Spectroscopic studies of carbons. XIX. The charring of sucrose

Materials

Chemistry

and Physics,

26 (1990)

465-481

SPECTROSCOPIC STUDIESOF CARBONS. XIX.

NING WANG and M.J.D.

465

THE CRARRING OF SUCROSE.

LOW

Department of Chemistry, New York University, New York, NY 10003

Received

June 25, 7990;

accepted

September

(U.S.A.)

5. 1990.

ABSTRACT Series in

of

vacuum at

infrared successively

spectra were recorded increasing

of chars produced

temperatures,

by heating

sucrose

up to 750°C. Photothermal

beam

deflection spectroscopy was used. Some of the aliphatic components of the sucrose melt aromatize at a temperature as low as 200°C; the structures of the sugars are lost entirely in the 3OO-350°C region, and a variety of carbonylic structures are formed.

The chars then change contin~usly in composition as the pyrolysis

temperature is raised. The initially aliphatic mixture is progressively converted into a predominantly aromatic material, dehydroxylation proceeds, aliphatic groups are eliminated and/or converted into aromatic material, and the carbonylic species decrease. Also, the aromatics polymerize to form larger, polyaromatic structures. These trends continue until about 600°C. Above 600°C there is an abrupt increase in the polyaromatization,and a further decrease in functional groups. All IR-active groups are removed when 75O*C is reached. INTRODUCTIffl Sugars have frequently been used as precursors of chars and activated carbons in laboratory studies; this is, as pointed out by Mattsen and Mark Cl], a thread of consistency running through studies of carbons for many decades. However, the large amount of work that has been done with sugar carbons includes but few infrared (IR) spectroscopic studies, and the sparse IR data that are extant are relatively poor because of the high opacity of the carbons CZ-67.

The best data

so far are those of Zawadzki C6; see also 71. He examined the pyrolysis at 300, 400, 500 and 600°C of sucrose deposited on silicon, quartz and silica surfaces.

0 Elsevier Sequo~a/~inted

in The Nethedands

466

Unfortunately,the strong absorptions of the supports obscured the spectra in the important 900-700 cm-l region where the aromatic C-H deformations fall. Conseq~ntly, in order to supple~nt the existing info~tion

concerning the

functional groups carried by the chars, we have recorded IR spectra of sucrose chars produced at various temperatures, and describe some results.

IR Fourier transform photothermal beam deflection spectroscopy (PSDS) was used to record the spectra at 8 cm"

resolution using 2000 scans; the method and

various techniques have been described elsewhere [7-lo]. The pyrolysis procedure Involved heating a sample of sucrose (SUGZO, pure, edible sugar, zero ash) in an evacuated quartz tube to a p~dete~ined temperature, T, to within 5OC, degassing at T°C for 2 hrs in a dynamic vacuum of 10m4 torr, and then cooling to room temperature in vacua. The sample was then exposed to the ambient atmosphere, ground in order to increase the photothermal signal, and a spectrum was recorded (no significant spectral changes were observed until a sample had been heated in air or oxygen to tem~ratu~s

in

excess of 300°C). Such a sample is identified by appending the pyrolysis temperature to the material code, e.g., SUG400 was obtained at 400°C. The sample codes are also used to identify the single-beam spectra, S, as well as computed pseudo double-beam spectra S/S, , produced from the reference spectrum, So, of Pt black or a reference high-tem~rature carbon. Qiffe~ntial spectra Si/Sj, ware also computed. The

abscissae of the Figures are in cm"

units.

