Small-angle x-ray and small-angle light scattering studies of the morphology of polymer blends.

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Doctoral Dissertations 1896 - February 2014
1-1-1976
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Farrokh Burjor Khambatta
University of Massachusetts Amherst
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Khambatta, Farrokh Burjor, "Small-angle x-ray and small-angle light scattering studies of the morphology
of polymer blends." (1976). Doctoral Dissertations 1896 - February 2014. 622.
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SMALL-ANGLE X-RAY AND SMALL-ANGLE LIGHT SCATTERING
STUDIES OF THE MORPHOLOGY OF POLYMER BLENDS
A Dissertation Presented
By
FARROKH B. KHAMBATTA
Submitted to the Graduate School of the
University of Massachusetts
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
May 1976
Polymer Science and Engineering
(c) Farrokh B. Khambatta 1976
All Rights Reserved
ii
SMALL-ANGLE X-RAY AND SMALL-ANGLE LIGHT SCATTERING
STUDIES OF THE MORPHOLOGY OF POLYMER BLENDS
A Dissertation
By
FARROKH KHAMBATTA
Approved as to style and content by:
Professor R. S. Stein, Chairman of Committee
Professor R. S. Porter, Member
Professor F. E. Karasz, Member
Sanchez Member
,
Professor W. J. MacKnight
Head of Department
Polymer Science & Engineering
May 1976
iii
DEDICATED TO
MY WIFE MAHARUKH AND MY PARENTS
iv
.
ACKNOWLEDGEMENTS
This modest research effort has been a source of tremendous personal
fulfillment but only because of the cooperation and assistance of several
persons which made it all possible.
The author is indebted in a very special way to his thesis director
Professor Richard S. Stein for not only his inspiration and invaluable
guidance during this work, but also his inexhaustible patience throughout.
Many thanks are due to the committee members for their helpful com-
ments and criticisms at various stages of this work and for accommodating
the author in many ways towards the end of his stay at the University of
Massachusetts
Samples of both polymers were provided by Dr. J. Koleske of Union
Carbide Corp. and a standard Lupolen sample was kindly provided by
Professor 0. Kratky of the University of Graz. Their generosities are
appreciated very much.
Thanks are also due to members of the research group for their
valuable suggestions during the course of several presentations, parti-
cularly to continued stimulating discussions with Drs. Prud Thomme, Misra
and Natarajan, especially with regards to small-angle light scattering
studies. The many interesting discussions with Drs. Wenig and Waisiak
regarding small-angle x-ray scattering are also appreciated.
v
ABSTRACT
The morphology of polymer blends using poly-e-caprolactone (PCL)/
poly(vinyl chloride) (PVC) as a model system has been studied by small-
angle x-ray scattering (SAXS) and small-angle light scattering (SALS).
Previous research efforts had concluded from the observance of a
single glass transition that blends of PCL/PVC were compatible for all
compositions inspite of one of the components (PCL) crystallizing up to
a composition of 50/50* (PCL/PVC). It had also been established that
the addition of PVC to PCL progressively impeded the crystallization of
the ester and for compositions rich enough in PVC, crystallization did
not occur.
Results of SAXS and SALS studies are consistent with the above
observations regarding the trend and have moreover served to establish
the morphological details on a more quantitative basis.
Compositions rich in PCL crystallize in volume-filling spherulitic
morphologies thus incorporating the PVC within the spherulites. While
the lamellae continue to be exclusively PCL as shown by wide-angle x-ray
diffraction (WAXD) the interlamellar region is a partially mixed amorphous
phase of PVC and uncrystallized PCL from analysis of absolute intensity
measurements and comparison with independent measures of volume crystal-
_______ *
*A11 compositions are in weight-percent unless otherwise specified.
Vll
Unities. The crystallinity of the spherulites and consequently the
system begins to drop resulting in coarser spherulites with more open
structures as shown by the corresponding increase in the long period.
On the basis of a one dimensional sandwich model of alternating crystal-
line and amorphous layers, the one dimensional crystallinity is in good
agreement with the volume crystallinities measured by the density
gradient column and differential scanning calorimetry. Simultaneously
the drop in the crystallinity of PCL itself is not so marked. The same
trend is seen in SALS experiments where the intensity of H scattering
(absolute units) shows a steady drop proportional to that of PCL's
crystallinity. The crystallite size seems almost independent of com-
position.
With more PVC saturating the spherulites, the excess of it forms
a matrix by virtue of its high concentration in the amorphous phase and
the system now crystallizes as a non-volume-filling one in which the
spherulites are partially truncated. The long period is difficult to
estimate accurately for such a system and the one dimensional crystal-
linity is also overestimated. The SALS intensity shows a drop simulta-
neous to that in the crystallinity of PCL itself and can be accounted for
on that basis.
Higher concentrations of PVC result in amorphous morphologies which
seem to show the presence of domains that vary in their average size with
the blend composition and have diffuse transition zones whose dimensions
are proportional to the domain sizes. The domain sizes are reasonable in
magnitude and trend and the same is true for the transition zone thick-
Vl•l*l•
nesses when it is considered that the PCL/PVC system is an exceptionally
compatible one with respect to the more widespread incompatibility
between polymers.
Also, on the basis of absolute intensity analysis it is concluded
that the compatibility is not segmental throughout the morphology but
that domains of mixed compositions exist with distributions in their
size and compositions and that the electron density is smeared out
across broad transition zones within the system.
When one considers the fineness of the dispersion from the specific
surface values it is not surprising that the system exhibits single but
not sharp glass transitions.
The techniques of SAXS and SALS have been suitably complemented
with other measurements viz. WAXD, optical microscopy, SEM, DSC, etc.,
as and when necessary.
The ideas and efforts of previous workers have also been comple-
mented and extended towards a deeper understanding of the system's
morphology and it has simultaneously been demonstrated that SAXS and
SALS used judiciously can be powerful characterization tools in the
hands of a polymer scientist.
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