buffalo, new york · green chemistry benign processing ... several industrial applications...

Buffalo, New York

AlexandridhV

Chemical and Biological Engineering @ UB

KoffaV TzanakakhV

tissue

engineering

stem cell

biotechnology

metabolic

engineering

Tsianou AndreadhV

molecularly

engineered

materials

http://www.cbe.buffalo.edu

MountziarhV

KalogerakhV

TsamopouloV

critical

issues

environment

energy

health

ChemE’s save the world!

clean energy catalysis, photovoltaics

energy storage batteries, capacitors

energy conservation efficient manufacturing

air VOC reduction

water & ground

Green chemistry benign processing

biomolecular structure & interactions

delivery carriers scaffolds

diagnostics surface modification

self/directed assembly

solvents

polymers particles

Alexandridis lab

Self-Assembly

Mixtures of properly designed chemical components can organize themselves into complex assemblies with structures from the nanoscale to the mesoscale, in a fashion similar to biological self-assembly.

National Research Council: ―Beyond the Molecular Frontier‖, NAP, 2003.

Grand Challenge for Chemists and Chemical Engineers:

Develop self-assembly as a useful approach to the synthesis and

manufacturing of complex systems and materials.

SCIENCE

VOL 309

1 JULY 2005

PG 95


solvents

particles polymers

Alexandridis lab

environment

energy

health


solvents

polymers particles

alternative solvents reactions, separations

nanomanufacturing hybrid materials

electrolytes polymers, nanoparticles

solubilization & dispersion

aqueous solvents interactions with

organics

formulations pharmaceutics,

consumer products

benign synthesis of nanomaterials

drug delivery carriers, dissolution

biopolymers in solution, on surfaces

Self-Assembly of Amphiphilic Block Copolymers

Fundamentals and Applications

PascalhV AlexandridhV

Department of Chemical and Biological Engineering

University at Buffalo

The State University of New York

Buffalo, NY 14260-4200

[email protected]

http://www.cbe.buffalo.edu/alexandridis

Acknowledgements:

NSF, NIH, NCNR-NIST, Dow Chemical, Kao Corp.

SCM-EMP, October 22, 2010

Outline

self-assembly <—> bio/nanotechnology

bottom-up manufacturing: nm-micron length-scales

molecular engineering

block copolymer self-assembly fundamentals

novelty - opportunities & challenges

thermodynamics & structure

intermolecular forces

applications in formulations

solvents as degrees of freedom and processing aids

structure-property relationships

applications in nanoparticle synthesis

domains for metal nanoparticle synthesis and stabilization

nanoreactors for semiconductor nanoparticle synthesis

Self-Assembly of Surfactants

v: volume of the hydrophobic portion of the surfactant molecule

l: length of the hydrocarbon chain

ao: effective area per head group

o

sla

vN

Sphere

Ns=0.33

Cylinder

Ns=0.50

Planar bilayers

Ns=1

Inverted

sphere

Ns 1

Vesicles

Ns 1

head tail

surfactant

number

Polymers

random

copolymer

block

copolymer

homopolymer

micro-phase

separation:

organization in the nanoscale

Self-Assembly of Block Copolymers

ordered morphologies formed by self-assembly of block copolymers

(one-component system)

depend on volume fraction of the blocks of the copolymer

and on degree of segregation (χN)

domain size (~10 nm) related to polymer chain dimensions

a given block copolymer would attain a single ordered morphology

above the order-disorder transition

A-B Block Copolymer + A_Solvent + B_Solvent

• isothermal structural

polymorphism of PEO-PPO

block copolymer in the

presence of two immiscible

solvents selective for each

block

Alexandridis, P.; Olsson, U.; Lindman, B.

Macromolecules 1995, 28, 7700-7711.


J. Phys. Chem. 1996, 100, 280-288.


Langmuir 1997, 13, 23-34.


Langmuir 1998, 14, 2627-2638.

Svensson, B.; Alexandridis, P.; Olsson,

U. J. Phys. Chem. B. 1998, 102, 7541-

7548.