RESULTS AND DISCUSSION Over-all aspects Figure

J

shows

a

series of spectra which

is

useful in gaining an overview of

vihathappens when sucrose is progressively heated from room temperature to 750°C. The band assignments of the spectrum A of the starting material, SUG20, have been amply described and need not be taken up again [ll-161. It is interesting to note that, even after a relatively mild heating, the spectrum looses detail: the sharp band of isolated hydroxyls at 3568 cm-l found with SUGZO disappears with SUGZOO, and other sharp bands in the 1700-800 cm"

region lose their definition, possibly

because of a decrease of structural order [12] and the formation of smaller sugars, so that bands overlap. Also, an absorption appears in the 1750-1150 cm-' range, the first sign of thermal decomposition. At a slightly higher temperature (C, Fig. 1), well defined bands appear at 1710 and 1607 cm-l. In this lower temperature range, of interest to the confectioner, the sucrose is split into Dglucose and D-fructosan, and 'caramelitation'begins [17]; the envelope in the

467

Fig. 1.

1500-1000 remained interest assumes

cm-l region intact.

to the failed that which

simpler

changes only slightly,

This trend continues

higher temperatures become

normalized spectra.

Compensated,

confectioner.

is retained

indicating

over the next Then, above

less intense

perhaps

300°C, the profile

more or less over the 350-500°C

(L-N, Fig. 1) the profile again

and all features

that most of the sugars

100°C range,

changes

of

changes and

range.

At the

and the spectra

until they disappear

above 725OC.

468

SUG30C

Fig. 2. The fingerprint

range.

At 350°C the pyrolyzate like those of other region,

will therefore

600°C range,

sequence

be neglected

functional

of functional

of Fig. 1 follow.

is much

of sugars and some decomposition

and emphasis

groups

groups decline

which can be discerned

of a char and its spectrum

chars or coals [18]. The louer temperature

is a mixture

in which the spectra exhibit

of numerous

the number details

low-temperature

where the pyrolyzate

products,

presence

has the appearance

placed on the roughly

continuous

changes

350-

but show the

, and the roughly 600-750°C range, in which severely.

on scanning

Some over-all

and on detailed

trends and

examination

of the

469

Fig. 3. Differential

The fingerprint Figure

spectra

range.

range

2 shows the fingerprint

chars. There are three major A pair of bands peaking heating

of the fingerprint

range of several

changes

near

prominent.

deformations

temperature

increases

both bands

(D-F, Fig. 1) but then the band near 1600 cm-l becomes

At the higher temperatures

An absorption

spectra of some

are destroyed.

1709 and 1603 form (they appear even after

at 200°C (B, Fig. 1)). As the pyrolysis

grow in intensity

representative

when the sugar moieties

appears

occur

both bands decline

(J-N, Fig. 1).

at 791 cm-l in the region where aromatic

[ll, 19-Z];

the absorption

the more

CH out-of-plane

grows and forms a trio at higher

temperatures. A complex

absorption

well developed

maximum

higher temperatures. assignment

as the aromatic

cm-l region with a reasonably

at 1439 cm-l; the latter becomes

These absorptions

is based on group frequencies

that the 1500-1300

decreases.

forms over the 1500-1300

cm-' absorption

C-H deformation

are assigned

less distinct

to C-H deformation

at the modes.

The

[ll, 19-221 as well as the observation

is related

to those of the aromatic

bands grow, the 1500-1300

It thus seems likely that the 1500-1300

cm"

C-H bands:

absorption

cm-l bands and particularly

G -

SUG650

SUGGOO

SUG550

Fig. 4. The O-H and C-H stretching

the 1439 cm-l band are mainly, aliphatic

range.

a?though

probably

not entirely,

The 1500-1300 absorption

cm-l absorption

in the 1300-1100

is overlapped

by another

would contain

deformations,

and other

ether-like

aromatic

in-plane

complex;

with cellulose

CO linkages

C-H deformattons [23, 241

of the absorptions

[ll.

19-221.

a similar

of species

not, on the basis of isotopic

i-251; a discussion

absorptions

single-bond

of discrete

maxima

due to OH

CO species,

and

The 1262 cm-l band, however,

is

band was found to be due to the

which contained

oxygen and those

that did

substitution.

