
combine

properties by
multicomponent
composites

Examples of
classic composites


Light weight metal alloys, such as aluminium and
duralunium alloys


Eg. airplanes, telecommunication, …


Widely used



Polymer composites


Add reinforcing fibers and fillers to polymers


Glass fibers, carbon fibers, Kevlar fibers etc


Some improvement achieved



Polymer nanocomposites


Add reinforcing nanofibers or nanoplates to
polymers


Carbon nanotubes, nanoclay, cellulose
nanofibers


Some improvements achieved



Improvement observed, why worry ?






However:

Biological materials shows
how to prepare
drastically
improved
properties using
nanocomposites

Mollusc Nacre as a model for daydream material





Stiff


Modulus 70 GPa


vs Aluminiun alloy


Strong


Strength 80
-
130 MPa


vs cast iron


Extremely tough


Lightweight


Synthesized under mild
conditions




CaCO
3

plates


Thickness 0.5
m
m, width 20
-
30
m
m


Polymer “glue” in between


Thin layers (only!)



Why


Thin reinforcing platelets reinforce


In deformation the cracks cannot
easily propagate, deflect, consume
energy



crack

Nacre cannot be produced industrially:

Can one mimic nacre ?


Sequential depositions of
inorganic platelets and
polymers


Feasible in the lab,
but slow!


Can take a week to
deposit


Not feasible in
bulkproduction




Ice templating


Energy consuming


Feasible in the lab


Not feasible

in production

Kotov et al, Nature Mat 2003 2 413

Kotov et al, Science_2007 318 80

Studart et al Science_2008 319 1069



Deville et al Science 2006 311 515

Ritchie et al, Science 2008 322 1516

We found a simple scientific concept for self
-
assembly

which opens the routes for production


Reinforcing units coated with soft polymers etc


Subsequent self
-
assembly


Simple and facile processing by technologically relevant ways



Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
Nano Letters
, asap, (2010)

Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
submitted
(2010)

Walther, Laukkanen, Ikkala,
patent pending

.


Mechanical properties


Low density & good
mechanical
properties



Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
Nano Letters
, asap, (2010)

Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
submitted
(2010)

Walther, Laukkanen, Ikkala,
patent pending

.




Modulus

Strength

Density



(GPa)

(Mpa)

(g/cm3)

Our Nacre
-
mimetics

45

250

ca. 2.0


Nacre


80

80
-
130

2.8

Silk



10


1100

(major ampullata)







Modulus

Strength

Density



(GPa)

(Mpa)

(g/cm3)

Steel


200

250
-
2000

7.8

Al alloy


70

410

2.8

Polypropylene

1.5
-
2

20
-
80

1.5

Lessons from the nature

Classic approach

Our biomimetic

approach

Polymer

Reinforcement

Modulus = 0.9 GPa

Strength = 20 MPa


Nanoclay composites were

Introduced by Toyota Ltd for car bumpers

Modulus = 45 GPa

Strength = 250 MPa

High shielding capacity against fire


See a separate film


Protects against ca. 2000 oC



Very low gas permeability


Out nacre mimetic materials shows 0.325 cm
3

mm/m
2
/day/atm for oxygen
transport even at high humidity (80%RH)


Painted layers!


One of the lowest known


Next...


A general principle : has been extended/is being extended a large variety of
reinforcing materials and polymers, also fibers!


Need


Improve still the toughness


Demonstrate bulk materials and laminates


Even if we are beginning to understand a glimpse how
nanocomposites

should be
designed, we understand as yet very little still the practical applications


Search collaborations for product ideas and joint efforts for products


Lightweight construction:


Laptops, mobiles, airplanes, aerospace,


Low gas permeation


Organic electronics, packaging


Heat/fire shielding


Aerospace, fireproof clothes, smart textiles



Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
Nano Letters
, asap, (2010)

Walther, Bjurhager, Malho, Ruokolainen, Pere, Berglund, Ikkala,
submitted
(2010)

Walther, Laukkanen, Ikkala,
patent pending

.