Synthesis and characterization of regular segmented copolymers of poly(pivalolactone) and poly(oxyethylene)

123 Pages·1991·3 MB·English

by  Matayabas, James Christopher

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SYNTHESIS AND CHARACTERIZATION OF REGULAR
SEGMENTED COPOLYMERS OF POLY (PIVALOLACTONE)
AND POLY(OXYETHYLENE)
BY
JAMES CHRISTOPHER MATAYABAS, JR.
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A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
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UNIVERSITY OF FLORIDA
"^' '^-'--^'"' :-:'. 1991 ^^"';^'=
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To my wife, Deborah, and son, Joseph Johnson, for their
patience, understanding, support, and, most importantly,
their love.
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ACKNOWLEDGMENTS
Support for this study was provided by the Army
Research Office. The preparation procedures and samples of
2-benzoxyethanol and 2-(dimethylthexylsiloxy)ethanol were
donated by Dr. Mattson of the University of South Florida.
Pivalolactone was donated by Dr. H. K. Hall of the Univer-
sity of Arizona. Narrow molecular weight distribution
poly(oxyethylene) glycol, PEG(IOOO), was donated by Dr. S.
K. Verma of Union Carbide.
I thank my supervisory committee for their contribution
to my education, with special thanks to Dr. William M.
Jones.
I thank R. W. Moshier and R. Stroschein of the Univer-
sity of Florida Glass Shop for their excellent craftsman-
ship. I thank Jason Portmess for his assistance in the
laboratory •''
' •
I am proud to have been a member of the University of
Florida Center for Macromolecular Science and Engineering,
more commonly known as the Polymer Floor. Special thanks go
to the Polymer Floor secretaries, Loraine Williams and Pat
Hargraves.
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Special thanks go to Dr. Kenneth B. Wagener for the en-
couragement and guidance he has given me in his warm and
friendly manner.
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iii
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TABLE OF CONTENTS
ACKNOWLEDGMENTS iii
ABSTRACT vi
INTRODUCTION 1
Segmented Copolymers 1
Microphase Separation
3
Poly(pivalolactone) 5
Thermoplastic Elastomers with a
Poly (pivalolactone) Hard Segment 8
Objectives of This Dissertation 13
EFFECT OF HARD-SEGMENT LENGTH
ON MICROPHASE SEPARATION 15
Introduction 15
Materials 16
Synthesis 16
Determination of Molecular Weight 17
Determination of Intrinsic Viscosity 20
...
Determination of Mark-Houwink Parameters 20
...
Viscosity Measurements in Other Solvents 23
Analysis of Microphase Separation 23
Analysis of the Soft Phase 25
Soft-Segment Segregation 28
Determination of the Hard-Phase Composition 30
.
Chapter Summary 34
SYNTHESIS OF DEFECT-FREE TELECHELOMERS 35
Introduction 35
Siloxy-Protected Initiator 35
Synthesis 36
Polymerization 36
Hydroxy Acid Initiators 42
Introduction 42
Initial Attempts 43
Synthesis of Defect-Free Telechelomers 45
Formation of Dianionic Initiator 45
Dual Anionic Polymerization 49
Sequential Addition Polymerization 52
Control of the Soft-Segment Length 52
Control of the Hard-Segment Length 57
Analysis of Microphase Separation 59
Chapter Summary 62
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STEP POLYMERIZATION OF TELECHELOMERS 63
Introduction 63
Model Study 65
Melt Esterification of Telechelomers 69
Chapter Summary 72
EXPERIMENTAL 75
Instrumentation 75
SEC Programs 79
General Description 79
Calibration 79
Sample Analysis 81
Chemicals 81
Syntheses 83
Synthesis of 7 83
Synthesis of 8 84
Synthesis of (PVL)in-(OE)n-(PVL)jn 85
Synthesis of 10 86
Synthesis of 11 86
Synthesis of 12 87
Synthesis of 13. 87
Synthesis of 14 88
Synthesis of jL6 88
General Procedure for
Dual-Anionic Polymerization 89
General Procedure for
...
Sequential Addition Polymerization 90
General Procedure for
Alanine-Mediated Step Polymerization 91
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REFERENCES ^^ a»-^ 92
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APPENDIX . . . ." .• . :|4,.|.f .1 4L. » L - 96
BIOGRAPHICAL SKETCH 112
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Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy
SYNTHESIS AND CHARACTERIZATION OF REGULAR
SEGMENTED COPOLYMERS OF POLY (PIVALOLACTONE)
AND POLY(OXYETHYLENE)
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JAMES CHRISTOPHER MATAYABAS, JR.
May 1991
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Chairman: Kenneth B. Wagener
Major Department: Chemistry
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Microphase separation in a series of triblock poly-
(pivalolactone-block-oxyethylene-block-pivalolactone)
oligomers, represented by (PVL)jn-(OE) 24-(PVL)jn, where m = 5,
7, 9, 12, 16, and 24, was investigated by differential
scanning calorimetry. With the poly(pivalolactone) hard-
segment length maintained at 24 repeat units, a very
distinct transition from phase mixed to essentially complete
microphase separation occurs when m is increased from 9 to
12. Complete microphase separation occurs for m = 16.
Defect-free poly (oxyethylene-block-pivalolactone)
telechelomers, represented by (OE) 34-(PVL)i„, where m = 5,
12, and 16, were synthesized by sequential anionic ring-