The band near 1600 cm-l is the mystery controversy

broad, complex

cm-l range; there are indications

near 1262 and 1186 cm-l. This region

summation

due to the

C-H system.

band about

is given elsewhere

which there has been so much

126J. A probable

explanation

is

471

that the band is due to a normally presence

of ring substitution

[23]. However,

These various temperature, relative

[26]. See, however,

it is a multiple

absorptions

appear

the discussion

absorption,

and remain

but do not remain at constant

band intensities

Effectively,

ring mode made active

near 1709 cm-l can be in part attributed

The band peaking carbonyl

forbidden

carbonyl

at the higher and medium

described

below.

changes

in

spectra of Fig. 3.

at the lower temperatures

temperatures

further

the highest

The complex

are shown by the differential

bands decline

below.

to a ketonic

up to almost

intensities.

by the

there is a continuous

(B, C, Fig. 3), but decline

in most

absorptions. The OH stretching

regions

The scale-expanded band of H-bonded

hydroxyls

SUG350 but retains contour

of Fig. 4

with progressively

the same rounded

is replaced

contour.

with a tooth-shaped

so that the absorptions

higher wavenumbers, the band maximum

show the gradual increasing

near 3346 cm -' with SUG20, is shifted

The band maximum,

has decreased

segments

has increased.

change of the broad

pyrolysis

temperature.

to near 3400 cm-' with

Then, on going to 400°C, the rounded

one, i.e., the extent of the H-bonding of unassociated

hydroxyls,

This trend continues

which absorb

as the temperature

at

rises;

3559 cm-' at 600°C, and near 650°C the solid is

shifts to about

dehydroxylated.

The CH stretching

region

As shown in Fig 4, the aliphatic region

change

progressively,

650°C are reached.

There is, however,

Fig. 4) which is accompanied

initial

and CH,

groups

decomposition

(SUG300,

a 'temporary'

can be attributed

reached

but then declines

The aromatic

CH deformation

The deformation stronger

of additional the

at 3044 cm-' (A, Fig. 4). of aromatic

C-H groups

C-H deformation

band

(C, Fig. 1) but also

progressively

until 600°C is

in intensity.

region

modes of the aromatic

than the corresponding

700 cm-l region

of the

rings formed during

with the 250°C material

at 200°C (B, Fig. 1). The band increases sharply

near 400°C (A-C,

791 cm-l aromatic

present

cm-l

gone when

intensity

to the formation

of furane

to the stretchings

band of the

Fig. 2) plainly observable

increase

in the over-all

steps. Also, a band appears

is the companion

bands in the 2900-2700

450°C, and are largely

by the destruction

The 3044 cm-l band, attributable [ll, 19-221,

above

by an increase

broad O-H band. These changes hydroxyls

CH, stretching

decrease

C-H groups of chars are always

stretching

modes

is more useful than the stretching

much

[18, 23, 241, so that the 900region in observing

the

472

SUG 760

SUG725

SUG660

SUGBOO

SUGISO SUGSOO

SUGIM) SUG4UO SUGSSO SUGSOO SUGZSO SUG200 SUGPO

960

800

700 cm-’

Fig. 5. The aromatic aromatic

C-H deformation

range.

C-H bands, as shown in Fig. 5. The initially

absorption

acquires

well resolved

a shoulder

and a companion

bands characteristic

drift progressively

to higher

individual

band at 350°C, and then a trio of

of most chars appears.

wavenumbers

791 cm"

The bands' frequencies

as the temperature

is increased.

At

450°C, the bands are at 876, 814 and 752 cm-', while at 650°C they are at 880, 817 and 756 cm-l, for example. then decline intensities

abruptly

above

The band intensities

650°C. The number,

of these bands are characteristic

increase

frequencies,

progressively,

but

and relative

of the substitution

of the aromatic

473

rings

[ll,

19-221.

