Aqueous bilayer dispersions, cast multilayer films, and langmuir-blodgett films of azobenzene-containing amphiphiles

Colloids and Surfaces, 19 (1986)225-236 Elsevier Science Publishers B.V., Amsterdam

-Printed

AQUEOUS

CAST

BILAYER

225

DISPERSIONS,

in The Netherlands

MULTILAYER

FILMS,

AND LANGMUIR*

BLODGETT

TOYOKI

FILMS

OF AZOBENZENE-CONTAINING

AMPHIPHILES

KUNITAKE

Department Kyushu

of Organic

University,

Faculty

Synthesis,

Fukuoka

of Engineering,

812, Japan

(Received 17 March1986;acceptedin final form 15 May 1986)

ABSTRACT Stable

molecular

(monolayer

spontaneously

formed

amphiphiles.

The component

membrane

is determined

state.

orientation

by the chemical

shifts

the tilted

is found

chromophore methylene

for the Cd-C6

membranes number

within

(water)

casting films

present.

Their

component

orientation,

dispersions.

spacer

shifts

and the physical

single-chain

orientation

blue

giving

ammonium

large

red

and the parallel

is found

for the Cl0

Stable

Contribution

0166-6622/86/$03.50

displays Deposition

gives

molecular

varies

in a way

and the cast

was presented

in Surfactant September

0

1985,

amphiphile

multilayers

and therefore,

to those

from these phase

the

amphiphiles.

behavior

similar

by the multilayers similar

of Organic

at Symposium Systems,

are

of the aqueous

in which

to those

in the

film.

No. 825 from Department

article

Meeting,

monolayer

technique

molecular

are formed

bilayer.

orientation

bilayer

Equilibria

characteristics

monolayers

surface

the azobenzene

regular

are similar

to that of the aqueous Langmuir-Blodgett

of the azobenzene-containing

in which

spectral

A two-component

This

the molecular

structure

methylene

giving

are

of synthetic

spacer.

transparent

aqueous

chromophore

orientation

Solvent

*

from a large

In the case of azobenzene-containing,

amphiphiles,

gives

and bilayer)

in water

Synthesis.

on Heterogeneous

American

Chicago.

1986 Elsevier Science Publishers B.V.

Chemical

Society

226 1.

Amphiphiles

That Form Molecular

We discuss

in this article

amphiphiles",

especially

dispersions, Aqueous

membranes

Their

"Bilayer-forming and synthetic biomembrane usually

and a phosphate moiety.

These

orientations

films

amphiphiles"

bilayers

comprise

acid chains

molecule

units

form bilayer

membranes

The subsequent

various

double-chain

presence group

Their

group

hilayer-forming however, such ways group

The phospholipid

molecule moiety

as the hydrophilic by the glycerol

CH3 N

(1)

ammonium

common

as to ensure

ammonium

upon dispersion

salts

connector

researchers

are suitable

groups.

in water

smooth

are the

of the

number

of

It is necessary,

alignment.

hydrophilic

(sulfonate,

head

The versatility

are attached

chain

that

for bilayer

that a large

can be designed. chains

salts

established

characteristics

indicating

with other

amphiphiles

is double-chain

These

(C,O - C20) and the ammonium

is remarkable, amphiphiles

(I).

by many

structural

chains

by proper

may be replaced

by Eq.

spontaneously

that the two alkyl

double-chain

of

as the hydrophobic

of phosphocholine

efforts

of two alkyl

combined

connector

analog

as illustrated

[1,21.

formation.

on one hand

component

dialkylammonium sall

synthetic

salts,

maintained

films.

amphiphilic.

Ctlj \*’

lecllhin

A simple

of oriented

lipids

are connected

becomes

simplify

ammonium

natural

like phosphocholine

two structural

unit and the whole

arrays

are in general

The major

is phospholipids.

derivative

in aqueous films.

and Lanqmuir-Blodqett

on the other.

two fatty

of "bilayer-forming ones,

are two-dimensional

cast

analogues

contains

of assembly

and in Langmuir-Blodgett

particular

in the corresponding

modes

azobenzene-containing

in cast films,

bilayer

molecules.

Membranes

to the connector The ammonium

units.

phosphate,

head

Anionic

carboxylate)

have

in

227 been

shown

to produce

polyoxyethylene)

bilayer

membranes

and zwitterionic

[3,4].

Nonionic

counterparts

also

(e.g.,

formed

bilayers

t51.