Amphiphilic Block Copolymers in Selective Solvents

Opportunities (almost) everything you can do with ―dry‖ block copolymers

(almost) everything you can do with surfactants

added degrees of freedom in product/process design

expanded phase space

extended structural length-scales

higher loading capacity (actives, particles)

local environment (gradient properties; partitioning; reactivity)

higher mobility (faster equilibration; easier processing)

structural transitions (faster trigger)

self-healing (around thermodynamic equilibrium state)

biomimetic (help connect synthetic to natural: cells, ECM)

several industrial applications involving solvents

Challenges need to establish the fundamentals

(too) many interactions to control/modulate

lack of robustness (more ―delicate‖ systems)

thermal stability

mechanical properties

polymer solvent

micelle formation, shape, dimensions, and composition tuned by solvents & solutes

Self-Assembly of Amphiphilic Polymers: Fundamentals

Micelles in solution and ordered (lyotropic liquid crystals) phase behavior and structure

thermodynamic origin of self-assembly

degree of block segregation

intermolecular and inter-micellar interactions

dynamics: polymer and solvent mobility

solvent location and self-assembled structure

solution/material properties affected by self-assembly

surface organization and interfacial interactions

Practical considerations thermodynamic vs. kinetic stability

processing and structure

multicomponent systems

natural polymers & surfactants

health and environment

cost (do more with less)

―Model‖ Amphiphilic Block Copolymers: Poloxamers

Poly(ethylene oxide)-poly(propylene oxide)

(PEO-PPO) block copolymers

MW = 2000 to 20000 (SDS has 12 bonds, Pluronic F127 about 800)

PEO is very flexible; whereas Pluronics are triblock copolymers, they can be

considered as diblocks for many purposes (cut the triblock in the middle)

Segregation between PEO and PPO not strong (PPO retains polar character)

LCST: PEO well-known to phase separate from water at high temperatures; the

same happens for PPO but at lower temperatures

PEO is crystalline up to 40-45 oC but

―melts‖ at lower T if some water is present

Nonionic

Commercially available as

Poloxamers or Pluronics

in a range of MWs and compositions

Block Copolymer + Selective Solvent = (Nano) Structure

Ordered structures formed by

diblock A-B copolymers of varying

block compositions (in the

absence of solvent)

H1

hexagonal

I1

micellar cubic

Lα

lamellar

V

bicon. cubic

PEO-PPO block copolymer

(P105) temperature-composition

phase behavior in the presence of

water (selective solvent for PEO)

Alexandridis, P.; Zhou, D.; Khan, A.

Langmuir 1996, 12, 2690-2700.

Alexandridis, P. Macromolecules 1998, 31,

6935-6942.

Thermodynamics of Ordered Solvated Block Copolymers

• self-consistent mean-field modeling

Svensson, M.; Alexandridis, P.; Linse, P.


Experimental data

(motivation)

Predicted phase diagram Segment vol. fractions

Scaling of spacing

MW

Intermolecular and

Inter-assembly Interactions

2

3

4

5

6

7

8

9

0 20 40 60 80 100

Osmotic pressure of Pluronic P105 gel

Lo

g1

0 P

ressure

(P

a)

P105 wt%

L1

I1

H1

La

H2

80

100

120

140

160

180

40 50 60 70 80 90 100

Lattice parameters of Pluronic block copolymer gels

La

ttic

e p

ara

me

ter,

d (

A)

Block copolymer (wt%)

P105

F127

Gu, Z.; Alexandridis, P. Macromolecules 2004, 37, 912-924.

6

6.5

7

7.5

8

8.5

9

40 60 80 100 120

Lo

g P

ressu

re (

Pa

)

Lattice separation, dw or d

h(A)

P105

F127

H2O/EO=0.67

H2O/EO=1.3

lp=16.6 A

lp=11.5 A

lh=1.1 A

lh=0.5 A

F127

P105

Osmotic stress is used to measure intermolecular forces in ordered assemblies formed by hydrated PEO-PPO block copolymers

The 16.6 Ǻ (11.5 Ǻ) decay length is comparable to the radius of gyration of the PEO block

Cryo-TEM

micrograph of 1 wt

% aqueous EO126-

B45 solution. Zheng, Y.; Won, Y.-Y.;

Bates, F. S.; Davis, H.