Apparently,

ring substitution

as the pyrolysis

The growth of the C-H wagging decline

of the aliphatic

eliminated

and/or

the material

converted

bands.

to aromatic

Effectively,

band accompanies

the aliphatic

species and, as the pyrolysis

from one which was entirely

aliphatic

As mentioned,

the absorption

of overlapping

obvious

shoulders

bands.

peaking

is

proceeds,

to one which is

still present,

at 1709 cm-l is not a single one but a

With the higher temperature

on the high wavenumber

Fig. 6. With the lower temperature

chars there are some

side of the band, as shown in Part A of

chars the shoulders

are much less obvious

as in Parts A, B and C of Fig. 6. Shown also is the inverse

second derivative

(the derivative

band positions.

band intensities,

multiplied

As the pyrolysis

some changes

seven) absorptions

proceeds

within the envelope

there are changes

22) aldehydic

and ketonic

carbonyls,

The region

of the 1709 cm-I absorption

and deformations

might

be found,

to be made without

will be avoided the complexity

but it is not certain

below about

of the chars,

resolved

undue speculation

in the interest

of brevity.

is unfortunate

in relative of the

with the [ll, 19-

what specific

1400 cm-l, where confirming

is not clearly

of the

to be five (and possibly

400°C char but only three with the 600°C char. All these are obviously

each represents.

but

and some

and a simplification

there appear

&,

-1d2,

by -l), marked

in band positions,

at the higher temperatures,

assignments

the

material

region

complex

spectrum

and type of

aromatic.

The carbonyl

estimated

the extent

bands and of the stretching

stretching

is converted

predominantly

proceeded,

changed.

enough

and lengthy

to permit

polemics.

This lack of assignments, but not detrimental

group(s)

stretchings

The

latter

in view of

to the present

purpose. Another

complexity

involves

cm -' over the 350-500°C temperatures. appears

&

range and then shifts to near

The derivatives

to be a minor

1600 and near

'the 1600 cm-' band.'

suggest

band near

ClaSSiC

two

bands

or intermediate mainly

at 1614

group frequencies

and

temperatures,

aromatic

molecules

highest

temperature

1589

the composite

of such

bands

modes.

there

absorbing

near

by Painter &

concentrates, matches

the

Thus, at the lower

1600 cm-l band can be attributed observed

the pyrolysis.

however,

bands

of vitrinite

ring stretching

modes normally

formed during chars,

cm- '. A pair

1603

1590 cm-I at higher

to that described

the 1600cm- 1 band

for aromatic

to the ring stretching

is similar

peaks near

up of three bands:

1650 cm-l, and two major

1580 cm-I. The situation

[27] who, on curve resolving

obtained

that it is made

Its envelope

with small substituted

The bands observed

are attributed

to induced

with the

ring modes

which

20’00

Is’00

16’00

2000

1800

1600

(A)

I

(B) Fig. 6A-0. The carbonyl

range.

475

20’00

20’00

7mp 1800

1 8@00

I 1600

16’00

476

CARBON BLACK

SUC725

SUG.550 SUGSOO SUG450 SUG400 SUG350 SUG300 SUG250 SUGZOO WC20

Fig.

7. Single-beam

are induced clusters,

spectra

by the presence

as discussed

(not compensated of peripheral

in detail

elsewhere

or normalized).

substituents

on the large polyaromatic

C261.

The IR continuum The compensated

spectra of Fig. 1 hide interesting

about the chars: their spectrum &,

'blackness';

of Fig. 7 is the uncorrected

of a 'flat black' absorber.

'instrument

function'

of the spectrometer's

1400-1300

cm-l region were caused

single-beam

The over-all

but is mainly

properties

that is better

and important

show

information

in Fig. 7. The top

spectrum

of a carbon

shape of the spectrum

black,

reflects

the

caused by the transmission/reflection

beamsplitter

(the two negative

by beamsplitter

contamination).

bands in the The intensity

477

of the spectrum of the carbon comparing

is a measure

[28-301.