A second

class

amphiphiles. solution.

of bilayer-forming

Monoalkyl When

the surfactant

surfactants

aromatic

units

molecules

bilayer

combination

of the structural

assemblies

and surfactants

form

are single-chain

fluid

are introduced

become

can produce

materials

compounds

better

oriented

Figure

[6].

rise

in dilute segments,

in aggregates

1 illustrates

characteristics

gives

micelles as rigid

of liquid

and

how a crystalline

to bilayer-forming

amphiphiles.

Table

liquidcrystal

1. Membrane-forming

amphiphiles C,H,Q-N-CH-Q-OCII,

C,,H,N4(CH,),

Br-

type of

illustrative molecular

Ullphiphile

type of

stmctUr@ membrane

single chain o-c3_ ~

0 -

rigid 6-t alkyl chain hy&ophilic head

0 Figure

1. Design

bilayer-forming

More shown

to undergo tails

When

ammonium spontaneous

could

and cyclic)

heads

formation

by polymeric

Summarizing

Table

1.

these

with

monolayer

hydrocarbon

hydrocarbon

It is clear

formation

of bilayer are also

[7].

formation.

were

[8,9].

ends of appropriate dispersions

aggregates

become

or bilayer

[12-141.

form molecular

can be classified

that a large variety

groups

possible

which

chains

Furthermore,

and triple-chain

to both

monolayer

compounds

aembranes

for membrane

long alkyl

perfluorocarbon

stable

amphiphiles results,

and bilayer)

are available

hydrocarbon

kugevariety

double-chain,

Polymerization

[lO,ll].

three

are attached

molecules,

available

(monolayer

bilayer

be replaced

the hydrophilic

(linear

salts with

in the single-chain,

amphiphiles

polymeric

monolayer

amphiphiles

recently,

alkyl

m

of single-chain,

tail

{;'J:;:; hydrowrbon fluorocarbon monolayerhydroc;ubon

as shown

of synthetic

in

amphiphiles

228 2. Component

orientation

in Aqueous

Dispersions

of Molecular

Membranes. The rigid than

segment

one benzene

groups

which

segments systems

in Ficrure 1 is either

rinq)

have

been

or otherwise are aligned

physical

or multiple introduced

in the bilayer

2.

The aromatic

membranes These

assembly

(more

as rigid

P-electron

and produce

interesting

properties.

Table

The

groups

bonds.

in molecular

are criven in Table

and chemical

aromatic

hydrogen

2. Riqid

component(chromophore)

systematic

way by taking

azobenzene

chromophore

Aromatic

orientation

advantage

Segments

was investigated

of the spectral

in a

change

of the

[151.

CHI(C~~~O~~=NQ-~CH~~~~~*I1H,OH

Br&H,

Ci,AzoC,N+

Azobenzene-containing, form bilayer In the case length

assemblies

when

influential

Stable

and double-chain

chain

lengths

are not formed

stable

bilayers

length when

the tail

for bilayer

the tail

are formed

but not for the C5, C6 and C8 spacers.

amphiphiles

are long enough.

compounds(CnAzoCmN+),

than the spacer

bilayers

the case of the C8 tail, spacer

alkyl

of the single-chain

is more

formation.

single-chain

is C6.

In

for the C,O

If the tail

length

is C,O, the bilayer is formed for the spacer length of C5 to CIO, and if the tail length is C12, stable bilayers are obtained without regard

to the spacer

We examined length with

length

previously

and bilayer

formation

the diphenylazomethine

(C2 to CIO).

the relationship for a series rigid

segment

between

the alkyl

of ammonium

chain

amphiphiles

[61 : CnBB-N+

and CnBBCm~+

229

CH,(CH,k

&=CH@(CH&

Br-

C,BB-N+

n = 0,4,7,12

C,BB<:,N+

In these

stable

cases,

is C,2, and moderately

n = 0,4,7,12 m = 4,lO bilayers

stable

are formed

bilayers

of the C 7 tail and the C!,O spacer. C,), the bilayer

is not formed

present.

contrasting

A most

and BB-CYON+.

The former

but the latter

gives

(in electron

substitute

for the alkyl

The azobenzene spectra,

in amphiphiles

in Figure

these

amphiphiles

extensive

with

alkyl

length

chain

using

variation

longer

(spacer

An estimate

and tail)

alone

as

possess are

indicating

that

In contrast,

an

The change

should

[16].

the

variation

interaction

of Kasha

in the

not affect

interaction

of the chromophore model

absorption

spectra

the observed

of the chromophore

exciton

be a

for the identical

lengths.

Therefore,

in terms

the molecular

dispersed.

chain

cannot

chromophores

solvents

Similar

in water,

is observed

alkyl

characteristics.

to be explained aggregate.

and C~AZOC~N+

are molecularly

spectral

chromophore

spectral

show varied

Amax at 355 nm.

for C6AzoC2N+

spacer

azobenzene

that are Idissolved in organic

temperature-independent observed

Isolated

C,2BB-N+ bilayers,

formation.

