Poly(amide-imide)s containing polybutadiene blocks

Article abstract of DOI:10.1135/cccc20000361

Poly(amide-imide)s containing polybutadiene blocks were prepared by reaction of 4,4′-methylenedi(phenyl isocyanate) with trimellitic anhydride and α,ω-diisocyanatopoly-butadiene. The polymers were characterized by spectroscopic methods and X-ray diffraction. Incorporation of 5 wt.% of polybutadiene structures into polyimide decreases the temperature of 10% weight loss in nitrogen by 90 °C. Glass transition temperature of the polymer also decreases with the increasing content of soft polybutadiene segments, but the decrease is moderate for the contents higher than 20 wt.%. Broad amorphous halo dominates wide-angle X-ray diffractograms of all the samples, but sharper peaks of a more ordered structure were observed in definite concentration range of polybutadiene blocks. The copolymers are soluble in N-methylpyrrolidone.

Full text of DOI:10.1135/cccc20000361

Poly(amide-imide)s
361
POLY(AMIDE-IMIDE)S CONTAINING POLYBUTADIENE BLOCKS
a2
Miroslav MAREK, Jr.a, Drahomíra HLAVATÁa1,*, Jana KOVÁŘOVÁ
,
b1
b2
Miloslav SUFČÁK and Jindřich PYTELA
a
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic,
162 06 Prague 6, Czech Republic; e-mail: hlavata@imc.cas.cz, kov@imc.cas.cz
Kaučuk, a.s., 278 52 Kralupy nad Vltavou, Czech Republic; e-mail: sufcakm@kaucuk.cz,
1
2
b
1
2
pytelaj@kaucuk.cz
Received July 14, 1999
Accepted Jan uary 20, 2000
Poly(am ide-im ide)s con tain in g polybutadien e blocks were prepared by reaction of
4,4′-m eth ylen edi(ph en yl isocyan ate) with trim ellitic an h ydride an d α,ω-diisocyan atopoly-
butadien e. Th e polym ers were ch aracterized by spectroscopic m eth ods an d X-ray diffraction .
In corporation of 5 wt.% of polybutadien e structures in to polyim ide decreases th e tem pera-
ture of 10% weigh t loss in n itrogen by 90 °C. Glass tran sition tem perature of th e polym er
also decreases with th e in creasin g con ten t of soft polybutadien e segm en ts, but th e decrease
is m oderate for th e con ten ts h igh er th an 20 wt.%. Broad am orph ous h alo dom in ates
wide-an gle X-ray diffractogram s of all th e sam ples, but sh arper peaks of a m ore ordered
structure were observed in defin ite con cen tration ran ge of polybutadien e blocks. Th e copol-
ym ers are soluble in N-m eth ylpyrrolidon e.
Key w ord s: Copolym ers; Polyim ides; Poly(am ide-im ide)s polybutadien e blocks; Th erm al sta-
bility; X-ray diffraction ; Syn th esis.
Polycon den sation reaction of low-m olecular-weigh t polyam ides, poly-
ureth an es, polyeth ers etc., con tain in g isocyan ate en d-groups, with arom atic
diisocyan ates an d arom atic dian h ydrides is a well-tried syn th etic route
leadin g to variety of block copolym ers con tain in g polyim ide structure1–3
.
Th e attractivity of such m odification of various polym ers by im ide cyclic
structures con sists in excellen t th erm al an d m ech an ical properties of
polyim ides4,5. Arom atic polyim ides gen erally sh ow h igh relaxation tran si-
tion tem peratures, com pared with m ost com m ercially available polym ers,
wh ich m ake it possible to preserve th eir h igh m odulus an d ten sile stren gth
at exception ally h igh tem peratures. Th erefore, in corporation of im ide m oi-
eties am on g polym er segm en ts of an oth er ch em ical structure by th e above
m en tion ed polycon den sation reaction is m otivated by th e effort to in crease
th erm al an d h igh -tem perature m ech an ical properties with out th e dan ger of
m acroscopic dem ixin g typical of polym er blen ds6–13
.
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