The intensity

the absorptions

component,

of the IR continuum,

of the vibrational

of the higher-temperature

summation

of the vibrational

and there

in spectra intensity

the entire

absorption

J and L (Fig. 7). There

range

superimposed

materials

A of Fig. 7.

of the spectra

but are slightly spectrum

positive,

is then the

on the IR continuum. spectrum

shifts away from the

as shown, for example,

is a gradual

range

by

flat; the spectrum

The baselines

The over-all

temperatures.

is significant

over the 300-450°C

over the 450-600°C

components.

component

With the higher temperature abscissa

can be estimated

by the arrow in spectrum

chars are not flat, however,

and become more so at the highest

absorption

where there is little or no vibrational

of Fig. 7 is essentially

The base of the SUGEO spectrum shows the summation

of the IR continuum

in some regions

2200 cm-I, as indicated

e.g., near

i.e., the electronic

increase

in the continuum

(D-G, Fig. 7), a somewhat

(G-K, Fig.7), and a drastic

by the arrows

greater

increase

increase

in going from 600°C

to 650°C (K, L, Fig. 7). The spectrum

M of the 725OC char (Fig. 7) resembles

high-temperature continuum

carbon

intensity,

standard.

In contrast,

the vibrational

component

of polyaromatization occurred

[28-301.

to a relatively

over the 450-600°C

shows a gradual decline

(Fig. 1) almost

all traces

(K-O, Fig. of the

have disappeared.

of the IR continuum

The intensity

N of the

while there is a jump in the

component

1; E-G, Fig. 4). After the 725'C pyrolysis vibrational

the spectrum

can be taken as rough measure

As is apparent

small extent

range,

from Fig. 7, polyaromatization

in the 300-450°C

but then increased

of the extent

range,

drastically

above

increased

somewhat

600°C.

The 1350 cm-' band The complicated the differential carbonylic

changes spectra

species absorbing

and the bands'

intensities

When the 600-700°C

in the 1800-1600

decrease

The spectra

become

progressively

the highest

temperatures,

The

become fewer in number, is raised.

only a broadish

1600 cm-l

cm-l range, and the C-H wagging

simpler as species

the spectra

bands.

as the temperature

there remains

in the 1500-1000

is raised are shown by

'negative'

cm-' region

continuously

region is reached,

band, a broad absorption

profile'

which occur as the temperature

of Fig. 3. These show mainly

assume

are eliminated.

what has been called

bands.

Finally,

at

'the standard

[29].

The standard 800 cm-l region are similar.

profile

refers to the over-all

where spectra

As there

appearance

of a large variety

is little

contribution

or profile

of medium-temperature

to the absorptions

in the 1800carbons

in that range by

478

SUG

I

2000

i

1500

1000

Fig. 8. The standard profile.

aliphatic

groups and/or

eliminated

it has been suggested

are predominantly

arguments

centered

range, as has been

[29]. Also,

in Fig. 1, and is show

of the 550°C and 600°C chars

explanation

of the absorption

as absorptions

spectra of cornminuted graphite

observed

occurs

becomes

to note that the described

in the temperature

[24]. Such

in Fig. 8.

with the 650°C

A tentative

and not

near 1350 cm-' is that it has in Raman and IR

carbon films, i.e.,

so that

the

cm-l region of the spectra

near 1355 or 1360 cm"

rules,

an Alg mode of the lattice

of the IR continuum

centered

system;

that an additional

more clearly

1450-1200

and hydrogenated

due to a breakdovrn of the selection

It is pertinent

up the standard

temperatures

of Fig. 8 which then disappears

char, much as if a band had grown in in that region.

is attained,

it appears

near 1350 cm-l grew in at the highest

is also observable

the same origin

making

due to the ring modes of the polyaromatic

Note that there is a 'dip' in the roughly

unreasonable

because they have been

that the absorptions

are given in detail elsewhere

absorption a change

fragments

in chars heated to about the 600-650°C

demonstrated, profile

oxygen-containing

when a certain

that it is crystal

size

active.

change

in the spectra of Fig. 8

range where there is a rapid increase

in the intensity

(K-L, Fig. 7). As the latter can be taken as measure

of the

479

size of the polyaromatic the increase

THE SUCROSE

changes

in the spectra

three temperature

suggested

lends support

The first

indicate

that the sucrose decomposition

The changes

ranges.

up to about

range,

and the mechanisms

interesting

300°C, produced

of sugars

to note, however,

The second

range,

disruption

of the structures

beginning

contaminated

300°C, initially

which are

range change continuously in the 600-650°C is converted

in nature.