(CnAzoCmN+) 2.

(C,(,) is

between

well-defined

The alkyl

in bilayer

(CO and

well-developed

without

microscopy). tail

a long spacer

gives

length

from combinations

is short

is observed

amphiphile

amphiphiles

as shown

even when

behavior

the tail

are formed

If the tail

large aggregates

structures

when

needs

in the was made by

The calculated

x

value varies from 300 nm to 430 nm, depending on the mutual max orientation and the aggregation number of the chromophore. The range

of the theoretical

estimate

covers

the experimental

Xmax

variation. Table

3 includes

the azobenzene correspond

a classification

interaction

and schematic

in bilayers

to four representative

(Amax at ca. 300 nm) is obtained

parallel

chromophore

C8AzoCJON+

bilayer

of

which

absorption

spectrum

orientation

illustrations

and micelles,

spectra. Type A for the aggregate with

(the so-called

(at T d: Tc) is a typical

H aggregate 1.

case.

Lamellar

The

aqueous

230 r

Figure 2. Absorption spectra of azobenzenecontaining bilayers

3%

x0

2%

Table

3. Schematic

bilayers

(nm)

representations

TYPE

A

TYPE

co. 300 "In

AmoX

of C6AzoC8N+

Type B spectra

assemblages

which

chromophore

interaction bilayers, as inferred

for ground-state

shift

dispersed

(relative

of the bilayer

interaction (Amax 360-390

by the head-to-tail

(tilted)

to

( Xmax 355 nm) are observed : amphiphiles

and azobenzene

Micelles

as in Types

in

amphiphiles

are apparently

too fluid

A, B and D to be possible. interesting.

chromophore)

orientation

appears

of double-chain,

nm) are most

to the isolated

The

state. in these

chromophores

azobenzenes,

matrix.

of the same

of the interaction

C spectra

azobenzene

micellar

in the bilayer

Type D spectra

spectra

not be extensive

from the spectra Type

D 360-390 run

.crystolllne btlwer

give

for most

and the extent

amphiphiles.

solvents,

isolated

would

A maX

l-like owegate

.mlcelle

and C~AZOC,~N+

are observed

less-ordered

for molecularly

AIFCX

are in the liquid-crystalline

be dimeric,

organic

TYPE

C 355 nm

monomeric

'~H~~~~,"'"'""'"

.crvstolllne bllaver

dispersions

TYPE

B

330-340 nm

dimer-like interaction

H-aggregate

azobenzene

of azobenzene-containing

(CmAzoCnN+)

h maX

type.

Eil

400

Wavelength

The red

is apparently

of the chromophore

produced (the

231 so-called

J aggregate). Amax shifts

Delicate

the crystalline orientation required

which

is observed

to Cc);

controlled

Aqueous

in the crystalline

(C, and CIO)

shift

These

effects.

results

in the rigid the spacer

of Aqueous

molecular

of the intermediate

chain

Molecular

membranes

establish

bilayer

spacers.

length

The tail

for the C5 spacer.

are

of the

The blue

(C,) and long

for spacers

in

bilayer

The direction

variation.

for the short

by varying

the following

only

length.

interaction

3. Cast Films

occur

by the spacer

is found

smaller

chromophore

bilayer

of the chromophore

mainly

the largest

produces

only

spectral

is determined

The red shift

changes

are possible

for the unusual

xmax shift shift

for the azobenzene Subtle

phase.

(C3

length

that the

system

can be

length.

Membranes

can be immobilized

in solid

forms by

techniques.

(a) blending

with

hydrophobic

polymers

such as poly(viny1

chloride) (b) coating (c) direct

of porous casting

(d) as composites

polymer

on solid with

films

and capsules.

supports.

hydrophilic

polymers

such as poly(viny1

alcohol). (e) formation

of polyion

complexes

with

oppositely-charged

polymers. (f) build-up

of multilayers

The formation aqueous

bilayer

Nakashima,

by the Langmuir-Blodgett

of transparent dispersions

Ando and Kunitake

structure

and by spectral this

Subsequently, hydrocarbon bilayers

changes

technique

was

first

ammonium

by the phase

of bound

was applied

and fluorocarbon

chains

from

amphiphiles

to other

transparent

films

aqueous

similarity

The macroscopic established

amphiphiles,

films

are essentially

corresponding structural

cast

[151.

dyes. amphiphiles

of

and to polymerized

identical

dispersions between

ordering

CnAzoCmN+,

Absorption with

those

similarly

spectra

of the

of the

(Fig. 2), indicating

the

the two systems.

of bilayers

in the case of CSA~OC,~N+

in the cast [Zl].

by

of the bilayer

transition

cyanine

[18,19]

reported

[201.