362
Marek, Hlavatá, Kovářová, Sufčák, Pytela:
An in terestin g way of m olecular rein forcem en t of a soft polym er with
stiff segm en ts seem ed to be preparation of poly(butadien e-im ide)s con tain -
in g oligobutadien e blocks of defin ite len gth . Suitable telech elic oligom ers
can be prepared by application of organ odilith ium -based in itiator to livin g
an ion ic polym erization of butadien e an d subsequen t proper term in ation
an d ch em ical m odification of ch ain en ds. Th is procedure leads to prepara-
tion of an isocyan ate-en d-capped oligobutadien e h avin g defin ite m olecular
weigh t an d low in dex of polydispersity14. Previously we used such
telech elic oligom ers in th e reaction with 3,3′,4,4′-ben zoph en on e-
tetracarboxylic acid dian h ydride (BTDA) an d 4,4′-m eth ylen edi(ph en yl
isocyan ate)15 (MDI). Un fortun ately, such poly(butadien e-im ide)s are suit-
able just for preparation of elastom ers with relatively low con ten ts of
polyim ide structures sin ce a h igh er con cen tration of im ide m oieties m akes
th e copolym er in soluble in com m on solven ts.
In th is work, related poly(butadien e-am ide-im ide)s were syn th esized by
replacin g BTDA with trim ellitic an h ydride (TMA). Poly(am ide-im ide)s are
m ore soluble th an polyim ides an d th erefore th ey m igh t be m ore suitable
for m odification of polybutadien e with h igh con cen tration of stiff seg-
m en ts con tain in g im ide structures. Th is com m un ication describes our ef-
fort to develop th e above m en tion ed copolym ers an d to sh ow som e of th eir
basic ph ysicoch em ical an d ph ysical properties.
EXPERIMENTAL
Materials
Th e α,ω-diisocyan ato-polybutadien e LBD-3000 was obtain ed from Kaučuk Co., Kralupy. Mn
of in dividual sam ples was 3 500 ± 300, with con cen tration of isocyan ate groups 730 m m ol/g
(sam ples 2, 3) an d 719 m m ol/g (sam ples 4–7), respectively, because of differen t con cen tra-
tion of th e free MDI. Th e polydispersity in dex of th e m ain fraction was Mw/Mn = 1.3, but
m in or peak in th e ran ge of sh ort reten tion tim es was also observed. Th e oligom ers con -
tain ed 60% of 1,2-, 25% of 1,4-trans, an d 15% of 1,4-cis structure un its.
Trim ellitic an h ydride (TMA, Aldrich ) was purified by sublim ation an d 4,4′-m eth ylen e-
di(ph en yl isocyan ate) (MDI, Aldrich ) was purified by pressure filtration at 60 °C (ref.16). An -
h ydrous N-m eth ylpyrrolidon e (NMP, Aldrich , water con ten t <0.01 wt.%) was used as
received.
Syn th esis
4-(Ph en ylcarbam oyl)ph th alim ide (1) was syn th esized by th e reaction of ch loride of TMA
(9.5 m m ol) with an ilin e (19 m m ol) an d pyridin e (2 m l) in NMP (35 m l) at 160 °C for 3 h .
Th e crude product was isolated by precipitation in to water an d crystallized twice from
n itrom eth an e. Yield 83%, m .p. 208 °C. FTIR (KBr): 3 476, 3 344 (NH, am ide); 3 060 (CH,
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Poly(amide-imide)s
363
arom .); 1 780 (C=O, im ide); 1 646 (C=O, am ide); 1 600 (C=C, arom .); 1 540 (NH, am ide).
1H NMR (DMSO-d6): 10.57 s (CONH); 7.07–8.49 m (arom .). For C21H14N2O3 (342.8) calcu-
lated: 73.57% C, 4.12% H, 8.17% N; foun d: 73.49% C, 4.32% H, 8.25% N.
O
C
N
O
N
H
C
C
O
1
Syn th esis of Poly(butadien e-am ide-im ides)
Diisocyan ates (MDI, LBD-3000) were dissolved in NMP in a glass reactor equipped with a n i-
trogen in let an d CaCl2 dryin g tube. Th en an equim olar am oun t of solid TMA was added
in to th e reaction m ixture an d th e reactor was h eated in an oil bath at 70 °C for 90 m in . Th e
solid con ten t (in cludin g LBD-3000) was 15 wt.%. Th en th e tem perature 90 °C was m ain -
tain ed for 90 m in , 130 °C for 120 m in , 150 °C for 180 m in , an d 180 °C for 60 m in . Th e
polym er was th en precipitated in to water an d wash ed with THF.
Measurem en ts
In frared spectra of sam ples in th e form of KBr pellets were m easured usin g a Bruker IFS 55
FTIR spectrom eter. 1H NMR spectra were recorded on a Bruker ACF-300 spectrom eter at
25 °C in DMSO-d6. Viscom etric m easurem en ts were carried out in an Ubbeloh de viscom eter
at 25 °C in m-cresol. Con cen tration of sam ples was 0.001 g/cm 3. Wide-an gle X-ray diffracto-
gram s were m easured with a HZG4A autom atic powder gon iom eter. CuKα radiation was reg-
istered with scin tillation coun ter an d m on och rom atized with Ni filter an d pulse-h eigh t an a-
lyzer. Th e diffractogram s were perform ed in θ/2θ scan in th e scatterin g an gle ran ge 2θ
4–40°. Sm all-an gle X-ray scatterin g curves were m easured usin g a Kratky cam era in th e re-
gion of th e scatterin g vector q = 0.1–2.0 n m –1. Th e scatterin g vector is defin ed as q =
(4π/λ)/sin θ, wh ere λ is th e wavelen gth an d 2θ is th e scatterin g an gle. CuKα radiation was
registered usin g a position -sen sitive detector17 (Join t In stitute for Nuclear Research , Dubn a,
Russia). Differen tial scan n in g calorim etry (DSC) an d th erm ogravim etric an alysis (TGA) were
carried out usin g Perkin –Elm er DSC-7 an d TGA-7 in strum en ts, respectively, with a h eatin g
rate 10 °C/m in in both cases.
RESULTS AND DISCUSSION
Poly(am ide-im ide)s con tain in g polybutadien e blocks, poly(am ide-im ide)
TMA/MDI an d poly(α,ω-diisocyan ato-polybutadien e-co-trim ellitic an h y-
dride), were syn th esized by a well-tried m eth od con sistin g in reaction of
TMA with arom atic diisocyan ates18 (Sch em e 1). Th is reaction is based on
th e reactivity of –N=C=O groups both with an h ydride group, resultin g in
th e form ation of cyclic im ide19, an d with carboxylic group, leadin g to am -
ide structures20. Traces of water are n ecessary for a quan titative im ide rin g
form ation 21. Th erefore, n o furth er dryin g of com m ercially available
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