T.; Scriven, L. E.;

Talmon, Y. J. Phys.

Chem. B. 1999, 103,

10331-10334.

amphiphilic

polymer

solvent

intramolecular

&

supramolecular

local environment

compartments

long-range order

formulations

metal nanoparticles

semiconductor nanomaterials

Kazuhiro KAIZU Kao Corp.

Lin YANG Unilever

Self-Assembly of Amphiphilic Polymers: Applications

Yining LIN

E. ANTONIOU TU-Crete

Structure

Solvent

properties

Solvent

location

Solvent

effects

1. Phase behavior

2. Lattice parameter

3. Interfacial area

Principle: Structure Solvent

δ

LogP

Solubility parameter :

Octanol / water

partition coefficient :

Cosolvent (vol%) / (Cosolvent + Water) (Vol%)

Triacetin

Glycerol

Propylene carbonate

p-Xylene

ap(Interfacial area per one PEO block) Φint(Volume of interfacial region)

1

d (Lattice parameter) ~ ×

Alexandridis, P.; Ivanova, R.; Lindman, B. Langmuir 2000, 16(8), 3676-3689

Holmqvist, P.; Alexandridis, P.; Lindman, B. Langmuir 1997, 13(9), 2471-2479

Triacetin

Glycerol

Propylene

carbonate

p-Xylene

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60

Solvent Location and Lattice Parameters

Solvent Effects on Phase Behavior and Structure

Phase behavior

Lα

H1

I1

L1

Water Glycerol

P105

Lα

H1

I1

V1

L

Propylene

carbonate

Water

P105

Lα

H1

I1

V1

L1

L2

Triacetin Water

P105

Lα

H1

I1

L1

L2

I2

H2

V2

p-Xylene Water

P105

Solvent location

With decreasing solvent polarity, the solvent location changes from water-rich

domains, to PEO-PPO interface, to PPO-rich domains Kaizu, K.; Alexandridis, P., unpublished data.

Shear-induced Alignment and Orientation Transitions

• low-block copolymer content lamellar phases

Zipfel, J.; Berghausen, J.; Schmidt, G.; Lindner, P.; Alexandridis, P.; Richtering, W.


Lα

Lα

10-100 mm 10-100 nm

―Smart‖ Formulations

Ivanova, R.; Lindman, B.; Alexandridis, P. Langmuir 2000, 16, 3660-3675.

Ivanova, R.; Lindman, B.; Alexandridis, P. J. Colloid Interface Sci. 2002, 252, 226-235.

US Patent 6,503,955:

―Pourable liquid vehicles‖

gel

liquid dilution

Solution Structure & Properties Tuned by Solvents

nanostructure of ionic liquids

ionic liquids & molecular solvents (interactions)

nanostructure in ionic liquids (self-assembly)

applications of structured ionic liquid media

In Progress: Structuring in Ionic Liquids

thermodynamic origin of self-assembly

phase behavior and structure

mean-field modeling

intermolecular and inter-micellar interactions

degree of block segregation

dynamics: polymer and solvent mobility

location of solvent and self-assembled structure

solution/material properties affected by self-assembly

processing and structure


Fundamentals and Applications in Formulations

amphiphilic

polymer

solvent

intramolecular

&

supramolecular

local environment

compartments

long-range order

formulations

metal nanoparticles


Toshio SAKAI Shinsyu University


Single-step synthesis of gold nanoparticles using

PEO-PPO block copolymers

Mixing of aqueous metal salt solution and aqueous solution of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer (Pluronic® or Poloxamer) at ambient conditions

Metal salt

HAuCl4

2.0 mM

(0.2 ml)

Solvent: Water

Pluronic P105

5.0 mM

(2 ml)

0 min 5 min 10 min 20 min 120 min 60 min

Sakai, T.; Alexandridis, P. Langmuir 2004, 20, 8426.

―Preparation of Metallic Nanoparticles‖, US Patent 7,718,094.