The azobenzene-containing

cast

films

The maintenance

[17].

in the film was confirmed

behavior

produce

cast

of double-chain

technique.

film was

In the absorption

232

spectrum,

there

attributed

are two peaks

to absorptions

and short molecular nm peak from

increases

axes, when

respectively.

(edge view)

In fact,

gives

The

to the eighth diffraction

order

shown

the film plane regular

although

in Figure

the long spacing

their

relative

that the is perpendicular

3.

to

section

The film was

diffraction

is seen up

of 3.90 nm, but

produced

molecular

is changed

of the cross

Equatorial

are

the long

of the 300 -

light

indicates

diffraction

position.

with

through

Therefore,

film plane,

X-ray

along

intensity

of the incident

dependence

the pattern

in the vertical

rings.

moment

of the long axis of the chromophore

the film surface.

placed

the transition

the angle

90" to 50". The angular

orientation

at 300 nm and at ca. 250 nm which

with

diffuse

layers

exist

arrangements

Debye-Scherrer

parallel

to the

in the film plane

are disordered. 3.90(n=1 ) 1.96(n=Z) 131

(n-3) 0.99Cn.4)

0.49(n=8)

0.5N-l=7) 0661nz6) 0.79(n=5)

Figure 3. X-ray diffraction pattern of a cast plausible model of the molecular packing A plausible

structure

the diffraction

of the molecular

pattern

as shown

chromophore

is normal

is adjacent

to the neighboring

The vertical

30 O. with

micelle

film

3.

from

The azobenzene and the alkyl

methylene

and is tilted

of the chromophore

tail by

is consistent

data. at this

is obtainable

point

to speculate

by simple

why the ordered The critical

casting.

concentration

low: usually should

spacer

arrangement

It is interesting

layer was determined

(i 10") to the film plane,

the spectroscopic

molecular

in Figure

film and a

lower

of these bilayer-forming amphiphiles is very -sM surface monolayers than 10 . Therefore,

be spontaneously

dispersions

are placed

from the surface, solvent bilayers)

removal

formed on solid

drops

supports.

as the solution

produces

parallel

when

molecular

of aqueous

is concentrated. multilayers

to the film plane.

bilayer

Multilayers

will

Complete

(immobilized

grow

233 4. Langmuir-Blodgett Many

Films

of the bilayer-f-orming

at the air-water

interface.

and azobenzene-containing surface

The miscibility

U21.

has been

examined

in their

of these

by spectral

absorb

at 300 - 330 nm while

absorb

at 355 nm I231.

monolayers

form stable

Double-chain single-chain

as seen

monolayers,

amphiphiles

amphiphiles,

amphiphiles isotherms

the monomeric spectra

azobenzene

species,

depending

on the molar

pressure.

Figure

5 summarizes

the phase

determined the cluster

formation

ratio.

(phase

of mixed

of clustered

At low pressures,

by the molar

as aqueous

Higher

4

bilayers

clusters

azobenzene

the presence

monolayer.

in Figure

: azobenzene

indicate

surface

2C,N+ZC,,

form mixed

given

two components

variations

Absorption

monolayers

species surface

OK monomeric

ratio

and the surface

behavior

cluster

of the mixed

formation

surface

is

pressures

promote

separation).

60

2

j

hC6AzoC,0N+

Figure

4.

T-A

isotherm.

Contents

of C6AzoC10N+ a. 5 mol%,

50 Mean area per molecule

1

100

are

b. 10 mol%,

c. 20 mol%,

d. 30 mol%,

e. 40 mol%,

f. 50 mo18,

q. 60 mol%,

h. 70 mol%,

i. 80 mol%,

and

j. 90 mol%.

(A')

Collapsed

monolayer

Complelely

immiscible

I

Condensed

phase

Figure 5. Phase diagram of twocomponent monolayers

Expanded

phase

Composition

u

9

234

Aqueous formation bilayer

bilayer with

characteristics

are maintained extended isotherms

in the polyion

in the subphase. are unstable

stabilized repeated

on aqueous

deposition.

photoelectron complexes

obtained

phase

complexes films

those

spectra

incident

light

bilayer.

maxima

aqueous between

for

films by

results

of 1:l are

of a

bilayer.

the

The

the direction

the same

anisotropy

dipole

is smaller

to the film plane,

These

identical

However,

to the transition

chromophore

are almost

identical

In the case of

the two forms.