364
Marek, Hlavatá, Kovářová, Sufčák, Pytela:
pre-dried solven t was used. Moreover, n um erous organ om etallic com -
poun ds (alkali m etal alkoxides, ph en oxides, n aph th oxides, lactam ates, etc.)
are kn own to catalyse th e am ide bon d form ation 20. On th e oth er h an d, ba-
sic catalysts, in particular sodium alkoxides, prom ote un desirable
cyclotrim erization of isocyan ate groups22. Sin ce organ om etallics an d traces
of water would deactivate each oth er, we did n ot add an y special catalyst
in to th e reaction system an d carried out th e reaction at h igh tem peratures
(up to 177 °C), in spite of th e fact th at a few side reaction s can take place
un der such con dition , as it is publish ed in literature (in particular, th e reac-
tion of isocyan ate en d-goups with solven t – NMP, ref.18).
O
C
HOOC
O C
N
CH2
N
C O
+
O
C
O
O C
N
POLYBUTADIENE N C O
+
- CO2
O
C
N
O
R
N
H
C
R =
CH2
C
or POLYBUTADIENE
O
n
SCHEME 1
Basic ch aracteristics an d com position of (co)polym ers are sh own in Table I.
Th e yields an d in h eren t viscosities are com parable with th ose of related
poly(butadien e-im ide)s an d oth er h igh -perform an ce polym ers. But in con -
trast to related poly(butadien e-im ide)s, th e (co)polym ers in question are
well soluble in NMP even at low or zero con ten ts of butadien e blocks.
In Fig. 1, FTIR spectra of poly(am ide-im ide) TMA/MDI (a) an d copolym er
sam ple 6 (b) are sh own . Th e spectrum of n eat poly(am ide-im ide) (sam ple 1)
con tain s absorption ban ds wh ich are typical of m acrom olecules con tain in g
am ide an d im ide groups. Ch aracteristic absorption ban ds of th e am ide m oi-
ety23 appear at 1 778 [νs(C=O)], 1 722 [νas(C=O)], 1 376 [ν(C=N], 726
[δ(C=O)], an d th ose of am ide group24 can be seen at 1 660 [ν(C=O)] an d
1 540 cm –1 [δ(N–H)]. Th e sam e absorption ban ds are also obvious in th e
spectrum of copolym er (b). In addition, absorptions of polybutadiene occur25.
Th e stron g absorption in th e region 1 640–1 665 cm –1 in dicates th e pres-
en ce of ban ds correspon din g to C=C stretch in g vibration s of both 1,2- an d
trans-1,4-polybutadien e structures. Weaker absorption ban ds in th e ran ge
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Poly(amide-imide)s
365
994–1 000 cm –1 are located in th e ran ge of th e C–H out-of-plan e vibration s
of both m en tion ed polybutadien e isom ers.
1H NMR spectra are too com plex to give an eviden ce of an y side reac-
tion s. On th e oth er h an d, stron g sin glet of am ide proton (at 10.4 ppm for
th e copolym er an d 10.5 ppm for poly(am ide-im ide)s, several overlappin g
m ultiplets in th e ran ge 7.0–8.5 ppm (correspon din g un doubtedly to aro-
m atic proton s) con firm th e aram ide-type structures in th e (co)polym er.
TABLE I
Con ten t of LBD-3000, yield, in h eren t viscosity, an d glass tran sition tem perature of poly-
(am ide-im ide)s con tain in g polybutadien e (LBD-3000) blocks
LBD-3000 con ten t
ηm n , dL/g
Tg, °C
Sam ple
Yield, %
wt.%
1
2
3
4
5
6
7
0
5
94
89
89
91
82
96
92
0.89
0.80
0.90
1.22
0.54
1.05
0.39
255
–
8
211
206
202
193
–
16
18
42
94
a
b
FIG. 1
FTIR spectra of poly(am ide-im ide) TMA/MDI
(sam ple 1) (a) an d sam ple 6 (b)
4 000
3 000
2 000
ν, cm
1 000
–1
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