Unique features of PEO-PPO block copolymer media for

metal nanoparticle synthesis

• PEO-PPO block copolymers act in tandem as reductants, colloidal

stabilizers, and morphogenic agents

• Much more effective than homopolymer PEO or PPO

• Minimum number of components: metal salt, block copolymer

(reductant/stabilizer) and solvent

• Single-step operation: simple mixing of aqueous metal salt solution and

aqueous PEO-PPO block copolymer solution

• Ambient reaction conditions: room temp. and air-saturated water

• No external energy input required

• Environmentally benign materials and conditions

• Commercially available polymers (Pluronic® or Poloxamer)

• Possibility of using various types of PEO-PPO block copolymers (MW,

PEO/PPO ratio, architecture, block sequence, CMC)

• PEO-PPO block copolymers self-assemble in solution and on surfaces

Relationship between particle size and reaction mechanism

• Metal ion reduction and the resulting size/shape of metal colloids can be

controlled by the amphiphilic character of PEO-PPO block copolymers

(PEO-promoted reduction and PPO-promoted adsorption on particles)

Nucleation (AuCl4

- reduction in the bulk solution)

AuCl4- reduction

to form Au0 Complexation of

AuCl4- with polymers

Seed formation

Polymer adsorption on seed

Complexation of AuCl4

- with polymers

AuCl4- reduction

on surface Particle

formation

Growth (AuCl4

- reduction on the particle surface)

Stabilization (AuCl4

- reduction completion and stabilization)

Growth Stabilization/no growth

• Higher PPO content

• Heating

• Less polar solvent

• Longer polymer

• Higher PPO content

• Longer polymer

• Longer PEO blocks • Smaller particles

• Larger particles

• Individual particles

• Aggregates

• Networks

Sakai, T.; Alexandridis, P.

J. Phys. Chem. B 2005, 109(16), 7766-7777.

Are lyotropic liquid crystal (LLC) structures required for

shape control of metal colloids?

– Au colloid synthesis using:

• EO100PO65EO100 (Pluronic F127)

– Higher metal ion reduction activity

– Micellar solution and heat-induced micellar cubic LLC

• EO13PO30EO13 (Pluronic L64)

– Lower metal ion reduction activity

– Micellar solution, hexagonal and lamellar LLC

– Au colloid synthesis in various phases, conc. and temperature

600 nm

6 μm

3D ordering of Au colloids in LLC media • Plates remain well dispersed in hexagonal and lamellar LLC

• Polyhedral particles well dispersed in micellar cubic LLC

• Thermoreversible formation of micellar cubic LLC containing Au colloids

Lamellar LLC (70 wt% L64)

Normal light Polarized light

at ~4 ˚C at ~50 ˚C

Micellar cubic LLC (20 wt% F127)

amphiphilic

polymer

solvent

intramolecular

&

supramolecular

local environment

compartments

long-range order

formulations

metal nanoparticles


G. N. KARANIKOLOS NCSR ―Demokritos‖

T. J. MOUNTZIARIS U-Mass Amherst


Reverse Micelles as Reactors for Nanoparticle Synthesis

Amphiphile (PEO-PPO block copolymer)

Polar Phase

(Formamide)

DEZn

in

Heptane

H2Se in H2

H2Se in H2

Gas Bubble

Diffusion

• synthesis of compound semiconductor

(ZnSe) nanocrystals (quantum dots)

size-dependent luminescence

broad excitation

narrow and symmetric emission

high brightness & sensitivity

high extinction coefficients

photochemical stability

Karanikolos, G. N.; Alexandridis, P.; Itskos, G.; Petrou, A.; Mountziaris, T. J. Langmuir 2004, 20, 550-553

5 nm HR-TEM images of

ZnSe nanocrystals

~6 nm diameter

formed by reacting

0.3 M diethyl-zinc

solution in 40 nm

heptane droplets

with H2Se gas.