is attributed

film of CSAZOC,~N'.

than that of

while

in the aqueous

is observed

data were

in the

explained

of the long axis of the azobenzene

is perpendicular

similar

enough

(305 and 250 nm) are almost

spectroscopic

anisotropy

they are

are not necessarily

and the LB films.

is perpendicular

chromophore

by

of

the formation

Similar

in the LB film when

fact that the orientation chromophore

shows

(peak position)

are different

azobenzene

are affected

monolayers

of the built-up

of KBr.

is

amphiphiles.

of the two peaks

cast bilayer

technique

due to dissolution,

(ESCA)

of CnAzoCmN+

LB film

Analogous

while

poly(vinylsulfonate)

at 305 nm which

absorbances

monolayers

analysis

of the corresponding

(short axis)

This

etc.,)

Pressure-area

potassium

of the long axis of the azobenzene at 250 nm

separation,

Elemental

dispersions

absorption

shapes

absorption

surface

by ion-pair

The fundamental

formed.

[25,26].

For example,

and the absence

polyion-complexed

spectral

transition,

spectroscopy

the aqueous

CSAzoCION+,

with

[24].

on pure water

for fluorocarbon

Absorption between

(phase

water-insoluble

polymers

of positively-charged

CnAzoCmN+

polyion

become

to Langmuir-Blodgett

polyanions

X-ray

dispersions

oppositely-charged

to the film plane.

in the LB film possesses

to that of the cast

film.

Thus,

the

macroscopic

by the

235

On the other C12AzoC5N+

of the aqueous tilting models

little

hand,

This

bilayer.

of the chromophore of these

spectral

The spectrum

LB film.

LB films

anisotropy

is virtually

is consistent

in the bilayer are shown

is observed identical

with

that

considerable

assembly.

in Figure

in the

with

Probable

6.

5. Conclusion It is clear

from the preceding

of the azobenzene bilayer

large variety method

cast

large

is closely

multilayers

numbers

that the organization

related

among

aqueous

and Langmuir-Blodgett

films,

of molecular

by using

already

chromophore

dispersions,

discussion

films.

can be produced

of bilayer-forming

A

by either

compounds

that are

available.

6. References 1

T. Kunitake

and Y. Okahata,

2

T. Kunitake,

Y. Okahata,

F. Kumamaru,

Chem.

J. Am. Chem.

SOC., 99

(1977)

3860.

3

T. Kunitake

K. Tamaki,

Lett.,

(1977),

and Y. Okahata,

M. Takayanagi

and

387.

Bull.

Chem.

Sot. Jpn.,

51 (1978)

1877. 4

R. A. Mortara, Biophys.

Res.

5

Y. Okahata,

6

T. Kunitake

Colloid

R. H. Quina Commun.,

81 (1978)

Sci.,

(1981)

82

and Y. Okahata,

Biochem.

1080.

M. Nagai

S. Tanamachi,

Interface

and H, Chaimovich,

and T. Kunitake,

J.

401.

J. Am. Chem.

Sot.,

102

(1980)

549. 7

N. Kimizuka,

T. Kunitake, Chem.

8

T. Kunitake,

9

T. Kunitake

10

Y. Okahata

104

106

Sot.,

(1982)

(1984)

Y. Okahata

N. Higashi

and N. Nakashima,

J. Am.

1978. and S. Yasunami,

J. Am. Chem.

Sot.,

5547. and N. Higashi,

J. Am. Chem.

Sot.,

107

(1985)

and T. Kunitake,

J. Am. Chem.

Sot.,

101

(1979)

692.

5231. 11

E. Baumgartner

and J. H. Fuhrhop,

Angew,

Chem.,

92 (1980)

564. 12

T. Kunitake,

13

J. H. Fendler

14

A. Akimoto, Angew,

Chem.

et al.,

J. Am. Chem.

and P. Tundo,

K. Dorn,

Act.

L. Gros,

Int. Ed. Engl.,

SOC., Chem.

103 Res.,

H. Ringsdorf 20 (1981)

(1981)

90.

5945.

17 (1984)

3.

and H. Schupp,

236 15

M.

Shimomura,

Chem., 16

M. Kasha Bartolo

17

R. Ando and T. Kunitake,

87 (1983)

in "Spectroscopy ed., Plenum

N. Nakashima,

Rer. Bunsenges.

Phys.

1134. of Excited

Press,

States",

New York,

p. 331, B. D.

1976.

R. Ando and T. Kunitake,

Chem.

Lett.,

(1983)

1517. 18 19

M. Shimomura T. Kunitake,

and T. Kunitake, N. Higashi

Polym.

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