As the pyrolysis

the decomposition

eliminated

and/or

of functional

is thought

substituted

into the aromatic

PAH-like

clusters

groups

aromatic

bridges.

are eliminated

absorption

begin to resemble functional

These groups

increase

as the temperature vibrational

induced

It

be linked by separating

and the PAH-like

clusters

which give rise to the greatly

have no (or extremely

elsewhere

such groups are eliminated,

by them is also eliminated,

such fuse

increased which

few)

and peripheral

to the rings, as suggested further,

there

increase

similar to small,

(PAHs) which might

or incorporated,

sheet fragments,

and

range, there is not only

some few ketonic carbonyls

is increased

component

continue

aromatic

in polyaromatization.

600°C, the last linkages

domains

IR activity

impart

These trends

and the 1350 cm-l band. Such larger structures,

graphitic

groups except

hydrocarbons

formed

species are

600°C, there is an abrupt

an abrupt

Then, above

aromatic

species

During this aromatization

has diminished. Then, above

and is

entirely

and aliphatic

of rings to form clusters

to form the larger polyaromatic

IR continuum

proceeds

at that stage the char is almost entirely

this signaling

polynuclear

aliphatic

carbonylic

species.

formed.

over the approx.

Dehydration

he sugars are eliminated

but some fusion

residual

material

It is

the complete

which is initially

increases,

that, during this second temperature

aromatization,

products.

into char which is predominantly

temperature

has also been polyaromatization. in the IR continuum,

involves

in composition. The material,

progressively

< incorporated

until 600°C is reached; the number

range.

of

of little interest,

The chars produced

of the sugars.

350-600°C

aliphatic,

materials

with decomposition

that even at 200°C some aromatic

near

completed

absorption

along with

1291.

are as follows.

these being a mixture

during

in the profile occurring

to the explanation

PYROLYSIS

The various involves

the change

clusters,

of the continuum

C-H groups. [29] Then, the

and only the continuum

is observed.

Effectively,

the various

data indicate

(not considering

the partially

The first formed,

'medium-temperature'

characterized

by relatively

decomposed

that there are two types of sugar chars mixture

of sugars formed

chars, are of variable

small PAH-like

clusters

initially).

composition

and have relatively

and are large

480

numbers

of surface

properties

functional

groups.

temperature,

so would the chemical

temperature'

chars,

clusters, activity

Such groups would define the chemical

of the chars and, as the functional

in contrast,

consist

be ascribed

the polynuclear

'skeleton'

to surface

vary with pyrolysis

The last-formed,

of relatively

and have very few or no peripheral cannot

groups

reactivity.

groups,

groups.

'high-

large polynuclear

so that their chemical

The activity

would

thus arise

from

itself.

ACKNOWLEDGEMENT This paper Energy,

was prepared

Grant

conclusions,

with the support

No. DE-FG22-87PC7992D. or recommendations

not necessarily

reflect

also

acknowledged.

gratefully

expressed

the views

of the U.S. Department

However,

any opinions,

herein

of

findings,

are those of the authors

of DDE. Support

by NSF Grant

REFERENCES

1

J.S. Mattsen Dekker,

2

New York,

V.A. Garten,

(1957)

R.A. Friedel

4

J.S. Mattsen,

5

6

Marcel

1971, p. 38.

D.E. Weiss and J.B.

Willis,

Austr.

J. Chem.,

10

and J.A. Queiser, H.B. Mark,

Anal.

Chem.,

28 (1956)

Jr. and W.J. Weber,

Anal.