366
Marek, Hlavatá, Kovářová, Sufčák, Pytela:
Th erm al stability of (co)polym ers was ch aracterized by tem peratures of
10% (T10) an d 20% (T20) weigh t loss. As can be seen in Fig. 2, in corporation
of 5 wt.% of polybutadien e in to th e poly(am ide-im ide) ch ain leads to a de-
crease in th erm al stability by 90 °C. However, furth er in crease of polybuta-
dien e con ten t in copolym ers causes relatively sm aller drop of th e respective
in itial decom position tem perature (Fig. 2). Furth er in crease of polybuta-
dien e con ten t in copolym ers does n ot decrease decom position tem pera-
tures (Tloss). On th e oth er h an d, as follows from Fig. 3, total weigh t loss for
poly(butadien e-am ide-im ide)s at tem peratures up to 550 °C con siderably
640
T
, °C
loss
600
560
520
FIG. 2
480
440
Th e depen den ce of 10% weigh t loss (ꢀ) an d
20% weigh t loss (ꢀ) on th e weigh t fraction of
LBD-3000, WLBD, in TGA experim en ts in n i-
trogen
0
20
40
60
W
80
, %
100
LBD
100
Weight, wt%
80
60
40
100
200
300
400
500
T, °C
FIG. 3
TGA curve in n itrogen for poly(am ide-im ide) (sam ple 1, – – –) an d poly(butadien e-am ide-
im ide) con tain in g 5 wt.% polybutadien e (sam ple 2,
)
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Poly(amide-imide)s
367
exceeds th e value correspon din g to T20, stron gly reflectin g th e effect of
th erm ally labile polybutadien e blocks.
Polubutadien e segm en ts flexibilize copolym er ch ain s, so th at just an ad-
dition of 8 wt.% of th ese soft blocks leads to a decrease in th e glass tran si-
tion tem perature Tg by 45 °C, as it can be seen from Table I. Furth er
in crease in th e con cen tration of polybutadien e does n ot in fluen ce Tg con -
siderably, probably due to th e lim ited m iscibility of soft polybutadien e, an d
h ard poly(am ide-im ide) blocks.
Wide-an gle X-ray diffraction (WAXD) pattern s of th e (co)polym ers are
sh own in Fig. 4. All sam ples exh ibit a broad am orph ous h alo, th e m axi-
m um of wh ich is sligh tly sh ifted to lower values of 2θ with in creasin g
polybutadien e con ten t. Wh ile th e n eat poly(am ide-im ide) (sam ple 1) h as
m axim um at 2θ = 20°, wh ich correspon ds, accordin g Bragg’s law, to th e av-
erage in terch ain distan ce d = 4.4 Å, sam ple 7 sh owed th e m axim um at 2θ =
18° correspon din g to th e in terch ain distan ce d = 4.9 Å. Difractogram s of
sam ples 4 an d 6 (sam ple 5 was n ot m easured sin ce its com position is al-
m ost th e sam e as th at of sam ple 4) sh ow on e addition al, relatively sh arp
but very weak peak dem on stratin g appearan ce of an ordered structure.
From th e position of th is peak at th e diffraction an gle 2θ = 25°, th e corre-
spon din g Bragg’s distan ce d = 3.5 Å was calculated. Th ese peaks m igh t re-
flect in tersegm en tal distan ce of rigid TMA-related segm en ts, sin ce in som e
e
d
c
b
FIG. 4
a
Wide-an gle X-ray diffractogram s of (co)poly-
m ers: sam ple 1 (a), sam ple 2 (b), sam ple 4 (c),
sam ple 6 (d), sam ple 7 (e)
0
10
20
30
40
2Θ, °
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