opening polymerization of ethylene oxide and pivalolactone
with hydroxypivalic acid. These telechelomers exhibited
excellent microphase separation, allowing both the hard and
VI
soft segments to crystallize. Essentially complete micro-
phase separation occurs for m = 12 and 16, and the sample
with m = 5 showed some microphase mixing in the hard phase.
Step polymerization of the (OE) 34-(PVL)jn telechelomers
was achieved by alanine-mediated melt esterification with a
titanium tetrabutoxide added in catalytic amounts, producing
low molecular weight segmented copolymers, represented by
(OE) 34-(PVL)in]p. Melt esterification of the sample with m
[
= 16 produced the pentamer, (OE) 34-(PVL) ^gls, with M^ =
[
16,000 g/mole. Alanine-mediated step polymerization was
investigated in a model study involving a-hydroxypoly-
(pivalolactone) telechelomers; however, only dimers were
produced. -''
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INTRODUCTION
xi,:-'• : -f- Secfinented Copolymers
Block copolymers can be envisioned as polymers composed
of two or more homopolymers joined at the ends. If homo-
polymer A and homopolymer B are linked together by a
chemical bond, the resulting structure is a diblock copoly-
mer, A-B:
aaaaa-bbbbb
where "a" represents the repeat unit of homopolymer A, and
"b" represents the repeat unit of homopolymer B. The
addition of a third block produces a triblock copolymer,
either A-B-A or B-A-B:
aaaaa-bbbbb-aaaaa or bbbbb-aaaaa-bbbbb
The coupling of four or more blocks together forms a
segmented copolymer [A-Bj^s
aaaaa-bbbbb]
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Block and segmented copolymers are of great interest
due to the unusual properties that may result, and McGrath^
has edited an excellent overview of block and segmented
copolymers. While properties that are dependent upon the
—
chemical nature of the segments for example, chemical
—
resistance, stability, and electrical properties are
generally unaffected, the block architecture has a strong
—
influence on the mechanical properties of the copolymer for
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example, elasticity and toughness. McGrath points out that
the interesting characteristic of segmented copolymers is
the strong repulsion between unlike segments that causes
like segments to segregate into two-phase physical networks.
There are a number of segmented copolymer systems which are
one phase at temperatures well above the melt but exhibit
phase separation upon cooling, resulting in a wide variety
of useful materials ranging from impact-resistant polymers
to elastomers.
Thermoplastic elastomers, which combine thermoplas-
ticity with rubber behavior, have received the greatest
attention. Schollenberger and Scott^ first discovered
poly(urethane ether) thermoplastic elastomers in 1958, and
poly(urethane ethers) remain active subjects of investiga-
tion.^"^ Poly(urethane ethers) typically are synthesized by
step copolymerization of an aryldiisocyanate with an
alkyldiol in the presence of a poly(ether) glycol. Poly-
(ester ether) thermoplastic elastomers, which appeared more
recently, are synthesized by analogous polyesterification
— —
reactions of an aryldiester or acid derivative with an
akyldiol and poly(ether) glycol. ^"^5 since the development
of living anionic chain polymerization, block copolymers can
be synthesized by the sequential addition of two or more
monomers; however, this technique is only practical for the
synthesis of diblock and triblock copolymers. Prud'homme^^
used this technique to synthesize poly styrene-block-
(
isoprene) copolymers for a study of microphase separation.
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Recently, these general techniques have been combined to
synthesize a variety of block, segmented, and graft copoly-
mers, and this is the topic of recent and future symposia. ^^
:-.-"" Microphase Separation
In general, multiphase thermoplastic elastomers contain
a soft segment and an incompatible hard segment. The soft
segments segregate to form an amorphous or semicrystalline
soft phase, and the hard segments segregate to form a
crystalline hard phase, which acts as a thermally labile
physical crosslink. These segments are chemically bonded,
and even complete segregation cannot lead to macroscopic
phase separation as is found in homopolymer blends.
Instead, microphase separation occurs where there is
sufficient incompatibility between segments.
The simplified two-dimensional drawing of the micro-
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phase separation of the hard and soft phases of an oriented
segmented copolymer given in Figure 1 offers a pictorial
representation of microphase separation. In reality,
monomer concentrations vary smoothly over the entire
microphase structure, ^^' ^^ in contrast to the abrupt changes
in concentration associated with a clearly defined interface
depicted in Figure 1, v t >-. iij, i.
Differential scanning calorimetry (DSC) has proven
useful in the study or microphase separation, demonstrating
that phase separation usually is incomplete. •'"^ The degree
of microphase mixing in multiphase copolymers is of great
concern since it reduces the effectiveness of the physical