Two-Phase

Region

Micellar (L1):

Spherical nanodroplets

Micellar Cubic (I1):

Spherical nanodomains

Hexagonal (H1):

Cylindrical nanodomains

under polarized light:

H1 I1 2-phase

Block Copolymer Templates for Nanoparticle Growth

Karanikolos, G. N.; Alexandridis, P.; Petrou, A.; Mountziaris, T. J. Nanotechnology 2005, 16 (10), 2372-2380

Stable Liquid Crystal Templates for Nanowire Synthesis

10

nm

10 nm

Stable Liquid Crystal Templates for Nanoplate Synthesis

Exposure

to H2Se

ZnSe thin layer formation

Xylene + PPO less polar domain

Water/Zinc Acetate + PEO polar domain


Lamellar Liquid Crystal

Exposure

to H2Se

ZnSe thin layer formation


Water/Zinc Acetate + PEO polar domain


Lamellar Liquid Crystal

Karanikolos, G. N.; Petrou, A.; Alexandridis, P.; Mountziaris, T. J. Nanotechnology 2006, 17, 3121-3128

Local block copolymer structure without and

with incorporation of nanoparticles at high

density:

(a) parent block copolymer

(b) parent block copolymer selectively swollen

with smaller nanoparticles at high density; the

diameter of the particles is much smaller than

the radius of gyration of the polymer leading to

a homogeneous particle distribution with little

effect on chain conformations

(c) parent block copolymer selectively swollen

with larger nanoparticles; the diameter of the

particles is of the order of the radius of gyration

of the chains, thus leading to significant

perturbations of the block chain conformations

which are energetically unfavorable

(d) at high particle fractions in order to lower the

chain conformational entropy the larger

particles segregate into a central core

Templated Growth Mechanism

nanoparticles & polymer chains (interactions)

nanoparticle effect on phase behavior & structure

applications of ABC-nanoparticle hybrids

In Progress: Nanoparticles in ABCs

one-pot and one-step synthesis of metal nanoparticles

PEO-PPO block copolymers as reducing, stabilizing and morphogenic agents

interplay between polymer localization and metal ion reduction activity

organized particle - polymer composites

self-assembled domains as nanoreactors

interplay between matrix dynamics and reaction kinetics

self-assembled templates for semiconductor nanostructures

interplay between polymer chains and growing nanoparticles


Applications in Nanomaterials Synthesis

10

nm

[email protected]

http://www.cbe.buffalo.edu/alexandridis

Thank you!

environment

energy

health


solvents

polymers particles

alternative solvents reactions, separations

nanomanufacturing hybrid materials

electrolytes polymers, nanoparticles

solubilization & dispersion

formulations pharmaceutics,

consumer products

benign synthesis of nanomaterials

drug delivery carriers, dissolution

biopolymers in solution, on surfaces

R

aqueous solvents interactions with

organics

Alexandridis lab

Solvated Block Copolymers: Degree of Block Segregation

The selective solvent swells the blocks of a given type and enhances

their segregation from the block of other type.

Evidence for intermediate-to-weak block segregation:

(i) chemical nature of PEO and PPO

(ii) random-coil-like scaling of lattice spacing with polymer MW

(iii) segment volume fraction profiles predicted from mean-field theory

(iv) ability to form many different phases at the same temperature by

varying the solvent ratio

(v) stability of bicontinuous cubic structures

(vi) reduction in the number and stability of ordered phases upon

decrease of the polymer MW in ternary isothermal systems,

reminiscent of the order-disorder transition observed in neat block

copolymers upon a decrease in c•N

Helmholtz free energy for multicomponent system

Internal energy arising from internal states

Mixing entropy

Interaction energy

)(ln)()( *

*

*

intint

* UUAAAA -

---

AB

ABi

ABB

ABii A

Aig

PUPnA ln

int

-

x cxc

xxc

xc

rnn

lnln

*

A A B B

iAiBABBABiAi

M

ii

PPLU' '

''''2

1fcf

internal energy and degeneration of the state

species volume fraction

nearest neighbors interaction parameter

xc

xc

ABi

BB

Ai

ABAB

n

P

gU

c

f

'

,

fraction of species A in state B

number of chains of component x in conformation c

degeneration of a conformation c of component x

The quantities marked with asterisk correspond to

the reference pure amorphous system

Lattice Mean-Field Theory for Self-Assembly Prediction Assumptions

space divided into lattice cells of equal size

flexible polymers

mean-field approximation in two dimensions

nearest neighbor interactions through c-parameters

Capabilities

multicomponent systems

multiblock copolymers

multibranched polymer architecture

computational efficiency

Micelle Dimensions and Composition Tuned by Solvent

• micelle association no.