22.

Chem.,

41

and H.B. Mark,

Jr.,

J. Colloid

Interface

Sci.,

31

131.

J.S. Mattsen, Interface

7

Carbon,

355.

J.S. Mattsen

(1969)

Jr., Activated

295.

3

(1969)

and H.B. Mark,

L. Lee, H.B. Mark,

Sci.,

J. Zawadzki,

33 (1970)

of Carbons.

New York,

1988.

J. Colloid

284.

in P.A. Thrower,

Chemistry

and W.J. Weber,

Jr.

Chem.

(ed),

Infrared

Phys. Carbons.

Spectroscopy

in Surface

Vol. 21. Marcel

Dekker.

p. 158.

Low and C. Morterra,

8

M.J.D.

9

P.G. Varlashkin

and M.J.D.

Low, Appl.

Spectrosc.,

40 (1986)

393.

10

P.G. Varlashkin

and M.J.D.

Low, Appl.

Spectrosc.,

40 (1986)

507.

11

K. Avram

and G.D. Mateescu,

in Organic

Chemistry,

Carbon,

Infrared

Wiley,

21 (1983)

275.

Spectroscopy

Applications

New York, 1972, p. 475.

and do

No. CHE-8516257

is

481

12.

13.

R.G. Zhbanbov,

Infrared

Spectra

of Cellulose

Derivatives,

Consultants

S.A. Barker,

E.J. Bourne and D.H. Whiffen,

Analysis Methods

Bureau,

in the Determination of Biochemical

and its

New York, 1966, p. 35-71. Use of Infrared

of Carbohydrate

Analysis,

Vol. 3, p.

Structure, 213.

14.

W. B. Neely, Adv. Carbohydr.

Chem.,

12 (1957)

13.

15.

H. Spedding,

Chem.,

19 (1964)

23.

16.

H.G. Higgins,

Adv. Carbohydr. C.M. Stewart

and K.J. Harrington,

-51 (1961)

59.

17

P. Honig,

Principles

18.

C. Morterra

19.

N.B. Colthup,

L. Daley and S.E. Wiberly,

Infrared and

Raman Spectroscopy,

of Sugar Technology,

and M.J.D.Low,

Mater.

in

J. Polym. Sci.,

Elsevier,

Amsterdam,

Chem. Phys.Phys.,

12 (1985) 207.

Introduction

2nd edn., Academic

1953, p. 10.

to Press. New

York, 1975. 26. 20.

L.J. Bellamy, edn.,

Wiley,

21.

R. Nakanishi,

22.

G. Socrates, New York,

The Infrared

of Complex

Molecules,

2nd

Infrared Infrared

Spectroscopy,

Holden-Day,

Characteristic

New York, 1962.

Group Frequencies,

Wiley,

1980.

23.

C. Morterra

24.

Morterra,

25.

Morterra

26.

M.J.D.

27.

P. Painter,

and M.J.D.Low,

M.J.D.Low

and M.J.D.Low,

Spectrosc.

Low and A.S. Glass, M. Starsinic

York, 1986, Chapter 28.

E.A. Kmetko,

29.

M.J.D.

21 (1983) Carbon,

Lett.,

Spectrosc.

283.

15 (1982)

Lett.,

and M. Coleman,

22 (1984)

5.

689.

22 (1989)

417.

in J.R. Ferraro and L.J. Basile,

Infrared Spectroscopy,

Vol. 4. Academic

Press, New

5.

Phys. Rev., 82 (1951)

LOW and C. Morterra.

The Spectral

Profile

of Surfaces,

Elsevier.

C. Morterra

Carbon,

and A.G.Severdia,

(eds). Fourier Transform

30.

Spectra

New York, 1958.

456.

in C. Morterra,

of Medium-temperature Amsterdam,

and M.J.D.Low,

A. Zecchina Carbons,

1989. p. 601.

Carbon., 21 (1983)

275.

and G. Costa

Structure

(eds).

and Reactivity