368
Marek, Hlavatá, Kovářová, Sufčák, Pytela:
BTDA-based polyim ides26, in tersegm en tal distan ces between two diim ide
structures were observed by m ean s of WAXD.
Th e existen ce of a partially ordered structure on ly in a discrete ran ge of
polybutadien e con ten t can be explain ed by th e flexibilizin g effect of such
soft segm en t. Sin ce steric h in dran ce of rigid poly(am ide-im ide) ch ain s,
com posed dom in an tly from h eterocyclic an d arom atic rin gs an d
in term olecular H-bon d-form in g am ide structures, preven ts reorgan ization
in th e (co)polym er, th ere are n o sh arp peaks in sam ples 1 an d 2 (i.e., th ose
with n o or very low con ten ts of polybutadien e). An in crease in th e con ten t
of soft segm en t flexibilizin g m acrom olecules m igh t en able partial orderin g
of TMA-related structures an d th erefore sh arp peaks in Fig. 4,
diffractogram s b an d c (sam ples with 18 an d 42 wt.% of polybutadien e)
were observed. Furth er in crease in polybutadien e con cen tration leads to di-
lution of such stiff segm en ts so th at th ey can n ot approach each oth er to
form a m ore com pact structure. Th is assum ption is supported by th e ab-
sen ce of th e orderin g in sam ple 7 (Fig. 4, diffractogram e).
In order to get more information about the origin of the ordering in some
samples, the TMA-related model compound, 4-(phenylcarbamoyl)ph th alim ide
(1), was syn th esized an d its WAXD pattern was m easured. Th e
diffractogram (Fig. 5) is clearly m ore com plicated an d th e peaks are m uch
sh arper in com parison with th ose in copolym ers because of th e
c
b
FIG. 5
a
Wide-an gle X-ray diffractogram s of 4-(ph en yl-
carbam oyl)ph th alim ide (a), sam ple 4 (b), sam -
ple 6 (c)
0
10
20
30
40
2Θ, °
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

Poly(amide-imide)s
369
low-m olecular-weigh t n ature of th e crystallin e m odel com poun d. Two
distances, d = 4.1 and 3.3 Å, are close to those in WAXD patterns of the copoly-
m ers, wh ich in dicates th e possibility th at sh arp peaks in Fig. 4 (diffracto-
gram s b an d c) origin ate from stiff TMA-related structures sim ilar to th e
m odel. On th e oth er h an d, som e distan ces (in particular th e in ten sive
sh arp peak correspon din g to d = 5.2 Å) are n ot presen ted in th e diffracto-
gram of th e m odel. Th is fact can be explain ed eith er by n ot exactly th e
sam e orien tation of th e m odel an d th e stiff TMA-related segm en ts in copol-
ym ers or by n on -iden tical structure of copolym er segm en ts in question an d
4-(ph en ylcarbam oyl)ph th alim ide (th e real stiff TMA-related segm en t in th e
copolym er is larger th an in a case of m odel com poun d).
Sm all an gle-X-ray scatterin g (SAXS) pattern s of th e sam e (co)polym er
sam ples are sh own in Fig. 6. Curves of scatterin g in ten sity, I, vs scatterin g
vector, q, sh ow a relatively sh arp in crease in th e in ten sity for q → 0 (even
th e sam ple 1 – n eat polyam id-im ide). Th erefore, we believe th at m icrovoids
of air (com m on ly presen t in polym ers like polyim ides) are presen t. Besides,
SAXS curves of th e copolym ers exh ibit a sligh t sh oulder in th e ran ge of th e
scatterin g vector q = 0.2–0.4 n m –1. Th is fain t m axim um can be attributed to
th e form ation of th e superm olecular structure typical of copolym ers.
10
1
FIG. 6
0.1
Sm all-an gle X-ray scatterin g curves: sam ple 1
(∆), sam ple 2 (ꢀ), sam le 4 (ꢀ), sam ple 6 (ꢀ),
sam ple 7 (×)
0
1
10
–1
q, nm
Financial support of the research by the Kaučuk, a.s., Kralupy is strongly appreciated.
Collect. Czech. Chem. Commun. (Vol. 65) (2000)

370
Marek, Hlavatá, Kovářová, Sufčák, Pytela:
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