Alexandridis, P.; Yang, L. Macromolecules 2000, 33, 5574-5587.

SANS experiments under conditions of variable solvent

contrast indicate that ethanol partitions in the micelle

while glycerol partitions in the aqueous phase

• micelle core radius • micelle radius

Drying and Swelling of Lyotropic Liquid Crystals

t = 0 t = t_intermediate t = t_final

h(t)

time

x

Water vapor (RH) Water vapor

Water vapor

Equilibrium properties Transport properties

e.g., intermolecular

interactions, water

activity, scaling

laws, etc.

e.g., drying or swelling of

polymers, polymer

dissolution, etc.

Ordered structures may

affect transport properties

Transport properties

(kinetics) may also affect

ordered structure

Self-assembled

or ordered

structure

Diffusion in Matrix vs. Evaporation from Surface

Self-Assembled Structure vs. Hydration Level

Gu & Alexandridis, Langmuir 2005, 21, 1454.

Drying: Self-Assembled Structure vs. Hydration

0

2

4

6

8

10

12

0 10 20 30 40 50 60 70

L64P105F127PEG4000PEG20000

Dry

ing

ra

te (

g/m

2.h

our)

Water content (wt%)

85% RH

PEO content

Drying rate decreases when PEO content

of the copolymer increases – interactions

between PEO and water stronger.

PEO content: L64 (40%) < P105 (50%) <

F127 (70%) < PEG4000 = PEG20000

0

2

4

6

8

10

12

0 20 40 60 80

L64

P105

F127

PEG4000

PEG20000

Dry

ing

rate

(g/m

2.h

our)

Corrected water content (wt%)

85% RH

When the drying rate is plotted against

―corrected water content‖ based on PEO,

the drying rates for different polymers

overlap, indicating that hydration level,

rather than the ordered structure, affects

primarily the drying rate.

Gu & Alexandridis, Langmuir 2005, 21, 1454.

1

10

100

10 20 30 40 50 60 70

Rela

tive v

iscosity

Temperature (°C)

8wt% P105

40wt% glucose

1wt% P105

40wt% glucose

8wt% P105

1wt% P105

Kaizu, K.; Alexandridis, P. unpublished data.

60 C

1wt% P105 1wt% P105

Plain water 40 wt% glucose in water

shape change

55 C

8wt% P105 8wt% P105

interactions

Solution viscosity increase

upon addition of glucose…

…coincides with micelle

shape change from sphere to

ellipsoid…

…and is attributed to the

dehydrating effect of glucose

on the micelle corona

Micelle Shape & Volume

Solution Viscosity

Metal ions Colloidal stabilization

PEO-PPO block copolymers

Metal ion reduction

Metal colloid formation

Size/shape control

Spherical Au

nanoparticles in

EO37PO58EO37 aqueous

solutions at ~25 ˚C

Sakai, T.; Alexandridis, P.

Langmuir 2005, 21(17), 8019-

8025.

Polyhedral Au particles

in EO37PO58EO37

formamide solutions at

~100 ˚C

Ag nanonetworks in

EO37PO58EO37 formamide

solutions at ~100 ˚C Sakai, T.; Alexandridis, P.

Chem. Mat. 2006, 18(10), 2577-

2583.

Au plates in


solutions at ~25 ˚C Sakai, T.; Alexandridis, P.

Nanotechnology 2005, 16(7),

S344-S353.

100 nm 100 nm

100 nm 100 nm

Spherical Ag

nanoparticles in

PO19EO33PO19

formamide solutions at

~100 ˚C

Au nanoparticles

remain dispersed for a

year in 5 mM


solutions at ~25 ˚C

PEO-PPO copolymers act in tandem as reducing, stabilizing and morphogenic agents

Amphiphilic Polymers for Metal Nanoparticle Synthesis

{111}

{100}

{111}

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